Excellent troubleshooting! I'm not good at wiring, but when you said the heater and the fuel pump both related issues on separate circuits, i immediately thought of a grounding issue - that seems to usually be what causes weird gremlins like this. I had a weird grounding issue on my car where the headlights would randomly turn off and I'd lose dash lights. It turned out I didn't have one of the main grounds secured. Thanks again!
+Norman Bates actually it takes him longer to find faults than it should since he is teaching while diag'ing, but any good diag tech would have figured that out, it is not as hard as it looks, honestly. you just need to know theory and system set-up
Very nice lesson as always. This also would indicate that the oil pressure switch/circuit is no good, as once the engine is running the relay can be taken out of the loop and it should still continue to run. I realize that I am commenting on an old video, but for anyone that comes across it should also be aware of the oil pressure switch, which you did address on operation in the beginning when looking on the diagram.
Great video. Your knowledge of electrical systems and how to diagnose them is awesome . You give easy to understand examples of how to diagnose and repair what seem to be difficult problems. I was a mechanic for ford for twenty years before falling at work and hurting my back. I miss it terribly. Your videos bring me back to a time when fixing automobiles was not only easy for me but fun also. Your enthusiasm is refreshing. Thank you for your videos they inspire me to want to rectify my ASE tests. Especially the L-1. And electrical. Those were my favorite vehicle problems to repair.
+Frank Senick that's awesome Frank! It's never too late to get back into it. Especially if you focus on electrical systems. It is a lot easier on your back :)
Want to information about it where the relays are in the Micra 1041 litre want to know where the relays are in the micro one day 04 too old for Micra 1 litre want to know where to realise that relays are in relays
thank you so much for this! we just replaced the fuel pump and were still having this problem. so I searched and found this video and fixed it! awesome job, I'll be coming back to you for any other problems we have!
Wonderful video. Learned a lot. My first reaction was to change the fuel pump, bad internal binding, etc. However, with proper testing and understanding theory of operation, I can see how my faulty reasoning would be an expensive lesson. Your methodical test procedure really made sense. Enjoyed following your explanation on the wiring diagram. Another thing, I learned was the importance of ground points. I didn't realize how critical they are and how they affect relays, etc. Thanks.
Excellent excellent case study.. I was baffled in the beginning with the heater in the mix of things, that really through me a loop. Shared ground never cross my mind. Wiring digram interpretation is really key to figuring out what is going on within a circuit.
Thanks! I've been watching several videos from you and I must say that not only your knowledge is great but also your teaching is superb!!! I'll keep coming back every time I have an issue with my Chevrolet Trans Sport, (Venture, Montana). 👍
thanks mr. Paul for yuor videos, im in Mexico and i like all yuor videos you r a realy good teacher, now i understand my scanner and i will buy a scope. GOD bles you and your family
no, there are some frame mounted pumps but it is more common to be in the tank. some models offer an access cover in the trunk or rear seat area, which is nice.
Hey Paul Danner, Well Explanation for this Fuel Pump Circuit is very clear and making me to feel simple when the Faults Related to the Fuel Pressure issues come to me and im agree with your Motto " Don't Be A Part Changer" Thanks Forever Danner ❤❤❤❤❤
Great video , shows that you have to look in odd places sometimes. One normally wouldn't think there was a larger current load on a relays control ground. Great info as always Paul.
Your a very smart and knowledgable young man I really appreciate you putting this video out because I I have a similar problem with my nissan pathfinder.Thanks again I will like and share.GOD BLESS YOU.
great explanation! it just shows when you know your job , you make it look easy! it appears you are a seasoned mechanic! great job! process of elimination only works when you know your trade!~ where can we find mechanics like you ? Oh! one more thing, it takes a little time to diagnose!~ you took less than 30 minutes...outstanding!!~
A bazillion $ scanner, schools and training to find a Chevy ground fault.... priceless...! but... it was a stovebolt to begin with and would never ever own one newer than '60's..great video SD.... I loved it, your diagnostic skills are greatly admired here...73 and still wrenching...but not on those dogs...
thanks my friend. I have much respect for my elders. I hope I live long like you to see my grand children. May God bless you and your family and continue to bless your hands and your mind as you continue in this field.
