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Nov 15, 2011 | 08:44 PM

bigbubba87

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From: New London, Mo

7.3 no start

Ok guys my brother is still having problems with bus truck. It still won't start. Can someone give me a simple rundown of what a 7.3 needs to start. And how to test it. Thanks Justin

Nov 16, 2011 | 05:58 AM

427 fordman

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From: Plankinton, SD

What have you done? It needs at least 500psi of high pressure oil to fire the injectors, scanner or a mechanical gauge hooked up to see this. Needs fuel pressure and lots of electrical things can go wrong.

Need more info.

Nov 16, 2011 | 08:21 AM

scottjbear

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From: helena,mt

Diesels are not the same as they use to be. Before there was 3 three simple things..1)compression, 2) fuel, 3)air.. Now you need oil to the injectors and you have individual injectors that can have all sorts of issues but always start with the basics. the compression I would wait for after you check the others.

Nov 16, 2011 | 08:35 AM

bigbubba87

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From: New London, Mo

I messed with it a little but not much cuz the pcm that was in the truck was supposedly bad. He put a new pcm in it. Tach moves while cranking, no wts light, faint smoke out the exhaust. I'm going home next week and going to work on it just want to get a good place to start and know exactly what all tests I have to do. I have all tools needed minus a scan tool.

Nov 16, 2011 | 08:44 AM

bryanlindborg600

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From: Bellingham, WA

Check fuse 22 under the hood, no wait to start light means no Power to the PCM. Fuel bowl heaters are known to cause this problem.. Hopefully a new fuse and possibly unhooking the fuel bowl heater will get him back up and running! Where did the new PCM come from? Are you sure it is the correct code for the truck? There are a couple different things that will effect a PCM working between trucks..

Last edited by bryanlindborg600; Nov 16, 2011 at 08:48 AM. Reason: Questions

Nov 16, 2011 | 10:13 AM

bigbubba87

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From: New London, Mo

Well he just had the pcm flashed. and is there a fuel pump in the tank? Checked fused and unplugged the fuel bowel heater still no start.

Nov 16, 2011 | 10:33 AM

Hussler

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From: Medford Oregon

Quote:

Originally Posted by bigbubba87

Ok guys my brother is still having problems with bus truck. It still won't start. Can someone give me a simple rundown of what a 7.3 needs to start. And how to test it. Thanks Justin

1. Truck need to sense RPM and cylinder ID (CPS).
2. Truck needs fuel pressure, >= 20 PSI while cranking.
3. Truck need ~ 500 PSI HPO before PCM instructs IDM to fire injectors (ICP - IPR).

If getting some smoke then injectors are firing and criteria 1 and 3 are being met. Check fuel pressure and make sure screen (inside fuel canister) is clean as that vents air from the fuel.

Worried about no WTS light as that usually indicates a fuse (can't be because you have RPM on tach) or bad PCM.