Engine/Transmission (1998.5 - 2002) Pusher Pump & PSI Solution?

[RADdodge]

I still think the idea of a pusher pump is a good one (thanks Steve St. Laurent). I felt that 20psi was a bit much, but if it didn’t harm anything, no big deal. But since the current thread on the VP-44 and EricBu12’s post about a Bosch Engineer’s comments respecting what might be excessive pressure on the inlet of the VP44 and the damage it can cause, it might be time to reevaluate the situation. There were also other threads on a TDR affiliate site that mentioned damage to the VP-44 caused by excessive pressure causing fuel to be pushed past a seal.



Eric is seeing pressure of about 12psi at idle which is apparently about the optimum pressure at idle. He is using two different Carter pumps, a Carter P4601HP rated at 100gph @15psi and a Carter P46000HP rated at 100gph @7psi. (He replaced the lift pump too. ) I don’t know which Carter pump I’m using for the pusher pump and I’m still using the original lift pump. The place I purchased the pusher pump from had scratched out the part number on the box, the pump itself lists no part number and the vendor didn’t return my e-mail concerning the part number.



Sorry to be so long winded, the point is to use a pusher pump that puts out about 5-7psi which is what the spec for Carter P4600HP is (or another pump with about the same specs). All we are trying to do is eliminate the suction at the lift pump. Does this make sense for those running two pumps in series and seeing 20psi? I think I’m going to have to replace the pusher pump I currently have installed or eliminate (i. e. by-pass) the factory lift pump.

 

[Gary - K7GLD]

I'm using the additional Carter 4600 pusher pump - along with an Edge Comp power module. I see 25 psi at idle, 22 psi at cruise, even towing our 5er - and RARELY less than 18 psi under heaviest load and Comp setting...



I won't begin to pretend to be an expert on installations like mine (see pointer below for various pictures), but it sure has worked well for me SO far...

 

[HeberRam]

VP-44 fuel pressure???

RADdodge..... This issue has been debated several times, and I think the answer is stock vs bombed truck. Eric's truck is pretty much stock and the fuel pressures he's quoting are about right for a "stock" truck. However, when you are pushing a lot of fuel, Via large injectors, fueling boxes etc. the stock lift pump can't maintain those pressures, hence, a pusher pump etc. Now I'm not disputing what the Bosh engineer said, I do know not enough fuel to the injection pump is NOT good. TOO much at prolonged intervals may be bad also????

My truck will idel at 20psi and soon as I get on the pedal it will drop to around 15 or so, and continues at that level crusing. At WOT I"ve seen it suck to 8psi. ( I also have a stock lift pump and a 100 gph 7psi pusher pump). If I didn't have the pusher pump, with my set-up I would starve the injection pump to failure... I know because it has happen twice. I have had this set-up for over 32,000 miles with no problems so far... The point I'm trying to make here is, if one is to seek performance, you need to push more fuel. . Its a risk perhaps, however, I have not heard of anyone having a injection pump fail because of too much pressure??? All have been because of low. . IMHO if you plan to stay stock, don't invest in a pusher pump!!! Perhaps time will prove me wrong, in the meantime I'm enjoying my increased power, watch my fuel pressure gauage and totatlly ignor my injection pump issues...



Steve

 

[cscott]

I removed my stock lift pump and installed a Competetion Products PE4100 back by the tank.



I used the stock lift pump wiring harness to operate the relays that power the pump. This makes the new pump act just like the stock lift pump.



I idle at about 13 psi and go down the highway (70+ mph) at about 12 psi.



The PE4100 is expensive but is designed for continous use and has a 2 year factory warrantee. It is compatable with diesel unlike some of the pump that people are using.



I have been running mine for about 10K miles with no troubles.



Granted I am not heavely modified like some people but I wanted to do the fuel system first.



Craig

 

[Bigsaint]

Ditto on what Craig said... I have the same pump, mine's set for 15 psi's post-filter at idle. Normal cruising at 55 sees about 13-14 psi's, WOT runs go as low as maybe 10 psi's for a fleeting second, then it rebounds to about 12 psi's while still in the WOT run. See my sig. line in my profile, but suffice it to say that I have moderate fueling needs and the PE set at 15 psi's is beyond overkill. Only concern is will it last, so far so good. It's been in since the spring of this year.



Scott W.

 

[RADdodge]

This Post Is Aimed At Two Questions (See Bold)

Correct me if I’m wrong. The amount of fuel delivered is what matters to a BOMBed engine (gph). The pusher pump idea came from the fact that the OEM lift pump is in the wrong place and does more sucking than pushing which Carter says will damage the lift pump (correct – yes/no). I think the consensus is that that’s a bad thing.



I’d have to go back through the treads, but one of the most enlightening threads on that subject (pressure vs. flow capacity) was where a member (Sorry, I don’t remember who it was off hand) tested his very BOMBed rig with a flow meter (it think Bill Kondolay lent the meter to him – hey if you read this, pipe up). Those were enlightening facts and I think we are past that aspect of the question, no?



