Engine/Transmission (1994 - 1998) Lift pump help

[BIG C]

Replaced fuel lines, and injection pump with a new filter on a 12V. I cracked open the bleeder on top of the fuel filter and manually pushed the primer button until both of my thumbs are sprained. After lots of pumping and using the starter I finally got all the air out of the bleeder bolt. I still cant get fuel to the injection pump. I took out the bleeder bolt on the fuel filter housing and if I manully pump it I get fuel out the top. If I crank it over with the starter nothing comes out of the bleed hole. Could I have installed the lift pump incorrectly or does this mean definatley a bad lift pump and I need a new one. What can I check for??



Thanks

 

[GAmes]

Which did you do, the lift pump or the injector pump? Once I get fuel out the bleeder hole on the filter housing I close it, then manually prime until I hear the overflow valve squeal. If it doesn't then I'd say the lift pump isn't pumping and if that is what is new then it is bad or the plunger fell into the oil pan

 

[BIG C]

sorry for the confusion. I am doing an engine swap. The block is a 94 along with the original lift pump that had about 180K on it and worked at the time I pulled the motor and rebuilt it. I replaced the injection pump, injectors, and fuel lines but decided to use the original lift pump because it worked when I pulled the motor.



Anyways, by pusking the priming button I got all the air to come out of the bleeded bolt on top of the fuel filter. Only fuel would come out when I manually pumped it. I tightened the bleeder bolt and used the manual primer button to push fuel to the injection pump. Despite 100k pushed on the primer I couldnt get fuel to the injection pump from the fuel filter. I loosened the bleeder bolt again and got fuel to come out by pushing on the manual primer button. I left the bleeder open and cranked it over with the starter and nothing would come out of the bleeder hole. So I expect the lift pump is not working. ??? Possibly installed wrong????



UPDATE..... I took the lift pump off and put it in a vise. I put fuel in the inlet of the lift pump and pumped fuel out the top by using the primer button. Then I tried to do the same thing by manaully pumping the rod/piston that rides on the camshaft. Fuel blew out the top of the lift pump much more than with the primer button. This makes me think the lift pump is working correctly. ????? Does this sound right?? Should I reinstall it and try it again??? Anything else I can try???

 

[Joe G.]

Take the fuel heater out of the pre-filter assembly, put it back together without it, and try that. The input fitting on top of the fuel heater has a grommet in it that can go bad.

 

[bmoeller]

The primer and the main part of the pump are seperate springs/plungers.



On my truck, I never open the bleeder screw after a filter change. I just use the primer 'til the OF valve squeals, then push the primer about 50 more times. Fires right up.

 

[Joe G.]

Your bench test showed that the pump springs and check valves are ok. I would suspect an air leak. If you still have the lift pump off the engine, put it back together with the fuel heater/pre-filter assembly, install the input and output steel lines, restrain the push rod so it won't come out, pressurize the whole thing to about 20 PSI and dunk it in a five gallon bucket of water. If you have an air leak that will show it. If the push rod is not in the proper depth you may get some bubbles from the weep hole in the mounting part of the lift pump.

 

[BIG C]

Your bench test showed that the pump springs and check valves are ok. I would suspect an air leak. If you still have the lift pump off the engine, put it back together with the fuel heater/pre-filter assembly, install the input and output steel lines, restrain the push rod so it won't come out, pressurize the whole thing to about 20 PSI and dunk it in a five gallon bucket of water. If you have an air leak that will show it. If the push rod is not in the proper depth you may get some bubbles from the weep hole in the mounting part of the lift pump.

I will give that a try tomorrow. Anyone know where to get some 1/2" fuel line. I might as well replace the line from the heater/prefilter to the lift pump while I have it off. I'll bet that is my air leak as the line looks a little shady. Thanks for all the help. I'll keep everyone updated. One question though, why would the manual primer button blow fuel out the bleeder but cranking it over with the starter would not?? I would suspect the lift pump being bad but the bench test indicated it to be working properly. Could or how would an air leak cause one to work but not the other??



