1997 Ambulance 7.3 will start off ether but wont run HELP!!!!!!!!!!!!

[Carl bane]

ok let me start from beginning on this. I picked this truck up yesterday the guy lied with every breath about it but I bought it anyways . it had a miss I drove it 150 miles home . I got it here and pulled it down and it was just a wire of the injector on passenger side . While I had it down I decided to go ahead and put valve cover gaskets and new injector harness . after installing them before putting valve covers back on I started the Ambulance and made sure it would start without the miss which it did . The engine runs great . So we went ahead and started to put it back together . While doing that I decided to plug the Body of the Ambulance in and let it charge the unit and make sure things worked inside going to use it for racing . As soon as I get everything together I try to start truck and all it will do is turn over . I feel cord plugged in its hot so it must of been back feeding somehow to motor of truck . I think the block heater is one of the things that was on while plugged in should not of been a big deal . I noticed that the glow plug relay I assume that's what it is is staying on and getting really hot so I disconnect that . I tried the engine on Ether and it starts and runs fine . So I changed the IDM thinking somehow I burnt that up . Unit will still not start . I know the second IDM is good I tested it yesterday when I first got it and it didn't clear the miss . I checked the # 22 fuse under the hood that is fine . Could I have burnt up my ECM ? you guys helped me a year ago on my 6.9 IDI still going strong . Any suggestions on where to start ??? like I said the engine runs great until I shorted something .

 

[Carl bane]

I was just reading if the glow plug relay is staying on that it could be a PCM problem . Anyone think I may have shorted my PCM . Does the PCM control the IDM ? I am lost guys and if I ask a Dumb question overlook me . I am really happy to have another 7.3 Power Stroke back in the yard But the IDI are so much easier to work on lol

 

[79jasper]

Pcm does control the IDM.
Idm controls the injectors, which is run by the pcm. In a sense, think of the IDM as a relay between the pcm and injectors.
What brand valve cover harnesses did you use?


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[Carl bane]

I am not sure I did not change both but the one I used already had the wiring built in . I think the body on the back of the truck back feed because I did not kill the master switch killing the power to the cab while I had it plugged in . Ran great until I plugged that body in . Question is can I check the PCM in any way . I know something is going on with it because of what it did to the glow plug relay it is staying on the whole time . I am sure I will have to change glow plugs now . your thoughts?

 

[79jasper]

Yes, glowplugs and relay. It's possible the relay stuck on.
Far as wiring and parts, only get Motorcraft. It is possible if you bought a cheap non Motorcraft uvch, that it could've fried the IDM. Pretty common actually.
Only way to test pcm is try it in another vehicle that has the same pcm code, or send it off to be tested.

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[Carl bane]

Any suggestions on who I can send it to get it checked ? I changed the IDM so I kinda ruled it out .

 

[79jasper]

Call power Hungry performance, and swamps diesel. Really any of the big names guys that do tuning.

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[compressionignitionrules]

so does it still start and run with an ether shot? or is it a no start at all now? did you touch the glowplug relay with the R side rocker cover when you were putting it back on? yeah its fricken tight could have burnt out all your glow plugs. have you tested the glow plugs at the harness connection yet?

 

[Carl bane]

Update : I am at my end with the truck I can not catch a break I really need help . Here is where I am . I Bought a IDM and a PCM both off the internet both from sellers with great feedback and replaced them in my truck still will not start . My TACH moves up when I crank it over so CPS is good I Assume . I unplugged the IPS and no change so I assume that is good . The Wait to start light comes on and goes off when I turn switch on . Once problem I have found is the GPR wire coming from the PCM has a constant ground on it . There is a Issue with the ground from the PCM to the glow plug because when I cut switch on the glow plug relay will not go out . I can unhook the wire and the glow plug relay kicks out . I unhooked the PCM and there is a ground full time with Switch off to port on plug where the PCM hooks to the plug. Its like a back feed ground because when I cut switch on the ground goes away and comes back on bright . Hope I am not confusing anyone . I do not know where to start to get it running . Suggestions !!!!!!!!!! Please !!!!!!!!!!!!!!!!

 

[79jasper]

Just so you know, the pcm supplies a ground signal to the glowplug relay to activate it. Glowplugs stay on for up to 3 minutes. So turn key on, wait 5 minutes, then see if it's still grounded.

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[Carl bane]

Its staying on so long the posts are getting Hot cant even touch them .

 

[79jasper]

It could be the relay itself is shorted inside.

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[Carl bane]

I cam unhook the ground from the PCM and it will click on and off with a jumper ground . I am sure glow plugs are burnt up by now .

 

[red41neck]

2001 7.3, at 60mph just stopped running. Long story what happened next.
Replaced the control box between the drivers side fender and wheel flap.
Actually borrowed one from another 7.3 to test. Fired right up. Bought rebuilt from
NAPA and back on the road.

 

[79jasper]

If it was the one going I to the firewall, that's the pcm.
The one on the fender is the idm.

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