7.3 won't start, I'm confused - Ford Powerstroke Diesel Forum
7.3L IDI (Non-Powerstroke) Diesels Technical discussion of topics related to vehicles powered by the 7.3 Liter In-Direct Injection Navistar engines.

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Old 07-20-2011, 04:39 AM
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7.3 won't start, I'm confused

My friend has a F-350, 5 speed, with the 7.3 IDI. Somewhere between a 1990 and a 1993, I can't remember for sure. It's been sitting for a year, and we can't get it to start.

There's fuel in the filter, and if you hit the bleeder at the top (might be to check pressure?) fuel comes out while cranking

I pulled an injector and watched it, fuel was coming out. I couldn't see it very well at this point, it was outside and starting to get dark. Not sure if it was spraying or just Lazily squirting, but it was coming out for sure. It was the injector that runs off the top line coming out of the injector pump, so it shouldn't be a priming issue.

We managed to get it to fire 3 times over the course of about 2 or 3 hours, each time it smoked a lot for about 3 to 5 seconds then shut back down.

I dumped a bottle of Lucas injector cleaner directly into the fuel filter twice, once it started immediatly after, the second time it didn't but started later. The first time I got it to start was before I had tried this.

The o-rings on the injector I pulled looked fine, but the rubber lines are looking rough. They don't leak as far as I can tell, but they are dry-rotted pretty bad.

Any ideas? He's doesn't have enough money to start throwing parts at it, we're hoping to hit this thing right the first time. Thanks for the help.
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Old 07-20-2011, 05:05 AM
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I wonder if your fuel has jelled up on ya from age? Take the filters off and fill them with fresh fuel and see if it fires up and runs for a few minutes (running on the fresh fuel out of filters). Since it is blowing black smoke I am thinking its not burning the fuel for some reason (as in jelled up or very low compression).
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Old 07-20-2011, 07:19 PM
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I didn't have a chance to work on it tonight, hopefully tomorrow I'll make it over there. I'll try dumping fresh fuel in the filter, see what it does.

If that seems to help, can I cut the fuel line before the lift pump and gravity feed fresh fuel out of a can? I don't think there's a pump in the tank, so that should work, correct? I'm thinking that I could put some good fuel treatment in 2 or 3 gallons of diesel and let it run for a while with a higher concentrate of cleaner, might help out. If it runs, of course.
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Old 07-21-2011, 05:54 AM
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How much fuel is in the tank? You might as well syphin it out and just add the fresh fuel in there. If the tanks almost empty, its probably full of water from condesation anyways. However, I think your idea should work as well.
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Old 07-21-2011, 11:51 AM
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There's about 1/4 of a tank in one, the other is on empty. You're right, we might as well siphon the old out and dump fresh in. Hopefully it siphons easily, I've never had good luck siphoning a tank out. I don't know for sure if the empty tank works, guess I'll find out.

A friend was telling me that it could be the injector pump, but it ran perfect last year. Would the pump go bad from sitting?

Is there a way to check fuel pressure, both at the filter and at the injector? I had a thought that maybe the injector pump isn't pushing enough pressure to overcome the compression of the motor, but might be pushing enough to shoot fuel out when the injector isn't in.
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Old 07-21-2011, 11:57 AM
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Nothing is impossible but I have never seen one go out from sitting. I would have to digging, but you can look on here to see where you can put manual fuel pressure gages at. I am a little rusty on the IDI motors.
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Old 07-23-2011, 12:22 PM
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Just tried to put fresh fuel in the filter, no change. Cranked it for 20 minutes or so, it started for a few seconds, then shut down again.
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Old 07-25-2011, 04:48 AM
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Before you start jerking out injetors,pumps, checking compression etc... Try this.Take an air hose with a rag and stick the hose in the tank sealing the hole with the rag. Pump air into the tank (only a couple psi at a time) to pressure the tank and force fuel up to the motor while cranking. The reason to do this is it will force any possible air bubles out of the system (if any is in there) and if there is a crack,bad oring, etc sucking air it will now leak and let you know you have a leak needing fixed. If all this does not fix it then yes its time to dig deaper into the motor.
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