How to test an electric fuel pump - using a test light

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2001 GMC 3500 8.1L engine with no fuel pressure. In this video I am showing how to test the fuel pump electrical circuit using a test light and scan tool.
Engine Performance Diagnostics chapter 16
Symptoms
- no start
- no fuel pressure
Fix
- replace faulty fuel pump
Tests shown
- how to measure fuel pressure
- how to test the fuel pump relay
- how to test for proper power and ground to a fuel pump
- how to test the transfer pump
- how to test for a proper ground on your test light
- how to command a fuel pump relay to turn on with a scan tool
- how to test the computers control of the fuel pump relay
- how to determine fuel pump wiring without a diagram
Tools used
- scan tool - Autel MS905 MaxiSys Mini Diagnostic System
www.jbtoolsales.com/autel-ms9...
- incandescent test light www.jbtoolsales.com/otc-3633-...
- back-probing tools - AES' Electronics Accupuncture Probes www.aeswave.com/cart.php?m=aff...
- S.U.R. & R FPT22 Deluxe Fuel Injection Pressure Tester Kit
www.jbtoolsales.com/s-u-r-r-f...
Playlist
- (Chapters 14, 15,16) Fuel Delivery and Fuel Pressure Testing
• (Chapters 14, 15,16) F...
Related videos
- How to test an electric fuel pump (1997 4.3L Chevy Blazer CPI)
• Fuel psi less than 50 ...
- Low Fuel Pressure from a bad fuel pump ground (Ford Ranger)
• Low Fuel Pressure from...
- How to test an electric fuel pump (no fuel psi testing) Ford
• How to test an electri...
- Fuel pump electrical circuit diagnosis (no fuel pressure testing) GM • Fuel pump electrical c...
- No Start No Fuel Pressure Troubleshooting
• No Start No Fuel Press...
- How to test fuel pressure, injector pulse and spark with basic tools • How to test fuel press...
For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available at www.scannerdanner.com as an eBook or paper book.
Want even more diagnostic training? Whether you are a DIY trying to fix your own car, someone looking to become an auto technician, or a current auto technician that wants to get more into diagnostics, subscribe to ScannerDanner Premium www.scannerdanner.com/join-sc... There is a 14 day free trial.
On ScannerDanner Premium I will bring you right into my classroom at Rosedale Technical College. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures. There is no better on-line training of how to troubleshoot automotive electrical and electronics systems anywhere!
Disclaimer:
Due to factors beyond the control of ScannerDanner LLC, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. ScannerDanner LLC assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. ScannerDanner LLC recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of ScannerDanner LLC, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not ScannerDanner LLC.

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2 фев 2012

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Комментарии : 497

@danielarney9729 4 года назад

Thanks. Thought you where gonna temporarily swap relays. Can't believe last person that wrote was 7 years ago, don't know how many of us screwed out here appreciate you sharing your knowledge, you'll be helping people 50 years from now.

@ScannerDanner 4 года назад

Thanks Daniel! This is one of the first videos I've ever done I I think

@mikecooper4712 2 года назад

Thanks I replaced the fuel pump relay, but because of how you showed the testing at the fuse block, I discovered I simply put the relay in backwards, with the numbers corresponding to the ground and GM using the positive, Works now! Thanks

@MrBurt54 10 лет назад

This was my 1st video...I did not have to look for another source of info. Man you ARE awesome. thanks ....and yes you are blessed with a gift of knowledge and teaching

@orlanmedina3693 6 лет назад

You're awesome Paul!. Black and white. Even with no knowledge is very easy to do with what you explained in this video

@csgorton 11 лет назад

i'm so used to the old school style of doing things, learning this stuff is just great!! thanks ScannerDanner

@iamhomerj4711 5 лет назад

Nice video. Having trouble with my 2002 2500 Silverado. Now i know how to test before moving on to pump removal. Hoping just a bad ground. Very informative. Thank you.

@garymarcel6372 5 месяцев назад

Man this is a quality video and very universal. Great fundamentals, i will keep this as a reference of my own. Many people young and old will enjoy your lesson

@ScannerDanner 5 месяцев назад

One of my first videos!

@ScannerDanner 11 лет назад

exactly confirming the problem is NOT a bad ground. you can call it faulty logic if you want to, it's not. Unless you want to tell me that the pump motor circuit is open and you have a bad ground at the same time...not going to happen. test light doesn't light on the ground = it is NOT a bad ground that is causing the pump to not run! I agree the ground circuit isn't loaded but so what in this case. you have correctly identified a bad pump!

