Question about GMC Sierra 1500

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Need to view where the fuel pump gets its very first source of power for the pump prime. circuit dia or answer to where the first place the ciruit could fail

Pump works when bypass relay. relay is good. Key on , pump never comes on for the 10 sec prime. Also all warning lights come on , except the check engine soon

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  • GMC Master
  • 5,316 Answers

Key on should energise fuses Fuel pump and EFI.

Posted on Jul 13, 2015

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6 Suggested Answers

6ya6ya
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Posted on Jan 02, 2017

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keemo68
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SOURCE: 1985 Volvo 240 no fuel no spark

well first the fuel pump relay is bad, that is easily replaced. next you have no spark. the first thing you do is take the cap off the distributerand crank the engine. if it spins that tell syou thyat at least the tang or gear on the shaft of the distributor is ok and not broken. next thing is remove the #1 plug and use a 1/4 drive extension 6" long and turn the crank by hand until the #1 cylinder is top dead center(put the extension in the hole of head where the plug was and you should feel the top of the piston also make sure you can feel the top of the piston with half the extension this way you don't drop it in the cylinder with the piston at TDC(top dead center) the rotor of the distributor should be pointed at the #1 firing position. IF it does not that means your timing is off and you need to retime it by taking off timing cover and either replacing the belt/chain or gears. now if you do not have a distributor and you have a coil pack there could be only 2 things that won't give spark. either a bad coil or your altenater is bad(the battery is responsible for starting not running the vehicle like alot of people assume. the altenator energizes the coil which inturngives spark. hope this helps you please rate this thanks

Posted on Sep 07, 2008

  • 1 Answer

SOURCE: My 1994 suburban engine stops. No fuel, no MIL light.

I checked all of the fuseable links and they were all good. Next I decided to check all the power wires to the ECM and also the grounds from a wiring diagram because the Mil is controlled by the ecm and the bulb was good. The ecm is located behind the glove box. Bingo, the orange wire was only reading 3-5 volts at the ECM, but 12.5 volts after the fuseable link at the underhood fuse block (passenger side firewall). I ran a temp wire directly from after the fuseable link to the orange wire at the ecm and the ecm turned back on and the Mil or "check engine soon" light came on too. The truck started up and has never run smoother.

Note that at first the truck just stalled out and I could restart it right away with no error codes. Eventually the stalling became more frequent with longer reset times required. Once it threw a "code 54" and I thought it was fuel related as each time the gas stopped and I could still start the truck with gas poured into the TB. Ignition ok. My fuel pump turned on and ran if I tested it. I even checked the pressure regulator and the fuel filter to no avail.The orange wire that powers up the ecm is technically part or the fuel pump relay circuit as it also feeds the fuel pump relay 12.5 volts all the time. The thin orange wire from the fuse block is joined to two other thin orange wires in the large group of wires that heads to the ecm along the firewall behind the engine. I had to dig it out of the many wires to find it and remove a lot of tape. It is amazing to me that this one little orange wire could cause so much grief and be so hard to track down. I could not have afforded to take this problem to the Dealer.

Posted on Mar 26, 2009

Molson02536
  • 3854 Answers

SOURCE: fuel pump problems 2003 s10 chev 4.3 v6

Your ECU is what acctivates your fuel pump realy. Put the key on the run possition and pull the ecu fuse for a few seconds and reinstall it ans it should accivate your realy for 5 seconds, Good luck.

Posted on Apr 06, 2009

  • 1 Answer

SOURCE: Fuel pump problems

you have a shut off button in the trunk find it turn it off and turn it back on

Posted on Nov 25, 2009

  • 1243 Answers

SOURCE: i CANNOT GET ANY POWER

have you check for power to the main fuel relay ,it is near the ECM. it also poers the ECM up. if no power is coming from it then the ECM will not ground the secondary fuel relay to transfer power back to the fuel pump.

Posted on Aug 13, 2011

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2 Answers

1992 Ford E150 has no power to fuel pump, inertia switch good, relays good, new pcm i am lost.


the pressure regulator controls the power requirement to the fuel pump
when pressure is reached , it allows power/circuit to the ECM to be broken which in turn stops the pump relay from working
when the pressure drops , that circuit is energized and the ECM switches on the circuit , to the relay allowing power to the pump to supply fuel to get the pressure back up
for the circuit operation you will need a schematics of the electrics for the vehicle ( workshop manual) as some may not use the ECM but go straight from the pressure regulator to the relay through a fuse

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I have no power at the fuel pump with the ignition on


With the ignition on , not cranking the fuel power will only turn on for two seconds > Just to prime the system . You need to test while cranking the engine . The PCM - engine computer energizes the fuel pump relay , most vehicles ! What year , make , model an engine size ?
Fuel Pump Electrical Circuits Description and Operation

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Fuel pump won't cycle when the key is turned on 93 Chevy astronaut 4.3 eng


For initial prime, you have to check fuel pump relay and wiring circuits. The control/coil side of relay gets voltage from pcm, green wire with white tracer. The ground for control side of relay, should be a chassis ground. Voltage for load side of relay is fuse protected.
This vehicle has an oil pressure switch in fuel pump circuit, just a redundant power supply to the fuel pump. Even w/o the relay the vehicle should start and run, once the oil pressure builds up and that switch closes, the fuel pump will get voltage. There won't be any initial prime w/o the relay.
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Nov 10, 2016 | 1993 Chevrolet Astro

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How do you prime fuel pump? 2003 Dodge Grand Caravan.


