Relays, fuses are fine. Fuel pump, injectors are new. Battery is charged to 13 volts, not getting full 13 to pump though. The pump will not kick on! Not even by jumping the G terminal. One day it just stopped running as it was idleing. Could the Vats be disabled? How do I check for that? What can I do next besides burn the car kidding

PS it is a 92 Z28 305 auto.

 

I am only getting 8.6 volts to the pump. I have 13 at the relay. What grounds do I need to check, if any?

 

Does the ses light come on when you turn the key to the run position?

If not check the fuse under the hood near the battery, feeds the fuel pump and ecm.

 

SES is on when ignition is turned. The fuel pump fuse near the battery is fine. I am getting 13 volts into my fuse pump relay and also switch it out with a new ac delco piece. I tried all variations of the oil pressure switch for volts, but only came up with 3-4. The car also had an alarm in it at one time and I removed the leftover pieces. I have concerns with the VATS deal and printed off the article from the tech page. I can't find any yellow wires that go to a connector though. There is one big yellow wire that the alarm was plugged into, but I have no idea what that was.

 

Where does the fuel pump ground at?

 

It grounds at connection "G304" at the rear of the body. It's the same place the rear lamps are grounded. If you suspect a poor ground, temporarily run another wire directly to the battery negative.

There is another connector in the fuel pump power system, either under the rear seat or along the LH threshold.

 

Thanks Vader, I will get out this evening and run these wires down. I know something is a miss here. I took the old fuel pump and connected it straight to the battery and it came alive. I still think the old one was to weak to create enough fuel pressure.

Am I reading this right? Does the orange fuel pump wire (from fuse) branch off to 2 connections before the relay? What is the fuel pump switch? Is that the same as oil pressure sensor?

 

Vader - what year is that diagram? Those colors and sizes don't look familiar to me. Specifically the 16 guage battery power to the relay and the 16 guage blue wire going to the fuel pump.

Edit: The green/white wire to the ECM is in the wrong cavity for a 730.

 

I am not going to go out until this evening, but if someone can give me a thumbsup if this is for a 92 I would appreciate it. I know I still need to look at the grounds anyway.

Thanks,
Chris

 

Okay, I ran a temp ground from the battery and still only 8.19 volts to the fuel pump. I pulled the ECM fuse and found the same 8.19volts in the fuse box. I thought maybe the battery was dying so I took the 1000CCA from my truck and it raised the fuel/ecm to 9 volts. Engine sure was cranking though. I removed the fuse and spliced in from battery to fuel pump and had 12.xx volts, but no pump action.

What would cause a 3-4 volt drop going from the relay to pump/ecm? I was told by a gm dealer that the fuel pump relay and cooling fan relays are the same. That is what I have been switching it with. Does the ECM get its power from the fuel pump relay as well or does that branch off before the relay?

I will probably pull the pump again and take another look at it. My fuel gauge in the car now reads past fuel. I checked ohms and they are at 56 going from the purple wire. How do I get the needle back to Empty?

Is there any little thing like a sensor or something that I am missing? I still could only get 3.x volts from either side of the oil pressure switch (unplugged).

 

The orange wires a the ECM (B1 and C16) are battery power. It's the same battery power as the orange wire at the fuel pump relay and the orange wire at the oil pressure switch.

 

I figured it out. My buddy told me to ohm the pump and it turns out the bad ground was at the inside tank top connections. The prongs just had to be cleaned up. Runs like a top, need to fine tune the time and get her on the ground and sold.

Thanks for all the help,
Chris