GM Fuel Pump Relay Testing

GM Fuel Pump Relay Testing

For more on fuel pressure testing, go to my website at www.scannerdanner.com 1999 Chevy Suburban with no fuel pressure. The following is covered in this vide…

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Stevie Wonder says:

My Fuel pump, and relay both work, but I have to spray starting fluid in it
to start it. Any suggestions?

Larry Lees says:

no light to control pin when cranking and no 2 second light when key on!
Now I am guessing this is a PCM issue I looked at PCM under dash there is
only one wire harness plugged into this PCM the smaller one there is no
harness connected to the area where a larger harness could connect 88 Chevy
k1500 4.3 is this normal?

Spy Mode says:

Do you really need to yell while making this video?

Larry Lees says:

Yes I have spark.

joelarcoable1 says:

good video

John Christopherson says:

Awesome!!!!! I have been in the automotive repair industry since 1983 as a
tech and as an instructor, you did a very good explanation of the bias
voltage.

Larry Lees says:

What if you only have power on one prong no light when key turned on for
any of the other three?

Matthew Lobato says:

I have a 2000 tahoe, what if I don’t have the second power feed when
cranking? the fuel pump was working before I changed it cause I was told
that i will need a new one soon. and now I can’t hear it turning on.

1R083rt says:

Awesome video ! I just feel like I added more useful knowledge to my brain
, but can just take it with out saying thank you!!! 

MARIO PROVIDEL says:

Hi there, tremendous video, well explained; am from Chile and I got the
situation the other way around with my ECM S10 apache 2.4 LG1 it gives
ground according to the schematics and pump sometimes yeah sometimes nope,
thanks to your info am about to check and see if I got the right ground
wire in the pump, any other idea will be appreciated

Jess Herdt says:

1997 CHEVY SILVERADO FUEL PUMP KEEPS GETTING VERY WARM TO THE TOUCH. IT
KEEPS MAKING THE TRUCK SHUT OFF AND I TAKE IT OUT AND PUTTING IT BACK IN SO
IT WOULD START. WHAT IS YOU IDEA OF WHAT IS THE PROBLEM.

northeast eric says:

I just wanna say thanks for this video, it helped me diagnose the reason my
fuel pump went out yesterday afternoon a few miles from home. before I
dropped the $300 on the new pump I ruled out all the other cheap fixes
(relay, ground, ecm signal). I’m a single dad and rely on my truck to feed
my family, I cant afford downtime. And who the hell wired that harness? Ray
Charles? 

Kevin Bingham says:

I’m having trouble with my fuel pump on my 2002 chevy Silverado 2500HD the
fuse is good the relay is good im not going any power going to the fuel
pump itself…test light was used on the lines going to the pump but not
lighting up…please help me

Jeremy Shanks says:

I thought I had replied to the 4.3 fuel pump testing.

Kendrick hunt says:

you make me feel like a retard with all this terminology lol. you’re very
smart with this shit man my mind is like melted, i will just watch very
closely to what you’re doing, i notice in these videos the car shuts off
when they pull the relay out..mine stays running

MrKarlitosnetwork says:

In which part of the video is the test for the relay?

Derick Mayberry says:

Thanks ScannerDanner ! I am really enjoying and learning much from your
straight forward videos.

Anthony Bruno says:

Great Vid. Any suggestions on what to do when the computer control side on
the relay Pin 87 isn’t sending power?

Jeremy Shanks says:

Great video. I like the comment on the lean pop through the intake at snap
throttle. I have been using these videos to troubleshoot electric fuel
pumps measuring current and the armature waveforms. These videos have been
very useful. Thanks.

spartan1071 says:

Need your help bad. I am working on a 2005 Cadillac sts 3.6 liter. Some
shade tree mech. Changed the fuel pump in it and did such a bad job. I
would have to show pictures for you to understand. Anyways I’m getting a
fuel pump “a” circuit open low voltage. It’s been a nightmare! I added you
on Google+ so any info you can give me the better. Thank you. 

