John Faughn

When I needed to replace mine , I remember something like 2 sizes both bolt on to either the 5.9 or 8.3 , little bigger on the 8.3 , more volume .
Then how there made - equal performance but cheaper , bronze vs. Alu cylinder , sell cheaper or more profit ?
I took mine old one apart , found that the check valves were coming apart , used to be able to find those in the old days to rebuild gas pumps , no chance now .

BearKiller

I had been keeping an eye on those $36 pumps for over a year.

The minute this thread got around to giving the comparison results, there were the same amount of pumps available as there had been for weeks, 26, less one.

I immediately got on the phone and got TWO; at that time, there were nine left.


I just looked; and now, there are only five.


I bet that girl is wondering why those pumps, that hadn't hardly sold at all, are selling like long-handle-drawers in Alaska all of a sudden.

kiszka6911

No real updates, as the holidays have got me waiting for my GDP big line kit and pressure guage. I am also waiting for A-tech (Summits wholesale side) to ship me my Aeroquip adapter & fluidamper. The fittings are made right here in Jackson, Mi but no local shop has one, they can order it. I have a few relatives still working there so they are trying to get one for me.

John,

The only reason I see there being a unit with a bronze sleeve is so that all of the expensive to machine castings can be machined the same, they then just press in the sleeve and hone it to size. I will make an assumption that all of the smaller VE pumped motors got the smaller bore pumps, and the p-pumped or motors over displacment of X got the larger bore.

It may have been the reverse situation, where the always put a sleeve in the pumps, but the p-pumps needed more fuel volume, so they just removed the sleeve, increased the piston size to match, increased the spring pressure to meet the p-pumps requirements. They most likely never expected us pushing near 500 HP out of VE pumped engines so there was no need for a high volume low pressure version.

kiszka6911

I now have the 2nd gen (large bore) piston pump installed with the softer spring from the 3936320 pump. So far the only thing I have noticed is the truck seems more responsive starting of in second gear from a light. We also replaced all the hard lines from the lift pump to the filter and the filter to the IP all with -06 (3/8") parker hose and push locks. I also installed one of glacial's fuel pressure ports so I can test the different pressure springs. I am using an Aeroquip 14mm x 1.5 adapter in the fuel pump. We plan on changing this to the vulcan (Parker) steel part as I have heard the anodized aluminum parts work harden and break over time.

As soon as the temperature climbs out of the single digit air temps I will get the pressure guage installed and do some testing. I plan on trying the 3936323 sping next as it falls in between the 1st gen and 2nd gen in stiffness.

Caver Dave

Anthony, can't wait to hear what you're getting for FP!

I'm currently running stock injectors (don't really have plans for larger), but want the piston pump for all the obvious reasons.

Would you mind posting the part numbers for all the various fuel line parts you're using? IIRC, the GDP bigline kit is for a late model 24V? Aside from the larger tubes advantage, I'm converting to WVO (in the next month or so) and need the soft lines to feed the IP from 2 separate sources (#2 & grease)... plus the ability to *easily* plumb both fuel pressure & temp gauges just before the IP.

kiszka6911

I ordered:
From GDP:
(1) 12mm x 1.5 to -06AN adapters stainless steel
(1) Big Line for a 98.5
(1) additional 90 elbow for -06 AN to 3/8" socketless
(1) additional straight -06 AN to 3/8" socketless

From Vulcan
(1) 14mm x 1.5 to -06 an adapter zinc plated
(3) Viton 12mm O-rings
(1) Viton 14mm O-ring

BearKiller

A. Kiszka,

Please do me a favor and check the thread size of the lift-pump bolts, next time you have them out.

I intend to find some studs to replace the bolts, thus making lining up all the components a much simpler task, i.e. gasket, spacer, gasket, pump; hanging head-down under the hood, and keeping all this stuff in proper orientation, while inserting bolts through all four layers and threading them into the block, can get to be a handful.

I had the sizes written somewhere; but cannot remember what I did with them.

Thanks.

wollfgang

I bought one of the 3936318 pumps on ebay and it also had the 1.019 piston with the bronze sleeve, I didn't measure the spring but I have all I can do to try and hold it with the spring compressed. I had hoped it would have the larger piston but it doesn't. I will be using a pressure regulator when I put it on so I guess as long as it's at least 20 psi I won't complain.

gary

BearKiller

I already have the 3936320 (old number) on my truck.

I bought two of the 3936323 pumps for possible replacements on some of the other trucks.

I went ahead and got enough gaskets and spacers from Cummins Crosspoint to install them when necessary.

I may stick one on my truck, in order to compare pressures.

Does anyone have any idea what kind of pressure to expect from the 3936323 ??

Thanks.

kiszka6911

It sounds like 3936318 is a high pressure version, the spring on the second gen pump was like that. I could barely hold it in or press it to the bottom.

So far I haven't had much luck finding a spring supplier that has a stock spring that meets the pumps envelope.

Bear killer,

The "23" pumps spring pressure felt like it fell between the 2nd gen and the "20" pumps. I would guess this would put the pressure in the 20 psi range.

winkdemon

ok so u guys kind of lost me , so u take a gen 2 pump and change the spring ? and what spring do u put in it ? and what should your fuel pressure be ??????????????????????

kiszka6911

well the VE pump has a maximum input fuel pressure of 15PSI, the 2nd gen pump and 7100 pump can take a much higher input pressure. The second gen piston pump has a larger bore, more volumn but a higher input presure. So by putting a first gens pump spring in a second gen pump you get a low pressure high volumn pump.