help

[chigger]

have a 95 7.3 ran fine but leaked badly had oil cooler redone now mec. said it is not getting enough oil press the oil resivoir on top has to be filled manualy to get it started when cold also when i turn on the key the oil press, guage goes backward from when key is off once it is stearted sounds fine runs fine was told needs new front cover & oil pump for 2000.00 sounds like b.s. to me but if i knew better i wouldnt be here asking q,s also said he replaced sending unit but would not fix guage prob thank you for help:

[mschn99]

i have seen very few low pressure oil pump failures, but the symptoms you described would fit with the symptoms you should get if the pump is weak. the low pressure pump feeds the high pressure pump. if the low pressure pump is not feeding enough oil at start up to the high pressure pump, the high pressure pump does not have sufficient oil to run the system. the most common cause of a hard start or no start due to lack of oil pressure is weak batteries. if the motor does not turn at least 600 rpm, and maintain over 10 volts during this cranking (i think its 10.5, but i dont remember right now for sure) the motor will not fire, or will crank excessivly before building enough oil pressure to fire the injectors. what you are being told is possible, altough not common. there is a small hex head bolt on top of the high pressure resevour. check it cold, after an overnight sit. if it is within about a half inch or so it is full enough to start with good batteries. just a few ideas, let me know if i can help you anymore.......Marc

[chigger]

when i let the truck sit i have to put about 1/2 a quart of oil in then it will start just fine what i a being told is that when the oil cooler was replaced air got in the system an my oil pump is to weak to reprime the system any suggestions appreciate your time & help

[mschn99]

Originally Posted by chigger

when i let the truck sit i have to put about 1/2 a quart of oil in then it will start just fine what i a being told is that when the oil cooler was replaced air got in the system an my oil pump is to weak to reprime the system any suggestions appreciate your time & help

that is possible, im assuming you are puting this oil you have to add in the high pressure pump resevour. what i am doubting is that after it fires, the high pressure system should purge all the air out after one good running, and the oil cooler is on the low pressure side, so the high pressure rail should not have drained back when it was changed, it should have been no different than an oil change, i would almost think that maybe it was an oil leak. here is what to do. the spec on that resevour is to have oil an inch from the inspction hole or less. fill your truck up, and go run it at least ten miles. when you shut it off, check the resevour level immediatley. if it is within one inch of the top, let it sit overnight. if it is not within an inch, condemn the low pressure pump. if it was within an inch, check it agian the next morning. if it is low then, you have a leak between the resevour and pump that needs to be fixed. hope this helps, this is right out of the ford repair manual, let me know if i need to clarify at all........Marc

[chigger]

ran the truck oil res was almost empty , baffeld if there is no oil getting to resrve then what is driving injectors once it is started it runs fine

[mschn99]

going off of that then, i would think it would be pretty safe to condemn the base engine oil pump, as the guys at the shop had done. i went and looked at the factory repair manual, and if the resevour isnt full right after a 10 mile or so drive, then the pump is weak. the injectors can run off of the oil pressure from the pump even if the resevour is low, as long as some oil is getting there. to start it requires that more oil is presant to keep air out of the high pressure system. if you cranked it long enough, it may fire even with a low resevour, but you would have to crank it longer than two or three sets of batteries would be capable. once its running there is enough engine rpm to keep the high pressure system flowing even though the resevour is low.........Marc

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Last edited by mschn99 : 01-25-2006 at 03:20 PM.

[chigger]

i really thank you for your time & help i would appreciate yor opinion this truck is a f350 4 door had it for 3 years put a new wiring harness & trans in those years it has 312000 miles runs great has had a bit of a miss sometimes but have been driving it day to day and back and forth from dallas to abilene which is a 3 hour drive am i looking at the end with this truck or is it possilble to get another 100,000 miles or so without more major repair

[mschn99]

if the maintanence has been very good, you could double that milage or more. the big thing with the 7.3 was oil changes at proper intervals. if this was done, that motor could hit 600,000.......or more, seen them with over 900k on a factory motor. if you have changed the oil regularly, the motor should be in tip top condition even at that milage. the miss could be an injector, or an under the valve cover injector harness coming partially disconnected. both are moderatley common on high milage engines. as with any motor, you can expect for more things to fail, such as injectors or cam sensors, but nothing major as far as base motor problems and the repairs would still be way cheaper than a new truck payment. if it was maintained well, i would drive it till it quits myself.

[chigger]

thank you i live in the dallas area can you recomend a good deisel mechanic in the area

[mschn99]

Originally Posted by chigger

thank you i live in the dallas area can you recomend a good deisel mechanic in the area

im prone to dealers, i have worked for them, and i like the "factory trained" idea. that said, not all dealers are good. i live in california and dont know anything about the dallas dealers. i would do homeowork, talk to a few guys, see who they use. they may even have a guy who is a former dealer mechanic that opened his own shop. just find out who has a good reputation and take it there. that would be your best bet.