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5.4 lt No oil pressure with new pump??


Old 10-18-2010, 04:46 PM
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Location: st thomas, Ontario, Canada
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5.4 lt No oil pressure with new pump??

Hi Everyone,

I'm new to the site, this is my 1st post.
I'm working on a friends 2000 F150 7700 series 4x4 5.4lt. The truck suddenly lost oil pressure while driving on the highway. The engine was shut down right away and appears to have taken no damage. I verified no oil pressure with an external gauge. This is a high mileage truck, approx 250 000miles (389000km). Upon dissassembly I found that the timing chains and guides were junk. I replaced the oil pump and timing set. I changed the oil and filter and cranked the engine with the starter to prime the pump and verify oil pressure before I put the front cover back on. When I removed the old pump I dissasembled it and found no damage. I even put about 15 inches of vacuum on the oil pressure guage port in an effort to help draw the oil into the pump with no luck. I removed the filter as well and the pump will not pick up the oil. I suspect the pickup tube is cracked, although I haven't been able to verify this as I changed the pump without removing the oil pan. As the engine lost oil pressure suddenly on the road I never suspected a broken pick up tube. I should add that when I changed the pump I cleaned out the inside of the tube and verified there was no blockage with compressed air.

Has anyone ever experienced this before? Does the starter motor spin the engine fast enough to prime this type of pump (gerotor)?

I am going to pull the oil pan later this week and see what I find. I will post my findings.

Thanks for the insight
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Old 10-19-2010, 06:09 AM
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Join Date: Nov 2006
Location: So. Cal.
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Aren't you supposed to grease the pump with something like white grease before install so that it WILL prime immediately when 1st started? I know the starter will prime a pump after an oil change because I always hold the throttle to the floor after a change to disable the injectors (about 3 seconds is all it takes) so that there's no rattle on start. I know that's not the same as a newly installed pump.
Did you mean you blew into the oil pick up tube with air into the pan? Meaning that would have verified that there wasn't an obstruction on the pickup screen.
Hasn't ever had FRAM filters used on it has it??? I wouldn't use them on a donkey wagon! Have read toooo many stories about them coming apart and clogging galleys.

Last edited by code58; 10-19-2010 at 06:12 AM.
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Old 10-19-2010, 04:15 PM
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Join Date: Oct 2006
Location: Michigan
Posts: 1,771
If the chain guides nylon pads were severely worn/damaged then there could be nylon pieces blocking the pickup screen (probably the problem). Also there is a rubber "O" ring that should be seated on the pickup tube right where the pickup tube enters the pump, just above the flange where the two 8mm bolts are seated to hold the tube on the pump. If it was missing then you will not prime. No need to prime the new pump. Yes, sometimes loosening the oil filter while cranking the engine will help relieve any airlock in the system.

Last edited by DYNOTECH; 10-19-2010 at 04:18 PM.
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Old 10-22-2010, 05:38 PM
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Location: st thomas, Ontario, Canada
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I did blow air through the tube into the pan, 90 psi shop air. The o-ring on the pickup tube is in place, however I did not grease the pump before assembly.

thanks for the replys.
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