Archived 96 lift pump air locked

[EKlem]

I changed my fuel lines today and cannot get the truck to restart. I cannot seem to prime the fuel system between the tank and the lift pump. The fuel lines are connected right because I can suck fuel through at the line between the fuel heater and lift pump but I cannot reconnect the lines without introducing air. Once they are reconnected, cranking the truck and pumping the primer with the bleed screw open does not suck fuel into the pump. I tried lifting the back of my truck as much as I could(only about a foot) and I also tried pressurizing the fuel tank with a bike pump but neither worked. I have pumped the primer bulb enough times to make my arms really sore but it does not seem to make a difference.

Any suggestions on this? It seems to me that I have air in the lift pump and it is unable to pull it through in order to get to fuel. How do you guys prime this? Thanks for the help.

 

[Joe G.]

Remove the plug to the fuel heater. Grease it up good and put t back in. See if that affects the problem. If it does then the fuel heater has burned up which causes an air leak in the electrical connection. It could have been this way for some time but with no other air in the fuel system the lift pump may have worked in spite of it. Mine was that way.

 

[EKlem]

Thanks for the reply. I changed the prefilter and greased the heater connection as you said when I replaced the lines. I guess that I better check to make sure that the new ring for the prefilter isn't leaking. I will check on that tomorrow morning and I will make sure that the plug is well greased.

 

[Joe G.]

The fitting on top of the fuel heater is another suspect. It's a pretty poor excuse for a fitting. In the struggle to replace the fuel line you may have damaged it. Not hard to do.

 

[wcjp]

When my 96' had an air bubble after repairing the lift pump I used my air compressor. I turned down the regulator to about 15psi. Had the wife hold the airline inside the fuel door with a rag to help seal the opening. This took 5-10min before it started to work. The fuel filter was removed initially. When fuel started to squirt where the filter was I reinstalled the filter. I cracked open three fuel lines. It took a few minutes to get fuel to the injectors. Once I was leaking fuel at the injectors everything was tightened down. Started with a slight hesitation that smoothed out right away.

 

[EKlem]

I will check those fittings and try to figure out whether there is an air leak. Will the lift pump actually be able to pump air or will I have to really get fuel into it to remedy this? Thanks guys.

 

[Cooker]

I know when changing the FF if the LP does not prime after the procedure the LP needs replacement. In this case I would also think if it does not have enough pressure to prime the system again it may have failed.

 

[EKlem]

How would I figure out whether the LP needs to be replaced? I don't have a pressure gauge. It was replaced with the injection pump 10k ago.

I pulled the electrical connector on the fuel heater and regreased it. There seemed to be a lot of diesel fuel diluting the grease in there so I am guessing that it is bad. I was able to get fuel to the injectors(black exhaust smoke) for a little bit but now I am back to air. I think that I will keep trying. Keep up the good replies.

 

[EKlem]

I want to thank you guys for your help. I believe that the problem now is that my lift pump does not work. I primed it using the primer and then cranked with it and even with my fuel filter off, it did not move any fuel. So I have given up because I need to go to school. Guess I will be riding the bus and the dealership will have to fix my truck because I am out of time. Thanks a lot, this is a great website.

 

[Cooker]

Where are you located? Maybe someone might be willing to lend a hand for a few $$$ or sodas

 

[EKlem]

I'm visiting my parents in Lincoln, MA but I go to school at Dartmouth in NH. That's a nice idea but I have to go to school so that I don't miss classes and I can't find any lift pumps near me(the fact that it is a holiday doesn't help). I am going to have to suck it up and pay money this time.

 

[Cooker]

NAPA sells lift pumps for our trucks. They are about $130. FWIW - NAPA aroud here is open today.

 

[Joe G.]

I was convinced that my lift pump was bad, but made one last test that discovered the air leak in the fuel heater. Another guy used this test to find another air leak. Take the lift pump off. Attach the input steel line to the fuel heater. Attach the output steel line to the lift pump. Restrain the lift pump push rod so it won't blow out. Pressurize the whole mess and dunk it in a bucket of water. If you have an air leak you will see where it is from the bubbles.

 

[EKlem]

I pulled my fuel filter to do my testing. I was able to pump solid fuel(no air) with the primer bulb but when I had my dad crank the engine, there was no fuel coming out where the fuel filter goes. I figure that the pump had to have been primed since the primer was putting fuel straight through it but it still did nothing. It was sure sad to see my truck taken away on a flatbed but now I won't miss the first day of classes trying to get my truck going. I will keep the test with the bucket of water in mind if I ever have problems again. Next time around, I am going to have a fuel pressure gauge. Thanks again.

 

[Joe G.]

Most of the time the lift pump is ok. Really sturdy gadget. So it's best to find out what exactly is wrong before just throwing parts at the problem. For example, you may replace the lift pump when the problem is a fitting. In doing so you may fix the fitting and think the lift pump was the problem. The way the primer button works it exercises all the valves in the pump. When it's pushed it will push fuel through the outlet check valve. When it is let go it will suck fuel through the input and piston check valves. My lift pump worked just fine in my vise. But when I put back on the truck it would not pump fuel. I could pump some fuel with the button so it would prime, but if I started it then the air leak starved it out and it would die. Sometimes it takes a bit of trouble shooting to find what really is the problem. If you don't have time then you end up spending a lot of money to get a shop to do it. Keep the old pump if you can. You may need it some day.



I have a fuel pressure guage to head off problems like this. My original lift pump will still peg my 40 PSI gauge in certain conditions.