No oil pressure under 1200 RPM

[lilb93]

I have a 1999 ford f-550 7.3 under 1200 rpm the oil light comes on. I changed the low pressure oil pump and front cover and seal . Same problem.. I checked the check valve inside the oil filter housing and that is fine also. The engine runes ruff real ruff. Wondering if anyone has a clue or has a similar problem. Thanks

[Brian]

may be a stupid question, did you try the oil pressure switch?
i had changed mine on my 92 250 after similar problems. engine did not run rough though..

link to switches

[lilb93]

I should have listed that , It was the first thing I changed.

[Brian]

hang tight, you will get some good educated guesses before to long.

[Lone Ranger]

How many miles on the engine? Is it just real tired? Low oil pressure can be worn rod and main bearings, and "runs real rough" can be low compression... Probably a bit basic, but how many miles on her??? She have much blow by? How about blue smoke? If yes to this, you have a answer, not a good one.... but...

Best of Luck from da Ranger in Oz....

[mschn99]

Originally Posted by lilb93

I have a 1999 ford f-550 7.3 under 1200 rpm the oil light comes on. I changed the low pressure oil pump and front cover and seal . Same problem.. I checked the check valve inside the oil filter housing and that is fine also. The engine runes ruff real ruff. Wondering if anyone has a clue or has a similar problem. Thanks

sounds to me like you have a bunch of blowby somewhere that the low pressure pump is unable to overcome at low RPM's.......how many miles??? and do you know the full mainanence history??? has there been any evidence of dusting.......Marc

[lilb93]

There is NO blowbye at all. There is about 90,000 miles on it. Blows no smoke at all. I am going to pull the engine this weekend.