lift pump help!!! no fuel out of top of filter

[PHAEG]

changed fuel filter , never had problems before with air in the system etc.. This time I followed the same proceedure and the truck fired right up and killed. Opened valve on the top of the filter
finally got the thing started but never had a drop of fuel come out of the valve. Does this mean that the lift pump is not working and the only thing keeping the truck running is the injection pump pulling fuel on its own?

[moondoggie]

Good Day!

Something in the lift pump SYSTEM isn't right, which includes many things, one of which is the lift pump.

You might want to click on "my profile" & let us know what year, etc. truck you are talking about. It's handy, because you don't have to remember to do it, it shows up at the bottom of all your posts automatically. smile.gif

Blessings!

Brian Johnson, #5044

[charliepeterson]

With the truck running you must have twelve volts down to the lift pump.

Depending on the year of the truck the next circuit might change slightly.

We have two separate circuits feeding the pump, cranking and run. On my truck if I put the truck in gear and hold the key in the start position the "cranking" circuit is live to the pump and fuel comes out of the filter as long as the key is held. After the truck starts the ECM takes over and goes through the oil pressure switch to feed the pump. This is a safety circuit in case of an accident. These oil pressure switches are known to fail here causing all kinds of performance issues.

[Hye]

Sometimes the lift pump will get a little piece of rust, dirt stuck in the plunger. Tapping it with a wrench can shake it loose. Worked for me once, but I replaced the pump later when it was more convenient. Crud in the tank will continue to clog pumps if you don't clean tank or install a filter between tank and pump.

[mad rad]

had the same thing with mine.I unpluged the lift pump ran a wire from hot side of battery to brown wire on pump and a ground wire to the frame from the other and the pump worked so I changed the ops(oil pressure switch) and everything worked.

[PHAEG]

have a 96 , lift pump runs when engine is running.
If I open the valve on top of the fuel filter the engine will run for a while then die. I tried the test of putting the truck in gear and turning the key and the lift pump does not run. Put in a new relay and still no lift pump running while key is turned. Any ideas?

[JohnC]

Originally posted by PHAEG:
I tried the test of putting the truck in gear and turning the key and the lift pump does not run. Reportedly that trick doesn't work on '96 and up. Get someone to hold their hand on the pump while you crank the engine over. It should run then.

[MTTwister]

On 96's there's a pre-start relay that runs the pump during the glow cycle. After start-up, the OPS takes over. You should be able to hear the pump during the glow cycle phases, and after start-up, you can slide under and feel the pump 'humming'. OPS points tend to burn -out, look for thread on OPS Relay install. May be able to salvage "almost" shot OPS points by taking the current off the contacts.

[rjwest]

On 96 and latter, Under the hood, driver side by hood hinge ,there is a wire bundle,. Look for a connector that has nothing attached. This is a
jumper port for the lift pump 12 volts.

Jump this connector to 12 volts, ( a fuse in line may be prudent ). this will run lift pump continuesly, bypassing all other controls.
Ign does not have to be on.

Check fuel pressure at filter, listen to pump,
, bleed filter ,etc..


Also a mechanic told me to feel the fuel shut off solenoid while he turned ign on and off. Said , thats what a good one feels like. Remember it. if truck does not start, do the " feel" test, you will know a bad solenoid.