Engine/Transmission (1998.5 - 2002) Cleaning the fuel system part two

[NIsaacs]

For years the factory standard has been flow volume not psi since psi has so many variables

Yes, uninformed and happy for 12 years, now I watch my gauge like a hawk and worry all the time

Nick

 

[SAndreasen]

Its encouraging to hear of people who run their VP's on parameters outside whats considered "safe"..... Thats not meant in disrespect either but because I've been collecting information about this pump for the past 14-15 years and overall the data points in a general direction of what the VP can tolerate. But then there's plenty of scenarios which dont follow along and seemingly doing fine.

I thought 5 minimum was the parameter?

 

[Bob4x4]

The origonal spec was 10 psi while at idle,then they came out with a tsb 14-002-03 it was revised to at least 45 oz in the 25-30 seconds the pump runs with the key cycle

 

[KATOOM]

Yes, when the VP ISB was introduced the stated minimum pressure was 10 psi. Not long after production VP issues were what you could call epidemic... Yes, we know that most of the issues were related to the Carter lift pump failures themselves as they were proving to be terribly unreliable and not maintaining their regulated 15 psi output.

Then the thought logic was maybe its not a pressure thing but a "volume" thing..... So the engine mounted lift pumps were occasionally replaced with the in-tank versions which run at a lower pressure but greater volume. Although we all know how well that fixed the problem.

In saying that, not all VP failures can fall on the garbage OEM fuel pumps either. Some of the issues were just inferior VP components from Bosch. Remember, the VP was only a temporary fix to allow Dodge/Cummins the transition towards making their emissions requirement while the Common Rail design was still in the works. The VP was not a long term component, and its been alluded that Bosch didnt have any long term R&D on this particular pump either to fully understand what it needed or would withstand on these engines. Had it not been for the crazy popularity it gained with the aftermarket world due to the immense plug-and-play power gains.....I dont think we'd all be having these discussions.

So with Cummins getting VP's which had weak diaphragms, problematic timing solenoids, soft fuel timing piston and sleeve, problematic PSG's, etc... the number of VP's getting replaced by dealers was enough to leave a lasting impression on the consumer for years. Still to this day people will run from a VP truck. Thus the "p-pump" conversions.....

So yes, over time the VP has seen some very impressive revamping which has not only improved reliability but also its reputation, somewhat. Nonetheless, given what I know so far (as I feel I've written enough about this pump over the years to format a book), I would not run any pressure to it less than 14 with supply lines no less than 3/8" with no banjo fittings. The data collected over the years proves that doing otherwise is risky. Does that mean ALL the VP's out there are subject to failure if this rule of thumb isnt followed?.....nope.

But thats one of the reasons why the VP has been a heavily conversed topic, because there is ZERO data from Bosch or Cummins which will answer anything definitive one way or the other in regards to reliability or failure. The entire burden has fallen on the consumer as the guinea pig and the aftermarket vendor and the companies who are privy enough to have an 815 test bench. Oh.....and in mentioning rebuilders, the case for reliability has also been an issue dependent on how the VP's were "re-manufactured". Meaning, as so commonly seen in the reman industry, why replace everything when all you have to do is replace whats not working? Well that mentality led to a lot of suppliers getting a bad rap as the consumers (and forums) realized that they were being shamed a $1500 part which was essentially "used" and soon to fail from one of the non-replaced components.

Anyways, I think I've rambled on too long.....