Hi all,

I'd like to pick your collective brains for a moment: My father has an 87 Vert that has had some no start problems. It first manifested as a situation where it would start fine, run, then all of a sudden shut down. It would not start,and I noted that the fuel pump wasn't running. Checked all fuses - all ok. Changed the fuel filter. Changed the fuel pump, and tested the entire assembly - all ok. Connected a power source to the "G" terminal of the ALDL, and just a clicking coming from under the hood. Later on, after removal of the pump, checking, reinstallation, then the power from the battery to the "G" terminal runs the pump as it should - engine starts, and runs fine for about 10 minutes, then dies out. Again, power to the "G" terminal and just a clicking from the battery area. Also, we crossed the D and E lines going into the fuel pump relay - clicking still, but not from the fuel pump relay. the sound seems to be coming from something around the battery area.

SO - who's got the knowledge on this one? It's a stumper to be sure. What's my next move?

Thanks in advance,

Dwight

 

Anybody heard of this problem? :seeya :confused: :confused: :confused:

 

The Fuel Pump Relay is located right of brake master cylinder behind battery ...

Replace it would be my guess ...

:steering:

 

You think so? I guess that is the best course of action. When I crossed the D and E terminals - only the clicking is heard - I guess this could be the oil pressure switch doing its thing - maybe you're right - the fuel pump relay must be bad - just don't wanna buy more stuff that isn't broken (already got a new pump in that was just fine :eek: )

Thanks for the input

Dwight

 

When it starts do you have an oil pressure reading?If not then thats your problem.Low pressure shuts off the fuel pump.
Next time it wont start spray some starting fluid in the intake.If it fires then you have a fuel issue.If not then a spark issue.If spark I bet module in dist.

 

No problem with oil pressure - it the damn fuel pump - it doesn't prime the pump when the key it first turned on, and thus no fuel pressure, and no start.


Once on a blue moon, the pump will prime - then it'll start, run for an indescriminant amount of time, then shut down (fuel starved cause the stupid pump shut down again). Keep in mind that i've tested the entire pump assembly, and it is all fine, its something that tells the pump to run, and it isn't.

:confused: :confused: :confused: :confused: :confused: :confused:

 

When you apply 12 volts to pin G of the diag. connector, the fuel pump should always run.

The MAF power relay is also energized when you apply 12 volts to pin G. There are two relays behind the battery. The MAF power relay and the MAF burn off relay. The MAF power relay is the one closest to the driverside fender.

If you apply 12 volts to pin G and the fuel pump doesn't run you need to see if 12 volts is at the 10 amp FP fuse. If it is you need to measure the Tan/White wire at the fuel pump. If you have 12 volts there and the pump still doesn't operate, you either have a bad connection at the fuel pump or a bad ground for the fuel pump. (I believe you said you replaced the fuel pump).

When the engine is running, if the fuel pump relay fails, the oil pressure switchy/sender will supply the 12 volts for the fuel pump as long as the oil pressure is above 4 psi.


[Modified by Hooked on Vettes, 6:51 PM 3/18/2003]

 

Now that is some excellent information. The last time it stalled while running (lots of oil pressure) - it had run for at least 10 straight minutes. I then reconnected 12 V to the "G" terminal, and the pump would not run.

If the oil pressure switch is bad, will this cause the car to stall, and refuse to restart? If so, then the oil pressure switch may be the problem. I still wonder what makes the click noise when i put 12 v to the "G" terminal (no pump running) maybe it is the MAF sensor relay?

This is going well guys - let me know if the oil pressure switch could prevent the car from starting - thanks alot!!

Dwight

 

I had a typo in my first reply (4 psi for the oil pressure switch to close).

The ECM (computer) is what closes the fuel pump relay so the pump runs
for 2 seconds when you turn the ignition switch to run. It will also close the fuel pump relay when you crank the engine as long as it sees some signal pulses from the distributor.

When the oil pressure reaches 4 psi the oil pressure switch closes and supplies 12 volts to the fuel pump as a backup in case the fuel pump relay fails. So when the engine is running, you have 2 sources supplying 12 volts to the fuel pump.

From your description of the problem, you should be able to solve your problem. When the failure occurs, with the ignition off apply 12 volts to pin G. With a volt meter you should measure 12 volts at the FP fuse, if yes, see if you have 12 volts at the fuel pump. If yes and the fuel pump is not running, the wiring to the fuel pump is bad or it's ground.

Also have you check for any error codes? The ECM monitors the voltage at the fuel pump relay and can set code 54.



[Modified by Hooked on Vettes, 7:52 PM 3/18/2003]

 

Very well described - my thanks go out to you - no, there haven't been any codes set - but, then again, this is my father's car, and I haven't even paid close enough attention (yet) to note that the SES light is definitely illuminated. I'll definitely check for this next time out. I'll get a volt meter and do what you say - measure at the fuse panel and at the pump assembly. I suspect this has it nailed though - likely a bad ground, or something along those lines. I'll post back to this thread once I've figured it out, or when I know something more - once again, thanks for the instructions!! :seeya :cool: :cheers: