'92 f250 power loss

[wildlifoodin]

hello. i'm currently crossing the country in a '92 7.3 idi and have been pulling a small amount of air into my lines. Eventually it builds up in my filter and power is lost. I tighten my fittings, figuring it must be behind my lift pump, but still pull air. Any DIY ideas of how I can locate the leak? other ideas? thanks.

 

[Shadetreemechanic]

Fuel filter should have positive pressure on it because the lift pump puts out way more fuel than the filter uses.
Is your fuel filter light coming on? That indicates negative pressure in the fuel filter housing.
Check lift pump. Disconnect the output from the lift pump and turn the motor over. You should be able to fill a pint jar in less than 30 seconds. There is the actual output volume for the lift pump somewhere on this forum, but I don't remember it off the top of my head.

 

[wildlifoodin]

I have a clear inline filter before injection and that fills with air as well as the fuel filter. Fuel filter light used to come on, but hasnt recently even though it continues to take in air. The lift pump is new and working, making me think its something before it. thanks for replying quickly.

 

[snicklas]

Have you replaced the rubber line from the frame to the lift pump? How much fuel in the tank?

 

[Shadetreemechanic]

You have a fuel delivery issue. The engine should not be sucking air between the lift pump and the injection pump unless the lift pump is not getting enough fuel to the filter, or the filter is clogged. If the lift pump is good, you need to check for obstructions between the pump and the tank, the usual culprits are the tank switchover valve going bad, or a bad fuel pickup in the tank.

 

[wildlifoodin]

i recently replaced the soft line before the lift pump. I've tightened those hose clamps and the fittings going into and leaving the pump. i'm now refilling/reprime-ing the filters every 100 miles and recently started blowing deep black smoke when climbing steep hills. its cold now too, around 0 where i'm at adding another element. thanks again you all.

 

[Shadetreemechanic]

How much fuel sprays out of the shrader valve on the filter head if you push it with the engine running? It should throw a good stream of fuel.
I think the black smoke is red herring to your problem. That sounds like high elevation.

 

[wildlifoodin]

yeah, the shrader valve will spray the accumulated air, then fuel.

 

[Shadetreemechanic]

So that means you have pressure at the head, not suction, so look somewhere between tank and lift pump.