1996 7.3, hard start, long crank

fordtech03 · March 15, 2016

I've got a 1996 7.3, previous tech had taken the motor out to reseal the oil pan and replaced the oil cooler O-rings. Customer comes to pick up vehicle and it doesn't start. Got it to start, low pressure oil was very slow to build, about 30 seconds or more of cranking before it registered on gauge, HP oil slow to build as well. IPR was about 51%. Once started vehicle has about 15-20psi LP oil @hot idle, and it smokes badly, definitely oil. clears up a little after driving but still smokes at all times. Shut it off, if you try to immediately re-crank it will start. Let it sit for 10 minutes and it goes back to a long crank, slow to build LP/HP oil. Checked the reservoir and it was full, though I suspect it may be leaking down slowly, overnight. I think I may have more than one problem going on, thoughts?

Brad Clayton · March 15, 2016

I have seen trucks that would not register anything on the gage until they were running, so I would not trust that aspect of the scenario. You can check base oil pressure at two easily accessed points on these engines, one at the usuall spot on top and the other down on the back left corner of the block near the bell housing. I always like to put two gages on these when checking oil pressure. They should both match up, if the lower gage reads higher than the upper gage then you can suspect a pressure loss whithin the engine.

ktmlew · March 15, 2016

I have seen trucks that would not register anything on the gage until they were running, so I would not trust that aspect of the scenario. You can check base oil pressure at two easily accessed points on these engines, one at the usuall spot on top and the other down on the back left corner of the block near the bell housing. I always like to put two gages on these when checking oil pressure. They should both match up, if the lower gage reads higher than the upper gage then you can suspect a pressure loss whithin the engine.

My guess is it's a two-fer. Worn out LP oil pump and leaking injector o-rings.

fordtech03 · March 15, 2016

I agree about the low pressure reading may not be correct until it starts. I'm leaning towards injector O-rings myself, that would explain a lot of the symptoms. Ford hotline suggested checking for it leaking past the injector spouts, though me and none of the other diesel techs here had really run into that. It's always been a case of bad injector doesn't pump oil out spout or it flows continuously while running.