ne_plus_ultra_1

I have pushed the button on my fuel pump a good several hundred times.

Not getting fuel through. Did a some hose replacement, screen cleaning, fuel pressure snubber and gauge and now I just cannot get it primed.

Very unlikely that pump with less than 5K went bad while I was changing out parts. Always had trouble with this truck losing its prime with both old and new fuel pump.

I thought it seemed smart doing everything at once...

I want to pressure test it before installing my new Tork Tek overflow valve if at all possible.

Any ideas on what to do would be appreciated.

Tate

Take the OFV out, it'll take the resistance from pumping out the air. You can do Bill's trick with pressurizing the fuel tank to get fuel to the IP as well.

infidel

Unless the primer pump portion of your lift pump has failed my bet is you have an air suction leak on the supply line side between the lift pump and tank. Even the metal lines fail.
Pressurizing the tank will prime the system and tell you where the leak is.
Most often air leaks don't leak fuel, pressurizing the tank is the only way short of throwing parts at it to find leaks.

Good info> http://www.cumminsforum.com/forum/94...m-writeup.html

rebal

double check your fuel line from the tank if it has a pin hole it wont prime and it will loose prime ,I had a 97 do that also check your filter drain it can let air in but not leak fuel

ne_plus_ultra_1

Loosening OFV worked just fine to get it to prime.

I too have always thought there was a leak somewhere.

A couple years ago, I pressurized the tank lightly and couldn't find any leaks.

I'd like to try that again.

I made a fuel cap that I could put a valve stem on. I could make that again.

How do you know when you have enough pressure and not too much?

There is no rust or corrosion on the metal lines however so I do not suspect them bad at this point.

j-fox

Bump the motor around a 1/4 turn and try again. I suspect the lift pump is 'up' on the lobe. I had that happen once. Do you feel resistance in it?

ne_plus_ultra_1

Once the air gets through there is resistance just fine.

This truck will lose its prime for no apparent reason sometimes. It doesn't matter if I am on a hill, flat, cold, hot, sometimes it won't do it for weeks.

Sometimes every day it will want to crank for about 20 seconds before working the air out.

Possibly I got rid of some of the air with the fuel lines I just replaced. Could be it's in the heater or back at the tank area, dunno.

What would be really useful now is knowing how to go about pressurizing the tank without overpressuring it.

infidel

Cam position makes no difference, the primer and main pumps are separate.

ne_plus_ultra_1

Yes, I think there could be a leak somewhere in the fuel line as you have indicated.

How would I go about making sure I do not over pressure the fuel tank please?

esde

Don't pressurize it too much or you'll cause all sorts of leaks that won't go away. Maybe 5 lbs? The lift pump doesn't generate that much vacuum so I'd worry about going too far beyong the limits the system was designed for.

ne_plus_ultra_1

Hmm, slightly off-topic but my fuel pressure went from 20 down to 15 with my new OFV.

It is adjustable though.

Nice having boost and fuel pressure gauges now.

infidel

5 psi max.
What usually happens first with too much pressure is your tank splits open

ne_plus_ultra_1

Yeah, that about aligns with my judgment.

How would someone gauge a PSI so low? Find a way to hook up a very-low-PSI gauge?

Oh, BTW, infidel, I don't believe I ever thanked you for the Chevy wheel cylinder mod. My truck has stopped extremely well since I did that.

j-fox

THanks for this info.
I had a 4bt and noticed that it-the primer- felt different when the motor was turned.
I will remember this.

j-fox

My 95 had a cold start issue for a month. Then one morning I found a fuel leak at the rear of the head.

I removed the clamp, slid the hose on farther, with a new clamp, and it was fine.
This is the return line from the injectors, I think.
It was confusing that the air would get in long before fuel leaked out.