1997 12 valve problem please help
 

when the truck is at idle you can hear a fairly loud clicking sound. I dont know if its happening while driving because you can't hear it over the wind. anyways someone told me that it could be a lifter pump. The truck still has good power however when i remove the fuel cap, there is a fairly significant vacume hiss. Could these two things be related. any help or suggestions would be helpful for a diesel newbe.

Yes, while I have yet to experience this....a clicking sound could very well be the lift pump.

Does it click the same all the time or does the noise vary?

Might be a good idea to check fuel pressure. Do you know how to do that?


Doubtful (in my mind anyway) the vacume hiss and clicking are related.

Dont quote me but it also sounds like it could be the KDP. Is it coming from the engine compartment? If you take the oil fill neck cap off does it get louder?"give:

you think so?

Ive never heard of that...Usually the Dowel Pin shoots through the case front and you have a rather good oil leak.

The KDP sounds more like a knock from the ones I've heard. I agree with Evil to check the fuel preasure. They start to click when they start going bad.

Andy

while the truck is running reach down below the fuel filter and locate the primer plunger bulb thingey on the lift pump on the driver side of the block and put some pressure on it.... like push it in about 1/4-1/2 inch like if you were priming the fuel filter..... press and hold it.... if the noise quiets down then i'm 99% it's the lift pump....

The clicking is pretty much the same noise level all the time. and no i don't have a fuel pressure guage, is there a way to check it without one, other than just with the seat of your pants which to me seems pretty strong with no hesitation or lag with i would expect with a lift pump failure.
would a fuel additive help if it was say a sticking valve in the lifter pump?

try what i mentioned above.... it'll click and still be pumping..... it's only when the truck won't run when it is :q: bad :q: you could try adding a quart or 2 of 2 stroke oil or some new non detergent motor oil to see if it quiets it down some.....

oh and it's not a lifter pump.... it has nothing to do with the cam shaft and lifters or valves.... it's the lift pump for fuel.... it the mechanical pump that pumps it to the p7100 injection pump....

This is a good tip.

If the lift pump is clicking....its very likely shot and no additive is going to help.

I can step you through checking fuel pressure but you will need to buy a few things you probably dont alreayd have. Its best to actually check the pressure then you know for sure.