Engine/Transmission (1998.5 - 2002) VP 44 Pump

[chazj]

I'm just finishing a trip thru Az. As I mentioned in a previous post, I now have the "new in-tank fuel pump" replacing the lift pump. My pressure never exceeds 4 lbs and zero is quite common under normal exertion. Case in point: This last trip up Hwy 40 at 75 mph, towards Kingman Az, EGT at 1000... Turbo pegged at 20 lbs... . fuel pressure dropped to ZERO! Lots of engine left... but was watching fuel pressure.



I've read in various posts what Bosch likes to see with respects to FP for their pump.



Does anyone know WHERE this is written down by BOSCH as a requirement for their pump???? I would like to be able to show it to the local Dodge dealer and see what they may be able to do.



Getting increasingly nervous just waiting for this pump to give out. About 1500 miles over the warrenty period of 100K. I don't think I should have to spend any more of my $$$ to prevent or fix what is still likely a DC problem.



They have a lot more $$$ than do I... ...

 

[DPS]

I don't know what to tell you to do because the common bosch test is x number of cc's of fuel in so many seconds at zero restriction. This is the common test that chrysler recommends it tech's to do. Sometimes it shows a bad pump and sometimes it won't. If your fuel pressure is that low I would get them to flow check it for you. My thinking is that 4 psi won't move enough fuel to pass the test.



Josh www.dieselperformancesolutions.com

 

[chazj]

From what I've read here my fuel pressure is running about normal (average) for the new in-tank fuel pumps. I brought the difference in pressure up the the dealer the minute I started my truck after the conversion. Their response is that DC doesn't worry about pressure anymore & is only concerned with volume. End of discussion.



Somewhere on this forum I read that Bosch needs to see in excess of 6 lbs in order to maintain the proper balance internally in their pump so it doesn't fail prematurely. That's the information I am looking for... . if available.



Thanks in advance...

 

[NevadaBackroader]

I have 12,000 on the in tank pump and VP44. 8,000 left under warranty. I get 4 psi at WOT and like you, there is plenty of engine left. So far, I have not heard of the pump failing.

 

[Texas Diesel]

Search the thread "pumps, lines and what not". There is lots of good info on pressure vs flow.



This debate will never end and there may be no fast answer. Two schools of thought:



1. Anything zero PSI or above is okee dokee (like the in tank pump you have). FLOW is the issue not PSI. This would seem to be correct since the LP flow goes THROUGH a vane pump (positive displacement) at the inlet of the VP44.



2. More feed pressure the better (up to 15PSI) Some run more but Brett at Industrial Injection seemed to think that exceeding 15PSI was out of the programmed map. Listen to Brett, he rebuilds them.



Then of course, cooling comes into play. The "extra" flow (measured in positive PSI i. e. , >0PSI) passes through the VP44 body (in an undetermined manner) to the overflow valve and returns to the tank carrying away latent heat. Aka, Bobs thread about keeping the VP at ambient temp. Bobs thread is one of the best ever started on extending the life of the VP (IMO).



:-laf

 

[Jeff Knight]

My in tank pump idles between 9-10 psi. I can drag it to "0" just accelerating on to the highway. Crusing on the highway it run about 5. 5 psi.



In another thread Brady from Industrial Injection said the VP44 needs 13. 5 psi to maintain balance in the injector pump. They are a certified Bosch dealer. I'll be watching my pressure very closely. I have 22000 miles left on my warranty.



Jeff

 

[rweis]

Brett at II said that the VP44 wants 13. 5psi to keep the deflection of the distributor diaphram from flexing more then . 5mm (from memory, correct me if wrong). He mentioned you can go up to about 18 psi without damage. He did not mention a low psi value (yet, I asked to get the value).



The diaphram apparently can crack from excessive deflection caused by too low or too high an lp (whatever you use) psi. I think one of many keys to the Vp44 is to get the input psi really close to 13. 5 spi +- 1 or 2 or 3 or 4 psi.



There are many threads on proper fuel lubrication. The whole pump is based on fuel lubrication.



The concept of lphv (low pressure high volume) to the vane pump I think contridicts the Bosch spec of 13. 5 psi. Of course line diameter could have a consideration here. Lphv implies larger feed lines than stock I would think.



Still baffling after hundreds of threads, tens of thousands of lines of thoughts, years of ideas, why is it so hard to pin down?



If one of the rebuilders could provide a (or several) voice recording(s) of their thoughts, what they see as trouble spots, trends etc I would be GLAD to convert it to text and get it sticky posted somewhere.



Bob Weis

 

[Jeff Knight]

Great post Bob. I guess thats where I'm at at this point. My 95 had 199000 miles on it with the original lift pump. It was simple and not an issue. Simple can be good. I see in your sig you have a rasp system. How do you like it?



Jeff

 

[rweis]

Jeff,



I REALLY like the RASP. You can check the backup lp at every engine start. I disconnected the lp for a while ( 3 weeks) to see what would happen with the RASP. Instead of 1 sec start it took about 3 sec. REALLY nice to see the psi rise as engine rpm rises (need more, got more). Just don't tighten the belt too much. It is a cog belt and is designed to run loose.



Another thing I like is the tank bypass is right at the VP44 inlet, and is a bypass valve that you can fine tune. Mine was about 15 psi as delivered and I trimmed the spring and put in a shim to get it a tad under 14 psi (see Brett (II) post about 13. 5 psi). "I" could adjust it easily.



I had a leak in the hobbs diaphram and DTT sent one ASAP. I bought a spare locally ($55) just to carry it. I also have a spare belt (suppose to be good for 50k). This little pump is just about as simple as it comes. They designed a very somple mounting system and then made it billet.



I really think the RASP is a final lp solution.



Bob Weis



PS IF I had a P7100 pump and know what I know now about the VP44 I would rebuild the P7100 a thousand times rather than venture into the VP44.