i have a 1989 ford f350 with a 7.3 ,there is a problem with the oil pressure ,i put a mech gage on it.allmost no oil pressure at a idle.when i rev it up the oil pressure comes up and then falls off ,it bounces around up and down.at idle it shows no oil pressure.what could this be ?? also it blows alot of blue smoke and idles really ruff.i just put in a new 1 piece lux flywheel .it was shaking before and after i put it in .i loosened the injector lines one at a time and they all seemed to make a difference .where would i find the block numbers to determine the yr of the motor thks

 

hmmmmmmmmmmm, might be bearings causing the oil pressue problem or in the oil bypass system - a wacky valve in there. There should be numbers on the block here ... standing at the front of the truck, to the right of the injection pump housing there is a flat area on the block --- look there.

 

where is the oil bypass valve on this 7.3 ?? or do you think the pump is bad ??

 

NOT SURE BUT I THINK ITS LOCATED IN THE FILTER BULKHEAD OF THE OIL COOLER.

I KNOW ON THE 6.9 ITS LOCATED IN THE FILTER END OF THE OIL COOLER. I INSTALLED A REBUILT MOTOR IN MY COUSINS TRUCK LAST SPRING. IT HAD A LOW OIL PRESSURE PROBLEM. SO WE REPLACED THE OIL FILTER BULKHEAD END OF THE OIL COOLER. PROBLEM SOLVED.

GOOD LUCK!

 

its like a switch one minute the oil pressure is good the next it just quits.and go;s away. hard to explain as i put a mech gage on it

 

Something else to check would be to see if the suction pipe has broken off the oil pump. I've seen this twice on trucks that had been wrecked in the past. You can go up through the drain hole in the pan with a screw driver and see if it moves up and down.

 

found the problem i think and hope .broken lifter retainer plate .lifter broken , bent up pushrod.ect.,i think that the oil pressure got wacky because of the non restriction in the oil passages. it was just oozing right along lol

 

Ouch! Never seen that one before (maybe a bent pushrod, but not all that). Did it take out the cam?

 

stuck me finger down into the lifter bore .did not feel any scoring or galling on the cam.i have had small block chevys bend pushrods and lifters come out of the hole and oil pressure go away but this i never expected or ever heard happening on a diesel motor

 

thanks for all the help , everything working good

 

I have a ford f350 w/7.3 diesel. it has 120K. I have a similar problem with oil pressure. truck runs fine and sometimes the oil pressure is really low then other times it's normal or othr times next to nothing. yet i never hear the expected low pressure sounds from the engine. I chaucked it up to a bad oil guage. but maybe it's more serious.

 

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Also, the oil sending unit on the diesel engines is worth about 30 cents. Best thing to do is install a mechanical guage to see the zacharies. (zachary what the oil pressure is).

 

ebg_51,
Welcome to FTE and the IDI diesel forum.

What the stock oil pressure gauge says really means nothing.
If you want to know what is going on, get a mechanical gauge.
Mine does the same thing but it is not that way on the mechanical gauge.
If you replace the sending unit it will work better for about 6 hours.

About the same can be said about the temp gauge, but it is slightly better.

 

Thanks, I'll give it a try