Engine/Transmission (1994 - 1998) Lift pump failure?

[GAmes]

Has anyone had a lift pump totally fail? What are the symptoms? Here is my problem. I replaced my lift pump as preventative maintenance. The old one had nearly 300k and I was anticipating a lot of summer driving. I immediately had intermittant starting problems. I tightened the fuel lines into the pump. I removed the fuel heater. I replaced the elbow from the pump to the prefilter even though it wasn't very old. Every once in a while I still had to manually pump up the pressure to get the engine to start, other times no problem. I returned home a couple days ago, shut down, spent 20 minutes in the house then went out to move the truck. No start until a LOT of manual pumping. This morning the same thing. Got it started, then shut it off. 20 minutes later, same thing. I replaced my rubber fuel lines even though they were only 2 yrs old. 30 minutes later, no start. I am tempted to reinstall the old pump but really don't want to go thru that hassle unless there is a good chance that the new one (made in China, bought from Cummins) is bad. Any ideas?

 

[AABEN]

Yes call GENO"S--800-755-1715 they might help you.

 

[GAmes]

One more thing, when I removed the fuel lines there was no fuel in them.



I'm not sure what an after market parts store could do for me

 

[CumminsPower98]

Have you check the overlfow valve? What about the fuel heater? My cousin had some trouble like that once and it turned out to be a leak back at the tank where the line had rubbed on the frame. Maybe a valve in the pump is malfunctioning, I don't know. I have replaced a time or two in 400k but that was only to get rid of some tapping. It never let me down.

 

[GAmes]

I replaced the overflow valve with no change. I didn't really expect any, but it was an easy thing to do. I removed the fuel heater and installed a new prefilter and o-rings. Reinstalling the old pump is easier than dropping the fuel tank, but that is something I have not thought of. I replaced the original because it was tapping at 300k. That is why I replaced it this time, 300k, not tapping. Thanks for the response.

 

[MAleshire]

You need to hook up a fuel pressure gauge to determine if the lift pump is putting out the proper pressures at idle and at road speeds. Then you'll know if the problem is in the lift pump. There are plans here on the TDR forum for making your own fuel pressure test outfit. With the hard starts and having to manually prime the pump it sounds like a pump seal or air coming into the supply system from somewhere else. Since you've replaced or looked at everything from the pre-filter forward, if the problem isn't in the pump, then maybe it's time to start looking from the fuel tank forward to the pump.



Skip

 

[Missouri Mule]

Unfortunately a bad lift pump has almost if not the same symptoms as cracked fuel line (air getting into fuel system)... .



Have you noticed any fuel leaking especially in replacing the lift pump?



The check valves in the pump could be bad.



Once you get it running a fuel pressure test is a good idea.



When my return fuel line was sucking air I could park it facing down hill it would start but uphill or flat it needed to be primed. Another member's truck did the same thing but it was his lift pump causing his probelm.

 

[GAmes]

Unfortunately a fuel pressure gauge is something that I have procrastinated on for years. Since I didn't have this problem until I installed the new pump I'm going to put the old one back in tomorrow. The first and third sentences of MM's post gave me the needed push. I'll post my results.

 

[CumminsPower98]

I personally relied heavily on my pressure gauge when I was driving and running a large aux. tank. It helped me know when I was starting to suck air and needed to switch tanks. It also let me know when I had a filter about to go out before it left me sputtering. I wouldn't be without one now! I ran my filters significantly longer this way as I was able to see the pressure loss over time. I hope you find the problem soon, this sort of thing can be tricky.



Something interesting to note is that both my original lift pump and one on my cousin's truck both had small part circle copper wires in one of the valves. They looked nearly the same. I have no idea where these came from but might have been contributing to the problems my cousin once had. Maybe there is something like that in one of your valves that's letting it bleed off. I have never had any trouble like this with mine.

 

[FordCummins]

I had one of the check valves in my lift pump fail. Didnt leave me stranded on the side of the road luckily, but it did fail. Pump has around 180k on it when it died.

 

[EKlem]

It really sounds to me like you have an air leak regardless of whether the lift pump is working properly. I have heard of a few lift pumps having air leaks or it could be something else.

I know that you said you have replaced the fuel lines but have you replaced the one between the fuel preheater and lift pump? This line is a poor design in my opinion and will cause the problems you describe and make repriming hard. I had an air leak develop in mine just from the stress of taking it on and off. There is a now a piece of 1/2" line that does a 270 instead of a 90 degree bend which seems to be working much better.

Good luck.

 

[GAmes]

EKlem, maybe great minds think alike After tightening the fittings with no results the first thing I replaced was the rubber elbow, as noted in post one.



OK, I've reinstalled the old pump and ruled it out, the truck will not start unless I manually prime it. Once it is started it runs great. Now I am nearly out of ideas. There are no fuel leaks anywhere and I can find no damage to the metal lines. I currently have it parked on a downslope. What part of the return fuel plumbing could be sucking air?



I guess I need to PM Joe George for his fuel system info.



Thanks for the help so far.

