Engine/Transmission (1994 - 1998) Odd noises since installing 12valve lift pump.

[RonA]

I installed a 12valve lift pump a few days ago. This is the first one I've tried. I get this odd fluttering sound when I am taking off or have to give it a moderate amount of throttle at lower rpm. It is tied to engine rpm. Never heard it before. It's not turbo related. Sounds like a small valve opening and closing in time with the motor.

 

[bgilbert]

You've got good ears Ron lol. I have no clue, so I'll ask questions back so I don't look like it. Have you checked your fuel pressure with this new LP? Is it a 3936316? Is the 24V cam different than a 12V cam, and would that account for this weird sound?

 

[Greenleaf]

Gotta be something to do with the cam lobe/pump plunger. There has to be just the right amount of space (preload) on the plunger.



Scott

 

[RonA]

Ouch. This is going to hurt. Having never seen a 12 valve before I bolted the pump up to the block with a gasket in between. Looked pretty straight forward. I guess that there is some kind of strainer that spaces it out a bit. Now I get to take it off and see what i ruined. I put a filter before and after the pump. Guess I should ask more questions.

 

[Greenleaf]

Ron,



Not clear what engine this is mounted to... . a 24v I assume??? The Industrial 12v engines use a shim plate with two gaskets and the Dodge trucks use a fuel heater that mounts here (I believe?) so it's a matter of spacing to achieve the correct plunger stroke/preload. I simply installed the shim plate when bolting one onto my '92 model 12 valve.



-S

 

[bmoeller]

Ron-



You had FASS before, correct? They don't create the pressure spikes that the mechanical lift pumps do. That is the only thing I can think of, off hand. My truck does the same thing. If you pit a fuel pressure gauge in (without a snubber/needle valve), the needle on the gauge is ALL over the place.



I think with a steady, constant pressure, it would smooth the engine out.



The pump install is straight forward.



Where is your fuel pressure at 2200 RPMs? Mine is up close to 40psi. Hard to tell, can't steady the needle. Don't have a needle valve, just a pair of vice grips to sqeeze on the rubber line, to attempt to smooth it out.

 

[RonA]

I got a hold of Mark at PDR and he told me how thick to make the shim. Wife is on the way to Cummins West to pick up another pump. I have some scoring on the cam. I am polishing that right now. I'll machine a shim and try this again.

 

[RonA]

You are right about the fass delivering a constant pressure. But they don't deliver enough pressure. Mine was at 24psi which was the most they were comfortable with. It died at about 20k miles. I have an Aeromotive pump but don't want to use it if I can get away with the mechanical pump. My pressure was at about 20 at idle and 35 or so at about 1700 when I checked the mechanical one.

 

[bmoeller]

Hmmm. Have you looked into the RASP? It is mechanical.

 

[RonA]

If the stock pump will work for me, that is what I would like to use. Now that i have pre and post filters and the right spacer between the pump and block, I should be ok. I'll put the gauge on it tomorrow. New pump was 180 dollars from Cummins. Ouch! Last one was alot less at PDR. But at 4 o'clock on friday I couldn't be picky. I have to deliver this load to SF tomorrow. It's back together and started right up. It's alot easier to get to the bolts through the fender well than from the top or bottom. Figured that out about an hour later than I should have. Thanks for the post about spacing Greenleaf.

Ron

 

[bmoeller]

$180, ya ouch. I bought mine for half that, at the local C-IH dealer.

 

[Greenleaf]

Speaking of gauges. The electric gauge I use will not bounce. It's a Westach unit. They have different gauges depending upon the estimated pressure it will monitor. Not sure if they have one that will surpass 30 psi though... ... ... ?





GL

 

[Joe G.]

I have a 40 PSI gauge. I asked them if they have gauges other than 30 and 60. The reply was "sure, what pressure do you want?"