@scottketchum2224 5 лет назад

This is what I call a great video, thank you for sharing your knowledge 😁

@mckoylach1622 6 лет назад

Paul,you are the best,with these tests diagnostic procedures,without having a high tech tool,it’s great to possess these old methodical skills...thanks...

@christesta7553 2 года назад

Great video Paul. You make diagnostic testing look easy which it's not. Going to purchase your book. I agree with your viewer you truly are gifted and blessed!!!!

@ScannerDanner 2 года назад

Thank you so much!

@aggiespilot 11 лет назад

As a young parts guy I love your videos. From watching I've grown to love the electrical and computer side of automotive repair which a LOT of people shy away from and treat it like witchcraft. I'm saving my pennies for your Ebook so that I can better help my customers with their issues (With the disclaimer that I am in no way a pro technician and could be wrong) Anyways keep them coming! great stuff Mr. Danner :)

@MrBurt54 10 лет назад

After I got the bed tilted and had access to the wiring....I found you were absoultely right about the color coding. 95 c2500 had different plug...same color code. thanks so much

@jono0309 10 лет назад

Great video!! It is people like you that help the hobby!!!!!

@Justicejamesb 6 лет назад

I just found your channel, awesome man, totally awesome! About time that someone made videos for people that are a little bit more mechanical, have the tools to do stuff. Thank you, thank you, thank you!!!

@ScannerDanner 6 лет назад

Thanks so much and welcome! My content has always been good but not my camera and editing skills. You will see a difference in my 2017+ videos. As time goes by, I've definitely improved. Look forward to hearing more from you.

@simbas61 11 лет назад

Mr. Danner, Loved your video on how to test an electric fuel pump! As a Systems Engineer working on High end computers and such, you make alot of sense in your trouble shooting skills, and the way you explain them. You just saved me a trip to the parts store to buy a Chiltons for my ride! Keep up the good work!

@ericheine2414 5 лет назад

Excellent, you're a teacher.

@SteveRobReviews 12 лет назад

Fantastic !! Had to think a while about the ground to ground test.

@terrydavidmullins 7 лет назад

Great video! Thank you.

@nigelstringfellow5187 4 года назад

Thank you for yet another really educational video Paul I am learning so much from your site

@ScannerDanner 4 года назад

Thank you Nigel!

@bassment03 10 лет назад

Good job man you explained that very well.

@mike-yp1uk 10 лет назад

God is blessing you with a great gift and you are sharing and that is what i call true success. thanks for your hard work may he bless you greatly.

@ScannerDanner 10 лет назад

He certainly has been my friend. And all glory goes to Him. "I can do all things through Christ who strengthens me"

@bammaez6745 Год назад

@@ScannerDanner ⁰

@jonathanwest3656 10 лет назад

Outstanding work professor

@patrickliverpool6487 Год назад

I have been following programs for the last two years and I have been able to solve problems true good trouble shooting skills from your classes

@ScannerDanner Год назад

Thank you Patrick!

@slofr8dan 7 лет назад

Very well explained. Thanks.

@ScannerDanner 11 лет назад

Thank you my friend! I also have paper versions available now too.

@Mikeoscope 9 лет назад

Very good video.You will make a good teacher.Good job.Keep it up!

@doug2993 5 лет назад

Good video and knowledge, thank you.

@nicholassmith4172 2 года назад

Great video. Thanks for the explanation

@billwells8054 9 лет назад

Nice educational video. When I was unsure if the fuel pump was the cause of my car not starting, I ran a hot wire from the car battery to the terminal on the pump, easy to get to inside the trunk of my Acura (Honda, others similar). I could hear the pump running, and the car would then start. With the fuel pump fuse OK, that pretty much meant a defective main fuel pump relay. Although I could not see any bad solder connections on the relay, I replaced it and the car starts/runs fine.

@speckspeck 8 лет назад

very cool presentation, luv it

@davidmcmurtry734 Год назад

Very informative

@MrLoboreview 12 лет назад

Thank you so clear and thanks for keeping the tools simple .........snapon scanners are way too expensive......i've learned a lot from you ...ill buy your book THANKS SO MUCH!!!!!!!! Please more vids on how to use dvmm

@ScannerDanner 11 лет назад

thank you Chris!

@jparson3309 2 месяца назад

Great video my friend thank you very much

@fordneuscheval 10 месяцев назад

my man! thank u for the video! its hard to get this fuel pump power figured out-but now its easy! 2001 gmc 3500 boxtruck fuel pump issues-39f-KS ♥scannerdanner

@shanebuckles9134 5 лет назад

Great vid life saver for sure thank u

@IntheBlood67 2 года назад

Most Excellent!

