I'm working on a 1996 Dakota 2WD with a 3.9 V-6 engine and an automatic transmission. The engine will start with starting fluid sprayed down the throttle body, but the fuel pump will not kick on and run for 5 seconds when the key is turned to the run position. Also, swapped the fuel pump relay and still won't kick on the fuel pump. Checked all fuses under the hood and in the truck and they're all good. The fuel pump was recently replaced. Where are the common places to check for the fuel pump not running?

 

Verify the pump is actually getting power when the relay is engaged. (probably gonna require two people) If that works, verify the pump has a good ground. (that was the problem on my 98 Ram, which I finally figured out after having the fuel pump replaced twice......)

 

I'm not the best at reading wiring diagrams. When you mention verifying getting power to the fuel pump, which wires should I be checking for 12 volts at the fuel pump and which one should I be checking for ground?

 

It looks like power feed is Dark Green/Black, Ground is just black. Pin 1, and 6 Respectively. The ground ends up in one of two possible places, Right Rear frame rail if you have the trailer tow package, left of the master cylinder on the bulkhead if you don't. (I assume that is left side from the drivers seat. Unsure if that is under the hood, or under the dash....)

 

I checked the Dark Green/Black wire on pin #1 at the female connector (six pins total in that connector, I believe) going to the fuel pump and it is not getting any 12 volt power on that wire. Swapped the relays and still nothing. What else can cause the lack of power on that wire and where does that wire tend to run so that I can trace it, if necessary? Could that be caused by the PCM? This truck has about 310,000 miles on it.

 

Excuse my ignorance if I missed it somewhere but how do you know fuel pump stops running after 5 seconds other than the fact it shuts off and have to use starting fluid. Only time you will hear fuel pump is when you turn the key before starting. You will hear it prime and shut off. Don’t see any mention of hooking up fuel gauge to fuel rail and see what happens during all this. Just trying to cover the basics here

 

The issue here is that the fuel pump doesn't run at all. When the ignition key is turned to run, the fuel pump doesn't run at all, however, the engine will crank without issue when the key is turned to start. Starting fluid was used to see if the engine would run if some fuel was added.

 

You will only see power at the pump for a few seconds at initial key on, after that, the PCM needs to see the engine turning to turn it back on.

Verify you have power at pin 30 in the relay socket. It *should* be hot at all times.

 

Thanks for the reply, but I have just one dumb question - where is pin 30 on that relay plug looking down on it?

 

Just took a stab at it and found pin 30 (denoted by the yellow arrow in the photo - luckily, the relay has a pin layout with numbers on the back) - it does indeed get full time 12 volt power with the key off. Where might I go from here to troubleshoot this issue?