Engine/Transmission (1998.5 - 2002) Eureka! post filter change hard start idea

[Schlickenmeyer]

So, I have always had a no start after a fuel filter change. Gave up figuring out why after I figured out that an air bleed using the schroeder valve on the VP44 would do the trick. However, my recent fuel system woes have made me read and then it clicked. Both the old and new stock pumps never put out over low 13 psi. If the valve in the VP44 opens at 14psi, then I can't bleed air with the lift pump as it has nowhere to go. Hence filter changes are always a pain.



So did I miss some thing obvious, or did I just stumble onto something?

 

[HGreen]

My 89 Ford 7. 3 had a schrader valve on the fuel filter housing, when changing filters it was easy to bleed the air, just unhook the electrical solenoid connection on the injection pump, loosen the valve core, turn over the engine a few times, and it was ready to go. It was even easier when I swapped an electrical pump for the mechanical pump.

 

[cyborg]

Interesting thought.
When I did my lift pump the third time, I wanted to install a "prime" button. One of those momentary switches with durable black rubber condom cover (so often seen as starter switches) battery hot to the fuel pump.
My thought was I could open the water drain, push the button until fuel came out.

 

[Oasis-3]

Fuel Filter

The best thing I found to do when changing my fuel filter is to fill up my fuel tank before I change the filter. I changed the filter one time with only a 1/4 tank and had a real hard time getting the truck started after the change. When the tank is full I bump the key 3 times and watch my psi. gage come up and start the truck. It works for me



Cliff

 

[jkalchik]

I cheat (kind of. ) I built a jumper cable to connect the lift pump directly to the battery when it gets changed. Once it's primed again, connect the pump to the original harness.

 

[Schlickenmeyer]

And that's great if your pump puts out enough pressure to open the valve.

On mine, I can bump it 4 or more times and still bleed air at the vp44.

The core problem I have is the air can't go anywhere until the valve in the VP44 opens to let it go back to the tank.

 

[rweis]

I put Aeroquip fittings on the VP44 and feed with An-6.



When I work on the fuel system, I disconnect the AN-6 at the Vp44 AND CAP the Vp44 with a An-6 cap so no fuel will dribble out of the VP44. Then I built a LONG hose back to the tank with the right fitting on the feed to the VP44. I temporarily install the long hose, bump the starter, the lp pumps fuel through the entire system and then though the long hose back to the tank. Bump the lp as many times as needed to get solid fuel stream and no air through the long temporary hose back to the tank.



Take the temp long hose off, take the cap off the VP44, and quickly connect the two. You have solid fuel right at the VP44 guaranteed. Starts first time every time for the last 2 years or so since I have done this system.



Bob Weis

 

[Nate]

All I do is change the filter, bump the starter 1 or 2 times to cycle the pump and after a couple seconds of cranking, it fires up. Pretty easy.

 

[Schlickenmeyer]

Every time I have changed a filter I have air locked. I have tried bumping 6 times, prefilling, you name it. I will be so happy to get the new fuel pump and filter assy on this weekend. Then I can try this as it was meant to be.

I wonder if the valve in the vp44 is stuck, it has not opened in 6 years.

I have never seen 14psi on this truck.

 

[obert]

The water drain is on the botom of the filter housing, it wouldnt get the air out of the housing.



The machines i work on have a bleed valve on top of the filter, you just open a screw and the air is allowed out. It will fit in one of the plugs on my filter housing, I'm working on getting one of those. >> I could buy one and be done, I must be too "frugal", waiting on one to show up on a junked engine or in the warranty pile.

 

[cojhl2]

When I change thefuel filter on any diesel I fill the canister with clean fuel first.

 

[Schlickenmeyer]

The valve I spoke of is the test fitting on the injection pump, not the drain on the filter. I always drain the bowl, install the filter and refill with the lift pump, otherwise unfiltered fuel gets to the injection pump.

