Engine/Transmission (1994 - 1998) Questions about lift pumps etc.

[Loghead]

I just removed the lift pump/ pre-filter assy from my '97. Fuel heater is leaking ( no surprise to some here) costs almost 300 balloons for the part at the local Dodge dealer. I think I'm going to trashcan the fuel heater ala JoeG. and save some $$$.



Here's the question:

I vacuum tested the lift pump and when vacuum is applied at the nipple (from the heater/prefilter) it will not hold. Also, when I removed the pushrod, what seemed to be fuel (smell and texture) came out of the hole. Normal or not?

The side of the pump that feeds the fuel filter/injection pump held vacuum pretty well.



One more question: The rubber hose that connects the prefilter to the lift pump seems a little deteriorated. Can it be replaced with 1/2 inch fuel hose or do I have to empty my pockets at the Dodge dealer?

 

[CTD12V]

Hi Loghead,



The 90-degree hose from the top of the fuel strainer/preheater mount to the lift pump is a preformed hose. If you try bending normal fuel hose to fit that tight of a space, you will very likely end up with a kink that will end up restricting fuel flow. I think I remember reading on here about someone that tried that.



I got my replacement 90 hose from the local Cummins dealer, MHC Kenworth. If I recall correctly, it was about $18. 00 (I think). The new hose was a tad long on the fuel strainer end. I had to trim off about 1/8 inch to get as nice of a radius bend as possible.



Hope this helps,



CTD12V

 

[Joe G.]

It sure sounds like the fuel heater is burned up and leaking air. If the push rod is not in exactly the right position you will get fuel from the weep hole. If the push rod is out it will leak fuel from that hole.

 

[JFaughn]

You should be able get most things , not at dealer , find a Cummins dealer in your area , for the heater leak it is probably the wire harness , that & seals can be bought separately from Cummns .
As for the LP , test on truck is best /easiest , fuel pressure test , if low slowly pinch return at main pump while watching gauge , if the pressure comes up , replace overflow valve , then retest , if pressures are good & no leaks out weep hole , LP is good [ 17-24 lbs idle , 26-34 about 1,300 RPM ] .
If it starts with less than 1/8 tank the pump is good , if not the valves are bad , I have yet to find valves , so new pump .

 

[Joe G.]

The fuel heater usually leaks from the electrical connector because the heating element has burned up. It's not a good idea to replace it because it's worthless no matter where you live. Just a failure waiting to happen.

 

[Loghead]

Thanks for the replies guys.

I wound up ordering the hose from the Dodge dealer (5 bucks). I had to wait two days to actually get it.

I took the lift pump apart yesterday, and it's obvious why it won't hold vacuum with the pushrod removed (duhhh!) I re-assembled it and when operating the pushrod manually, it seems to hold at around 5"Hg continuously while it spikes to around 7" with each stroke of the pushrod. I'll re-use it and see how it goes.

I'm fairly confident the lift pump will be alright and not the source of my trouble because when I tried to apply vacuum to the heater/prefilter assembly I could hear a hissing sound coming from the female terminals in the heater itself. It's headed for the trash can, never to be replaced.



When I assembled the prefilter minus the heater, I couldn't get the thing to hold vacuum worth a nickel. It turns out that the aluminum casting had at least a dozen minute flaws which prevented the o-ring gasket from sealing. I spent a few minutes with a file- smoothing out the flaws (and they want almost 300 bucks for this thing?) It holds about 25"Hg now. Time well spent I guess.



Thanks again folks.

 

[JamesRoberson]

fuel pressure?

When you clamp the return line just behind the overflow valve how high will (or should) the pressure read? Mine idles at 20 and when I bring the rpms up it dips and then returns to only 20psi. Clamp the return hose and it goes to 50psi at idle.

Thanks

 

[JFaughn]

James , it sounds like you have a bad overflow valve , idle should be 18-24 idle , 28-36 lbs at 2000 RPM .
I do think I've seen a spec for max from pump with OFV blocked off .