Fuel Starving on hills

[flathead6]

My son has a '92 atomatic, about 105 k miles. It has begun to starve for fuel on hills. He has changed the filter. I tought maybe tank filter, or weak pump, or bad fuel. Anybody have any suggestions. Thanks

 

[Greenleaf]

Is it because the hill offers a load unto the engine? Or is it the inclined state in which the truck is at?



Does it occure only at, say, half a tank of fuel?



Have you tested the lift pump pressure?



Does the truck have any apprecitable injection pump modifications?



Is he @ WOT when this occures? What is his boost and Pyro on them hills?



Boost and Pyro tells the big story.



Scott

 

[McCRam]

our 91 did that. It had a leak in the fuel fitting on the filter. It was sucking air and eventually vapor locked. You might have a leak somewhere.

 

[flathead6]

This is additional info from my son:

1992 W250 auto with 112K, well maintained.

Tank is full, filter is new, no water. Happens on a long grade or when accelerating hard, even empty. Below about 50 mph seems to not show up, unoticable around town. Only when pulling a long grade or accelerating at speed. No response from accelerator, like when the connecting rod fell off. No difference in exhaust color or amount.

Truck has had minor adjustments to pump by knowledgable Dodge mechanic many miles ago. Boost can be at 8, but lugs down to 2 when the accelerator is pressed at speed. EGTs seem to stay constant.

Seems like it just runs out of fuel. No missing or hesitation, just slows down to a point and then once the "demand" is over it is normal again.

Didn't know if a lift pump or fuel pump either works or doesn't. If the fuel pump is weak or bad what would be a good upgrade for the "next stage"?

 

[Greenleaf]

If the truck is in good order and the pump has only mild tweaks, then at WOT on the hills you should see about 18/22 psi boost and about 1000/1100°F on the pyrometer pre turbo temps.



What is the pyrometer temp at WOT on the hill.



Boost only tells half the story. He could have a boost leak somewhere. The pump would not see the need for more fuel.



I would imagine if it starts well and has no hes hes hes hesit hesitation at all, anytime (other than really cold) then the pump isn't, for lack of better term, putting out.



I'm guessing he sees no black smoke.



-S

 

[Grey Wolf]

It's sounds like it needs a new lift pump... ... .

 

[paccool]

I agree with Grey Wolf. Sounds like the lift pump.

 

[Greenleaf]

Nawwww.



Sounds like the AFC ain't seeing any boost psi.



-S

 

[JLEONARD]

Sounds like the AFC ain't seeing any boost psi.

I tend to agree especially since he's only seeing 8 psi... and EGT doesn't rise.



I'd check for boost leaks first off.

Jay

 

[Dman]

I just had one like this. The fuel pickup assembly in the tank was plugged with algae and what looked like sand/silt. Would pass some fuel and drive normaly but fall on its face towing or under hard acceleration. Never stuttered or anything just wouldn't pull hard.

 

[cojhl2]

Time to drop the tank

This sounds like it could be either as someone else stated, 1) algae in the pickup or my opinion the flex line(s) above the fuel tank.



Things go good as long as the fuel requirement is low, but when a sustained load is applied these lines leak enough air to cause fuel starvation at the pump.



I have the same problem and although I have not yet fixed it,, I have tested using an alternate supply of fuel (5gal can) bypassing the line from the tank and the prob goes away.



I am getting ready to drop the tank or as someone else suggested take the bed off and fix them from above.

 

[bgilbert]

Boost at 8?? Then lugs down to 2??? Sounds like a charge air leak somewheres as GL stated. Does he have a loose intercooler pipe clamp or boot? Has one slipped off?

 

[cojhl2]

The reason boost drops is becasue you cant overfuel enough to provide energy to the turbo. . So this is still consistant with a loss of supply fuel.



Im anxious to follow this problem to its solution.

 

[flathead6]

Thanks for everyone's help. We are having freezing rain/snow right now. When it quits, we will start with the easiest tests first, and go from there.

 

[flathead6]

The truck doesn't seem to consistantly starve out.

Today I ran several hills and punched it at speed. Only twice did it lug down.

At 40 mph with 1 boost & 400F I punched it to 70mph with 9 boost and 700F and no fade.

The other hills I ran 11/900F, 4/600, 11/900F with no power loss.

One hill I started with 10 boost and 800F and choked down to 2 and 600F.

The other hill I started with 10/800F and dropped to 6/700F and then 2/800F before topping the hill. Otherwise it seems fine.

Only seems to do it on hills and maybe after long demands?

 

[Greenleaf]

Still,



You have only 10/11 psi boost?????? You have a problem. No fuel available or no boost to the pump.



A bad lift pump will not hinder the engine in terms of fuel starvation. The VE44 will draw it's own fuel. Even through a failed pump.



Scott

 

[cojhl2]

I still think its that soft line coming out of the tank. The reason it works delayed is because as you drive under moderate load,, the line does not let air in the system and the line therefore is full,, but under more load air begins to enter and does not get to the pump for a short time. .



I think the tank should be dropped and in addition to replacing that flex line the input from the tank should be cleaned as propose by another Thread responder.



Im very interested in this Thread cause my 1990 has had this prob for a number of years,, it just recently has gotten worse so that even if I dont have a trailer hooked the engine begins to stall down after a real short time on a long grade.



Like I said earlier I ran a test (and you might do the same) I ran a hose from a 5gal can directly to the lift pump,, problem went away. The prob therefore it seems to me has to be in the line I replaced withthat test, namely the line form the tank to the lift pump.



Be aware,, you can only run for a short period cause you are still returning to the main tank with the return line

 

[flathead6]

The truck doesn't seem to consistantly starve out.

Today I ran several hills and punched it at speed. Only twice did it lug down.

At 40 mph with 1 boost & 400F I punched it to 70mph with 9 boost and 700F and no fade.

The other hills I ran 11/900F, 4/600, 11/900F with no power loss.

One hill I started with 10 boost and 800F and choked down to 2 and 600F.

The other hill I started with 10/800F and dropped to 6/700F and then 2/800F before topping the hill. Otherwise it seems fine.

Only seems to do it on hills and maybe after long demands?

 

[flathead6]

It barely made it home last night. I ran the interstate to Lou on cruise at 80 mph with 8psi boost and 800F EGT with no problem. Coming back it did the same but seemed to stumble some every now and then. Once off the interstate it shifted all the way down to 2nd and 1st to pull Bald Knob hill. Once back out in the flat it did OK.



Can you ask the forum if a fuel lift pump can be “weak”. I thought they either worked or didn’t. When I changed the filter I tried to prime it by manually pumping the lever but it never “tightened up”. It was like it wasn’t doing anything. I had already filled the filter with diesel and it started right up anyway

 

[Greenleaf]

A weak lift pump will not always show up in terms of drivability problems. The VE-44 has it's own internal pump that pulls fuel.



If I understand you correctly... ... you changed the fuel filter, filled it with fuel and it started right off? That indicated to me the pump is working. If you have indeed a weak/failing pump and break prime. , the engine is sometimes hesetant to pick up fuel and run.



You need to begin testing, with fuel gauge etc.



-S