History - Truck is a 96 Dakota with the 3.9l. It hadn't been used in a couple years. A few weeks ago, I got it running and inspected. It had a bad ping, which was resolved with better (ie, not 2yr old) gas. About a week ago, I went to go somewhere, but the truck died about 2 seconds after starting it. It has not started since.

Fuel pressure gauge says no pressure at the test port. Before replacing the pump, I was going to check the voltages. When putting the key in run, pin1 of the pump connector only gets voltage long enough for my autoranging meter to change range (less than a second). I switched the relay with the start relay, no change. I tested the connections from the relay - pin 30 gets good 12v, pin 87 has continuity to pin1 of the fuel pump connector, pin 86 gets 12v whenever the key is in start/run. Pin 85 has good continuity to pin 19 of the PCM connector C. I'm not getting continuity to ground from pin 85 of the relay while the key is in start and the starter is engaged.

The service manual does not show any other conditions for the fuel pump relay control to activate. The fuel level sensor (not the gauge) is shown in the same diagram, but its description says that it is used to prevent false codes from being thrown when fuel level is below 15%, so it doesn't seem to be involved with fuel pump relay control (sound right?). BTW, the fuel gauge is not working properly.

Any thoughts? I'm going to try pulling the pump today just to put eyeballs on it.

As I'm double checking my post before hitting submit, I had another thought. The PCM is supposed to activate the fuel pump relay for a second or two when the key is first put into run, but it stays activated while the key is in run and the engine is running. Any ideas where the PCM gets that "the engine is running" signal?

Keith

 

First of all do you have any codes? The PCM will know the engine is turning by the crankcase sensor as well as other inputs.

 

My OBDII code reader is showing no codes. If I'm reading the dakota owners manual correctly, the check engine light should be to the immediate left of the high beam light, correct? If so, the check engine light bulb is burnt out/missing/etc as I get nothing.

Keith

 

The light will come on for a second or so during start up from key in off. It does a self check on it all. If you don't see the light at that time, then yes your bulb may be dead.

 

Looks like I was over complicating this. The signal was there, just not what I expected. I ran a jumper wire in place of the fuel pump relay and the fuel pump did not do anything - and there was definitely voltage at the fuel pump connector then (verified with test light).

Ordered a pump yesterday, installed it today and the truck started right up. One benefit of removing the bed instead of dropping the tank is that you can test the truck without having to put everything back together. I was working alone, so enlisted some mechanical help for lifting the bed then backed the dakota under it and lowered it.

Thanks for the comments Crazy. I'll look at replacing the burnt out/missing CEL bulb later.

Keith