I have a 1999 f350 with a 7.3l in it. A week ago I stopped at the pump and topped of my tank and when I went to restart it it it would crank and not fire. I had it towed and replaced the cam sensor with an aftermarket one. It ran but it would cut out when I got into the throttle and wouldn't start when hot. I bought another aftermarket one and it did the same thing. I tested the hpop pressure at the back of each head and everything checked out perfect while running. I replaced the Ipr with no luck. And I also tried unplugging the icp sensor and it didn't make a difference. It starts perfect when cold but when it's hot and you shut if off it will just crank. I replaced the cam sensor once again with a ford one and everything worked perfect and it started no problem for a day then started doing the same thing again. Any ideas? I've taken a close look at all the wiring on the motor and it looks good. Battery's and starter are new. All the cylinder contributions test good as well as the injector buzz test. I'm not noticing any change in oil. Oil was changed 800 miles ago

 

Do you have a scanner that can read the codes or monitor live data?

If no start when hot and everything else is perfect, it's usually an IPR (or chaffed wires to the IPR), ICP (or the wires again), or oil that is sheared down and needs to be changed.

 

Ditto on that...Aftermarket sensors should always be motorcraft because they're reliable whereas the others most time fail. Only hot no-start Ive had was the ICP on a torrential downpour of a night and it started while unplugged to get me home. Seeing that you checked the hpop pressure is the oil level up there where it should be?

 

Are you seeing any rpm on the tach when cranking. If you see a reading on the tach then your cmp sensor is probably ok. My best guess is that you have a high pressure oil leak under the valve cover causing it to bleed down when it's hot

 

If you can get a scan tool hooked up to it, we could help you narrow this down better. Need to know icp pressure, ipr duty cycle to start with

 

You could also check the oil level in the hpop res it should be about 1 to 1 1/2 inches from the top if I remember right but not 100% sure on that maybe someone else can chime in on that.

 

Just had another thought, is your fuel filter black? And is there fuel in the bowl, how does it look, black or clean. I may be off on a tangent here but it's worth a look

 

Here's a quote from HKusp........... "having issues with no ICP when the truck was warm. It was winter and the truck would start when the oil was cold and thick, but as soon as I was at operating temp, if I turned the truck off and went to restart, I didn't have enough ICP to fire the injectors. The external o-rings were failing"


How many miles on the motor? Have injectors ever been changed? Have you been losing any oil lately?

 

Yes the tach is moving while cranking. My fuel filter looks good it is fairly new and the one I took out last service looked real clean. Oil is fairly new and still seems to be good quality. The oil level in my hpop is close to the top. It's only about a quarter inch down. My Ipr has been replaced with another ford one and nothing changed

 

If you are certain the IPR is good, which if it is a brand new Motorcraft one it should be, injector o-rings if bad can bleed off ICP when the oil is warm. These are all guesses without the monitoring of ICP, Voltage, duty cycle, and RPM. Do you have any way of monitoring these things?

 

I might I'll see what the scanner I have access to can do. If I had a leaking injector o ring would that drop the pressure reading I've be been taking off the plugs on the back of the head?

 

These were the readings while the motor was cold

 

You may not see a drop in oil pressure with a bad injector o ring get on you tube and type 7.3 hard start when hot. A guy named diesel tech Ron has a great video on it and he shows how bad of a leak you can have and still see good high pressure oil readings.

 

Okay I'll check it out thank you

 

Your welcome keep us posted on what you find