2002 Scab 4.6 118,000 miles. The truck has been stalling, when starting only, every now and then. Well yesterday. It almost left me stranded. I drove the truck for about one hour and turned off ignition. Went to restart about 15 min later and strong cranking and no start. I was quite an few miles from home and no tools. The dash lighting was normal, no dashes on the odometer. I pulled and swapped the power modules under the underhood. No change. I had lined up a tow truck. While waiting about 20-30 min I attempted to start and it did! I am confused as to Cam Position Sensor or Idle Air Control Valve. The truck runs flawlessly when started. Today I pulled the IAC and cleaned, it didn't seem that dirty. The throttle body was cleaned about 200 miles ago. There are no CEL or stored codes. Today no problems. I want this to be a dependable truck again.
Any suggestions?
John

 

Will it start if you floor the pedal? If so, you have leaky fuel injectors.

 

Flooring did not change the no start problem.

 

Would there be any other reasons for the temporary no start when hot? It's starting now with no problems.

 

suspect the relays for either the ECM or the fuel pump....if the top any of them is getting warm....I'd replace it.

have you scanned for codes??

check the battery connections & grounds

 

Fuel filter??? Also cycle the key a couple of times before actually starting. if it happens again. just to electricity is on then turn to off,, do it a couple times. The fuel pump maybe your problem telling you its going south. check your fuel pressures.???
Before you crank just sitting there what is it,, after sitting overnight. after you crank it weather it starts or not what is it.


good luck

 

Again no start. When attempting to start seemed to stumble First then feathered pedal and start.
Any suggestions?

 

fuel filter or fuel pump are the likely causes

 

Truck is sitting at local mechanic. They are unable to find a problem since it is intermittent. Will keep posted.
Thanks for help
John

 

Last week threw codes of PO171 and PO174. Brought back to mechanic and found bad PCV hose. After repair. Crank and no start. Positive power to coils and injectors. Positive power before and after the inertia switch. Truck started before fuel pressure checked. Mechanic doesn't want to commit to repair fuel pump yet. Will keep posted.
John

 

They can check fuel pressure without the truck running...it is good to get fuel pressure readings with it running and not running . Even if the no start condition is not present, then at least they know what is PSI levels are there prior to starting.

With the lite throttle applied and then it started ....might be leaning toward a dirty or bad IAC (Idle Air Control)....especially if there was a vacuum leak and now still getting this intermittent no start condition after the vacuum leak repair.

 

Fuel pressure 28 psi at idle. Doesn't sound like enough pressure. I've read that fuel pressure should be about 32 psi. May change the pump in next few days.

 

28 psi is the lower limit of the pressure specification at idle (28-50 psi) for your truck. The engine should work on 28 psi. Key on, engine off should read 35-45 psi.

Don't screw with the fuel pump until you have tested KOEO pressure and have tested the operation of the fuel pressure regulator. If the regulator is bad or if it has the wrong vacuum applied to it, it will lower the pressure at the rail. With the engine idling, pull the vacuum line to see if the pressure rises to the KOEO range.

 

After sitting for about 6 hours 0 psi. KOEO 35 psi. Started and 28-30 psi. When vacuum removed from FPR increased to 45 psi. With key off psi dropped off within 15-30 seconds to 0.
Pump seems to be working. What about it not holding pressure? Started and ran fine.

 

That sounds like a bad FPR.