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7.3 won't start when engine is hot

7653 Views 1 Reply 2 Participants Last post by  klhansen
99 F350 with 168k, turn the truck off and try to restart and it won't restart for about 45 minutes when the temp gauge shows cold again. I had this happen a couple times last year and it has now resurfaced. I just had a fuel leak repaired on the filter housing, and they also tightened up a bolt on the IPC. New O-rings last year, new engine oil pump, new ICP, new CPS via the recall. Its a real stinker because it never makes the CEL light come on. The issues last year were was low injection pressure at start up so we replaced the low pressure pump, and not enough volts at start up to fire the injectors. Been running good for a long time since then but I definately want to get this taken care of. Any ideas guys?
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A no-start when hot condition is usually because of a leak in the HP oil system. There has to be 500 psi minimum (not volts) to fire the injectors and if the oil is hot, it gets thru small leaks easier than when it's cold. Once it's started it runs OK hot, because there's more oil delivered at ~600 rpm idle than at 100-200 rpm cranking.

Could be leaking injector o-rings, sticky/leaking Injection Pressure Regulator, or other causes. A pressure gauge on the HP oil system (0-3000 psi) could help you diagnose. There's a procedure in the Service Manual to isolate each head to see if it's in either one, and then deadhead the HPOP to check the ICP and HPOP.
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