Hey SD thanks for that...You know of course I was not being disparaging in any way of your talent and training..love and appreciate your efforts you use to educate us old school dummies to the new tech..who would have guessed it in high school auto classes in the 50's working on Ford flat-heads and Chevy stovebolts it would have come to this ..?
so a question i seen the ground problem but as you shown in the wiring diagram the relay/oil pressure switch run in the same circuit so when the relay dropped out why did the fuel pump quit unless the oil pressure switch is not working or was the ground totally going in a open condition thanks hope you like questions i alway want to know
good question, with the bad block ground nothing was really working correctly. I have to look at the diagram again to give you a better answer than this.
Super cool case study. Reminds me if your similar issue with the s6 Audi and how it had a loose nut on the firewall ground. Being a Euro specialist you have no idea how many times I see that.
@ScannerDanner Another clue to this problem is when you first turn the key on you should still get a fuel pump "prime". This is the ECM turning the FP relay on for a second to bring fuel pressure up. After this "prime" the ECM will NOT turn the FP relay back on until it receives an RPM signal (on the purple-white ref. wire). If you do not have a "prime" happening when you first tune key on, then we are barking up the wrong tree. I can still help you though.
Great case study!!! You’re the best too bad you’re not in the Los Angeles area, it would be a pleasure to let you diagnose my car problems but I’m learning a lot from you great guys! (Scanner, Eric o, Ivan)
I wish I had an easy answer for you. Unfortunately it is hard to find a good diagnostic tech in this field. Most mechanics are parts changers. A suggestion is go to iATN and search iATN's Auto Repair Shop Finder. This isn't going to guarantee that you find a good diagnostic tech, but I think it will increase your chances.
@ScannerDanner If the FP relay turns on and the injectors fire you need to replace the ignition module. I know, I know, "but I have spark" is what you are thinking. Listen, these modules will fail in that it will still control the coil, but not send the reference pulse (0-5v square wave) on the purple-white wire to the ECM. Without this signal the ECM will not see an RPM signal and will not fire the injectors and will not run the pump.
@fivefortyeye540i Thank you, this one was a little tricky to film. There are so many different directions I could have taken this. Hopefully it was clear and not cluttered with too much info.
+Will Rogers That is because sometimes it is for engine safety. This may be the exception or maybe safety is the exception. I'll leave it to scannerdanner to give the average percentages either way. I know it is a safety on older GM diesels of the 90's era. Least ways they won't run when that switch goes bad.
Some nice multiplexed circuits over long spans. Pulse width modulated fuel control valves on CNG engines. Gas mass flow sensors. Coil on plug ignition with a separate module from the ecm
one last thnig! a good mechanic, listens to the customer~ it's called communication! it's like a doctor patient relationship~ So the customer was correct in his explaination of the cause of pump failure. didn't show on diagram sometimes it won't. great meachanics are the best trouble shooters!!
@CoolasIce2 I just checked out that scope. It is an old analog scope. It will do want you want but you will have problems with "glitch" captures because there is no play back. I would recommend you go on ebay and buy a used Vantage (not pro, unless you can afford it)). It is a graphing multimeter and will get you by for awhile. Plus the data base in the tool is unmatched in this field. I have had students pick them up for around $200
i guess the best way to learn faster is to create faults on our own cars. The waveforms makes electricity visual instead of a invisible theory. I love it !!!!
@kenjackson1977 Do you have spark and injector pulse? Or does the engine run when you hot-wire the pump. All you said was the pump runs when you hot-wire it. I need to know to help you further.
That is one sweet capture. I was cool to see that the fp would operate with 4v on the ground. Very cool patern. One look at the ground voltage on the yellow trace, that was too cool
@spelunkerd Nice, I have never heard that quote. I like it too. The oil psi switch is simply there as a backup in case the relay fails. Of course the other side of that oil psi switch runs the oil psi gauge or light, so it serves two functions. I don't know why GM felt the need to backup the FP relay. No one else is doing that. Seems like a waste of copper wire to me. They must have had a lot of problems with this circuit early on?
Loved the video walk-through, as well as the process of elimination you used to get to the root of the problem! I'm not a mechanic by even a loose interpretation of the term (I like to do simple maintenance like change the oil, brakes/rotors, spark plugs, etc on my e39 540i). What would you recommend as a way to find a good mechanic to work on a car? One that will diagnose problems like you did in the video. Most I've been to would simply replace a pump/relay/etc and "see if that works".