Now the question and separate issue is “Does excessive fuel pressure damage the injection pump and what constitutes excessive pressure. ” If it can be ascertained that excessive pressure damages the VP-44, then some of us are at risk. Why risk it if you know better? The key is – who really knows? I’d just as soon not have to replace my injection pump because of my ignorance. Heck Golly Gee Gosh Darn, that’s why I’ve read the TDR web since it started and joined the TDR to support it. It’s one thing to be ignorant and quite another thing to be warned, even though somewhat nebulous, and remain ignorant. Please note, I said ignorant and not stupid. I’m concerned enough to spend some money now to correct a possible problem than to have to spend considerably more later fixing a problem I caused. Wouldn’t you?



Craig & Scott – Does the PE4100 have adjustable pressure? Do you know the what the flow is? And Craig, that comment about diesel compatibility. Would you mind expounding on that if you have the time – please?

 

[Big White Beast]

Moderately bombed.......

New lift pump and Carter 4070 pusher, it's low pressure higher volume. This set up yields 20 PSI at idle and then it drops rapidly to 14-15 at cruise never below 12 at WOT. If it were any less at the start I could drop it below what the low end specs are for WOT. Catch-22! Now in reality stock trucks shouldn't have this problem. A healthy lift pump will have 15 psi @ idle and shouldn't drop below 10 psi WOT. That's a 4-5 psi drop. As stated above I can drop mine 8-9 psi, so bombed trucks obviously need more pressure to start.



I understand you questionand I'll try to apply my logic to it. Once I bombed the truck I became my own warranty station! So I weighed what I wanted the truck to do with what the possible bad effects were. Knowing the VP-44 uses fuel to cool itself and I increased the amount of fuel that I am taking away from cooling I added a larger fuel supply to make up for it. I'm willing to take the chance that the higher pressures will hurt it less than low pressure at WOT. The truck is moving along at 15 psi way more than idling at 20 psi. That helps to make me think what I did was better also.



Pressure to me would be better described as back pressure. I don't think that the VP has one ultimate constant flow rate to keep it cool and supply fuel at all throttle postions. So the flow rate needs to be increased as the throttle is increased. The only way we have now of doing that is to supply enough pressure so that at WOT it doesn't fall below specs. Unfortunately we build back pressure again as the need decreases. That way when it increases again it's readily available.



The ultimate system would be one that senses fuel consumption and raises flow accordingly. Logisticly speaking that would be a nightmare. Think of the people with adjustable boxes.



I think the better question would be if I bomb my truck am I willing to be my own warranty station.



Garrett

 

[Gary - K7GLD]

You sometimes have to just read a lot, and make you own (hopefully!) informed decision...



We know for a FACT, from long expen$ive experience, that the VP44 fuel pressures DC and at least one Bosch "expert" claims as "within spec" is low enough to cause injector pump failures in abundance...



We ALSO know that higher PSI provided by various means, both at idle and WOT, has VASTLY reduced those failures - so the choice shouldn't exactly be rocket science, now should it!

 

[Big_Daddy_T]

I am my own warranty station and Ive replaced two pumps from inadequate pressure. I read on here that it takes 24 psi or more to kill these pumps. I think I will stick with my pusher pump setup.



Dont these pumps send anything over 16psi back to the tank anyways.

My bosch man recommended a pusher pump setup. Cummins NW liked the ingenuity of the tdr members.

I cant get my pressure under 11. 5 psi even with mentals and the drag comp. I personally would like slighty over than horribly under. Before the pusher I would see negative pressure at the pump. Probably why I am on my third injection pump.

 

[cscott]

RADDodge



To address your questions.



The PE4100 is free flow rated at 270 gph, note that is free flow rating. I spoke with the pump designer and he said in our trucks that it would most likley be flowing 100 gph or there abouts.



As far as it being deisel compatable the manufactirer tests all thier pumps using diesel. The use of diesel is for safety purposes, less explosive than gas or mineral spirits (yse some pump manufacturers us mineral spirits to test with).



The pump can be adjusted by removing a plug that holds the pressure spring and either installing shims (stainless steel washers would most likely work) or stretching the spring. I beleave that Bigsaint has done this.



The pump is internally bypassed so there is no need for any fuel pressure regulator to be added to the system. It is also a self priming design.



https://www.turbodieselregister.com/user_gallery/displayalbum.php?&albumid=273



This link will take you to some pictures of my installation.



I have lots of time right now so if yoou have any more questions let me know.



Craig

 

[Bigsaint]

Once again, ditto on what Craig said. I adjusted my PE pump by slightly streching the spring, presumably a bypass, until I received the psi's I needed. It's not an exact science with the PE pump. Mine was showing a drop of about 1 psi after a few months, I called PE and they gave me the info to alter the psi's. So far so good.



Scott W.