Hi, I'm new here and would like to ask for a little help. My sons 1997 F350 351 turns over but will not start. Has spark,.has good fuel pressure, but fuel pump (KO), won't shut off as they normally do after they prime. Same goes for either tank. Has plenty of fuel. So far the only part that was replaced is fuel the regulator. Not sure if the PCM is bad or? Any help would be appreciated. What can we look for/trouble shoot? It seems to me that the injectors aren't firing,.but not sure of that. It's not getting fuel.
Thank you,

John

 

Classic symptom of a bad computer BUT there can be other causes that you'll want to rule out first.

First pull the fuel pump relay out and check it with an ohmmeter across the contacts to be sure they ain't stuck/welded closed.

Next you'll want to check to make sure the relay really is being commanded on. The relay coil has continuous + voltage to it and is commanded "on" by the PCM grounding the - side of the coil. So check from ground to the relay coil - with the key off to make sure that circuit ain't shorted to ground somewhere.

If those two quick tests pass don't hesitate to pull out the computer and crack it open. There's been a lot of cases of the electrolytic capacitors in there failing due to age and the fix is as simple and cheap as replacing the caps as long as the electrolyte didn't destroy your board. Even if it did and you're good at working with electronics you can probably repair the board by soldering jumpers across the damaged traces.

EDIT: forgot about the no start condition. Go straight to the PCM for that, nevermind the above tests. That would be valid if it DID start/run but the fuel pumps continue to run.

Welcome to the forums!

 

Welcome to FTE!

Continuously running fuel pump (s) and a no start condition is a sure sign of a bad PCM (computer).

 

Thanks guys. Going to order a new PCM. I'll let ya's know the outcome after we get it in. Thanks again,

John

 

Another question. Does the new PCM need to be flashed. Someone had something to me about that. I'm not sure if it does or not. I thought we could just pick one up, put it in and go?

 

No, it comes programmed from the factory.

 

Thank you very much.

 

Ok,.installed the new PCM and same thing happens. Fuel pump keeps running and no start. Happens with either tank. Relay is working as we can hear it clicking when pulled out and put back in and we also switched them with the other relays in the box. We can pull the relay and the pump stops of course,.put it back in KO and the pump continues to run and no start. We are at our wits end with this thing.
Any ideas? Thank you....

 

I would suspect another bad computer. Have you tried to pull any codes on either one?

 

Ok,.looking at the truck a little more today,.my son had 3 ground wires off when he was replacing the grill and right fender. I asked him 20 times if he had all the ground wires connected,.he kept saying yes. There were 3 off after I checked. I connected them back and truck fired right up. Back in businesses. Thanks for the help guys.

 

Great find. Weird symptom, I'll file that one away for future reference.

 

I'm guessing that it completed the circuit for something making it not start, but I'm happy it's running.