@ScannerDanner That sounds a lot like a quote from Isaac Newton. It went like this, "If I have seen farther, it was by standing on the shoulders of giants...." I love that quote, and I love standing on shoulders, ha ha. Why is that backup circuit from the oil pressure switch there?
This was a main block ground problem so it wouldn't matter where the power was coming from (relay or oil pressure switch), the problem would still be there.
Excellent diagnostics Dan but seeing you pierce wires freaks me out. I live in the damp northeast and greenitis is a death sentence to a wiring harness. I know those tools are easier than rigging up backprobe taps and bridges but those little holes cause BIG problems. That said keep these great videos coming.
Dan excellent video wondering? Would a ground V-Drop test have been a valid test to prove the existence of a bad chassis/signal ground at the OBDII connector terminals 4 and 5??? and... where is your e-book link?
Paul,Guess I am asking the question from the perspective of being an owner/user of a Load Pro Dynamic Test Lead, and wondering if it would have revealed a bad ground from the terminal... perhaps I'll get a chance to test (or create a test environment to experiment and see if it will work)...
Thanks man! If you get me some buyers, I will take care of you in the form of some free video lectures. Just have whoever it is mention your name in their communications with me. Thanks again
I know this video is old, but I'm confused about the relay... You said that oil pressure switch provides alternate power to the fuel pump once the engine is running and that you could pull the relay after it's running and it would stay running... So why does the relay switching off and on like that kill the engine? Obviously there is a problem there, but the oil pressure switch still should've kept it running... Edit: nevermind, I understand now. With that ground issue effecting the entire system (most likely), the oil pressure switch would also be loosing connection.
You were right in your initial idea. The only way this engine fuel pump would stop and start because of a relay ground problem is if the oil pressure switch was not working. The oil pressure switch get power from a fusible link and it bypasses around the relay and connects to the same fuse and on to the fuel pump. The Oil pressure switch has no ground to worry about. The fuel pump itself has a totally different ground than the relay itself.
would you be able to pull the relay, if the fuel pump still runs then that would narrow down to relay. Thought process on that was like you said the oil switch would take over and still allow voltage to the pump.
Your videos are invaluable! I'd love it if we could set up a way for you to come do some videos at our shop! All brand new fleet of peterbilt CNG trucks!
You are awesome Paul. If i buy your e-book i'll have some kind of guide to learn how to diagnose problems like you did? I'm a begginer mechanic and current(and begginer) student of Electronic Engineering and i'm interested in learn this stuff. Thank you for your excellent videos!
TCM ATA relay which is controlling with "-" from TCM. Black probe to pin on TCM and Red on relay "-" side. I got 1.5V (on ign.key on only). Is it the bad ground? I found how to check bad ground later on your channel. Thank you for all these videos🎉
probably going to buy this ebook once paul replies to a question i emailed. anyone have any other recommended youtube channels or ebooks that are worth watching or buying?
Great video. Nice to see what you can do with a scope. I have been doing this for years with a test light and a cotter pin. I may use a multimeter if I get really hard up. Granted this is an instructional video but why not use a cotter pin to ground out the control side of the relay and verify (a) relay works, (b) pump and load side work? All diagnostics in the video are great, I'm not trying to criticize here but a relay needs 2+ and 2- to work which is basic electrical....
Found a good one the other day. Had a 99 pontiac trans am 5.7l it was it the shop for a engine light runs fine had a code for maf circuit. Found fuse blown for power feed. Replaced fuse when it was sitting there fuse would not blow but soon as you power braked it fuse blew. Found o2 sensors on same circuit and the wires on one of the down stream sensors rubbed through and would ground out on a heat shield when you would put a load on the engine. Like the weird ones.
Hey Dan have a question I have a 1999 GMC safari van Meyrou fuel pump relay gets extremely hot could it be that it's holding too much load because the oil pressure switch is bad thank you
Finally an actual auto electronic/electric master mechanic. Every one that I have dealt with only guessed.. By the way my 1991 Lexus was doing the same thing except it was blowing the fuse when I would turn on the radio. So I wrapped some copper wire on the fuse until whatever it was affecting it on the radio side burned up. The car works now, except no radio. I did this after multiple wanna-be's mechanics kept giving me bullshit diagnosis.
