I decided to start a thread with all of the research I have found about the piston pump applications. The goal here would be to provide alternate sources in case your stranded somewhere.

Piston pump p/n's.
Orginal Cummins P/N: 3936320
Superceeded by: 4944714
Superceeded by: 4988751 quoted $170 by local cummins dealer. Quoted $150 from local IH truck dealer.

Someone mentioned the Case/IH p/n's were the same just replace the first 3 with J and you can get the same parts. This is true, the p/n for the low pressure piston pump from Case/IH is J936320. The local CASE/IH dealer crossed this to a New holland p/n 87648730 which I have coming for $130+ground shipping, the had this one the shelf.

The 3936320 application is a 4B/BT/BTA 3.9L for a Case 5120 or 5220 tractor.

Cummins made lift pumps with p/n's 3936316-3936324 which are the same form factor just unknow applications, volumes, pressures, and internals. I recently found p/n 3936323 on ebay for $36.00, application was supposed to be for a 4b, I decided to buy it just to investigate the internals. In CASE/IH this p/n crosses to the same tractor application listed above.

So could the be the same internally? More updates to come as I learn.

 

Thank you.

Good Job.

I have been intending to do the same, but have too many irons in the fire to get the research done.


I also spotted those $36 pumps and have intended to install one, just to see what kind of pressure/volume it put out.


Very interesting to know the tractor applications and part-number cross-references.

 

I'd bet the return spring is different from pump to pump. Maybe not. Don Tanklage on another site did some R&D, and posted some results.

I'm going to keep an eye on this one.

Daniel

 

Could you find that and point us in the right direction, so we can compare what he found with what is here ??

Thanks.

 

I found it, is over on TDR.

I am not a member over there so I can only see the first post. It would be interesting to see the rest!


http://www.turbodieselregister.com/f...pressures.html

 

That was the jest of it. The rest was mostly arguing, I mean professional discussion back and forth on some specifics between 'em. Mainly that different applications had different pressures (something about springs) and to watch the front seal with higher pressures.

But then again I understand how that stuff works about as well as an auto tranny .

I could cut and paste if you wanted to follow the action as long as that is not a violation of either forum...

 

I recieved my Case/IH/New Holland version of the low pressure pump today, it appears to have the correct spring and bronze sleeve. Price was $130+shipping.

I measured the piston which measured 1.019".

 

I measured the piston on the 2nd gen piston pump, it meausures 1.181" the first gen pump is 1.019"'

Doing some basic math I should be able to calculate the GPM of the two pumps, see below. The key difference between the two pumps is 25% greater volume on the 2nd gen pump, this is directly related to piston's area.

The spring design is the same for both pumps, both ends diameters are the same, so the low pressure spring seats on the higher volume piston. I will be using this combination on my truck to start, then I will be trying to find a spring which can boost the output pressure to the VE's optimal 15 PSI.

Low Pressure Spring Dimensions:
Big end OD: 1.020"
Small end OD: .785"
Install height: 1.692"
Free Height: 2.175"

Gallons per min. calculations.

piston area x stroke = displacement in^2
I used .5" for the stroke It was measured .530"
On a four stroke the came turns 1:2 with crank
((Engine RPM)/2) x displacement = in^2/min
in^2/min x 0.00432900431 = GPM

Engine RPM:3200
CAM RPM:1600
1st Gen pump in^2/min : 654.40
2nd Gen pump in^2/min: 876.80
1st Gen pump GPM: 2.83
2nd Gen pump GPM: 3.80

 

I recieved the ebay p/n 3936323 $36.00 pump today.

It has a different inlet nut, there is an addtional spot face on the nut. It has the same inlet 1/4 pipe thread as the 3936320 p/n so functionally it is the same.

Outlet height and thread 14mmx1.5 is also the same as the 3936320 p/n.

Piston diameter is the same (1.019") as the 3936320 p/n.

Spring length is 1.806", wire diameter is .122"
Spring diameters are: small end .800"; large end 1.020"

Without a spring compression guage, just by the feel of my hand pushing the pump, this spring is not as stiff as the second gen spring, but stiffer then the 3936320 p/n. Using my hand as a gage I could bottom the push rod on the 3936320 p/n, I could not bottom the second gen pump, I can just bottom 3936323 p/n but not hold it for long.

P/N 3936323 will functionally replace the P/N 3936320 except for the pressure spring so it could be an inexpensive spare after swapping the spring. I would guess that using this spring, the after the filter pressure is going to be close to the VE's 15-18 PSI optimal.

I will plan on using this spring with my 2nd gen large bore piston pump to create a medium pressure high volume pump when I install the GDP big line kit over this weekend. We will be installing an after the filter pressure guage.

 

This is some good info. I'd be interested in just how many different spring rates there are.

Keep us posted with the results.

And thanks

 

wow this is a great thread. im in awww. i would love to see the results.

 

Keep up the good R&D. I look forward to your pressure numbers.

 

Are you meaning that the hole that the fuel-line-fitting gets screwed into is threaded 14mmx1.5 ??

If so, is there a source for an AN-adapter to screw in this hole and use AN-swivel fitting ??

I have managed to successfully screw 1/4-NPT fittings in the top outlet of three different pumps, and managed to achieve a leak-free fit; BUT, it always takes more than one attempt to stop the drips.

What I accomplish by this is the elimination of that aggravating hard-line, between the lift-pump and filter-head.


Also, is it do-able to cut off the section of the factory rigid-line, that goes in that outlet, and either FLARE the factory tubing, or use a COMPRESSION-FITTING on it ??

If so, what size line-fittings will fit ??

Thanks.

 

Aeroquip, Parker, and Earl's all make adapters that will work with the 14mm x 1.5 thread.

Glacial Diesel Power will have a stainless one soon.

Aeroquip and Earls go to a -6 or -8 AN fitting. The parker part goes to a 1/4 pipe.

The parker part came with and o-ring and an anti-crush washer, the others will need this as well.

I don't see why you couldn't flare out the factory tubing other then its very small.

 

Any updates?

Not that I'm the only one waiting on your results or anything!