 

[WDaniels]

GAmes,

I too am going through exactly what you describe. I got Joe G's fuel system troubleshooting guide(great stuff!) and went through it. Could find nothing wrong. I inspected the ends of the rubber hose going from the fuel heater to the lift pump. No cracking, nothing. Took off both the pump and fuel heater and am replacing the lift pump this morning. Then got to looking at the rubber hose because there was alot of gunk and stuff on it and when I bent the hose backwards a little it revealed a 3" slice in the hose that went down to the braid. Most likely problem found. Look closely at your WHOLE rubber tube, twist and bend it to find any cracks and pin holes. Hope this helps.

WD

 

[GAmes]

Thanks WD, but the tube is less than 3 months old and is perfect. How many miles on your lift pump?



Update: Prior to parking the truck on a downgrade I had driven it a few miles and checked for WOT boost, egt. ,etc. After 30 minutes it started like it should, on the first crank. Then I drove it back up on the front wheel ramps, watched some football (MN really sucks some times), drank a little beer, played some online poker. So over two hours later I try it again. Started on the first crank. Now I'm back to thinking the lift pump was bad and I just didn't get all the air out of the system by just starting it and letting it idle for a few minutes.



I need to have confidence that I have fixed this problem, I can't afford to be broke down in northern Canada or wherever my job takes me. I did find some chaffing wear on the return fuel line about 3 ft forward of the tank. However, I can't believe that this particular section is under any kind of pressure.



Any more ideas? Thanks for your support.

 

[WDaniels]

GAmes,

I have 250k on both the lift pump and the hose. So I guess it is time to change both anywise.

WD

 

[GAmes]

I got up early this morning and tried it. Started on the first crank. Woo-Hoo!

Went to breakfast with a friend in the wife's car. A couple hours later I went to drive it off the front ramps. It started, coughed and died No amount of manual priming would get it to start. I pulled the bleed bolt out of the filter head and got nothing but foam as I primed it. The filter was empty and would not fill. So I'm back to square one. After reading Joe's article I decided to drop the tank and pressurize the supply line to look for leaks. Not an easy job in a gravel driveway and 25-30 gallons in the tank. Once I got the tank on the ground I pulled the module and it is in pretty bad shape so will order a new one tomorrow if they are available. And to top it off my dispatcher called with a job and I had to turn it down. This really sucks.



Is 20 psi about the right pressure to check for leaks?

 

[GAmes]

I was hoping for some more input.



Today I pressurized the supply line in the module and blocked the return line to the module. I could shoot 20 psi in and wait for 5 minutes, release the return line plug and get a whoosh of 20 psi back out. A friend and I did this numerous times while listening for air leaks and putting shaving cream on every fitting from the tank to the engine and back. No joy. I then put the draw straw into a container of fuel and tried pumping the primer. After a lot of strokes I finally got foam. No amount of work would give me a solid stream of fuel out of the bleeder bolt hole. My friend who is a professional mech, but has no experience with diesels, suggested that the lift pump I put on may have failed. Before I take it off does anyone have an idea what else to try? The only one I have is to disconnect the rubber supply line that I just replaced and try to draw fuel from there, which would eliminate the plumbing from the tank, the hard lines on the frame and the braided line. That will be job one in the morning. HELP!!!!

 

[CumminsPower98]

I had my metal return line behind the injection pump crack while up in Grand Prairie AB in the winter so I know what you mean. That is a tough line to get at and I found the problem on a Saturday. I road around a little with my cousin (lucky me he was still driving at that time) and finally found a guy in a shop that wasn't even open and he brazed it up for me at no charge and its still holding fine to this day. We went by the Dodge dealer to get some rubber hose and they just gave it to me, wow, they are nice up there! It was freezing, snowy and the wind blowing but I got it back together and hit the car wash.



The line cracked on the bottom side right next to the mounting tab. I'm pretty sure I know why too. I probably put the tube in a slight bind long before when I last installed the overflow valve so be real careful anytime you are working with metal lines not to put any bind on them as the vibrations can kill over time.



I once fixed a metal fuel line on a 24 valve that the dealer had fixed twice before. I brazed it and installed correctly and it never had another problem. I know they were putting the line in a bind when tightening the banjos just as I did on mine.



I know this has nothing to do with your problem, just food for thought to whoever it might help.

 

[GAmes]

I think I may have found the problem!!! I was puzzled by the portion of Joe G. 's writeup that talked about a fiber washer that goes on the supply line fitting into the prefilter. I thought he was talking about a flat washer and could not see one. My thought was a 97 is different. Today I started to remove the lift pump. When I disconnected the line into the prefilter I felt an odd piece of material between the tube and the nut so I contorted myself enough to actually see this fitting. Now I know what he is talking about. I thought it is a normal flair fitting.



Now the problem is, where do I get this seal? It looks like a short length of fuel line but the 3/8 fuel line I have is too thick to go under the nut. The local Dodge dealer doesn't list it.



BTW Joe, if you read this feel free to include the picture along with the verbage on page 4 of your PDF. Some of us don't interpret english as well as we should. :-laf

 

[MAleshire]

That part is a square cut "O" ring for the top of the pre-filter assembly. It's available through Cummins and the part number is 3923194. Hope that resolves your problem.



Skip