97 Dodge Ram 318 engine.

when attempting to start, the fuel pump primes for seemingly forever. At times it will cut off after both the check engine and “gen” light flash repeatedly for a couple seconds. I can then start the truck and drive without any issues. Sometimes I can sit there with key in “on” position and it will just keep priming (and I’m talking for 15 minutes).
Checked the relay and all seems fine there.
cleaned any and all corrosion off cables and terminals to ensure best electrical connections.
Starter sounds strong and has no issues. When I’m unable to start the truck, the starter will just whine away. When I am able to turn it over it is only after the lights flash and the pump stops pumping.

Im at a loss as to what could be the culprit. Any ideas.

 

Verify battery voltage, and clean the terminals.

Swap the fuel pump relay for another one. (horn relay is always a good candidate.)

Are there any codes?

 

Battery voltage tested at 12.62 V.

Swapped the horn relay and everything operated the same as before.

all terminals and cables are cleaned, ground wires and ground surfaces cleaned up. Only the engine ground cannot be cleaned up as I need the proper size wrench.

The pst couple days it was better in a sense I could wait a few minutes or grab my bundle of wires coming off the ignition switch and maybe do something. But now again nothing. Just spent hours cleaning up the wiring under the dash - removing excess items (like old electronic door controls spliced in) and making sure there were no shorts. And back to square one with an endless fuel prime scenario.

 

Pull the fuel pump relay, set your meter on continuity, (or, resistance if it doesn't do cont.) Test pin 85 to ground, first with ignition off, to see if that is a short to ground, and if it isn't, turn the ignition on, and see if the PCM keeps it grounded.....

 

Thanks man.

Checked out that and continuity was kept grounded with ignition on off or on.

Forgot to also mention the oil light remains lit the entire time.

Also doing a search for oil pressure no start instead of fuel pump issues - I came across a thread between yourself, Tboned, and Moparite from just over a month ago where it sounds like a similar issue and the PCM replacement worked.
Looks like I might be headed that way too.

 

Figure out which connector on the PCM the control wire for the fuel pump relay goes to. Unplug, and check continuity to ground again. If it is still grounded, there is a short somewhere, if it isn't, yet, possible bad PCM.

 

Fantastic - I will check on that after work tonight.
And forgive my ignorance in this question, but am I still going to be check continuity at the relay pin after the PCM is unplugged. Or am I testing at that PCM connector.

 

From the relay socket. You want to know if that particular wire is grounding out somewhere, or, if the PCM is responsible.

 

Nevermind - had my multimeter with me and checked at lunch. Unplugged the connector from PCM I knew had the pump attached to it. And still grounded.

And for good measure unplugged the entire PCM and still grounded.

So you’re saying I’ve got a short. Any tips on how to find it?

And could I just abandon in place all of the existing wiring for that relay and run new (obviously tying in close to any connector I can’t get into). Just throwing things out there.

 

Replacing the control wire from relay to PCM *should* solve that particular issue..... but, finding when the short is would be better. I know, it's a pain to pull that harness apart..... Might be easy though, and be somewhere under the PDC....