Valerie Jaramillo says:

Hey. Awesome video ..you made it so clear . .did he have his wires
backwards to ground due to shut down relay. Alarm system

Edgar Gonzalez says:

Why do you think my 97 Tahoe starts pulling back as soon as I go faster
than 50

Colton Norman says:

I am not sure how active you are, but I am driving an 88 bronco 2 2.9l. The
previous owner replaced the air box with a spectre air filter. This means
he deleted the factory air box. In the process, it looks like he left these
relays exposed as well and they’re clustered yet exposed to the engine bay.

Yesterday, my car caught some heavy water during a storm with the hood up
for 4+ hours. I tried cleaning these relays with no luck. I am testing
these because when the car in the the on position, there is no fuel pump
‘hum’.

Am I possibly stepping in the right direction? I used google and search
everything from 88 bronco 2 fuel relay location all the way up to fuel pump
bad water just so I could get the most broad idea of whats happening.
Unbelievably, google did not supply me with an answer.

Larry Lees says:

I have 5 volts on both TBI and Map sensor.

Rex Laney says:

ScannerDanner,will you please tell me were the fuel pump relay is located
on an 95 Camaro 3.4l 6cyl.?? Thanks a whole lot

LilKittyKittyCat says:

My Chevy 96 Lumina had only 5 lbs fuel pump pressure. The pump was never
changed. Getting some pressure indicated the electric circuits were good.
Replacing the pump gave about 35 lbs pressure which made the engine run
correctly. Opening up the old pump showed the flat in the hole in the
rotor which fits on the pump motor to be warn off. Going through a lot of
complicated testing was eliminating by observing electric and pressure
conditions. The important fact to realize is the simple flat inside the
pump rotor hole can be warn off to cause low or even no pump pressure.
Don’t overlook even a pound or two of pressure to show electronics are
good and to show the flat may be warn off the plastic pump rotor. My
replacement pump did not require wire changes which eliminated wrong
connections. Remember to KISS the troubleshooting and observe the
conditions to see clues for simple diagnosis. George

J Moore says:

I have a Buick century custom 2002. I followed your video testing the
relay. Pin 87 12volts, pin 30 I get 7 volts or .46 volt. I shouldn’t have
any voltage there. Pin 85 computer control pin does not light when key is
turned to on. No prime. Is this a bad engine computer unit? Originally
the car just died and wouldn’t start. I put 2 used fuel pumps in it.
Jumping pins 30 -87 runs the pump. When I fist put the last pump in it did
run for awhile a hour or so then turned it off and wouldn’t start or
prime. Once in a while it will prime and start, then go back to not
priming at all and not starting. It very confusing problem. Can you lead
me to a direction to take? Thanks

Todd Jones says:

THANKS BRO 

Larry Lees says:

OK I did verify 5 reference for Map sensor and Idle air control sensor both
are receiving 5Volts with key in the on position.

冯磊 says:

Thanks for the video. My 05 Grand Cherokee 5.7l has the similar problem.
The difference is my car can start on but go off after a few seconds. Can I
replace the relay to solve the problem?

B King says:

What if no power on Pin 87?

naturestan says:

89 buick p/a, 3.8 205k. For years it will not start nomatter how long a
crank. Its temp related probably because it starts up below 58* one crank.
Over 70* we have to jolt the key/ignition, then turn it again and it will
start.
Professional mechanics can’t find the problem. Can you help? Ireplaced the
water temp & air temp sensors w/non GM sensors. Its a well maintained
vehicle. Also Ihave checked the b+ ground under the coils. As you probably
know, it will start with low fuel pressure no problem Thank You.

MARIO PROVIDEL says:

…..if u can give me an e-mail I´ll send the schematics right away!
the Lord bless you greatly!

