piston lift pump pressure ?'s

[sdstriper]

I measured my P-Pump piston lift Pump No. 3936316 free length at 1 25/32 inch.

It was off QuickServe, read it myself. It sure could be outdated or wrong. Again take it for what it's worth, I am definitely not an expert but anything I post here is meant to help so by all means if it is wrong or out of line I will not be offended if corrected.

 

[therabbittree]

after I took out one spring it makes 20-25 vpsi ans draws down to 15psi or so. . but now it leaks a little a drip drip thats constant when I first put it back on it was leaking when I used the plunger. . any one have any tips to prevent the leak?. .

Thanks

Deo

 

[Greenleaf]

The school bus pumps squirt out fuel when I activate the primer button (plunger) They do not leak when the engine is operating.

 

[therabbittree]

Mummn it was squirting out when I used the plunger . . I noticed the the other day when I was parked and not running on my Uncle's paved drive way. . (mine is dirt . . )and I was like, crap I got a leak. I crawled under, it was diesel and looked to be from the lift pump. Mummn I have to investigate further maybe it is the fittings. .

Thanks,

Deo

 

[Greenleaf]

after I took out one spring it makes 20-25 vpsi ans draws down to 15psi or so. . but now it leaks a little a drip drip thats constant when I first put it back on it was leaking when I used the plunger. . any one have any tips to prevent the leak?. .

Thanks

Deo

I am unaware of what spring you removed. There is only two that can locate. One is on the primer plunger (light duty/ silver in color) and the other is the piston return spring. The return spring is VERY HEAVY and black. I seriously doubt you removed the return spring. The pump would not longer function.



There is a seal down inside the primer plunger bore. Looks to be a lip seal. The guys over in the 12 valve engine section mentioned something about an O ring. I think everyone has gotta be on drugs, cuz I don't see ANY O ring inside these pumps. It was mentioned that when the pump begins to leak, you simply replace the O ring. Where is there an O ring, I ask you.



I have to wonder if Cummins has a family of lift pumps. Some with DUAL SPRINGS and some with O rings. Or maybe it's just me... ... ... . it makes no sense.

 

[Greenleaf]

Lift Pump Update

I investegated further and disected a lift pump from a 1995 model year. This pump is an A/C model part number 3925709.



Inside I found three (maybe four) O rings and TWO plunger return springs.



I doubt there is a rebuild kit. These pumps are outdated and replaced with the Carter. The two pumps are interchangable but look much different.

 

[therabbittree]

cool. . yeah the spring i left in the pump is the one that holds the poppet valves in place. I should have checked the part # from that pump when I did the install... I'm thinking my drip is from teh top metal line. . i couldn't break it free to remove the pump . . so i think my trying may have loosened it i have to try to tighten it a little now.

Thanks,

Deo

 

[Greenleaf]

You should have posted the pump number, or I should have thought to ask. Anyrate, I found the extra spring you mentioned and appologize to the 12 valve guys for assuming they are on drugs. (Well, they should have SAID the O rings are on an A/C lift pump and not assume they are ALL and A/C lift pump )



-S

 

[dieselcruiserhead]

can someone post the year/application and/or part number for the low flow piston style pump?





If they are interchangable, I imagine it needs the same part numbers / spacer etc shown on "the other" cummins site?

http://www.dieseltruckresource.com/dev/showthread.php?t=93722

 

[dieselcruiserhead]

Never mind found BGilbert's Reader's Rigs Gallery...



https://www.turbodieselregister.com/user_gallery/displayalbum.php?&userid=13880&albumid=17221

 

[dieselcruiserhead]

at some point I am going to put one of these on a 4BT. I will post up fuel pressures, see if there are any differences in pressure between the two...