Engine/Transmission (1998.5 - 2002) VP-44 and low fuel pressure when running

[fox]

After several months of dealing with low fuel PSI only when running, here is what I see.

Cycle the lift pump and It goes to 16-18 psi, start the engine and it drops to 10-12. Then when you drive it, it drops to 5 or less.

I have air in the filter housing. Everthing has been changed from the fuel canister to the filter!! Same problem.

It appears to me the VP is returning fuel at a high rate and frothing up the canister where the fuel pick-up is. This is then sucked into the lift pump as a air/fuel blend.

So, today I connected a hose to the lift pump inlet, dipped it into a bucket with 1 gallon of fuel. Then cycled the lift pump to prime it. It showed 16-18 psi. Then I started it and it drops to 10-12 psi. The fuel in the bucket was 1/2 gone in 30 seconds. Obviously returned to the tank.

Can the VP be fixed on the truck? Can anyone explain what is going on?

 

[Graphic man]

pull the check valve and spring on the return outlet of the VP





Scott

 

[fox]

I did replace that bypass valve. No change.

Is this an internal issue?

 

[DCreed]

mine drops to zero =dead VP pintle solenoid( they can corrode and stick)

 

[16919]

You did check the gauge and line going to it right? I would start at the easy stuff first.

 

[fox]

mine drops to zero =dead VP pintle solenoid( they can corrode and stick)

Is this solenoid something I can get and change myself?

I am sure this is the issue.

 

[fox]

You did check the gauge and line going to it right? I would start at the easy stuff first.

The gauge was checked, as it also has a mechanical gauge under the hood.

Thanks.

This is all tied to the loss of fuel pressure at 1/4 tank. It is moving too much fuel and putting bubbles in the tank module.

I bet it is also tied to the fact that sometimes--erraticly- it smokes heavy leaving a stop light, it doesn't do this all the time.

 

[DCreed]

you can check out this read for info. Diesel Performance Specialists, VP44, 47RH, 47RE, Cummins Diesel Performance

 

[16919]

The gauge was checked, as it also has a mechanical gauge under the hood.
Thanks.
This is all tied to the loss of fuel pressure at 1/4 tank. It is moving too much fuel and putting bubbles in the tank module.
I bet it is also tied to the fact that sometimes--erraticly- it smokes heavy leaving a stop light, it doesn't do this all the time.

Have you changed the pick up tube in the tank? Some trucks have cavitation problems @ 1/4 tank or lower... . mine does under an 1/8 tank. Just a thought... . that will have similar issues to what you describe..... you basically suck air from the tank. If it is only happening under 1/4 tank I would say that it is not the VP.

 

[fox]

Ok, the tank module has been changed out. I did have a draw straw on it for 2 years. Last spring this issue came up and was erratic. Then it became permanent. ( as far as pressure) It all started with complete loss of pressure at 1/4 tank, but just fill the tank and all was better-with 10-12 psi. This was not normal--16-18 was.

in the last couple of months it has gotten worse, so I started changing things out.

First was the lift pump. I went to the areomotive 1000 with a regulator. same issue. So, I went to the tank to make sure everything looked good and the fuel was clean, it was fine. Then I went to the lines, changed everything to hoses. Still the same issue. I'm also using an inline filter. But even replacing it shows no change.

So, everything has been changed out EXCEPT the vp44 ( and title)!!! I'm really spent.

I just ordered a new glacier pump. Richard has been very good about this and wants feedback. Of course I will give him that.

So in summary,

Two lift pumps

two new lines-complete from tank to filter.

A new fuel canister in the tank.

Even verified the pressure with a second gauge.



So, I know it is getting air( I've seen it bubble in a bucket).

I believe it is coming from the vp return line. This I will re-varify this weekend.

Are you going to the GDOA meet tomorrow?

I hope to make the trip in this truck, but I won't if it won't keep some fuel pressure.

Any one had this issue?????????

 

[DCreed]

Have you changed the pick up tube in the tank? Some trucks have cavitation problems @ 1/4 tank or lower... . mine does under an 1/8 tank. Just a thought... . that will have similar issues to what you describe..... you basically suck air from the tank. If it is only happening under 1/4 tank I would say that it is not the VP.

Agree, if it ONLY happens @ under 1/4 tank then its tank related. the lower the level in the tank the more "pull" the lift pump puts on the pickup. so ANY minute leak will draw air. kinda like a cracked plastic straw in a milkshake
However... looking at your original post you put the pick up in a bucket and showed a pressure drop when the truck started = dying VP44, sorry!

 

[fox]

Ok, the vp is the only thing left, but it still runs, so how to prove it is the vp?

 

[fox]

Ok , to give everyone an update.

I have a new Glacier ordered, it is not here yet. (holiday mail is slow)

I was playing with it and really needed my truck running, so I removed all the fittings from the Aeromotive pump and cleaned them. Put it back together with the Glacier return line.

I now have constant pressure-12-16!!!

Even with it running and under load it won't pull down below 12.

It appears to have had a leak--on the intake side of each lift pump.

I suspect I over torqued the Glacier fittings and cracked it. I will look at it more this week.

Richard at Glacier and Chip at Blue Chip were both very good working with me.

( about the only way they could have been better was to fly into my town and wrench it for me). BUT, I wasn't going to ask!!!!!!!!!!

 

[coreyallan]

Any other trouble?

Fox, did you ever have an issue with your truck not starting when it was below 1/4 of a tank?

 

[fox]

No, it would start but not carry decent fuel pressure.

I was lost as to why the fitting started to leak after months of no issues.

I just got out of it and it has great, consistant fuel pressure today.

Since I changed out the module in the tank, it has been below 1/4-1/8 several times and I believe that issue is solved too.