Engine won't shut off

[5.7L oldsdiesel]

Well guys,with the help of everyone who responded,and with the help of God,i was able to get the engine running today. smile.gif I found a wiring diagram for the engine and i traced the wires leading from the fuse panel to the ECM.I traced the orange wire leading from the ECM-B fuse and i found a break in that wire before it got to the computer.I found the break.It was only hanging by a strand of wire.I cut the bad section out and i got voltage to the service throttle soon light,glow plugs and check engine light.I removed the ground wires from the back of the engine because they looked terrible and they were corroded badly.I used new terminals and moved the ground wires to the top of the engine for a better ground.The engine runs perfect,but it has codes 17 and 18.I'm not too worried about that yet,but at least its a great start and the engine runs.

The engine runs great,but when i turn the key back off,the engine stays going.The check engine light and ABS light stay on.Even with the key on,i have a ABS light.But i'm okay with that.But why won't the engine shut off with the key?To get it turned off,i had to pull the 20 amp fuse for the fuel solenoid under the hood.Then the engine quit.I put the fuse back in and i cranked it and the engine runs okay.But it won't turn off with the key.

So,with the engine running,i unplugged the connector for the shut-off solenoid on the injection pump(tall round cylinder type component)and the engine ran for maybe 3-4 seconds and then quit.I checked for voltage at the connector with it unplugged,and each time the ignition was switched off,i had no voltage and when the key was switched to run,i got voltage which is right,but why won't the engine shut-off with the key in the off position?Pretty puzzling.Do i have a bad ignition switch?

That right now is my only problem.You guys have been great so far.Thank you to everyone.I appreciate everyones help on this.

If anyone has a solution to this,please let me know.

[rapidoxidationman]

Reminds me of an old truck whose headlights wouldn't turn off at the switch; you had to pull the relay to reset it cuz it stuck in the closed position. I wonder if you might have a similar, relay-related problem that is keeping things energized due to a relay that won't let go when it is told to. Good luck!

[Hubert]

It may be due to a shared wiring node or circuit power still powering the ecm and fuel shutoff solenoid after key off.

I had a short in my trailer harness when I was in reverse and foot on brake I could turn key off but power would back feed through the reverse lights circuit to the ECM and fuel shutoff solenoid. Some dash lights would glow but volt meter would not bounce or act crazy.

Your test with engine off key on or off and correct voltage to solenoid wire tends to make me believe switch is OK.

But with a running engine there is a little more voltage on circuits than when engine off key on. When you cut key off with engine running something back feeds power to the fuel shutoff solenoid. When you pulled fuse it opened the short and cut engine off.

Any rewiring of oil pressure switch or other?

Most everything ties into the ignition switch one way or other but try and observe what is on and off when the engine stays running. ie lights, brakes etc.

[redbird2]

I would go back over the ground wires we have had ground problems in the past on 6.5 that can cause all kinds of strange problems.The one that stands out the most is with the key in your pocket you step on the brake pedal the engine would start cranking. It was at an outside vendor they could not find the problem. I sent it out to dealer this truck was under Warranty they had it 12 days before they found the problem. It was a rusted ground connection, it looked fine, no corrision after sanding matting surfaces of the grounds and wire the problem went away.

[5.7L oldsdiesel]

Thanks guys for the much needed info.Thank you to everyone for that. smile.gif Well,with the engine running,i switch the key back to the off position and the volt meter needle goes back to the left as it does with my truck when i shut it off.While the engine is running with the key off,i switch the key back to run position and the voltmeter climbs back to 14 volts.So the ignition switch must be working okay.The thing about the fuel lift pump is whenever i turn the key to run,the fuel pump comes on right away and stays on until i turn the key off.So,i think somewhere along the line,someone rewired the truck to have the lift pump activated whenever the ignition is in run mode.Looks as though i have more troubleshooting to cover. :D I found a few melted wires under the fuse panel under the hood.I fixed the melted wires and put everything back as it should be.This truck has almost 300,000K on it.Before i worked on it,alot of the wires were cut off with a pocket knife,and the insulation on many of the wires were skinned off,maybe by someone who did'nt know what they were doing.I wish people would'nt do that.

I do have another problem with the truck.On the steering column underneath,is a rod which goes back and forth inside some sort of a sleeve that works along side the gear shift lever.It has a 2 wire connector on it of some sort.I'm pretty sure its a 2 wire connector,but it looks like its melted or something.Does anyone know what that part is for?It's along side the transmission cable that connects to the gear shift lever ball stud.My main problem now is that i can't get the truck to shut off,but i'll have to try to find out why that is by testing every wire that i can for some sort of problem.I'll also check for more ground problems as well.There is one yellow wire left thats not connected and goes into the cab by the look of things and one thin black wire near the fuse panel thats not conected either.

I wish people would'nt butcher wires like that.It just makes things harder for the next person to work on it.

Thanks guys for all your help. smile.gif I'll be sure to let everyone know what i find out next.

[Hubert]

What year is it again? Update your sig line with truck details.

My 97 (something like 96 and later???) the Lift pump comes on with switch on for something like 15 seconds. Then if oil pressure does not register it will cut back off with oil pressure switch ie if engine is not running. Earlier models I think required oilpressure and or a transmission in gear switch to power lift pump. Check that circuit carefully it might be your problem.

FYI
Some have added a one way diode to lift pump to come on with iginition on always. If bad diode and lift pump has power it can back feed to the ignition circuit with key off. Some have bypassed the oil pressure switch but left wires. Then if for what ever reason the oil pressure switch comes back to life the circuit is again live and the lift pump power back feeds to a common node connected to ignition wires with key off.

I don't know much about inside of steering column good luck.

[tom.mcinerney]

I was going to suggest you might check wire diagram for diodes, that one may have shorted out(there's one in the start-to=LP circuit in mine).
However,if you've found fried sections of harness, then you might save some time by installing a good harness from a vehicle that is in a wrecking yard.
These harnesses are good if not overloaded, generally. Be very careful ... the ecm/pcm is vulnerable.