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Why Why Why

F

frostedapp

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Well here I am again begging for help, just can't seem to get it right. I blew out the fuel line from the engine side of lift pump to the fuel filter. Now I can't keep fuel in the fuel housing, it pumps up to the filter, and only runs until the fuel housing is empty. did I possibly blow something loose in the fuel housing? o-ring? maybe the check valve? Oh by the way, I have a 97 chevy vortec 6.5 diesel k-3500 Pickup. Already changed lift pump twice, changed lines from tank to lift pump, changed float assembly in the tank, changed vac. pump, changed and relocated pmd to top of manifold, changed ops. Thanks for any help:mad2:
 
So it will pump fuel to fill the FFM but after it's running it doesn't pump?

How did you blow the line out? Just wondering if something could be plugging the line.
 
How about the 'last chance screen' smack dab in the middle of the FFM (inside of it).

Check the inlet barb of the FFM also.

Lift pump?
 
When I bought my truck it had fuel problems. That's why the seller finally gave up. I removed the FFM (fuel filter manager). Two bolts and 3 hoses. Inspect and clean out the inside. Then hooked up a pressure gauge with a hose barb, turned on to build pressure. Let it set over night. Same pressure in morning. So now I know problem is past the gauge if it won't stay running.

Just isolate part of the system at a time. Then it becomes much easier.
 
Start over. Assume new parts could be defective as the old parts. (Or not the problem in the 1st place.)

Put a pressure gauge on the water drain. Sounds like something is killing the lift pump when the engine starts. Like the prime function works but not the OPS. Fuse? Fusable link? Relay? Ground? Lift pump installed backwards? (And I would never admit that to anyone. :hihi: ) What is the voltage at the lift pump, back probe the connector, with the engine running?
 
I have changed the lift pump twice, im sure that it's installed correctly, have changed the ops and the fuse(the one you can jump to keep the lift pump pumping) Don't have a voltage meter and not sure I would know how to work one if I did. where is the water drain?
 
Looks like we need a pic of this in the LP thread. Water drain is a brass looking valve with a metal "T" handle on it usually on the thermostat housing. You can attach a 1/4" hose to it for draining water or Lift pump pressure test.
 
WarWagon said:
Looks like we need a pic of this in the LP thread. Water drain is a brass looking valve with a metal "T" handle on it usually on the thermostat housing. You can attach a 1/4" hose to it for draining water or Lift pump pressure test.
Click to expand...

This should help for now.
Parts locations.jpg
 
Seems to me that your lift pump is not running during engine operation, but it does by jumpering it, and it should also run during WTS and cranking. That means the relay or fuse is probably bad. There is a lift pump relay and the OPS provides a parallel power source, so both would have to be bad or the one fuse. Or the wire from the power source (LP relay and OPS) to the fuse is broken if it works when jumping power to the fuse, which you dont have to do since you have a diagnostic port by the fuse center. You need to check voltage at the power source side of the fuse. You can do that with a meter or just a test light to see if there is any power there.
 
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