I just had to replace the lift pump and the problems started.

See the discussion here:https://www.dieseltruckresource.com/...p-t297194.html

The pressure is consistently 28-32 at all times. Now it loses the prime after only 1/2 hour.

DONE - I have replaced the supply line all the way to the tank. Checked the filter can gasket, replaced the short piece of rubber return line behind the filter (this had a known split and was leaking fuel).

TO DO - I'll pull the heater strainer again tonight to verify that the gasket is good, I'll pull the elbow hose between the pump and heater to see if there is a problem there and replace the clamps.

What is the way to find where there may be an air leak? Where else could it possibly be?

 

While you have the prefilter apart, just eliminate the heater, put the prefilter back on.

The 90 degree hose you probably should just replace, it wasn't bad from Dodge the last time I bought one, one less thing to worry about. At that point you have just about covered it, you are into hard lines and weird problems from here. One thing, does it do it with a full tank as well? I know you replaced the strainer in the tank, perhaps a crack in the pickup tube when it went back together? That usually is eliminated by filling the tank though, that's why I asked.

 

Oh yea, one other thing, replace the return line all the way back to the tank as well........... And for giggles, are you sure you don't have a pinhole rusted in the tank module lines where they come out? I can usually just reach up there and feel the lines for sale.

 

I'll go the the dealer today to get the elbow hose (04883978AA) as well as the strainer kit (04762962). Thankfully my truck is in great shape with minimal undercarriage rust/corrosion. I was able to get a good look at things when I replaced the supply line and didn't really see any rust concerns around the module tubes. I'll pick up some 5/16 diesel line and replace from the engine to the tank as well. I have not dropped the tank or removed the bed due to a full tank and a fifth wheel setup. I was able to do the supply line from the wheelwell with the wheel off.

It currently has a full tank right now so I am unable to test any further regarding the pick up tube in the tank. (I didn't replace the strainer in the tank, I meant to say I cleaned the heater screen earlier...) My gut reaction is that it would be OK right now.

 

Yep, if the module line is cracked, it will not usually show up with a full tank. I would almost bet the elbow hose is your culprit.

 

Had to order the elbow from the dealer.

Just came in from the shop. Took off heater bowl and made sure all surfaces clean and straight and the gasket in good shape. CAREFULLY put it back on and verified with a mirror that the gasket was in position when I finished spinning it on. Tightened snugly but not enough to damage the gasket ring.

No difference.

Took off elbow and factory spring clamps. Visually inspected the hose and tried to see any cracks by flexing it. Reinstalled with new worm clamps. Still will replace when new one gets here.

No difference.

Later pushed primer like last night to pressurize system. Noticed that there is fuel coming out of the pump when pressing the plunger. Never leaked during running though. Fuel is actually coming out of the plunger area and not from any fittings.

Now can't even get the pressure to rise. I called the parts store and they are getting me a replacement pump for the one I just put on.

I will sell this truck in a heartbeat if the right offer comes along.

 

I used to train field engineers for IBM sys/38 computers. The hardest thing to get into their heads was:

If you walk up to a running machine, do something to it, and it now does not run.


It's what you did.

 

Hang in there man, once you get all the little stuff out of the way, there are very few better more reliable trucks to own.

You think we have it bad, look at the Common Rail years............

 

Can't work on it till the weekend now. Went out and bought right fittings to run supply rubber line directly to the heater, no metal lines at all. Picked up a lift pump since it may be that the one I just put on is bad. Picked up a ton of injection line clamps to make sure none of the worm gear clamps are leaking. I'm just going to start back at the tank and work forward. Have a full tank so I may try to drain it and drop it as well. That would really go from start of system to finish. Heat of the moment is very frustrasting. I'm sure I'll get everything clicking but it is driving me crazy right now.