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Truck Repair/94' freightliner


edenmark77 wrote at 2014-10-22 05:25:01
I have a '93 freightliner 120 FLD with a 11.1 L Detroit.  Computer would shut down motor after about 3 min of driving.  Then you could turn off the motor and start it up again and it would run for another 3 min and shut off again.   I didn't have the correct link to diagnose the problem correctly.  Cleaned the computer twice, replaced battery to computer wiring, replaced coolant level sender.  Still had the same problem.  I replaced the oil pressure sending unit and that was the problem.  My oil pressure sending unit was leaking oil externally and must of had other problems too.  On my motor this oil pressure sending unit is located on the drivers side of the block way twords the upper rear of the block.  There are 2 sensors in this position one about 3 inches below the other.  The oil pressure sending unit the lower one.  This is a very easy cheap thing to fix once you figure out the problem.  I hope this helps.

Also, It would be good to replace the nylon star coupling that is located on the firewall side of the air compressor and is used to drive the fuel pump.  I would say one should replace this every 5 years or so as they tend to break apart.  I found out the hard way after diagnosing why my fuel pump and air pump quit working.  The accessory drive couples power to the air pump by a nut and tapered shaft with no key in this shaft.  I think it was designed to slip on purpose to save the accessory drive from shattering if too much load is placed on it.  On mine the nylon star coupler was broken up and I believe the pieces caused to much of a load and resulted in this tapered shaft to nut to slip to the point of failure.  This was very expensive to fix not to mention the down time.  Replacing this little nylon coupler is cheep and easy.  It could save you from an expensive headache.  Just remove the 4 bolts holding the fuel pump to the end of the accessory drive and there is the nylon coupler.  It is easy to get to. I wish someone had told me about this as I would have liked to avoid this $1,200 repair.  The part is only about $10.00  .

I hope this helps.

Jose Castillo wrote at 2015-08-02 23:06:28
Check coolant level also if Detroit engine they have two oil pressure sending units one for gauge and one for computer. If you have oil pressure it could be the other sensor. They both are located by starter

jason wrote at 2015-10-15 17:09:07
I just expieinced this with my 07 freightliner classic .... it would shut down than rest in seconds... I like you thought breaker issue but upon inspection the ECM harness had started to rot causing a rub... replaced ECM harness issue gone!! hope this helps

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Jeff Drumm


I Can answer any question pertaining to semi trucks and trailers. Have no experience in the automotive field so not able to help in that area.


My experiences in Semi Trucks is. I own my own truck and i presntly maintain a 80 truck fleet. Can handle any questions pertaining to a truck have tore apart and rebuilt every aspect on them. Fleet I deal with is Mainly Volvo trucks and a handful of freightliners. Work on automated transmissions on a daily basis along with carrier apu's. With engines my specialty is the 60 series Detroit but do work on the cummins isx the n-14 and the ism. and also the Volvo engines.

Have a College Degree from university of northwestern ohio in diesel and agriculture mechanics. Have 10 years behind the wheel driving a truck and 4 years working on trucks full time. Also have grown up on a farm so have been tinkering on trucks and tractors all my life.

Awards and Honors
I've gone through online schooling and have received certificates from webb wheel, Timken and Volvo academy.

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