No spark, no fuel, no communication

ALSEASNS

MEMBER
1999 GMC SAVANA
5.7L
V8
2WD
AUTOMATIC
200,000 MILES

Vehicle listed above is a 3500.I recently installed a new fuel pump and it has run for a few hundred miles. My guy was driving it and pulled to make a right turn, the engine stopped, and all systems stopped. I was able to start it with starting spray, but it wouldn't run without the spray. Suspected maybe a bad pump and bought a new one to try. No power to the pump. Tired scanning and it won't connect. Checked for spark and no spark. I have replaced the fuel pressure regulator because prior to the original fuel pump replacement the fuel would bleed back to the tank, and it would take forever to bring the fuel pressure back up. I have changed the relay and checked every fuse and diode with all being okay. I have confirmation of ground to the pin A1 The engine Control Module Ground to the block. I don't have power to pin B1 which is the fuse output battery. I have 12 volts to the all the fuses in the box under the hood. I don't know where else to look or what it could be.

4 Replies

JACOBANDNICKOLAS

MECHANIC
109,747 POSTS

Hi,

The ECM1 fuse in the under-hood fuse box is responsible for powering the fuel injectors and the ignition coil. You mentioned power to all fuses. Confirm there is power out from that fuse or go to any of the pink wires at the fuel injectors and with the key in the run position, check for voltage. Also, there will be a pink wire at both the ignition coil and the ignition control module. Check there as well. If the computer doesn't see ignition, it will shut the pump down.

Next, at the ICM, there will be a black wire. Check it for continuity to ground. The part that is confusing me is you mentioned it ran with starting fluid, but there is no spark. Are you certain there is no spark? If there isn't, the vehicle shouldn't have run at all.

I attached the entire wiring schematic for the powertrain management system. I highlighted the wires related to the fuse of interest. Use this as a reference. Also, here is a link you may find helpful.

https://www.2carpros.com/articles/how-to-check-wiring

Let me know what you find. Note: If there is power to and from the aforementioned fuse but the components are not getting power, suspect an issue at the giant splice after the fuse, S132.

Take care,

Joe

See pics below. Note: I had to cut each schematic in half to make them readable. I did overlap them so you can follow from one to the next.

Images (Click to make bigger)

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Sunday, October 31st, 2021 AT 8:22 PM

ALSEASNS

MEMBER
3 POSTS

Okay, so I do have the computer talking with the scanner that isn't picking up any codes. I can now start it again with starting fluid, but it run beyond the duration of the starting fluid. I do feel a click in the relay, and I get a momentary battery voltage (12V) at the pump connector measuring ground wire to pump hot when I cycle the ignition key. But it is not constant or pulsing when I crank it. I found a fuse that I couldn't see because the under the hood fuse box is under everything and under part of the front fender as it is a van. When I put a probe to the #85 relay socket, I have constant power. When I probe with a multimeter on the #87 relay port with the key on the reading is 12.5V. I am at an impasse on this one. Could it be the VCM? Or another control that I haven't found contributing to the operation of the fuel pump.

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Wednesday, November 3rd, 2021 AT 2:42 PM

ALSEASNS

MEMBER
3 POSTS

Also, I want to add that I did verify the pump does run. I hooked a car battery to the gray post and the heavy black post on the pump and it pushed gas to the engine. I didn't try starting the engine because the leads going from the battery to the pump were under size and got pretty hot.

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Wednesday, November 3rd, 2021 AT 4:16 PM

JACOBANDNICKOLAS

MECHANIC
109,747 POSTS

Hi,

It could be the VCM. It turns the relay on when the engine is running or cranking. If there is no crankshaft reference signal (CKP), it shuts the relay off. Since it runs with starting fluid, there has to be a CKP reference.

Take a look through the diagnostics below. They are specific to the diagnostics for the fuel pump circuit. Take a look through them and let me know if you are comfortable performing them.

Let me know.

Joe

See pics below.

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