Thanks

 

[Joe G.]

It may because you are pumping fuel slower with the push button so the air leak won't kill it. I went through this same thing about a year or so ago. I was about to replace the lift pump but decided on a couple more tests. In one of them I took the short bent hose off and installed a hose from the lift pump to a bucket of fuel and a hose from the lift pump output to another bucket. Then I jumped the starter so I could watch what happened. The lift pump really moved fuel!!! The hose came out of the output bucket and I got fuel all over the place. Should have used a longer piece of hose for that. With the short curved hose it would start to pump ok and fizzle out. Then I took the whole mess off the engine and did the five gallon bucket of water test. Much to my surprise I had bubbles coming out of the electrical connection to the fuel heater. There are pictures of it demonstrating what was wrong with it in my Reader's Rigs gallery. I told another guy about the bucket test who was haveing what he thought was a bad lift pump problem. He tried it. His air leak was the grommet in the input fitting to the fuel heater. Both of these problems are cheap to fix. If it's the fuel heater just leave it off the engine. If it's the grommet replace the fitting. Lots cheaper than a lift pump. I always like to check all the cheap stuff first. The short curved hose may very well be your problem. If so you will get some bubbles from it.

 

[BIG C]

First of all THANKS to Joe G. The test you recommended was fairly simple and very effective. Why coudnt I have thought of that. Anyway, the good news is my fuel heater has a good seal to it. The bad news (or good news really) is the fuel line connecting the lift pump to the fuel heater/pre filter has a leak. I hope NAPA has some 1/2" fuel line. If not where I can get some? Cummin$??



After putting the lift pump/pre filter in the busket of water and pressurizing it I can answer my own questions and maybe help someone out in the future who might have the same problem.



here goes..... when I cracked the bleeder bolt on top of the fuel filter assembly I could get air and fuel coming out the bleeder hole. When I cranked the engine over with the starter I couldnt get any air or fuel, nothing. Well the lift pump must be bad?? Not so fast. After performing the bucket test and finding the hole in the fuel line I would guess by manually priming the lift pump it did not cause enough pressure or enough suction to suck air through the hole but would suck fuel up through the line. When the starter was engaged and drove the piston on the lift pump it creates much more pressure and therefore was forceful enough to suck air though the pinhole in the fuel line.



Anyway, thats what I learned and a big thanks to all that helped.



Now I just need to go out and install the pump again and go through the priming process all over again. Wish me luck!!!



THANKS!!!

 

[GAmes]

Believe it or not, that 90 degree hose is cheaper at the dealer. I know because I just picked one up today. mopar part # 4883978-AA $6. 86 + tax. My buddy at Cummins quoted me about $20 + tax. But if you want to check, their part # is 3931523.

 

[Cooker]

I paid less than $10 at Cummins. I would have to dig up my receipt to double check the exact amount but I want to say it was $7 and some change.

 

[Joe G.]

Good news! You found it. I forgot to mention something. When I fixed my air leak it was a few days before my fuel pressure was like it should be. I don't know how many miles, but it was not many. Just running around Eureka going to the store and things like that. Maybe air trapped in the system or something like that. The kind of worried me, but the truck was running fine.

 

[BIG C]

As long as I have the lift pump and fuel lines off what is the best/easiest way to run a fuel pressure gauge. I have to run a boost and pyro so I might as well run a fuel pressure while I am at it.



Thanks

 

[biggy238]

Drill and tap the banjo bolt that feeds into the side of the injection pump. Joe has a close up shot of it. The banjo seems almost as off it was made to be drilled when you look at it.



Easiest method seems to be to drill to 1/8th inch NPT and run a grease gun hose out of that over to a fixed location on the fender and then the sender for a gauge. Joe's had a needle valve to dampen the pulses from the lift pump installed in the banjo and the the hose.

 

[Joe G.]

Drill from the inside because the way the fitting is made will guide the drill bit do the hole is straight.



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