I finally got my new lift pump put in today. I used the take the front tire off method and reach thru the fender well. That worked great doing it that way. After getting the new one on, my idle went from 650 to 765. Wow what a difference it made it in running. Then we decided to work on my pump a little. I turned the power screw 2 1/2 turns. The lock collar is still on and I have not bottomed it out yet. MAN, I thought my truck run strong before and it smoked. WOW, does it run like a different beast now. And let's not forget the smoke factor now. I can be going 55 mph now and tep down on it and it takes off. Before it would just slowly accelerate, now you step and your gone. My temps are only 1050 if I really stand on it. Before I could only get 22 pounds of boost if I was pulling a loaded trailer. Now I can hit 22 pounds empty. Now I just can't wait to get my HX-35 on and my Pod's in.

Bill

 

Excellent! Why did you have to change the lift pump?...just wondering if there is some hidden power in mine...other than tweaking the pump which I am tempted to do....

 

[quote author=Craig93 link=board=9;threadid=20990;start=0#msg196930 date=1066184331]
Excellent! Why did you have to change the lift pump?...just wondering if there is some hidden power in mine...other than tweaking the pump which I am tempted to do....
[/quote]

Mine was shot. It wouldn't pump any fuel what so ever. It was starving my injection pump and making it do all the work. That was obvious by the over 100 rpm gain at idle by just putting the new one on. Also I was making oil. The old lift pump was letting oil go straight into my crankcase. Most of the time when the fail, fuel runs out the weep hole on the bottom of them. But not on mine. Later when I get the time, I am going to add fittings to the top of the lift pump so I can add a fuel pressure gauge.

Bill

 

Glad to hear everything worked out..

Once you find a little boost of power, you start looking for more and more.

I had about 22 psi boost till I fooled with the AFC and the Governor to bump it up to about 25. Sounds like your timing is pretty good if your temps are that low.

Keep on tweeking..

J-eh

 

How much pressure does the lift pump put out?

Paws

 

From notes I have gathered its around 10 psi at idle I think. I know the newer trucks run 15 psi, but I don't know if our rigs were at that level.

J-eh

 

What are the typical symptoms of a weak or dead lift pump?

 

[quote author=bigredbrick link=board=9;threadid=20990;start=0#msg200155 date=1066883957]
What are the typical symptoms of a weak or dead lift pump?
[/quote]

Loss in power, smoke, idle. Rough idle, hard starting. Leaking fuel from the bottom of the lift pump or you could be making oil as it is letting diesel in the crankcase. Those are just off the top of my head.

I had all those symtopms except the leaking out the bottom, that's why mine was making oil.

Bill

 

Bill,
Power on pulling grades seams weak, cold idle is a little rough, hot idle is low and real rough and when I changed the fuel filter last weekend that priming lever doesn't seam to work. Not much smoke except for the "puff" on start up and no leaks.
Is it a candidate for a new pump?

Chris

 

[quote author=bigredbrick link=board=9;threadid=20990;start=0#msg200166 date=1066885065]
Bill,
Power on pulling grades seams weak, cold idle is a little rough, hot idle is low and real rough and when I changed the fuel filter last weekend that priming lever doesn't seam to work. Not much smoke except for the "puff" on start up and no leaks.
Is it a candidate for a new pump?

Chris
[/quote]

Well that sounds exactly like my problems, minus I had the leaking into the crankcase problem. Did you make sure your pump wasn't on a cam lobe when you tried to pump it. They can get stuck on top and you have to bump the starter to get it off.

When I changed my lift and started the truck I gained a little over 100 rpm's at idle. That tell me how much fuel the injection pump wasn't getting.

Bill

 

When I said the priming lever didnt seem to work I should have said I can push it down with no resistance felt, like there is nothing there. I guess the best way to tell is to hook up a pressure gauge. How do you do that?

Over and out, Chris

 

I have a problem starting my ole 91 after it sits a day. I crank the motor over for up to 10 seconds and it still doen't start unless I pop the hood, pump the primer 3 -5 times and it starts right up. After changing the rubber fuel lines it still did it. Could it be the lift pump??? ???

 

[quote author=deereman link=board=9;threadid=20990;start=0#msg200543 date=1066954318]
I have a problem starting my ole 91 after it sits a day. I crank the motor over for up to 10 seconds and it still doen't start unless I pop the hood, pump the primer 3 -5 times and it starts right up. After changing the rubber fuel lines it still did it. Could it be the lift pump??? ???
[/quote]

I would say no because you can get the lift pump to prime. I think you have a air leak some where. But I could be wrong, someone chime in here.

Bill

 

When the motor cranks, will the lift pump prime as if you do it by hand?

 

The design of the pump is such that if the pivot for the lever that runs off the cam was worn out, the pump would not be real effective when cranking due to the reduced stroke, but pushing the priming lever would still pump fuel. Not sure if this is your problem, but I could see it happening. It's a cheap and easy job, throw a lift pump at it and see what happens. Got mine from these guys, worked fine once I used blue goo instead of the paper gasket.http://www.usdieselparts.com/ $32.51, listed under engine parts.