@j.onofre6613 5 лет назад

Gracias compa por el detalle.. 👏👏👏

@dreamer2355 12 лет назад

Another great video!

@codywaite3765 3 года назад

Great video Helped me with a volkswagen.

@ScannerDanner 3 года назад

Glad it helped!

@ScannerDanner 12 лет назад

@MrLoboreview No problem, keep watching for them and thank you

@snurb48 Год назад

Good trouble shoot process and methodical point A to B skill set. Damn hard to find because not all pick this form of diagnostics up weather is be Automotive, HVAC like myself(39 years) to even a Doctor or Eye specialist. It is a rare trait to have and I hardly see it anymore these days. Keep after it, I always found the process a absolute challenge and loved it when I won(which was everytime) Lol.

@driscry 5 лет назад

Awesome, thank you for the detailed tips. Very helpful.

@curtisjar 11 лет назад

Good video. Really helped.

@mezgebuabebe2503 10 лет назад

thank you very very very very very much. appreciate for taking your time to share your know how,,,,,,,,,,thank you again

@ScannerDanner 10 лет назад

Thank you very, very much for watching and for your comment. I have a lot of other fuel pump related videos if you needed more help in this area. Thanks again

@lcsliao15 11 лет назад

thumbs up for the touch screen scanner :D

@MrJgonzalez2 12 лет назад

Paul, what I've done in this situation when working by myself is hook the T-pin to the relay control (dark green & white)hook the alligator clip to T-pin and find a good ground to stuff the test light and place somewhere visible from the drivers seat to crank teh engine.

@Darjan_Spasojevic 2 месяца назад

As a professional parts shootah, this is great!

@fehronation8310 4 года назад

Good job

@p0k7lm 4 года назад

tnx 4 video ! donthave a scanner , but i use ohm meter to test continuity with power off drawing and figuring the circuit on paper , some times with battery installed taking voltage readings of wiring points and knowing how the relay is wired , using my own jumpers to power up fuel pump at the relay terminals .

@ScannerDanner 12 лет назад

thank you

@syedimranshah4721 7 лет назад

In the service manual of an early fuel injected car, I saw that manufacturer recommended to check the resistance of the fuel pump in case of no fuel pressure. Newer cars usually do not mention checking the resistance of a fuel pump, don't know why.

@ScannerDanner 12 лет назад

@PDSVIDEO1966 no problem, thank you for the info. I am shooting these with an HD camera but I am not sure what the best viewing is on youtube. It seems to me that 480p looks just fine. ?? In fact I don't see any difference other than it loads slower and there are issues like you describe.

@RJC3po 12 лет назад

@ScannerDanner Thanks for the response. I understand your point and I think it is a good one.

@mikemesaful 8 месяцев назад

Awesome!

@nickayivor8432 Год назад

Proficient Sir ScannerDanner Tutorial great video loved it thank you very much for sharing it .take care and have a great day Proficient Sir ScannerDanner From Nick Ayivor from London England UK 🇬🇧

@ScannerDanner Год назад

one of my first videos my friend, thank you

@cheesemons 7 лет назад

Wish you could have seen my reaction when i finally understood this video. Thanks ScannerDanner! Your video is very informative!

@ScannerDanner 7 лет назад

Thank you! I wish I did too :-)

@michaelpearce8661 4 года назад

@@ScannerDanner on the relay for the fuel pump. I don't have a good ground. Not sure why. Pulled up this video but the grounding wasn't explained other than getting to the fuel pump to check if it was bad at the pump or someplace else.

@michaelpearce8661 4 года назад

I have a big problem to drop my fuel tank on a used U-Haul truck with Grandma attic. She's a 94 GMC Sierra C3500 with a 7.4 liter engine. Have 12.3 at pin 30. No other voltage shown.

@ScannerDanner 4 года назад

@@michaelpearce8661 no other pin shows voltage during the initial key on or cranking? (very important distinction)

@michaelpearce8661 4 года назад

@@ScannerDanner being stuck in this parking lot is no fun. I've got power to 85 if what I was told is place to the left side of the female plug. Also with test light shows power on the center of the plug. The third is 86 the ground. If this is the ground it has an open circuit. I'm wondering if I set up a secondary ground to the relay plug gound to activate the fuel relay to see if I need a new fuel pump?

@mikewithers7685 11 лет назад

Paul you both are correct in your approach except howler using the Ohm meter for circuit testing. I think Howler is using the Load Pro test leads to check circuts. It is a easy way to check for corrosion or bad connections on a circuit since the leads allow you to apply a voltage on the circut and measure voltage drop. "see the videos on you tube under load pro". Love your videos Paul hope to see some new ones soon ! ! Would like to hear your opinion on the load pro test leads. Thank you.