![New Fuel Pump - Still No Fuel Pressure - Now What? [2012 Ford E350]](http://i.ytimg.com/vi/GJ9O8pTkK4w/mqdefault.jpg)
Excellent troubleshooting! I'm not good at wiring, but when you said the heater and the fuel pump both related issues on separate circuits, i immediately thought of a grounding issue - that seems to usually be what causes weird gremlins like this. I had a weird grounding issue on my car where the headlights would randomly turn off and I'd lose dash lights. It turned out I didn't have one of the main grounds secured. Thanks again!
Fella, I gotta say you know your stuff. I don't think very many people would have figured that one out. Thanks.
+Norman Bates actually it takes him longer to find faults than it should since he is teaching while diag'ing, but any good diag tech would have figured that out, it is not as hard as it looks, honestly. you just need to know theory and system set-up
Very nice lesson as always. This also would indicate that the oil pressure switch/circuit is no good, as once the engine is running the relay can be taken out of the loop and it should still continue to run.
I realize that I am commenting on an old video, but for anyone that comes across it should also be aware of the oil pressure switch, which you did address on operation in the beginning when looking on the diagram.
Great video. Your knowledge of electrical systems and how to diagnose them is awesome . You give easy to understand examples of how to diagnose and repair what seem to be difficult problems. I was a mechanic for ford for twenty years before falling at work and hurting my back. I miss it terribly. Your videos bring me back to a time when fixing automobiles was not only easy for me but fun also. Your enthusiasm is refreshing. Thank you for your videos they inspire me to want to rectify my ASE tests. Especially the L-1. And electrical. Those were my favorite vehicle problems to repair.
+Frank Senick that's awesome Frank! It's never too late to get back into it. Especially if you focus on electrical systems. It is a lot easier on your back :)
Want to information about it where the relays are in the Micra 1041 litre want to know where the relays are in the micro one day 04 too old for Micra 1 litre want to know where to realise that relays are in relays
2oo4 micra 1 liter were are relays
thank you so much for this! we just replaced the fuel pump and were still having this problem. so I searched and found this video and fixed it! awesome job, I'll be coming back to you for any other problems we have!
Wonderful video. Learned a lot. My first reaction was to change the fuel pump, bad internal binding, etc. However, with proper testing and understanding theory of operation, I can see how my faulty reasoning would be an expensive lesson. Your methodical test procedure really made sense. Enjoyed following your explanation on the wiring diagram. Another thing, I learned was the importance of ground points. I didn't realize how critical they are and how they affect relays, etc. Thanks.
This is the best educative video I've ever seen in this site,You are a real professional ,Thanks for helping.
this is a perfect example of why i think your videos are the best--> well thought out real world troubleshooting!!!
Brilliant video, very good example of how to use a scope and diagnose either a bad ground or supply feed. Brill!
Excellent excellent case study.. I was baffled in the beginning with the heater in the mix of things, that really through me a loop. Shared ground never cross my mind. Wiring digram interpretation is really key to figuring out what is going on within a circuit.
Thanks! I've been watching several videos from you and I must say that not only your knowledge is great but also your teaching is superb!!!
I'll keep coming back every time I have an issue with my Chevrolet Trans Sport, (Venture, Montana). 👍
thanks mr. Paul for yuor videos, im in Mexico and i like all yuor videos you r a realy good teacher, now i understand my scanner and i will buy a scope. GOD bles you and your family
Good Troubleshooter, Good Teacher - Thank you very much
no, there are some frame mounted pumps but it is more common to be in the tank. some models offer an access cover in the trunk or rear seat area, which is nice.
I can't wait to get paid and buy your ebook. I've been watching your videos and they're great!
Hey Paul Danner, Well Explanation for this Fuel Pump Circuit is very clear and making me to feel simple when the Faults Related to the Fuel Pressure issues come to me and im agree with your Motto " Don't Be A Part Changer"
Thanks Forever Danner ❤❤❤❤❤
Great video , shows that you have to look in odd places sometimes. One normally wouldn't think there was a larger current load on a relays control ground.
Great info as always Paul.
being able to see that relay open and close was pretty helpful. i want to order a set of clear relays to help with diagnoses
That was totally cool!! Seeing the relay open and close and the diagnostic screen spikes was awesome! Thank you!