 

[cojhl2]

The valve I spoke of is the test fitting on the injection pump, not the drain on the filter. I always drain the bowl, install the filter and refill with the lift pump, otherwise unfiltered fuel gets to the injection pump.

Which brings up a very good point,, You gotta be careful and use only clean fuel and make sure you don't drop something in the filter during install.



Of course that's true even when installing a filter with no fuel in it I guess. .

 

[rweis]

That is where my hose back to the tank also works well. You cycle as much fuel through your system as you want back to the tank until you are comfortable that you have clean air free fuel. Let's say you accidentally get some contaminant dirt in the filter cannister during install. How do you get it out? You wipe it out only further exposing the filter housing, or you flush it back to the tank, no harm done only to be refiltered as it is refed back to the VP44. Maybe some trash on the inside of the filter element you did not see, you flush it back to the tank.



The only possible contamination fouling you have is unscrewing an AN-6 fitting and screwing it onto the Vp44 fitting. You can control both of these fittings fairly well and it is significantly less total surface area to keep clean than the surface area of the filter housing / filter which you are taking out the old filter and inserting a new filter on a regular basis.



10um is not a very big piece of lint left on the inside fo the filter during production.



Just an idea,



Bob Weis

 

[Schlickenmeyer]

Wish I could go nuts, but I will be lucky to get the Airdog installed. Gonna be really cold. Ok, is already really cold. Borrowing a garage, but when it will not get above zero degrees for 3 days (even in the daytime), we shall see how warm his garage is. .

But I do now wonder how many stock systems can't even activate the overflow valve in the VP44. . Gotta love chrysler.

 

[obert]

When I change thefuel filter on any diesel I fill the canister with clean fuel first.

You havn't changed the fuel filter on a '98 ctd, have you? :-laf Its sideways and/or upside down on the way in and out.

But I do now wonder how many stock systems can't even activate the overflow valve in the VP44

I dont think it's supposed to. The VP has its own gerotor charge pump for filling the gallery and running the timing servo. Which does bring up an old question-- Why does low fuel pressure kill a VP44? The engineers say any positive presure on the VP means the lift pump is pushing more fuel volume that the VP needs. To their benifit, I have seen a VP pull a vacum on a failed lift pump, knock on wood its still alive today. We all know that is an exceptoin to the rule. Experience has proven that.





It just seems odd to me as a hydraulic mechanic that a gerotor needs to be charged with 10-14 psi in order not to fail. Maybe the inlet port is too restrictve? Ive read lots here, but its still a paradox to me.

 

[cojhl2]

You havn't changed the fuel filter on a '98 ctd, have you? :-laf Its sideways and/or upside down on the way in and out.

Holy Sh... That is a prob. Haven't thought about it before but the filters I've changed (on mach other than dodge also) I never ran into that prob.



I guess you jsut gotta be real fast to overcome gravity.



Thanks obert for updating my knowledge. .

 

[Ncostello]

If I remember correctly from diagrams and looking at my 99's parts...



My truck didn't have the schrader valve. I believe the schrader was added later. Anyhow... the relief valve for the return line was actually part of the banjo bolt that held the return line to the side of the VP.



There is a pinhole sized galley in the bolt that allows air back to the tank without the need for the 14psi check valve to operate. I looked and mine was in fact like this.



So I'm not sure the relief valve needs to operate at all. Or if air can be forced through this opening as well as pass throught the VP as well and return without going to the injector lines. I think its possible.

 

[Schlickenmeyer]

Well, at least for me here is the deal:



Before: 2-3 bumps on the starter after filter change, airlock



Today: put in airdog, only prefilled water seperator, all new fuel lines (1/2 inch) from the tank to the stock filter housing, plus the filter all full of air. bumped 3 times. Hit starter, cranked 2-3 revs, hit the pedal, boom. truck alive again. Now with the amount of air in the system - A LOT. . especially vs. a filter change. I so wish I had done this years ago.