Turn the key on , the fuel pump is computer controlled . The PCM - engine computer will energize the fuel pump relay for two seconds when you first turn the key on ! This primes the fuel system ! Watch this video on fuel system electrical circuits ! Fuel Pump Electrical Circuits Description and Operation

Aug 26, 2016 | 2003 Dodge Grand Caravan AWD

1 Answer

Why is fuel pump relay getting no power?


The fuel pump relay has B+ voltage on pin 87 at all times , Pin 85 has B+ voltage only when cranking engine or for first two seconds from key on .( to prime fuel system) .Watch this youtube video ( how to test GM fuel pump circuit ) GM Fuel Pump Relay Testing

Mar 31, 2016 | 1995 Buick Regal

2 Answers

Fuel pump not working, will not prime, cranks but no start unless putting fuel in intake


Check voltage and ground at fuel pump, pink wire is voltage black wire is ground. The initial prime is only for key on engine off, lasts a couple seconds. You use a testlite to check voltage and ground.
Check voltage and ground for fuel pump relay. Also, you have an inertia switch, you have to check that.

For testing, you can use jumper wire at load side of fuel pump relay, the load side is that line with the arrowhead. When relay is energized that line moves to the other terminal and sends voltage to fuel pump, just unplug the relay, use jumper between terminal 30 and 87, terminal 30 is hot all the time.
The voltage and ground for the control side of relay is controlled by computer I believe, If the control side is the problem, I'd have to check wiring circuit and computer.
With engine cranking, you have injector pulse, also?
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Mar 15, 2016 | 1995 Ford Explorer 4.0

1 Answer

No power to fuel pump or feul shutoff


Fuel shutoff? Are you talking abouty the inertia switch? Are you aware that you will only have power to the inertia switch and to the fuel pump for about 2 seconds when the ignition switch is turned from OFF to RUN? If you are checking for voltage here after that time, you are not SUPPOSED to find any.

If you are not getting any voltage there during the 2-second "fuel prime" cycle, then you need to check your fuel pump relay circuits. (Primary AND secondary)

Nov 15, 2011 | 1999 Ford Econoline

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1986 Toyota rv fuel pump issues. Changed fuel pump still not not getting fuel. Can pour gas into efi and it will start could it be bad fuel pump solenoid? Where would I find that solenoid?


When you turn the key to start it, do you hear the fuel pump whine as it begins to prime the system?
if not then your pump is not getting power, it could be a fuse, a relay, or the cut off, which will kill the fuel pump if it senses force powerful enough to be a collision. Also you may want to replace your fuel filter, it could be clogged and not allowing fuel to get to the engine fast enough or with enough psi.

Mar 03, 2011 | 1986 Toyota Pickup 4WD

1 Answer

1996 tahoe wont start


There should be a 2 second prime by the fuel pump. This prime by the fuel pump is standard for GM vehicles, and if it is not present a hard start is encountered. Turn the ignition to the run position and listen for the fuel pump operation. You may have to have an assistant listen at the fuel filler by installing a long slender funnel into the fuel inlet to the tank, remove the gas cap and insert the funnel, listen at the large end of the funnel to see if the pump can be heard running. Using the funnel acts like a megaphone and makes it easier to hear the pump. If the pump runs for 2 seconds after you turn the key to the run position (DO NOT attempt to start the engine during this test) and the engine doesn't start due to lack of fuel, check for an obstructed fuel filter. (Just change it, it's probably overdue for service anyway since everyone thinks it get changed during oil changes, but never really does.) If the pump doesn't run during prime interval, the computer may not be turning on the fuel pump relay, or the relay is defective. To check the relay, use another of the relays in the power distribution box to substitute for the suspect fuel pump relay and retest. Be sure to wait at least 30 seconds between key cycles since some systems have a delay timer built in to keep the pump from over running. Be sure the relay you sub into the fuel pump socket is identical to the one you remove and properly oriented in the socket. The engine will run following your manual prime because an additional set of contacts in the oil pressure switch will power up the fuel pump relay once proper oil pressure is achieved by an idling engine. If you find that the relay is not defective, but doesn't provide a priming impulse, the engine computer may have failed. DO NOT use a conventional test light with a filament type bulb to check any of the computer circuits that drive the fuel pump relay, or any other computer controlled circuits on an automobile ( or pickup) The driver circuits in a vehicle computer can be blow-out by over-current when using a conventional test light. You can use a high-impedance DVOM for testing safely.

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1 Answer

1987 nissan pulsar


Question is, does fuel pump relay come in/ go out when ignition switched on? How do you know "no power source to fuel pump", was that because bypassing the relay didn't cause it to run? Or did you check for supply to the pump and find nothing doing?.
Sounds rather like a frozen pump to me... or a blown fuse??

May 28, 2008 | 1989 Nissan Pulsar

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