My El camino has a clear distributor it is awesome
Your a very smart and knowledgable young man I really appreciate you putting this video out because I I have a similar problem with my nissan pathfinder.Thanks again I will like and share.GOD BLESS YOU.
Thank you my friend, God bless you too!
great explanation! it just shows when you know your job , you make it look easy! it appears you are a seasoned mechanic! great job! process of elimination only works when you know your trade!~ where can we find mechanics like you ? Oh! one more thing, it takes a little time to diagnose!~ you took less than 30 minutes...outstanding!!~
A bazillion $ scanner, schools and training to find a Chevy ground fault.... priceless...! but... it was a stovebolt to begin with and would never ever own one newer than '60's..great video SD.... I loved it, your diagnostic skills are greatly admired here...73 and still wrenching...but not on those dogs...
thanks my friend. I have much respect for my elders. I hope I live long like you to see my grand children.
May God bless you and your family and continue to bless your hands and your mind as you continue in this field.
Hey SD thanks for that...You know of course I was not being disparaging in any way of your talent and training..love and appreciate your efforts you use to educate us old school dummies to the new tech..who would have guessed it in high school auto classes in the 50's working on Ford flat-heads and Chevy stovebolts it would have come to
this ..?
Great interpretation of the scope readings. Gotta love Danner if he's on You Tube or any where else!!
Dan... Freakin Genius!!!!!! This helped save my 89 Regal from the crusher....
Bad ground on the transmission?
so a question i seen the ground problem but as you shown in the wiring diagram the relay/oil pressure switch run in the same circuit so when the relay dropped out why did the fuel pump quit unless the oil pressure switch is not working or was the ground totally going in a open condition thanks hope you like questions i alway want to know
good question, with the bad block ground nothing was really working correctly. I have to look at the diagram again to give you a better answer than this.
Super cool case study. Reminds me if your similar issue with the s6 Audi and how it had a loose nut on the firewall ground. Being a Euro specialist you have no idea how many times I see that.
wow, thank you very much! what a great comment. keep watching, I have over 100 videos now and more to come.
@ScannerDanner Another clue to this problem is when you first turn the key on you should still get a fuel pump "prime". This is the ECM turning the FP relay on for a second to bring fuel pressure up. After this "prime" the ECM will NOT turn the FP relay back on until it receives an RPM signal (on the purple-white ref. wire).
If you do not have a "prime" happening when you first tune key on, then we are barking up the wrong tree. I can still help you though.
Great case study!!! You’re the best too bad you’re not in the Los Angeles area, it would be a pleasure to let you diagnose my car problems but I’m learning a lot from you great guys! (Scanner, Eric o, Ivan)
Excellent piece of methodical diagnostic work 👍🏻👍🏻👍🏻
Thank you very much. Eric is a great friend. Nice you have you aboard!
I wish I had an easy answer for you. Unfortunately it is hard to find a good diagnostic tech in this field. Most mechanics are parts changers. A suggestion is go to iATN and search iATN's Auto Repair Shop Finder. This isn't going to guarantee that you find a good diagnostic tech, but I think it will increase your chances.
@ScannerDanner If the FP relay turns on and the injectors fire you need to replace the ignition module. I know, I know, "but I have spark" is what you are thinking. Listen, these modules will fail in that it will still control the coil, but not send the reference pulse (0-5v square wave) on the purple-white wire to the ECM. Without this signal the ECM will not see an RPM signal and will not fire the injectors and will not run the pump.
@fivefortyeye540i Thank you, this one was a little tricky to film. There are so many different directions I could have taken this. Hopefully it was clear and not cluttered with too much info.
@ScannerDanner TY!!! For years I always thought the oil pressure switch was for safety. Clearly it is in parallel with the circuit.
+Will Rogers you welcome! thank you
+Will Rogers That is because sometimes it is for engine safety. This may be the exception or maybe safety is the exception. I'll leave it to scannerdanner to give the average percentages either way. I know it is a safety on older GM diesels of the 90's era. Least ways they won't run when that switch goes bad.
