Truck won't start - Diesel Forum

windsqueezer · 11-06-2009, 10:00 PM

I have worked on dozens of 7.3s, but I'm stumped on this one. Truck died and won't start unless I use ether. Once it runs for about a minute, I can turn it off and it will start normally. If I let the truck idle, it ill run for about ten minutes, then die. At this point it once again will not start unless I use ether.

Truck is a basically stock 1996 f350, 124k miles. No codes when hooked up to a snap on diagnostic. Everything seams within spec. Injector buzz OK, Fuel pressure tested while cranking with a mechanical guage and is fine, new batteries, new glow plugs, tach reads about 200rpm when cranking, pcm & idm swapped with a running truck and are OK. Fresh oil change. Oil level in HPOP res. is full. Fresh fuel filter. New Super Duty HPOP. No smoke while cranking.

I'm guessing something with high pressure oil, but we swapped the ICP and IPR with a running truck, and still didn't fix it.

Any suggestions?

speeddemon31176 · 11-06-2009, 11:09 PM

Possible fuel restriction in the FPR? Is the filter clean? How about the little screen between the FPR and the fuel bowl? Could be a weak lift pump. What pressure readings are you getting from the fuel pressure gauge? Did you leave the fuel pressure gauge attached and read pressure while it was idling to see if it just drops off all the sudden or gradually? Is there an extended period you have to wait in order to get it to start again or can you start it right back up with the ether? It could still be CPS going out of range as the engine begins to warm up. Just a few ideas to throw out there.

massbadass · 11-06-2009, 11:31 PM

yeah my question would be after it runs for ten min and dies and you fire it back up does it stay running or not?

windsqueezer · 11-07-2009, 09:57 PM

I can't remember the exact fuel pressure at the fuel filter, but I think it was around 60 psi. I don't think its a fuel issue. I have had the filter housing off, cleaned, fpr cleaned, new filter. Reinstalled, no change in the symptoms.

After it idles for a while and dies, I can start it back up if I use ether, but it will not start without it. It strange that once I start the truck with ether, I can turn it off with the key, and then immediately start it without ether. I did this about 20 times today. But once I let it run 5 - 10 minutes, it always dies, and the only way to start it is to ether it.

Any ideas? Thanks

massbadass · 11-08-2009, 01:25 AM

sounds like you tried all the difficult stuff already. I would go back through and check small stuff like fittings, wiring and check the injectors to ensure they are spitting oil properly. Check for leaks too. How does it run once you get it fired up. Can it accelerate ok?

**midwestconnection** · 11-08-2009, 07:20 AM

It sounds like the glow plug relay. I'm told that they can test "good" on the output terminal and still be bad. Ether starting indicates that your injectors are not getting hot enough to start diesel unless you restart it quickly after you have started it with ether. It's a cheap and easy fix that you need to change often anyway.

**Excavator** · 11-08-2009, 07:30 AM

I would check the hpop pressure when you are cranking. I think you are low on the hpop pressure when you idle and could have injector o ring dumping oil or the ipr is not seating. The hpop psi needs to be at 500 or higher to start or injectors will not be told to work from computer, When you shhot either in then it fires up and now the rpm are high enough to possibly hit the needed 500 psi so it then starts,
Again you need to monitor the hpop psi when it no starts
You could have worn poppet valves in some injectors and depending on upper or lower poppet seats worn it could cause no start warm or no start cold.

94strokerace · 11-08-2009, 09:13 AM

I agree with Jim. By letting it sit for a few minutes gives the hpo time to bleed off, then you have to let your engine sniff drugs to catch which builds the psi back up. Injector o-rings, internal injector o-rings for example.

windsqueezer · 11-08-2009, 10:21 AM

I'll hook the Snap On scanner back up and get the high pressure oil readings while cranking and at idle and post them. This truck has new injectors and HPOP, probably less than 5,000 miles on them.

Thanks for all the posts.

94strokerace · 11-08-2009, 10:25 AM

Quote:

Originally Posted by windsqueezer

I'll hook the Snap On scanner back up and get the high pressure oil readings while cranking and at idle and post them. This truck has new injectors and HPOP, probably less than 5,000 miles on them.

Thanks for all the posts.

You may have cut an o-ring when installing those new sticks....