Quick Test for VP-44

Tejas TJ

Tejas TJ

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Apr 17, 2009
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I was reading the instructions for an install of a FASS system on a '98.5-'02 model 24V truck. I read this on how to test a VP-44 to see if it is able to start without the fuel pump cycling.

"Here is a simple test:

Note: Not all failed pumps with broken diaphragms will start with low to no supply fuel. Sometimes the
diaphragm is so broken that charging pressure is not able to build to a level that allows the pump to deliver fuel.
Try starting the vehicle without waiting for the fuel pump to cycle. Meaning when you turn the
key to the on position immediately engage starter."

I'm in the market for a 2nd Gen. truck. If I'm looking at a 24V and try this, will it prove if the VP-44 has been ran with less than 5psi?

P.S. I fully don't understand all this diesel stuff yet either, so bare with me.
 
You can also bump the starter without starting the truck as a test for the lift pump. You should hear the lift pump kick on for 15-30 seconds. If you don't hear it then the lift pump is dead and the IP is likely shot. If its an '01-02 you can turn the key on/off/on/off/on without starting it to get a readout of codes on the odometer.
 
2000 will also show codes in the odo. There are other damages that occur to these pumps than the metering diaphragm. The metering diaphragm usually just causes hard starts when hot. Being subjected to low fuel pressure can also start the pump down the road of not being able to reach enough injection timing advance. There are also electrical issues that can develop as well. In short, if you plan on buying a VP truck, plan on replacing the VP at some point. A lot of guys have gotten a lot of life out of their pumps, but eventually they will all fail.
Sean
 
got 120000 miles on my vp i know its not alot of miles just saying when you buy a used truck you always take a chance on something that should have been done just when buying one of the vp trucks if you think it might need one plan that into your budget for buying one just remember upgrade the lift pump whether its a towing daily drver or what ever its going to be the
 
Tejas TJ said:
I was reading the instructions for an install of a FASS system on a '98.5-'02 model 24V truck. I read this on how to test a VP-44 to see if it is able to start without the fuel pump cycling.

"Here is a simple test:

Note: Not all failed pumps with broken diaphragms will start with low to no supply fuel. Sometimes the
diaphragm is so broken that charging pressure is not able to build to a level that allows the pump to deliver fuel.
Try starting the vehicle without waiting for the fuel pump to cycle. Meaning when you turn the
key to the on position immediately engage starter."

I'm in the market for a 2nd Gen. truck. If I'm looking at a 24V and try this, will it prove if the VP-44 has been ran with less than 5psi?

P.S. I fully don't understand all this diesel stuff yet either, so bare with me.
Click to expand...

I'm not sure what this test is proving, all these trucks will start and run down the road w/o a fuel pump running at all. I know, on my 98 I drove 15 miles once without the pump on. And sometimes when the diaphram is broke they start easier w/o the pump on. Nobody fully understands the diesel stuff.
 
Ok, well is there some how I can check this electronic fuel system stuff when I'm looking and test driving a truck? For example: I'm at a dealership and they don't know much about the previous maintence of the truck.
 
Tejas TJ said:
Ok, well is there some how I can check this electronic fuel system stuff when I'm looking and test driving a truck? For example: I'm at a dealership and they don't know much about the previous maintence of the truck.
Click to expand...

I don't know of any, but you can look for a 00-02 because you can do the key test and see what kind of trouble codes it's pulling, and if you see a P0216 don't even bother with a test drive.
 
Phily 911 said:
I don't know of any, but you can look for a 00-02 because you can do the key test and see what kind of trouble codes it's pulling, and if you see a P0216 don't even bother with a test drive.
Click to expand...

Ok what's that order to turn key?

And will it flash out multiple codes or how does it work?
 
This test that is described is for when you are suspect that your VP is going south but have no codes. If it starts with no lift pump pressure, but won't start with the lift pump running then its a sure sign the diaphram is bad. Ether also works, only after unplugging the relays for the grid heater. The typical scenario is that you have replaced a old weak LP on a 98'-00' with a FASS or AirDog, and after a few weeks it starts to get hard to start. The early VP's had a thin diaphram that would weather and stretch from not having enough fuel pressure on one side to offset the pressure from the opposite side. Then after a new high flow/15+psi pump the diaphram then moves the opposite direction, and starts cracking and eventually fails. No codes, no start.
 
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