Brother, you keep out doing yourself. Amazing. God bless
Some nice multiplexed circuits over long spans. Pulse width modulated fuel control valves on CNG engines. Gas mass flow sensors. Coil on plug ignition with a separate module from the ecm
Fascinating Paul you should have been a forensic Detective this was so interesting
great stuff i see this nearly every day with the older cars were the earths play a huge part in things like this...
great teacher showing us how to think by deduction thanks a lot
one last thnig! a good mechanic, listens to the customer~ it's called communication! it's like a doctor patient relationship~ So the customer was correct in his explaination of the cause of pump failure. didn't show on diagram sometimes it won't. great meachanics are the best trouble shooters!!
Every time I watch one of your videos I learn something! Keep up the brilliant work Paul!
@CoolasIce2 I just checked out that scope. It is an old analog scope. It will do want you want but you will have problems with "glitch" captures because there is no play back. I would recommend you go on ebay and buy a used Vantage (not pro, unless you can afford it)). It is a graphing multimeter and will get you by for awhile. Plus the data base in the tool is unmatched in this field. I have had students pick them up for around $200
This is my new favorite video. Awesome fix. Very nice
@CoolasIce2 Im not sure, I'll look into it when I get a chance. I think any scope is better than no scope but then again there is some crap out there.
Thanks man! Hope you're enjoying it so far
i guess the best way to learn faster is to create faults on our own cars. The waveforms makes electricity visual instead of a invisible theory. I love it !!!!
Good video. Very amusing problem and very amusing colored diagram explanation
thank you very much and if you do you will not be disappointed.
@TRcustomengineering No problem and than you for your comment. I have nothing and can offer nothing outside of Him.
That was awesome. Thanks for sharing the knowledge.
@kenjackson1977 Do you have spark and injector pulse? Or does the engine run when you hot-wire the pump. All you said was the pump runs when you hot-wire it. I need to know to help you further.
That is one sweet capture. I was cool to see that the fp would operate with 4v on the ground. Very cool patern. One look at the ground voltage on the yellow trace, that was too cool
thanks brother
@spelunkerd Nice, I have never heard that quote. I like it too. The oil psi switch is simply there as a backup in case the relay fails. Of course the other side of that oil psi switch runs the oil psi gauge or light, so it serves two functions. I don't know why GM felt the need to backup the FP relay. No one else is doing that. Seems like a waste of copper wire to me. They must have had a lot of problems with this circuit early on?
Loved the video walk-through, as well as the process of elimination you used to get to the root of the problem! I'm not a mechanic by even a loose interpretation of the term (I like to do simple maintenance like change the oil, brakes/rotors, spark plugs, etc on my e39 540i).
What would you recommend as a way to find a good mechanic to work on a car? One that will diagnose problems like you did in the video. Most I've been to would simply replace a pump/relay/etc and "see if that works".
@ScannerDanner That sounds a lot like a quote from Isaac Newton. It went like this, "If I have seen farther, it was by standing on the shoulders of giants...." I love that quote, and I love standing on shoulders, ha ha.
Why is that backup circuit from the oil pressure switch there?
another good vid.
been meaning to get the ebook, finally did.
Thank you for the comment
@silkylove1000 if the car is running fine and your fuel psi is good i wouldn't worry about it. the rpm test has some gray areas if you ask me.
This was a main block ground problem so it wouldn't matter where the power was coming from (relay or oil pressure switch), the problem would still be there.
Excellent diagnostics Dan but seeing you pierce wires freaks me out. I live in the damp northeast and greenitis is a death sentence to a wiring harness. I know those tools are
easier than rigging up backprobe taps and bridges but those little holes cause BIG problems. That said keep these great videos coming.
Thank you! and may God bless you too
Must say, very good video, very informative.
Thnx man that will help me at my auto tech school
Dan excellent video wondering? Would a ground V-Drop test have been a valid test to prove the existence of a bad chassis/signal ground at the OBDII connector terminals 4 and 5??? and... where is your e-book link?
Paul,Guess I am asking the question from the perspective of being an owner/user of a Load Pro Dynamic Test Lead, and wondering if it would have revealed a bad ground from the terminal... perhaps I'll get a chance to test (or create a test environment to experiment and see if it will work)...
Excellent, excellent, excellent video.
but, shouldn` t that oil pressure switch take over when the relay fails???
Thanks man!
If you get me some buyers, I will take care of you in the form of some free video lectures. Just have whoever it is mention your name in their communications with me.
