Stuck Help would be much apreciated

[vsandme]

I have a 94 6.5td mostly stock other than the straight pipe and intake which im positive have nill effect here. My truck starts in the morning fine, then while warming up likes to cut out the key was shut off... if it doesnt stall and i shut it down after a drive and try to start it within an hour or so it wont start. the stalling is becoming more often.

I started the truck and cracked the t valve at the front of the engine compartment and no fuel came out and the truck quickly stalled. wont start back up right now. came out 10minutes after that while the truck was off and a little fuel came out when i re opened it.

Theres no noise from the lift pump when i turn the key on not sure if there should be or not. I checked the lift pump fuse and it was fine (in the compartment against the firewall under the hood.

[Robyn]

The lift pump is not working.

The lift pump should run any time the engine is running.

Missy

[vsandme]

Would I hear it run when turning the key on without starting it?

[john8662]

On a 94 the lift pump is not turned on by the key before the engine is running.

Sounds like you need a new Oil Pressure Switch, get an AC Delco, most others are quite inferior. Especially avoid Borg Warner OPS's.

The oil pressure switch provides power to the lift pump after the engine is running and the engine is making oil pressure.

There is a cover above the A/C Dryer (aluminum cylinder on the firewall passenger's side) that is held on by 3 plastic thumb nuts. Remove the thumb nuts and gain access to the electrical connections underneath it. You will see several lugs/posts with electrical connections going to them.

You may not have the cover as mentioned above, but probably do unless someone has removed it already.

Look for a fuse connection. It will be a two-wire fuse holder that will be clamped to the firewall. Undo this to get to the fuse, remove the fuse, this fuse is the fuse that powers the Fuel Lift Pump. Check the fuse. Don't put the fuse back in. Now take the fuse holder and enable one of the prongs to touch one of the posts sticking out of the firewall (the electrical posts near it), they're all HOT 12v w/o the key on or anything. Listen to see if you hear a thumping noise (that's the lift pump working), if you don't get that, try the other pin in the fuse connector. Some pumps are quiet so you won't hear them really running, Most are noisy. So if you can't hear it, get someone to grab it (it's in the frame rail under the driver's seat) and have them feel when it's pulsating.

This is how you hot-wire the lift pump temporarily to test it, and to bleed your fuel filter.

If the pump never comes on, bad lift pump. If the pump comes on, bad Oil Pressure Switch.

I'd go ahead and prime your fuel filter while you're testing if you have a good pump. Turn on the lift pump as mentioned above, then while it's running, slowly open the bleed on the filter top (assuming you don't have the TURBO POWER COVER on, if so you gotta remove it to get to the fuel filter) until you start getting fuel/air. Bleed it until you quit getting bubbles and air.

J

[vsandme]

So I did what you said, the lift pump kicked on. So I touched the contact with the plug and while the lift pump ran i cracked the bleeder slowly on the fuel filter cover. a little air and bubbles came out initially then solid fuel. I assume the initial air is normal? or should no air have come out?

Now I just need to figure out where the oil pressure switch is and is it possibly to test the existing one before buying a new one?

Also Im not sure if this is a related problem or not. I assume it is... If i hit the accelerator pedal hard most of the time it will sputter and jerk untill i let off....UNLESS I put it in nuetral and rev it while rolling, then back into gear and it wont sputter.

[a5150nut]

I think I would be getting a little clear fuel line on the pump return and see if there is air bubles in the line. Sounds like you might be sucking air some where between pupm and tank.

[sctrailrider]

There should not be any air in the fuel lines at all unless you open the system and change filters..

It does sound like you need a new AC OPS, your LP should run when the motor is running, next time it's running feel the LP to see if it is thumping...

A short clear plastic fuel line at the top of the return line will make it easy to see if air is getting into the system ....

[Big Green]

The oil pressure switch is on the back of engine, near the drivers side cylinder head.

You can get to it from above as it points toward the center of the truck.

If you plan on keeping the truck I would highly recommend the relay kit that Kennedy sells.

Big Green

[vsandme]

Well i changed the switch and the truckran fine... Now it wont start i jumped the lift pump and it wouldnt run until i opened the bleeder... When i close the bleeder the pump goes quiet...

[a5150nut]

Well i changed the switch and the truckran fine... Now it wont start i jumped the lift pump and it wouldnt run until i opened the bleeder... When i close the bleeder the pump goes quiet...

Are you using the key to run the lift pump or are you using the fuse on the firewall?

Are you getting fuel out the bleed or just the air?

[vsandme]

The fuse on the firewall. And no air.

[a5150nut]

The fuse on the firewall. And no air.

So the fuel stops flowing on its own?

Is the fuel shut off soloid clicking?

Have you cracked any injector lines to see if your getting fuel to the injectors?

Do you have a spare PCM you can plug in?

[john8662]

The pump gets quieter when it's under load. Have someone give it power while you crawl underneath and feel whether it's pulsating.

I suspect the pump is working fine.

[vsandme]

Pmd or ip then? It idles well but tje dying is intermittent but has gotten worse and now it will only start and run for a few seconds

[a5150nut]

Only way I know to check PMD is to trade with a known good one.

To check injection pump, there are two methods I have heard of but not tried.

1 thicken fuel with 2 cycle oil
2 pour cold water over pump

Maybe somone will provide additional info. . .

[Warren96]

Like john8662 says, you have air in the fuel. If you open the bleeder on the filter and you get air, this is a symptom not the solution. Look under the truck for a wet spot near a fuel line between the lift pump and the sides of the tank.When you find a wet spot, your air leak is nearby. Good luck!

[DmaxMaverick]

How to test a questionable PMD/FSD:

Throw it into a large body of water (lake, ocean, etc.).

If it floats, it's good. If not, replace.

[vsandme]

Ha...i had an existing pmd mounted to the ip. Plugged it in and it ran. I cracked an injector before and turned it over and got no fuel. Works now so pmd ot was...threw it in a lake and it sank....im kidding but thanks everyone