Need help figgering this one out

[scredneck]

Working on a friend's truck. 98 Ram 1500 4x2 5.9 auto with 32,000 miles. Everything original. No mods. Truck will not stay running. Cranks up great. Runs great for about 15 seconds and dies like it's not getting fuel. Owner has already had another shop replace the fuel pump and the PCM. Can hear pump prime itself when key turned on. I don't have a fuel pressure tester, but when I pres the stem on the schrader valve on the fuel rail while the ign switch is on, get one quick strong spray, then just barely a dribble, and pump does not kick on unless switch key off then back on. When cranks up, it runs fine for about 15 second until it runs out of fuel. Can keep it running by dribbling fuel in the TB. Unhooked fuel line from rail while doing this and let fuel pump into bucket while keeping the engine running as above. Took roughly 45 to pump roughly 1/2 gallon of fuel into the bucket. But will not run longer than about 15 seconds on its own. When it dies, it will immediately start right back up if turn the key off then restart.

Advice Please.

[Marshal Carpenter]

have person go back to that shop that replaced the fuel pump and have them check it for volume. new pumps can be bad.

[John Kunkel]

The FSM states the pump should pump 1/4 liter in 7 seconds so your half-gallon in 45 seconds in in the ball park.

It's normal for the pump to only run a few seconds each time the key is turned on, this prevents the pump from running continuously if the key is left on without the engine running. Once the engine starts the PCM sends a signal to the fuel pump relay to keep the pump energized.

You might try replacing the fuel pump relay, if that doesn't fix it the problem might be in one of the devices that give a run signal to the PCM.

[scredneck]

Pump cuts on for a few seconds when key turned on, as it should. BUT does NOT come back on when engine is started. Have replaced the relay. No change. Tried running a jumper wire directly to the pump, bypassing PCM,etc. and truck ran great. So I know it's something electrical leading to the pump. Don't know where to look next.

[John Kunkel]

The basic wiring for the fuel pump is pretty simple, the PCM supplies a ground for the coil in the fuel pump relay so, if the PCM drops the ground, it must be because some other component isn't making the PCM happy.

Have you hooked up a code reader? It might take a DRB to find the fault.

[scredneck]

Originally Posted by John Kunkel

it must be because some other component isn't making the PCM happy.

Have you hooked up a code reader? It might take a DRB to find the fault.

That's what I'm afraid of. As of today the pump is working properly. All other symptoms remain. It seems that the injectors are not firing after about 5-10 seconds, and no spark after about 5-10 seconds. Suspect issue is with the ASD.

[Coonass]

if it lands up being a problem with your PCM I have a extra one off of a 99 Ram 1500 with the 5.9 4X4. Your more than welcome to it if you need

[scredneck]

Replaced PCM...all good now.