Thanks again
Very professional lecture.
thanks.
I know this video is old, but I'm confused about the relay... You said that oil pressure switch provides alternate power to the fuel pump once the engine is running and that you could pull the relay after it's running and it would stay running... So why does the relay switching off and on like that kill the engine? Obviously there is a problem there, but the oil pressure switch still should've kept it running...
Edit: nevermind, I understand now. With that ground issue effecting the entire system (most likely), the oil pressure switch would also be loosing connection.
You were right in your initial idea. The only way this engine fuel pump would stop and start because of a relay ground problem is if the oil pressure switch was not working. The oil pressure switch get power from a fusible link and it bypasses around the relay and connects to the same fuse and on to the fuel pump. The Oil pressure switch has no ground to worry about. The fuel pump itself has a totally different ground than the relay itself.
nice video good explanation ,i learnd a lot of your videos !!
Really good video and well explained, excellent video i have to sayd
Great Video Demonstration! Thanks
would you be able to pull the relay, if the fuel pump still runs then that would narrow down to relay. Thought process on that was like you said the oil switch would take over and still allow voltage to the pump.
Your videos are invaluable! I'd love it if we could set up a way for you to come do some videos at our shop! All brand new fleet of peterbilt CNG trucks!
great video ..you get me nervus using the screwdriver as a pointer on the scopemeter
.LOL
You are awesome Paul. If i buy your e-book i'll have some kind of guide to learn how to diagnose problems like you did? I'm a begginer mechanic and current(and begginer) student of Electronic Engineering and i'm interested in learn this stuff. Thank you for your excellent videos!
Thank you so much Jim!
TCM ATA relay which is controlling with "-" from TCM. Black probe to pin on TCM and Red on relay "-" side. I got 1.5V (on ign.key on only). Is it the bad ground?
I found how to check bad ground later on your channel.
Thank you for all these videos🎉
Thanks for all the videos .!!
Thank you Russ!
probably going to buy this ebook once paul replies to a question i emailed. anyone have any other recommended youtube channels or ebooks that are worth watching or buying?
Paul,would the fuel pump feed wire show high amperage if it was intermittently touching ground?
Always educational
I enjoyed this video very much.
Great video. Nice to see what you can do with a scope. I have been doing this for years with a test light and a cotter pin. I may use a multimeter if I get really hard up. Granted this is an instructional video but why not use a cotter pin to ground out the control side of the relay and verify (a) relay works, (b) pump and load side work? All diagnostics in the video are great, I'm not trying to criticize here but a relay needs 2+ and 2- to work which is basic electrical....
Wow! Amazing!
Just amazing 🙌
Lots of knowledge to keep my 1990 Buick regal 3.1 running smooth like a baby's butt! Haha
Well documented and explained. Thanks!
Found a good one the other day. Had a 99 pontiac trans am 5.7l it was it the shop for a engine light runs fine had a code for maf circuit. Found fuse blown for power feed. Replaced fuse when it was sitting there fuse would not blow but soon as you power braked it fuse blew. Found o2 sensors on same circuit and the wires on one of the down stream sensors rubbed through and would ground out on a heat shield when you would put a load on the engine. Like the weird ones.
like this one a lot!!! I need to buy your book!!!!
Hey Dan have a question I have a 1999 GMC safari van Meyrou fuel pump relay gets extremely hot could it be that it's holding too much load because the oil pressure switch is bad thank you
Finally an actual auto electronic/electric master mechanic. Every one that I have dealt with only guessed..
By the way my 1991 Lexus was doing the same thing except it was blowing the fuse when I would turn on the radio. So I wrapped some copper wire on the fuse until whatever it was affecting it on the radio side burned up. The car works now, except no radio. I did this after multiple wanna-be's mechanics kept giving me bullshit diagnosis.
@ScannerDanner OK Thanks. I'll look into that.
Would you be able to identify the bad ground by voltage drop from relay control ground to battery negative?
I wish you could do some transmission work. I would defiantly subscribe.
thank you very much!
Good Video Thank you
thank you Bill
@spelunkerd Backing up the FP relay can't hurt. I'll take it. My '87 Cutlass Ciera has the same layout
Similar to the nut that came lose on that Audi you were doing. Maybe the factory should put some loctite on those ground connection nuts.