Lift pump diagnosis
 

All for a 91 1 ton.

I'm a total newbie when it comes to diesels (as if my 8 million posts haven't made that clear). I need some help figuring out if my lift pump is toast or not. Here is what I know:

1. On the engine, I get no fuel at the injector pump inlet when cranking the engine.

2. If I manually pump using the primer I get good flow at the inlet. This tells me the filter is ok and the lines are intact.

3. The lift pump seems to be intact, no broken arms, or anything like that.

4. Off the engine, the pump seems to move a lot of liquid. I put the input hose in a glass and manually moved the arm and it pumped a good flow.

Inside the hole for the lift pump there seems to be a cam or some sort that moves the arm. What is this driven off of? I'm hesitant to stick my finger in there while the thing is cranking over to see if it is moving or not.......

Thanks for any info. I'd really like to figure this one out.


stu...

I think that would be the cam, dont be stickin yer finger in there while its crankin or it might come out shorter. sounds odd to have flow while manually working the lever. Maybe your moving it more than the cam does when crankin it. a lift pump is around $45 or so so it would be in your benefit to replace it anyhow. cheap insurance to keep your injector pump alive.

I'd throw a new lift pump at it. The lift pump runs off the cam, and it's unlikely that the cam is broken. Best price I've found is at http://www.usdieselparts.com/