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Discussion Starter · #1 ·
I am working on 2002 f-350 7.3 4x4 auto. It cranks but wont start. wts light stays on. Scanner will not communicate. Fuse #22 has 12.3 volts on both sides. Pcm relay is good. Checked computer pins all power feeds have 12.3 volts, all grounds good. The truck had edge ford attitude on it. It is now unhooked. The truck wont start so the kid put three different gpr from auto zone on. He said it started on third on. Truck was started 5 or 6 times and then wouldn't start so he put a gpr from advance on it. I'm not sure about he's reason for replacing, I don't think it had anything to do with not running. IDM relay does NOT click. My uncle is a ford diesel tech but think he's been working on 6.0s for too long. he wasn't much help other then he let me borrow a good IDM and pcm. but still have same problem with them. Most of the forums I've read with this problem have been bad fuse 22. Any ideas would be great. Thanks
 

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In an '02 it's actually more likely to be fuse #30 (the fuel heater) but, if you've checked the PCM plug for power & ground, that too isn't going to be it...

BUT, if the IDM relay doesn't energize, AND you can't communicate with a New PCM either, you've got something really weird going on. I agree, it has nothing to do with a GPR (which you don't even Need over 40*).

What are you using for a scanner? (the generic OBD-II aren't of much use with these engines but it certainly should communicate). I'd wonder about the OBD-II port but you say the WTS never shuts off. That's a sign that the PCM is really confused, it shouldn't ever do that.

On one hand I'd be thinking this is all a computer or electrical issue (the WTS, Communication problem, intermittently working again, then not) But, it sure would be nice to confirm you had HPOP/Fuel/Oil pressures and that the injectors were getting signal to fire. All of which we rely on the scanner for but, I guess, could be confirmed, mechanically, with out it.

On the electrical side, does everything look solid? Body Grounds too? How about the fuseable link connection? (http://www.powerstroke.org/forum/99...sion-if-your-truck-like-mine.html#post1343921)

You've got your hands full ;) The fact that, after one of the GPR changes, it worked for a while would drive me crazy! :D
 

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Discussion Starter · #3 · (Edited)
Thanks for the reply. Ive checked all fuses several times with a power probe. #22 had low voltage on one side. was blown and replaced. Its been checked several times since then. The truck went to another shop before I got it. Their scanner didnt work, I tried a matco scanner and a generic. I could get into the abs and airbag with matco. I need to find how the can bus works. I mosty work on 6.0 so I been reading everything I can on the 7.3. also the fuel pump doesnt kick on and glow plug relay.
 

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OK first, we're not CanBus really. See if the Matco menu has a place to change it to SAE J1850 PWM (an OBD-II variant) and if that allows a scan. Have you scanned other 7.3's with it before?

Again, the constant WTS and now it not activating the fuel pump (you checked the Inertia Sw - right?) says to me the computer isn't doing it's job, for what ever reason, and if you've swapped with a known good one (of the right type) it's gonna be in the wiring to/from it that would be where I'd be thinking first.

Fuses OK, Grounds OK, Batteries OK, PCM OK, $hit man, I donno. You got a stumper there...
 

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Discussion Starter · #5 ·
It cranks over great. Have 11.5 volts when cranking. I've never used the matco on a 7.3 but have used it on 6.0. I'm goin to print off some wiring diagrams at work today. Hopefully I can come up with something tonight. The kid who owns truck is little inpatient. I think I got him to understand that it takes time to track down problems like this.

Sent from AutoGuide.com Free App
 

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Discussion Starter · #8 ·
I got it figured out other night. After goin there the pinpoint chart I figured out it was the exhaust back pressure sensor shorted out. Unplugged it and truck started
 

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Discussion Starter · #10 ·
Check the reference voltage on the data link. Thats what my problem was. If you have low or no voltage there, should be around 5 volts, something in the voltage reference circuit is shorted out. Which will pretty much shut down the computer. Let me know if you need anything
 

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I disconnected each sensor one by and tried to start it. There was no change at all in the condition. The WTS never goes out and the truck doesn't even sputter. Is there anything I can do to check the IDM? What is a buzz test and can I do it without any special tools?
 

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Discussion Starter · #13 ·
No you can't do a buzz test. Buzz test tells you if injectors are good on the Electrical side. Without communication with computer you can't do it. Pull up a diagram of the data link. With the key on make sure the reference voltage is 5 volts. Its the 2nd or 3rd from top left. I have all the wiring diagrams but I might have left them in the truck. I'll see if I can find them
 

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Please can I get an update on the issue you had with your 7.3. I'm having the same issue and it's driving me crazy. I've chased down every know wire and sensor. Please I would be greatly appreciated if you could help me out with this issue
 

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