engine stays running

[jspd234]

hi everyone! my 97psd has a new problem. sometimes when i turn off the key and remove it the engine stays on for anywhere from 15 to 45 seconds. it doesn't do it all the time but its happening moore often. any ideas on what would caus this? seems to me to be that maybe the fuel is still being delivered?

[Slimline]

That seems very fishy to me. I cant think of any reason that it should stay running when the key has been turned to off and the computer is no longer actuating the injectors. My first, and scariest thought is you are potentially running on lube oil? Have you noticed increased oil consumption on the truck? Any odd smoke issues? You dont have a turbo timer do you? If not something is either telling the pcm to continue firing the injectors and not shutting down properly or your running on lube oil which I think would be fairly obvious.

[jspd234]

no turbo timer, no smoke issues, no oil consumption issues. i'm stumped.....

[codyh]

I've got the same problem with my 96. Changed the ignition switch and still the same problem. Everything else is fine. Strange

[madpogue]

Two completely speculative WAGs (wild-@$$ guesses):
* Copious oil coming up through the crankcase vent (CCV) in the intake, through the turbo, in through the intake valves and combusting as fuel
* Worn/damaged valve guides allowing oil into the chambers via the valve stems, going in and combusting as fuel.

One test that _might_ narrow down the source a little - while it's happening, pop the hood, quick jump out and pull the #22 maxifuse under the hood. If that kills the engine, then the run-on is honest-to-goodness injected fuel, and it's more of an electrical/electronic problem with some rogue continuing to fire the injectors. If it continues to run, it's not conclusive, but it _suggests_ that it's not injected fuel that it's burning. About the only other, more conclusive test I can think of would be to pull all four UVCH connectors, but you probably wouldn't be able to get to them before the thing shuts down on its own anyway.

[forddieseldoctor]

Originally Posted by madpogue

About the only other, more conclusive test I can think of would be to pull all four UVCH connectors, but you probably wouldn't be able to get to them before the thing shuts down on its own anyway.

Not a good idea. That's alot of voltage going to the injectors. There's a reason that they have the red tape wrapped around the harness. I've been shocked by a 6.0 which runs on about half the voltage of a 7.3 and it hurt like heck.

As far as the not shutting down. Does the radio, climate control and wipers cut out as soon as you turn off the key?

[gaspipe]

My '95 does this, but *only* right when I start it, and try to shut it off before the alternator comes online. When the volt meter swings over to full charge (about 10-15 seconds after I start it), it will shut off normally. If I turn off the key prior to this, it'll keep on running.

[madpogue]

The alternator is always online, when the engine is running. The voltmeter swings left-of-center for the first minute or so because the glow plugs are on. What you are seeing with the voltmeter is the glow plugs cycling off.

But that may be a clue to your run-on. The relay is probably mis-wired or shorting, in some way that it is back-feeding power to the PCM even with the key turned off. Do you know anything about the history or status of the glow plug relay?

[codyh]

Some of the lightns in the dash stay on but are dimmer when I shut it off and it stays running which tells me it is getting back fed or something similar. Pretty sure it is not running on oil. Doesn't use any and engine is tight. I,ve looked for a short with no success but will continue to look. Thanks for the help

[madpogue]

^^^^ Yuh, that sounds like a GPR malfunction. Was it replaced recently, by any chance? I'd have to noodle it out in my head, or draw it out using the GP circuit diagram from the EVTM, but I'm thinking it's possible that this could be one result of using a mount-grounded relay (like the starter relay) for a GPR.