no fuel pump with ingition

D

DGC

Senior Member
Joined
Jan 10, 2004
Looking for help with fuel pump on my 87 turbo. Followed blogs to these checks:

1. fp/inj 15 amp fuse. good
2. fp relay at pass fender. new
3. +12 to grey fuel pump wire near alternator triggers pump. pressure builds to 30 lbs.
4. ECM codes to only 12. No faults
5. +12 to pink/black lead at fp relay
6. +12 to brown lead at firewall fusebox connection powers pump

Looking for help. Searching through blogs finds "crank position sensor" as possible reason for failure. Anyone else solve this problem with a crank sensor? Also checked oil pressure sensor leads for shorts and find none. Analysis rules out ECM, fuse/shorts, fuel pump and fp relay.

I'm out of ideas. So I'm interested in anyone's experience with this problem.

Thanks,
DGC
:confused::confused:
 
TurboRick,

Yes I received your message. The relay has leads 1,2,3 and 5. +12 applied to leads 1 and 3 short 2 and 5. When I remove the fp relay and short 2 and 5 I still get no fuel pump. Is this what you mean by the two middle leads?
From what I can tell, and what I found out today, there must be something in the circuit preventing the signal getting to the pump. Tomorrow I am going to crank it long enough to trigger from the oil pressure switch. Maybe the 2 seconds to the pump from the relay circuit when ign is initially turned on are not being done. If so, I will need to find where the 2 second burst is coming from. Since the circuit is directly through the ECM, I'm not sure where the signal originates. As I indicated in my post, one blog suggests the crank sensor. Have you found this to be a possible solution?

Thanks,
DGC
 
The crank sensor triggers spark. Nothing to do with the fuel pump.

Unplug the fp relay on the passenger fender. Jump terminal B and D on the relay plug. See if it starts.
 
TurboRick,

Thanks for the followup. Did some more reading and am able to prime fuel pump using
the gray lead at the back of the alternator. Once primed, she fired up just fine. I'm going
to have to find a way to determine if the 2 second pulse isn't functioning in my ECM, or
if another portion of this circuit is failing. For now, I'm happy to have a live engine. Apparently the only drawback to not having the 2 second pulse is that the oil pressure
needs to go above 4 lbs to activate the oil pressure switch to the fp.

Do you agree??

Thanks for your help,
DGC
 
Basic FP circuit T/S Tree

Unplug the fuel pump relay.

Check for 12 VDC at pin D on the FP relay harness using a body/chassis ground. Is power present?
If yes: Continue to section A.
If No: Proceed to section B.


Section A

Hook a DMM up between a chassis/body ground and pin A of the FP relay wiring harness. Turn the key on while watching the DMM. You should see 12 VDC for 2 seconds. Do you see this?

If yes: Proceed to section A1

If no: Turn off ignition and leave the fuel pump relay unplugged Gain access to the ECU (passenger side kick panel). Back probe wire A1 (either dk green/white or grn/blk depending on the schematic you look at) and turn on ignition. Is 12 VDC present for 2 seconds.

If yes: A problem exists in the wiring between the ECU and the fuel pump relay.

If no: Unplug ECU connector A (don't forget to unplug the ecu memory wire at the battery and turn of the ignition) and check for continuity between A1 and ground. If continuity exists there is a problem (short to ground) in the wiring between the ECU and the FP relay. If no continuity exists the ECU is at fault.

Section A1

Check for continuity between FP relay harness pin C and body/chassis ground.

If continuity is present (should be less than one ohm) see section A2

If continuity is not present a fault exists in the wiring between FP relay pin C and body/chassis ground.

Section A2

Locate the Grey "prime connector" on the passenger side of the engine compartment. Check for continuity between the "prime connector" and FP relay harness pin B. If continuity is not present a fault exists in the wiring between the FP relay and the pump.

If continuity is present connect the FP relay harness to the FP relay. Connect a DMM between "prime connector" and body chassis ground and turn the key on. 12VDC should be present for 2 seconds.

If 12 VDC is present and your pump doesn't run a the problem is either your pump or a broken wire or faulty connection in the wiring going to your pump or a faulty ground at the tank.

If 12 VDC is not present your problem is either a faulty FP relay or the wiring between the FP relay and the pump. (broken before the prime connector or shorted)
I left out the trouble shooting for this because I'm unsure of the resistance between the prime connector and ground. There should be continuity because the FP in a load in that circuit I'm just not sure how much.

Section B

Check FP/INJ fuse.

If fuse is good check that FP/INJ location in fuse block has 12 VDC present with the key in the RUN position. If 12VDC is present a problem exists in the wiring between FP/INJ fuse and the FP relay harness.

If power is not present you'll need to figure out why the ignition switch isn't applying power there.
 
Sorry I flaked a little on the trouble shooting of the wiring going to the pump. If I get a chance to take some measurements on mine (walboro 340) and if some others with other pumps could measure continuity between prime and ground for different pumps I could type something up for that later.
 
BlackBandit said:
Sorry I flaked a little on the trouble shooting of the wiring going to the pump. If I get a chance to take some measurements on mine (walboro 340) and if some others with other pumps could measure continuity between prime and ground for different pumps I could type something up for that later.
Click to expand...
I was reading your fuel pump thread, what and where on the passenger side is a gray prime conector
 
TurboBuRick said:
The crank sensor triggers spark. Nothing to do with the fuel pump.

Unplug the fp relay on the passenger fender. Jump terminal B and D on the relay plug. See if it starts.
Click to expand...
My fuel pump won't come on. I burned the transistor in the ECM that controls the fp relay,now I'm getting power to the fp relay harness and still nothing, I can jump b and d out then it will crank, I bought a new relay from autozone and it still doesn't work, any ideas
 
Check the ground wire on the relay socket. Use a test light or dvm. One end on positive battery terminal the other to the ground socket in the relay plug.
 
TurboBuRick said:
Check the ground wire on the relay socket. Use a test light or dvm. One end on positive battery terminal the other to the ground socket in the relay plug.
Click to expand...
I went from positive to green wire and yes the test light lit up, so I have a ground,any other idea. I read on search post that some people jump it out and leave it that way,but I really want to find what's going on and happened
 
Black with white stripe is ground.

If you can, go between the black w/white stripe and green w/white stripe. It should light up for a couple seconds when key is turned on.
 
I don't have my schematics right here. Did you follow the above trouble shooting tree from the beginning?
 
Plug the relay in. Have someone else turn the key to on position. The relay should click on then off.
 
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