jethroish

Just got my injector pump replaced today. They tested the LP and said it has good delivery rate of 52 oz (of fuel in 25 sec).
This really means nothing to me.
Anyone know what that might equate to in psi?

rockwithjason

Flow rate has little to do with psi. A pump might flow well into an open container(no psi) but into the vp44 it may not hold enough pressure. The only way to know if you are above the 8 psi absolute minimun is to hook up a gauge and go driving. 12 psi is about standard for idle, 10 for wot.

jethroish

I kinda thought that might be the answer.

Next question, where to get a fuel pressure gauge and how to properly install?

rockwithjason

There are several ways to hook up an fp gauge. You really should have one in the cab full time. You can get mechanical or electric gauges from a number of suppliers like Jegs and Source Automotive. Do a search for more info. I bought my Stewart Warner electric gauges from XK unlimited in CA. I have dual senders Mounted remotely from the enging through tapped banjo bolts from Geno's Garage. Here is a link for a mechanical tester also.

www.protintnw.com/sa_dodge-fuel.htm

overhill

I sent email to Cummins powermaster advising I was getting only 4-5 lbs at WOT and
asked if that wasn't harmful to the vp44. His answer today was "as long as there is a positive flow to the vp44 everything is ok"???

rockwithjason

He is full of crap. You need 8psi minimum to feed a vp44 end of story. Do a search on lift pumps, vp44, and fuel pressure. You will read a mountain of info on the subject.

overhill

Not arguing with you just telling you what he said. Will send you a
copy of his email if you would like?

bluebull

I also beleive that as long as there is a positive pressure to the injection pump it is o.k.

Some will agree most will not agree. Alot of what people beleive is what the have been told or read some where and are just repeating it, not actual proof, which is very hard to verify.

I will tell you this, if the fuel pressure drops below 8 PSI on a constant bases I would absolutely without a doubt change it out.

52 ounces in 25 seconds translates to approx. a gallon per minute of flow. I think the flow rate is suppose to be higher but can not remember the actual rate. I do know that there is no way your engine will consume a gallon of fuel a minute so it should be enough. Again I can not remember the actual flow rates specified for this application.

mysing418

This is on our site at present... In "Tech Facts" at the top of this page. Hope to help...

https://www.dieseltruckresource.com/...n&onlynewfaq=1

bluebull

The way I read that article is for the 12 valve mechanical lift pump. The 24 valved trucks already use an electric lift pump.

I agree with flow rate is whats important.

cujo

Cummins told me the same thing

infidel

No' it's for a 24 valve, on the 12 the minimum fp is 22 psi.

I've read that the stock 24 valve fuel filter will only flow 17 gallons per hour. Try to push any more though it and it turns into pressure loss.

2500CTD

Then how is everyone saying the IP needs at least 100GPH?? Unless I'm way off. Seems the Holley pump is overkill then consiering the flow rates.

bluebull

I have a pre and post fuel filter pressure gauge and there is only 1 psi difference. If the filter only passes 17 gallons per hour and the lift pump will pump 60-80 gallons per hour but the filter will only pass 17 gallons per hour and there is no return line until after the injection pump wouldn't there be a greater pressure pre filter than post filter? I have also used the sending units in each others positions just to see if they both read correct and they do.

bluebull

It was these lines in the paragraph below that had me confused. I guess he was talking about adding a different lift pump in the line (closer to the tank) instead of the stock position. On a 24 valve truck there is no hole to block off it's the 12 valved trucks that need the hole blocked off if you install an electric lift pump.


From Tech Facts at top of page:: The only requirement is to hook the pump to the ignition side of the ignition switch and block off the hole where the old fuel pump is removed from the block with a steel plate and some gasket material. The added advantage of an electric fuel pump is the ease of priming the fuel system. Should you change fuel filters or lines, all you have to do is turn on the ignition and bleed the fittings without cranking the engine. Of course adding a electric fuel pump requires some modification and it is easier just to replace the lift pump if you so desire.