@oscargutierrez8180 2 года назад

Good video

@ScannerDanner 12 лет назад

@ScannerDanner circuit loaded of course. A high resistance ground may have tested good (no light), however I would have had some fuel pressure and pump operation. In this case it was completely dead. Never rely on a test light to check the ground circuit of a working component. It isn't accurate enough.

@mikewithers7685 11 лет назад

you are both correct in your ways of diagnosis. Im sure you are probably using the load pro test leads on your DVOM. Paul is just using some fundamental approaches to his diagnosis using a test lite. Paul loading the circuit with the fuel pump plugged in during testing is the way to do it by only using a test lite. I agree Paul should have used a DVOM at least during his testing.

@ScannerDanner 11 лет назад

correct, and with that comment, you yourself have just condemned the pump! Because a good pump would load the circuit and cause voltage drops in the wires that we would have seen as soon as we plugged in the connector.

@felplayvina 12 лет назад

thank you.

@ScannerDanner 11 лет назад

Thank you very much! I've gotten better at shooting and editing of videos since this one was done, so sorry about that but at least the content was still good.

@RJC3po 12 лет назад

I have a general question. Why is it that some systems switch the supply side of a circuit (Fuel pumps for example) and other systems switch the grounded side? (Injectors, ignition coils for example) What is the advantage? It would seem to make more sense and save some wiring costs, by switching the supply side and have a central distribution for the signal common return path (body ground). Thanks for making these videos, I really enjoy watching them and they help me to become a better Tech.

@djjammindave 3 года назад

AWESOME !!!

@ScannerDanner 11 лет назад

yes a parallel circuit upstream of the pump. with the pump circuit plugged in and energized. I promise you if there was a wiring problem on the feed circuit to the pump, the test light would have gone out as soon as I plugged the pump back in. You could argue that the voltage could still be low, but my response to that would be there was NO FUEL PSI! A pump will still run and produce psi with low voltage. Also another thing, the test light brightness was exactly the same unplugged and plugged in

@psycoticreaction9135 6 лет назад

Man you are a genius!!!

@1188clean 3 года назад

cool didnt know that the transfer pump can still work without the high pressure. going to do this on my car because only the transfer pump turns on when i jump the fuel pump relay but i dont hear the high pressure pump. going to do this test of back probing it. thanks

@cagonesss 12 лет назад

ok thanks alot yes i used crimp connectors but i didnt trust them so i dropped the tank again to make sure they were good and tight and they were ,it takes me less than one hour to drop and install back the tank not hard on this truck.guess i had a glitch in my mind nawing on me lol maybe im mental lol had a weird filling .hey but thanks now i know next time i wont blow up ill be more confident learned something new.thanks alot for sharing have a good day guy.

@ScannerDanner 11 лет назад

The pump current will heat this high resistance wire up even more causing a large voltage drop. Something the test light cannot do alone. And something that the ohmmeter may never see.

@ScannerDanner 12 лет назад

@FreeThoughtCrime If the pump ground circuit is good there will only be a few hundred millivolts on that wire. If you connect your test light to the pump ground and battery ground, a few hundred millivolts will not light the light. I know this isn't the best test for a ground, but I wanted to show how to use the test light if that was all you had. Also I realize the only way the test light would light on the ground is if the ground was completely open ......

@niterbum 3 года назад

thanks Scanner Danner for thinking of us less fortunate backyard mechanics Go Flyers

@ScannerDanner 12 лет назад

@FreeThoughtCrime Forget the light for a second. A good ground on a running electric fuel pump is typically less than 300mv. If it was higher than this then a bad ground could be the cause or the pump motor is frozen and the circuit is carrying 5 times more current than designed. This would drive your ground voltage higher due to heat from too much current. I don't think I am answering your question, can you ask it another way?

@ScannerDanner 11 лет назад

first, substituting a know good component is not troubleshooting, not to mention when you work on 20 different car lines like I do you don't have vehicle specific relays laying around. Also there is NOT one way to do things. I'm sure your method works great for you. You come in here and want to critique my methods and tell me I am wrong? You have yet to do that. Show me where I am wrong. Give me a scenario where the methods I show in this video will lead to an inaccurate diagnosis.

@ScannerDanner 12 лет назад

Yes, as long as you have the adapters to "T" into the psi line or connect to a shadder valve. Most good fuel pressure kits that have all of the adapters will run you about $500, but if you are only doing GM or Chrysler you could get away with a $30 pressure gauge from your local parts store.

