I know I have almost beat this to death, but im trying to get my truck fixed. The stuttering at high rpm's kills me. Anyways. What should the fuel pressure be on a 12 valve at wide open throttle? Anyone know? What are you guys seeing at WOT driving. Piers told me I should have about 20psi At idle, and about 30psi at 1800rpm's. I have 15 at idle, and about 20 at 2800rpm or so in neutra, and 15 in drive at WOTl. I have already cleaned my prefilter by the lift pump, and I dropped the tank last night, and cleaned that filter out, which wasnt really dirty. If it helped any, it wasnt much. Timing shouldnt be my problem. I guess the next move is for me to replace my lift pump. It runs kind of rough at lower rpm's anyways, and I hear a weak lift pump/low FP will do that to a 12 valve. What do you guys think? And Im guessing Marty Thompkins has the best price on lift pumps? Thanks.

Eric

 

Pressure should be 17-22 psi at idle speed. A minimum of 25 psi should be seen at 2,500 rpm with no load.

If supply pressure is less than 17 psi at idle or 25 psi at 2500 rpm (no load), restrict the fuel return hose by pinching it with pliers. If pressure rapidly returns to normal or above, replace the overflow valve, your pump is ok. If the presssure doesn't climb replace the lift pump.

Marty is a good choice for both the OF valve and pump.


Return line in red below

 

Marty Thompkins ??

where and who?

maybe a website...

Thanks!!

 

He doesent have a website, but here is how to ghet ahold of him:

Precision Diesel Injection and Turbo Inc.
Marty Tompkins
888-734-7349


And sorry, his name doesent have the h in it like I thought it did
I ordered an overflow valve from him, and he is great to deal with.

Eric

 

Hm, lucky you! I can get mine under 10PSI when I really get into the throttle. I think Ive got an air leak someplace but I cant be sure until Ive gone through the whole fuel system and replaced all the rotten stuff. Its not stumbling but it sure doesnt look good on the gauge.
You could try running the feed and return directly into a 5gal can of diesel and see if anything changes. Of course you can only do the idle and 2000rpm no-load test like that.

 

well, I will have a new lift pump on the way tomorrow from Marty Tompkins. Ill report when I get it installed. Hope it fixes this problem. its been driving me crazy for a while now.

Eric

 

Also forgot... Is there anything special I need to know about installing the lift pump? Thanks

Eric

 

Pretty straightforward man

Heres some readin for u on my 96... but it should be bout the same...

Rick

https://www.dieseltruckresource.com/...d.php?t=111775

 

To make it much, much easier buy a stud and nut to replace one of the pump hold down bolts. This way you don't have to try and compress the spring by hand to get a bolt started.

Sometimes when lift pumps are worn out the actuator arm will fall off when you remove the pump. Be careful that it doesn't fall into the engine or your work will turn into a major job.

 

Yeah, replacing the bolts with studs and nuts really works. Using a hacksaw or bandsaw, cut a slot in the stud and then it is easy to use a flat blade screwdriver to screw them in all the way.

 

also, look at what the name of the pump is.

i put a "Carter" lift pump on a buddys truck the other day

costed me over $190 bucks!

they had another, smaller one, for about $80 fits but is not meant to be for the 6bt

 

Ordered from Marty today. Pretty sure its a good one if its coming from him. $95 shipped

Eric

 

About the only difference between Marty's pumps and one from Cummins is that you have to use fittings off the old pump.
No big deal at all.
Don't use teflon tape, it will leak. Permatex #2 is a better choice.

 

Thanks a lot for all the tips guys. How much HP is a healthy stock LP good to on a 12 valve. Seems like a lot of people go to the fass, but honestly a good mechanical pump is much better in my opinion. So how uch can be made with the stock Lift pump? Thanks

Eric

 

A little downward presure on the pump when removing will keep the plunger from falling into the pan.