Larry Lees says:

Just wondering if a harness should be in the larger slot of PCM on 88 Chevy
K1500 4.3L?

robertw984 says:

never tested amperage on anything other than a battery or starter. i like
to jump relays often or used adapters when i can find them, to have the
relay still plugged in for testing, but i have never thought of using my
meter as a jumper and amp meter at the same time. that was awsome! i know
the a/c and fuel pump circuits on my truck and will definitely try that.
seen this play list twice so far and just noticed what happend the last
minute of the video. thanks for the get it done quick and save me money
tips and tricks +ScannerDanner 

Wallace Rose says:

Great video! I am an electrical engineer and you explained the bias circuit
well. I think you can say the 12 volts is across the high ohm internal
resistor and your test light has very little resistance and can not create
an voltage drop (no load). That’s why you see zero volts with the test
light. Freaking outstanding explanation of the fuel pump circuit!

Don Weckman Jr says:

Mr Danner.. Thank You . Working on my first fuel injected GM product. How
about a video why the engineers .?.They must be Suffering from a mental
health issue to not put in there design a metal panel that can be removed
topside to remove an repace the fuel pump.Instead of dropping fuel tanks.

Larry Lees says:

ok you have lost me with check for 5 reference at map sensor how would I go
about doing that please!

jose5080007 says:

I have a coworker that has a 1996 ford Taurus and the fuel pump has gone
out. He said I can have it for free . We will see what’s wrong with it. But
who cares it’s free. 

Larry Lees says:

NO Light.

George Snead says:

High praise for this video! Danner is thorough and provides all the
necessary background to understand what’s going on. Great diagnostic
technique. Very professional! Thanks.

Rob Lee says:

Scannerdanner, I have a 2004 cadillac srx tha runs great but the temp guage
and the fuel guage stay on empty,all the way to the left at all times, all
other guages work. I CHECKED fuse, could this be a relay problem, plez
help??!!


Bob Sherman says:

Nice video. Glad I found it. I did the relay center tests which duplicated
yours. The only difference is I don’t hear the pump coming on.
I have not done the checks back at the tank, yet. When I checked the
voltage at the control side and then added the test light, volts did drop
to zero but my light did light. Is there any significance in that result?
What if I don’t get power back at the tank, where do I go from there?
I’m sure I’ll have more questions but that will get me through next steps.
Thanks for the help you are providing!

wai2machine823 says:

Also try jumping power to the ground signal on the relay. This fixes it
99.9% of the time. 🙂
Pro tip

RealFloridaHorseman says:

Danner…at 12:40 duration immediately after the bias voltage tutorial you
are back at the relay socket and probing “pin 86”. That’s the ground
socket, upper right corner. Did you mean pin 85 in the lower right corner?

Jimmie James Wright says:

Hey Danner , Let me share this with you and maybe you can share it with
others, for two months I put two different pumps in the tank both times all
the pressure I got from both of them was 15psi and it never did start, then
I got mad and kick the fender then looked at the pressure gauge it read
50psi that meant it should start, crank it up and vroomm! took the gauge
off crank it backup and took off, got to a friends house and it quit again
and wouldn’t start call a tow truck up that took me back home. the driver
ask whats wrong and I finally came to the conclusion it’s the computer.
But the driver pop the hood shinned his light at the body ground straps and
ask me to see if it was connected, well it looked like it was, then he told
me to grab it, I did but it was not connected to the body, he told me thats
the problem because that’s telling your computer not to send the fuel pump
a signal He said if you replace that ground strap it’ll start, once I
replaced that thank God, I back on the road again. Thank You for that
video though
Jimmie

dianemarie909 says:

i did this test im getting three grounds one hot why

Chevy92SS says:

Thanks for the detailed video. I have a more serious problem that maybe you
could help with? When testing for power at the fuse box as you did, I have
zero power/volts. Where does my problem lye? Is my ECU Shot?

Morrie Bell says:

Hey Danner I have the 97 chevy express I replaced the pump hooked wires up
correctly pump wasn’t coming on so I got under the vehicle with a tester
light hooked it up to a ground and the grey wire and pump ran I turned the
van off let it sit and cranked it again now it comes on with no problems
any ideas whats causing this

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