@autumnrowe1297 Год назад

On. Pt cruiser. Just had the ad key remade due to j broke the one w/ fob Need key no fob, first. Ivhf rear lights stayed on without key in ignition. Still no start at this time. Few hours later car started but still tail lights stayed on. Got a new battery. And now no start . Question is how do I get this fumed started

@RJC3po 12 лет назад

@ScannerDanner I agree… Test lights can be deceiving sometimes. I recently switched to using the Power Probe II. I do not know how I have been getting by for so long without one! The Power Probe would have made this job go a lot quicker.

@mikehigby7897 3 года назад

That fuse box picture is about the only thing GM is good for these days.

@emgelia 7 лет назад

Thank u.

@HowlerWelding 11 лет назад

... After testing to this point, I can turn my attention to the load connected to the 87 terminal. If it is a pain in the butt to get to (like a tank mounted fuel pump) I can use the DVOM on the Ohmmeter and test between terminals 87 and 86 which tests all the wiring and connectors between the relay base and the pump, the pump itself, and the ground wiring and connections to the battery AND back up to the relay base at terminal 86. Pretty simple, and darn fast... No T-Pins, No Stabbing wires...

@ScannerDanner 12 лет назад

@PDSVIDEO1966 I just checked it and it is good on my end. Not sure what is going on?

@wyattoneable 7 лет назад

Love tests a DIY'er can do.

@ScannerDanner 12 лет назад

@chamosvin Great point! First we don't know if there was current flow, I never checked it. Second, lets say there was no current, you are correct, the test in itself would be inaccurate, however combined with no fuel pressure and a good power feed, if the ground was bad (causing the no current flow problem) the test light would have light when I turned the pump on. I agree the test light is not the best tool for this however I wanted to show using it just in case it is all you had.

@ScannerDanner 11 лет назад

Actually there was John. The fuel pump wiring was underneath the dump truck bed, so access was not easy until the bed was lifted. On a typical truck or car, you would have to get underneath to do these checks. So not necessarily easy, especially when you are doing road calls. Also I wanted to show the relay tests because it seems that people have a need to know how to do that.

@ericheine2414 5 лет назад

There's nothing like a nice box. Iron American Dream on RU-vid. Guns and Harleys.

@HowlerWelding 11 лет назад

Re-read what I typed Paul - I said VOLTMETER... I have a set of test leads that allows me to introduce a load into the circuit while measuring Voltage. This DOES stress the circuit - If the voltage drops off when the circuit is loaded then I have a wiring issue. It is one simple test after that to prove if the wiring fault is on the positive or the negative side.

@PlasmaHH 7 лет назад

2:18 you can use a little bit of rather thin wire, wrap it around the relay leads, and then attach any meter you like to it. Its quite a hack, but it works well, unless you short the wire, which isn't a big problem anyways as thin wire will melt right away ;)

@arkansastrey9694 7 лет назад

Thanks , I learned something on this video

@nellyxavier8923 2 года назад

I am Happy.

@LifeSavingDefense 8 месяцев назад

The cap on those relays comes off really easy and you can access the terminals and watch it click or even tape it to on but relays have a purpose so do at own risk

@ScannerDanner 12 лет назад

@roro560v8 Can you check for me to see if the sound is fixed now?

@harryheck4532 10 лет назад

thnx!

@keithjohnson7311 10 лет назад

HEYYYY ITS SCANNER DANNER AFTER WATCHING U WITH ERIC CAME TO YR CHANNEL

@ScannerDanner 12 лет назад

What did you use to hold the wires together? Hopefully at least a good crimp connector. Anyway, if the hot-wire touches ground it will blow the pump fuse. There will not be an explosion as long as there are no external fuel or vapor leaks. If the wiring splices were done inside of the tank unit, there is no danger as there is no oxygen in the tank. Even if the power wire touched ground it wouldn't explode.

@kg1016 10 лет назад

Thanks for this. Nice and thorough. But if I may ask, what if at arriving at the connecter there was no power. Where would you then start your search for the voltage loss. I have a 2001 Corolla and checked the relays as you show. but when I get to the tank there is no voltage when I turn the key to crank. 15 amp Fuse under hood not blown but when I removed it to check condition the radiator fan started.

@ScannerDanner 11 лет назад

I KNOW! That is why it HAS to be an open in the PUMP!

@TheReptilianman 6 лет назад

Hey, I have a 95 Astro van it has 0 fuel pressure. I replaced the fuel pump and strainer, icm, and filter. It cranks but won't start. I know I have spark, itll turn on with starting fluid but then shuts off after.

@ScannerDanner 11 лет назад

go to my website scannerdanner d o t c o m fill out your name and email and I will send you more information about the ebook. Thanks!