Hey guys. I have a buddy whose '99 7.3 is in the shop. It's running VERY ROUGH and spitting raw diesel out the exhaust. Where should I tell him to start for troubleshooting?

if raw diesel is coming out of the exhaust, then there is an injector over dumping fuel. start disabling each injector and find out which one stops the smoke. more than likely, the rough running is related. depending on the miles, a set of injectors may be in order.

Or one cylinder may be lacking compression for fire the fuel. If you have a scan tool check to see if there are any cylinder misfire codes and thats where i'd start looking.

Thanks for the information so far. We're looking at it and I'll post back what we find!

Subscribing......

d-kuzmen said:

Or one cylinder may be lacking compression for fire the fuel. If you have a scan tool check to see if there are any cylinder misfire codes and thats where i'd start looking.

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His code reader apparently won't read those codes.

Sooo, is there an easy way to disable the injectors or is it pull the valve cover, unplug one, put it back together and try?

6L PWR said:

His code reader apparently won't read those codes.

Sooo, is there an easy way to disable the injectors or is it pull the valve cover, unplug one, put it back together and try?

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You can try to remove the pin from the connector at the valve corver or the bulkhead connector on the driver side valve cover. Or pull the covers and do it that way.

code readers wont do very much good on a 7.3, they were not that sophisticated. you can remove the valve covers and undo all of the metal clips on the injector connectors. dont worry about making a mess because very little oil is splashed under a 73 valve cover. unplug the connectors one at a time and rev the engine untill the smoke clears up enough to tell whether or not it has improved.

the only good thing a scanner can help with in this case is a buzz test. if you can perform a buzz test, you can hear for weak/bad injector solenoids which will be a start for diagnosis of which injector has failed.

Ok, disconnected the injectors one at a time on both sides and noticed that it did change the sound in the engine everytime, but fuel continues to come out raw. I'm thinking O-Ring. Anyone got another idea?

take the pipes off the manifolds just enough for it to be open to the outside and watch and see if any fuel or smoke pours out.

it could be an oring but you would need to remove all injectors to look at visually due to the circumstances.

Ok, now we've loosened the exhaust and found that all the smoke and fuel is coming from the right side. We've pulled the injectors and the O-Rings all look to be in good shape. No tears or anything. Any other ideas on what to do next?

So we've reinstalled all the injectors now and it won't start at all! There is smoke coming out from the third hole back on the right side and only that one now. We're REALLY lost now??

Ok, NOW it started, it's idling better, but still lacking power.

It is ALSO now giving a code. It says IDM Codes detected on their reader.

Is there a way to test for a weak injector?

Have you checked the wiring on that bank for signal continuity? Those harnesses are prone to failure, and even the pass-thru on the valve cover gasket is. I just happen to have a full set of gaskets and UVC harnesses if you need them

mrfixit said:

Have you checked the wiring on that bank for signal continuity? Those harnesses are prone to failure, and even the pass-thru on the valve cover gasket is. I just happen to have a full set of gaskets and UVC harnesses if you need them

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So, just check from pin to pin for a connection? Should there be any resistance? Anyone have a wiring schematic or is this simpler than that. I'm not actually looking at this engine. It's in my buddies shop and I'm telling him over the phone what you all are telling me to check.

Ok, so, the wires all check out ok. Still runs a bit rough and smoke and dumps raw fuel. Any other bright ideas? I'm so lost it's not funny.

6L PWR said:

Ok, so, the wires all check out ok. Still runs a bit rough and smoke and dumps raw fuel. Any other bright ideas? I'm so lost it's not funny.

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Do you know what hole is the problem? Since you have the cover off, unplug each injector one at a time and run the truck to see if it clears up at all. There is a copper oring on the bottom of each injector that needs to be replaced every time the injector is removed or it may not seal correctly when reinstalled.

6L PWR said:

Ok, NOW it started, it's idling better, but still lacking power.

It is ALSO now giving a code. It says IDM Codes detected on their reader.

Is there a way to test for a weak injector?

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You need a better scan tool one that'll do a buzz test, and you should be able to read idm codes, it'll be the answer to your problem maybe.