7.3 Idi Non Turbo Runaway

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Dec 4, 2018 | 01:37 PM

#61

DarkOverCast

Posting Guru

Joined: May 2015

Posts: 2,036

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If nothing else the metering valve was gummed in the wide open position, this would render both the fss and governor linkage useless. But you can work it back and forth with the top off. Most pumps that sit get stuck in the off position so I always pull the top and move some stuff around with the help of some diesel or spray oil

Dec 4, 2018 | 03:25 PM

#62

genscripter

Cargo Master

Joined: Oct 2012

Posts: 3,072

Likes: 48

From: California

Quote:

Originally Posted by Vegetable0

I agree that it is very unlikely to get a full Run away from just a FSS. But I have seen a FSS on a 6.5 Turbo Diesel that had the shaft bent during a careless install. It caused some wacky stuff. Over fueled it for sure, although this was not the standard DB but the electronic monster that was... junk... I do however see if a defective cruise control was maybe wired in wrong could cause it to go for broke on RPMs though. If you have ever had one fail on a 7th gen they can rev it pretty good. Again though, FSS alone couldn't send the RPMs over idle, or just off... not without help.

Quote:

If it were stuck open because of constant voltage from ignition it wouldn't shut down at idle by the key.

If it occurred on 2 IP's, then I'm convinced the wiring up to the FSS had some shorting issue. Perhaps it was getting moderate voltage at low RPM's (enough to function the FSS), but once the alternator voltage increased at high RPM's, then it would keep the FSS open even when the relay has supposed to shut it down. IDK. It's just a theory.

All this could have been tested by wiring up a simple wire from the battery to the FSS and bypass the IP wiring circuit.

Dec 4, 2018 | 05:49 PM

#63

tjc transport

i ain't rite

Joined: Mar 2005

Posts: 65,606

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From: Marlboro Mental Hospital.

Quote:

Originally Posted by DarkOverCast

If nothing else the metering valve was gummed in the wide open position, this would render both the fss and governor linkage useless.

i think this is the most likely cause .

Aug 6, 2022 | 08:47 PM

#64

Fafvengence

1st Gear

Joined: Aug 2022

Posts: 1

Likes: 0

Well 92 7.3 idi with 5 speed and 91 7.3idi with ats turbo
so none turbo idi run away exactly same issue hes haveing
injector stuck open useing the return fuel from return line to feed the run away I can stall it to kill or key off and floor it then it last 5 seconds then dies this is your issue