Fuel supply pressure

[formula]

What is the maximum safe fuel pressure that should be supplied to the VE pump? Also, what is the minimum allowable fuel supply pressure at WOT? Where would be a good spot to tap into for a pressure reading?



Cheers,

Sean

 

[BushWakr - RIP]

Lemme put it this way... . when you get a good answer let me know... the stock pump is rated at 6-8 psi. My pump was actually running outta fuel today, for the very first time... .



bob

 

[SnoDawg]

Originally posted by BushWakr

Lemme put it this way... . when you get a good answer let me know... the stock pump is rated at 6-8 psi. My pump was actually running outta fuel today, for the very first time... .



bob

If you are running out of fuel you might want to look into running a larger fuel line from the tank to the lift pump I am planning this in the future using a holly (7 psi 97 gph rated) electric fuel pump mounted as close to the fuel tank as possible then blocking off the place where the stock pump is mounted.

 

[BushWakr - RIP]

Yes, I was thinking along those lines too... . the one thing we have to be careful with in our application is the lift pump was not made to be pressurized on the tank side. We have to make sure we don't damage it from excess supply pressure... but I was running outta fuel, no question...



bob.

 

[formula]

Originally posted by BushWakr

Lemme put it this way... . when you get a good answer let me know... the stock pump is rated at 6-8 psi. My pump was actually running outta fuel today, for the very first time... .



bob

Bob, are you talking about the stock lift pump is rated a 6-8 psi or the input pressure to the VE is rated at 6-8psi?



How could you tell that you were running out of fuel?



Sean

 

[Dieseldemon]

Upgrade Fuel pump

Cummins makes an upgrade fuel pump that changes the diaphram pump to a piston pump like the one on the 2nd gen

No it is not the same pump that is on the 2nd gen.

Let me know if you are interested and I will post the part #s

 

[BushWakr - RIP]

Yes, if the pump is interchangeable then by all means post the part #'s for us... that would be great...



I feel I was running the inj. pump outta fuel by running two fast/consecutive high RPM burns in quick succession. The engine started to stumble and run rough "evenly", it that makes sense... . in other words the miss or stumble was not a single cylinder miss but rather an engine wide stumble.

I eased down on the throttle about 1/4 travel, and after about 1/2 block it evened out, and ran smooth as silk. This has actually happened on two other occasions now that I think back on it... .

All under the same conditions... .



I believe the outlet pressure of the lift pump should run about 6-8 psi. I'll dig into the manual and confirm that though..... unless someone know the hard facts on this... ...



**edit** ok the manual does not say what the pump itself should generate, but it does say the min output pressure of the lift pump must be no less than 3psi, it should pump no less than . 70 US Quarts for 30 seconds of engine cranking.



Maybe my fuel filter is getting dirty, it's been a while... hmmmm...







BoB.

 

[Old Smoky]

Carter makes a pusher pump that works well for our application. It produces 7psi, and can be found at PDR.



Mike

 

[Dieseldemon]

Diaphram pump upgrade

Here are the part #s you need to get to upgrade to a piston pump on the 1st gen engines



1-3933256 pump

1-3914753 tube

2 3931348 Gaskets

1- 3914284 spacer

2- 3918191 seals





Some of these parts might be superseded These parts are from cummins

Hope this helps

This pump is also rebuildable

 

[Joe G.]

If you are thinking about changing to a 2nd gen pump you should be aware that it puts out 20 to 40 PSI depending on conditions. It also has large pressure spikes that can wreck a pressure gauge if it is not protected. It may be too much for a VE injection pump.

 

[formula]

Dieseldemon,

The pump, part number 3933256 has been superseded by part number 3936320. Cummins parts here could not give me any specs on it. Do you know the specs on this pump? Max psi, volume, etc? Also, what improvements does it offer relative to the original diaphragm lift pump?



Cheers,

Sean

 

[rossg]

Hi, Bob; You problem sounds like a classic case of fuel filter "getting there". I would start there. These early pumps seem to be the least problem parts of the Cummins systems. Ross

 

[Dieseldemon]

Lift pump

The pump that I gave you the # was designed to replace the diaphram pump it puts out 11 to 12 psi ai have Installed a lot of these pumps and they work fine.

It is not a 2nd gen pump

 

[formula]

Jim,

Thanks for the pump specs.



Sean

 

[formula]

Has anyone here run one of these lift pumps?



Sean

 

[formula]

TTT



Update... ... .....



Went over to Massdiesel today to have my lift pump pressure checked. Hooked up the gauge to filter outlet banjo. Got 5 psi at idle and up to 6 psi at 2000rpm. Next we put the gauge through the driver's vent window and closed up the hood to take it out for a rip. So, driving down road, steady 40mph and 1700 ish rpm, got 4psi. Give a about 1/4 throttle, dropped down to 2-3 psi. At 1/2 throttle had barely 1psi. WOT sucked the gauge right down to ZERO psi in a hurry This is exactly what I suspected was happening. Will be getting the new lift pump installed this week.



Sean

 

[Hart]

Originally posted by Old Smoky

Carter makes a pusher pump that works well for our application. It produces 7psi, and can be found at PDR.



Mike

whear can I buy one and how $$$$$

 

[Paychk]

this is Piers Diesel Research (PDR) good people!



http://www.piersdiesel.com/



PS Welcome to the forum!

 

[bgilbert]

Well Shawn, whats the deal, did you get a piston style lift pump? If so what were your pressures?? This sounds like great info for me and Greenleaf, if it can run at 10-12psi, but then what will it run at WOT. Also, if its not a 2nd gen LP, and an upgrade for 1st gen diapraghm LP, then I imagine one wouldn't have to find fittings to match up with the 1st gen LP fitting yes??

 

[MontyDyer]

Went back thru some of my old documents and found out why the number was superceded.



This service/parts topic provides part number information for B and C Series lift pumps. Design changes have been implemented on Federal Mogul lift pumps requiring the use of new part numbers.



These design changes address the following issues: Lift pump “chirping” and tappet seal leakage. Table 1 lists the previous Cummins part numbers and the superseding Cummins part numbers.



Old Part Number: 3933256 New Part Number: 3936320



Pump Stand Measured Flow: (LPH) 108. 1 - 230. 9



Pump Measured Flow @ 1250 RPM



The LPH flow measuremets for the P pumps transfer pump shows to be 187. 4 - 304. 2





I also found the part number for the fuel pump block off plate and thought I would post it as well. This may come in handy if anyone ever wants to do away with there mechanical pump. Part number is 3863441