More power when running out of fuel

[FordGuy100]

Lean doenst apply to diesels. They can idle around 200:1 air:fuel ratio.

It advances the pump timing a ton, when it starts starving for fuel.

 

[ZWilson07]

Lean doenst apply to diesels. They can idle around 200:1 air:fuel ratio.

It advances the pump timing a ton, when it starts starving for fuel.

So I guess just the huge advance in the pump timing causes a sudden "surge" of power before it either A. gets fuel back and goes back to normal or B. you are actually basically out of gas and it will start to cut out and run horribly? I wouldn't think advancing the timing like that would actually increase power for lack of a better word.

That seems to be what happens to me. Ive noticed it a while back that it will occasionally do that surge with low fuel but that is probably because I am always trying to see how far I can go . No fuel low light plays mind tricks on me but to be fair I have only ran it low enough to cause it to start cutting out once and then I just switched tanks to the other that was full; just more trying to see how far I can go on the gauge.

 

[Zaggnutt]

So I guess just the huge advance in the pump timing causes a sudden "surge" of power before it either A. gets fuel back and goes back to normal or B. you are actually basically out of gas and it will start to cut out and run horribly? I wouldn't think advancing the timing like that would actually increase power for lack of a better word.

That seems to be what happens to me. Ive noticed it a while back that it will occasionally do that surge with low fuel but that is probably because I am always trying to see how far I can go . No fuel low light plays mind tricks on me but to be fair I have only ran it low enough to cause it to start cutting out once and then I just switched tanks to the other that was full; just more trying to see how far I can go on the gauge.

I have the same issue, but the key here is that it only happens when you are nearing 1/4 tank. Pay close attention to when it happens also. I would bet that it happens when you pull out from a dead stop, go up a hill, or go down a hill. There is a lag time here, but if those are the scenarios you have a rotted of fuel pickup.

You are right about the timing advance. It is the self-regulating nature of the Injection Pump to advance the timing due to lack of fuel - it is trying to compensate for air that contains no fuel - so the advanced timing happens while it is drawing irregular and low quantities of fuel. It is just the pumps way of mechanically compensating....

If my truck ran like that all the time I would have a shoe box full of speeding tickets and an ******** that would make ****** takers envious...

 

[Clb]

Lean is mean. Til it seizes up. Ask any racer.

+1
Any 2 stroker leaned out will run like a rappedape till it friezzzz
Thats most likely why these do not have fuel mixture adjustments

 

[bbjordan]

It advances the pump timing a ton, when it starts starving for fuel.

Please explain how this happens.

 

[Zaggnutt]

Mine is surging while running level with over half tank now. Didn't start til recently, but I also stalled it several times til I realized I could only run it to 1/4 tank. Got the tank, shower head, steel line, and compression fittings... now all I need is the time. Anyway, I've noticed the difference is the surging only, no stalling when I am dealing with air. I'm guessing I have gunk or junk jammed into the fuel pickup, but I guess it could also be the injector pump going bad? It doesn't seem to surge on the front tank, so I guess I've isolated the problem area!

 

[FarmerFrank]

My 86 started this just after i put a different pick up tube and sender in the front tank to try to get my guage back but it only does it on a sharp turn. Like when your sitting in a turning lane waiting on traffic, when you make the turn and get on the road itll starve itself for a second then come back alive. This is with a full tank of fuel too

 

[Agnem]

Here's the deal. These pumps have to run with a certain amount of case pressure. The case pressure is part of what maintains the advance mechanism settings. When you gulp air, the air goes into the case... hence lowering the hydraulic fuel pressure inside. Hence... more advance. The "***** ape" running is the result of over advanced ignition. No, you don't want that. It's eating up your glow plugs as that is happening, but thankfully you run out of fuel before it gets serious.

 

[Zaggnutt]

My 86 started this just after i put a different pick up tube and sender in the front tank to try to get my guage back but it only does it on a sharp turn. Like when your sitting in a turning lane waiting on traffic, when you make the turn and get on the road itll starve itself for a second then come back alive. This is with a full tank of fuel too

Is your tank clean? I wonder if the parts that rotted off originally are sliding around in there... When you turn maybe they are getting sucked to the pickup or just getting in the way.

 

[Zaggnutt]

.....But I am a diesel noob so my advice and opinions are questionable unless I have done the work directly... Go ahead, ask me about leaf springs, ball joints, glow plugs, brake lines, 4x4, blah blah blah..........

 

[79jasper]

Is your tank clean? I wonder if the parts that rotted off originally are sliding around in there... When you turn maybe they are getting sucked to the pickup or just getting in the way.

That's what happened on my Powerstroke.
I had a few month old fuel pump. Decided to swap it out. (Yeah look at the fuel pump location)

Some reason I thought the Powerstrokes went to a better design, so it didn't cross my mind.
I would drive a ½ mile (if I was that lucky) then sit and repeat for 25 miles.
I extended the pickups and blew out the lines. (I suggest running the opposite line in the other direction, ask me how I know)
All's well so far. Cept a minor leak at the high pressure side of the lift pump.

Sent from my USCC-C6721 using Tapatalk

 

[FarmerFrank]

The only thing wrong with the first one was the gauge wouldn't work. It was a gasser one so i already had rubber hose to the bottom. On this one I put a T fitting on the bottom and secured it better. This weekend if it gets near 20 outside ill throw the old one back in. I must have missed something small somewhere.

 

[Zaggnutt]

That's what happened on my Powerstroke.
I had a few month old fuel pump. Decided to swap it out. (Yeah look at the fuel pump location)

Some reason I thought the Powerstrokes went to a better design, so it didn't cross my mind.
I would drive a ½ mile (if I was that lucky) then sit and repeat for 25 miles.
I extended the pickups and blew out the lines. (I suggest running the opposite line in the other direction, ask me how I know)
All's well so far. Cept a minor leak at the high pressure side of the lift pump.

Sent from my USCC-C6721 using Tapatalk

Any idea how much air pressure the lines can handle? I'm dropping the front fuel tank to replace it, but the rear tank has been giving me more trouble with the surging. I plan on blowing the lines out for now til I can drop the rear and clean out/extend the pickups...

 

[79jasper]

I did lowest setting, which was 20psi or so on the compressor I used.
Start lower if you can. Maybe 5psi.
You'll know if something is clogged.

Take the line off at the lift pump. It can be damaged by too much pressure. How much? I don't know.

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[Zaggnutt]

I did lowest setting, which was 20psi or so on the compressor I used.
Start lower if you can. Maybe 5psi.
You'll know if something is clogged.

Take the line off at the lift pump. It can be damaged by too much pressure. How much? I don't know.

Sent from my USCC-C6721 using Tapatalk

Okay, will do. Yeah I read that somewhere else too. Thanks for the advice.