Engine/Transmission (1998.5 - 2002) One more LP / VP44 question....

[ISBPilot]

A few days ago I developed a stutter / stumble at around 1800 RPM. Hooked up fuel gauge, had "0 psi"!!! Put in new filter and lift pump = 15 psi down to 10 - 11 psi at WOT. Not sure how long LP was dead. Checked pressure about 4000 miles back and had 10 psi at idle, not sure about WOT. Since new pump and filter install engine runs fine, good pickup no stumble at any speed or rpm up to 90 mph @ 2500 rpm.



Now here is my question. How much has the VP44 been damaged to allow the stumble at mid range rpms?



Todd

 

[Turbo Tim 1]

It would be hard to say and I am no expert but I would tend to think that the stumble was more of an air pocket in the fuel type of deal and did little damage if any. When I bought my 2001 used it had 24,000 miles on it. Previously I had a 93 and didn't know anything about lift pumps till I got on here. About 2-3 months after buying the 01 I checked the fuel pressure, it was 5-8 psi at idle and zero going down the road at 70 mph so I got it replaced. I had put 5000 miles on the truck myself and who knows how long it hadn't been working right but I have 87,000 on there now and the VP is still going strong

 

[ISBPilot]

Thanks Tim, I am hoping that is the case. The whole situation just made me a little nervous.



Todd

 

[csevers]

My VP-44 has seen at least 6k with NO fuel pressure, it never gave me a stumble/studder and still runs now at 116k.



Good Luck

Craig

 

[ISBPilot]

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

Everything has run fine until this morning. Truck runs great, just doesn't want to start! Have to cycle the LP several times before it will fire. Each time it runs 15 psi, but will not start until about the 3rd time. Pump is also running longer than normal before it cuts off. Acts like a priming problem with air in system, but it is raining and can't tell if I am leaking fuel anywhere or not. What are ya thoughts?



Todd

 

[Gary - K7GLD]

I thought the initial priming run of the LP was purely ECM TIMING controlled, and NOT dependent on fuel PSI - in other words, should alwaays run the same amount of time REGARDLESS of PSI generated?



Keep us posted...

 

[ISBPilot]

OK...........

Still in limbo... ... .

Had my buddy who is a cummins tech, hook his computer up. The only code showing is a low pressure reading on the VP44 and it is inactive, was probably from the dead lift pump. No current codes of any kind. No external fuel leaks and no internal that we have found. Changed fuel filter, removed and checked relief valve in banjo, reinstalled. Will now start, but still sounds rough and has to turn over longer than normal. Thought it might be defective LP, it will pump to 15 psi but does not hold any pressure. After pump cuts off pressure drops to 0. Is this normal, or should it hold pressure to supply VP for starting?



Todd

 

[rodneync]

Originally posted by ISBPilot

Everything has run fine until this morning. Truck runs great, just doesn't want to start! Have to cycle the LP several times before it will fire. Each time it runs 15 psi, but will not start until about the 3rd time. Pump is also running longer than normal before it cuts off. Acts like a priming problem with air in system, but it is raining and can't tell if I am leaking fuel anywhere or not. What are ya thoughts?



Todd

My 1998. 5 has exactly the same symptoms. Do you have any new info?

 

[Gary - K7GLD]

It's normal for fuel pressure to rise when the key is first switched on, then fall back to zero - the LP is priming the fuel supply, then after a second or so, shuts off until the engine starts, then starts operating again...

 

[ISBPilot]

Update........sad but true.........

It was the injector pump. Tried everything else and finally went to the dealer that I use for service, who I trust and have had much help from in the past. Once I described the symptoms and they hooked up the code reader, it verified it. One lift pump later, it cranks on a dime and runs like a top. I guess 200,000 miles ain't bad, but I would have liked to have got 200,000 more out of it. So if you do not have a fuel pressure guage, get one and keep it checked!!!



Todd