Won't shut off! Stumped

[autopat]

Hey guys and gals, I've got a weird one for you. I have an 84 CFI, 4+3, I put a new ignition lock cylinder in it a month ago (just worn out), everything worked fine, had the clutch replaced last week, trans shop says they couldn't get the car out of reverse so they disabled the column interlock, replaced the clutch, now the car will not shut off. No it's not dieseling, it does not shut off when you turn the key off, everything stays lit up, just like it were driving down the road. If I turn the key off, hold the brake, and stall it by letting the clutch out, all the guages, and powered equipment, turns off just like it's supposed to when you turn off the key. Did they forget to reattach a ground cable? Is the interlock to blame? Haven't really had the time to dig into it, I did check the fan relay, the fan is not keeping it running. Any and all help will be appreciated.

Pat

 

[XLR8]

Sorry to hear you're having an issue, Pat, but glad you found us! And welcome to the !!

We've got a fantastic group of Corvette enthusiasts here and hopefully someone much more mechanically inclined than I am will be along shortly with some sound advice and good suggestions.

Good luck resolving your problem and post photos of your Vette when things are back to normal.

Jane Ann

 

[Paul Higg]

Pat, this one sounds REAL interesting. I have been looking through my wiring diagrams but I have a 94 and you have an 84 so I don't think I could help.

However, was everything working fine before they disconnected the interlock? If so then I would assume that has something to do with it. I do however have another question. Does everything else on the car work okay. Since they disconnected the interlock and did that work on the transmission did you notice anything else not working? If so that would be a clue too.

Do you have an FSM? I would love to check out the wiring diagrams for the 84 and see what I could find.

 

[Tin butcher]

It sounds like the interlock is your problem. It was originally designed to keep you from locking the column without being in reverse. The cable from the shifter goes to a pin on the column that if it isn't in the right position will stop the key from being turned off. I'm not sure exactly how it works, I never drove my vette with the interlock hooked up - I bought it with a fried OD. I disabled the interlock three years ago when I swapped in a Tremec 5 spd. I must have done it right - the key works!

 

[GerryLP]

When that happened to me on Nebraska, while on the way to Cruise Fest on 2004 at Auburn, IN, it turn-out to be the ignition switch.

Yoda hooked me up with his friend's house garage, and we replace it in about 2 hours.

On a C3, one has to disconnect the rag-joint on the steering wheel shaft assembly to the steering mechanism, to lower the steering column.

I am not sure if it is the same with newer Vettes.

 

[autopat]

More info

Well, I gained a little more info yesterday. I found that when I shut off the key (engine still running), the A/C, PW, stereo, stop working, and the antenna goes down, that tells me the ignition is turning off, it makes me think the field in the alternator is still energized (IIRC, these use a resistance wire, since there's no batt light) which means it's feeding back to the ECM to keep the car running, It's been so hot here, I haven't really wanted to mess with the engine after it's been running, but I think if I unplug the alternator field, the engine should quit (if I'm right). I don't know how much I'll get to mess with it this week, the A/C in the house just pooped yesterday ad, so I'll be looking for some way to come up with the required $8300 to fix that, long before my "project" gets another minute of my time.


Pat

 

[Toms007]

autopat, sorry to hear of your issues, stick with it, you'll get it figured out especially with the help of the people here. Funny you mention your AC, I just got a bid for new AC here....same figure too. It's the pits.

 

[autopat]

Ruled out

Ruled out the ignition switch, now checking oil pressure switch.

Pat

 

[autopat]

Got it!

Found it was the P.O. fault! He added a jumper from ignition hot, to fuel pump wire, which was causing it to backfeed through the oil pressure sending unit, powering up the ECM. I'm also going to replace the oil pressure sending unit as well, since it has been reading weird when you turn the key on, and sometimes takes a while to start when warm. Also big props to JonM for the help. I think the ECM may have a couple of bad outputs as well, but I'll deal with that another day.


Pat

 

[Paul Higg]

I don't know if this is related but just last week I had to replace the fuel pump because it was very difficult to start when warm. It turned out the fuel pump was only putting out 10 pounds. Put a pressure gauge on the fuel rail schrader valve. Now when I start it it starts so fast I have to be careful to not hold the key in start too long. HUGE difference.

Good luck.

 

[autopat]

Thanks Paul, I'll put a gauge on it and see what it says.

Pat

 

[GerryLP]

Wow! Good work!

Why do you think that the pump was jumped?

GerryLP:cool

 

[autopat]

The pump was jumped because the wire from the ECM was no longer providing power, probably a bad driver in the ECM.

Pat

 

[Paul Higg]

GOOD troubleshooting!!!