engine will not turn off

jbrand540 · 09-15-2007, 06:21 PM

Wondering if this could be the DME relay or if not what it could be.

Just started to day and it does this everytime.

Car runs great but when I kill the ignition everything goes off but engine, which continues to run happily for uyp to 5 minutes which is when i finally dumped the clutch. Obviously it seems to me for it to run this long fuel pump, injectors, brain, etc all have to be working properly.

All I can think is that my DME Relay is fried itself closed so power stays on. Anyone else had this.

ischmitz · ischmitz's Garage

MikeZ had the exact same issue on his car. His is a 3.6 conversion. One day it started doing it. I had my money on the diode between the alternator and +15 being shortened. That way the alternator keeps +15 energized even if you turn the ignition to OFF. However, he ended up putting the fuel pump onto +15 rather than having it being powered from the relay connected to +30. This "fixed" it. I assume the pump draws enough current to bring down +15 once the ignition key is switched to OFF.

In your case it could be the DME relay being fried closed. However, it is unlikely that both stages fry shut at the same time. I would check the ignition switch (the electrical part) and check the diode between the alternator and the +15 circuit. One or the other keeps +15 enegized enough for the car to run on.

Ingo

jbrand540 · 09-26-2007, 03:03 PM

Is this diode part of the voltage regulator or is it seperatley located.

dshepp806 · dshepp806's Garage

For sure: check the ignition switch. Mine ('89) would VERY INTERMITENTLY exhibit up to a (max) 3 second delay for the engine to shutdown AFTER I had the ignition switched off...seemed to occur after extended driving (maybe heat? dunno...)

DME? I doubt this, but: simply change her out and see (i.e., "use your spare!)

I'll have to check the circuit as to the diode spoken of....wasn't even aware of this existed at the alternator........................................ .....

ischmitz has it on with your checklist...have you manuals?

My $$$'s on the switch!

Best of luck,..happy hunting!

Best,

jbrand540 · 09-26-2007, 03:39 PM

I would lean toward switch except now that i have changed out the dme relay switch, once I kill the motor there is no power to coil or pump.

I would think if it was a bad switch then power would stay on at the coil and the pump.

ischmitz · ischmitz's Garage

Quote:

Originally Posted by jbrand540

Is this diode part of the voltage regulator or is it seperatley located.

I think it depends on the year. Here is a schematic of 84 (85 is virtually the same). Note the diode between +15 and the charging light. It should be located behind the instrument cluster somewhere.

And here is the 86-89 charging system. Note that they did away with the diode. So since the need for this diode is still the same I assume it is now part of the alternator (internal regulator)

To test whether this is the culprit do the following: Get the instrument that has the charging light out of its socket. Make sure nothing shorts out. Next start the engine, then turn the key off. If the engine continues to run pull the connectors at the charging light. If the engine turns off you found your issue.

Hope that helps,
Ingo

jbrand540 · 09-26-2007, 04:25 PM

Thanks for the input, I was trying to think of a good way to test this as the culprit. I was looking at my electrical diagrams and trying to find the diode so I believe there are all in the alternator on the later cars.

dshepp806 · dshepp806's Garage

I'll look for this component,..my 89 follows the provided print (it's NOT there.....) are we sure it's in the alternator? Aside from the bridge diodes? Dunno....Interesting question for sure.

...that damned ignition switch?

Best,

jbrand540 · 10-10-2007, 07:10 PM

In follow-up I have just finished replacing the alternator with a rebuilt unit with no change. I am now down to questioning the switch, is there anything else to look at first? Is there testing methods someone could recommend on the switch.

Peter Bull · Peter Bull's Garage

I had a similar problem which turned out to be a faulty ground connection.

/Peter

Wayne 962 · Wayne 962's Garage

I had this happen to one of my cars - was a faulty ignition switch.

-Wayne

jbrand540 · 10-11-2007, 09:36 AM

If I was to replace the ignition would I need to replace the entire ignition as I notice our host sells the electronic portion of the ignition itself and I would assume that this would contain all strikers and items that could possibly cause my problem and the rest of the assembly is only the mounting and tumblers. Does anyone know if this is correct as the price difference and labor involved between the two is substantial.

911mot · 911mot's Garage

Yes you only need the electrical side of the switch.
If you can borrow one you only need to reach up and pull off the multiplug, plug in the new part and try it first

jbrand540 · 10-18-2007, 04:27 PM

ok so I now have replaced the alternator, DME relay, and the electrical portion of the ignition switch with no change. Everything behaves correctly on the car and it runs great but still the ignition will not turn off with the key. Does anyone have any ideas for me on what to check next?

Prior to having this problem I had done nothing to the car for almost 2 months and everything had been working perfectly so I have to think it is a part that has failed.

jbrand540 · 10-18-2007, 04:53 PM

Any chance this could be caused by a fault in the factory alarm?

chrisp · 10-18-2007, 06:50 PM

I have been dealing with the exact same issue on my '83. I haven't chased it with nearly the same effort you have. Mine is a track car and I just stall it in first.

I'm chiming in because I had the same thought about the alarm. My alarm keyhole is turned to about the 2 o'clock position. I can't get my ignition key in the socket to turn it to 12 o'clock (if that's the correct off position - i don't know). I've never played with the alarm on my car so I don't even know if it works.

My run on problem started about two years ago.

jbrand540 · 10-18-2007, 06:57 PM

Unfortunately on the 89 I do not have the key for the alarm to disable it. I am thinking this will be the next thing I try but at this point I am just grasping at straws. I would have to think the alarm would by default only cut power if an alarm was tripped, however, I am starting to wonder if the alarm actually cuts power when the key is turned off.

Anyone know how to bypass the alarm on an 89. I found instructions on bypassing for an 87 but the alarm wiring is a bit different for an 88-89 and am not sure if the same cutting and splicing of wires will work.

dshepp806 · dshepp806's Garage

DME relay SOCKET OK? Terminations look good? I recall reading somewhere where a guy had issues with the DME relay socket itself,...you could change out DMEs all day and not see the change.

WIRING Integrity............?

I would imagine on an alt rework, one would certainly include the new bridge, reg, brushes, etc, and any other diode that may be within the housing.

ischmitz recc's would certainly provide go/no go as to alarm (which will be interesting to look in to).

mmmmmmmmmm...

Best,

SOunds like you've a good one.

jbrand540 · 10-19-2007, 08:19 AM

How hard is it to replace the DME relay harness? I am not sure exactly where it runs to when it leaves under the seat but I would imagine the wires spider out all over the place.

My next step I guess will be to bypass the alarm system as this is fairly simple and I hate to start going down the road of rewiring the car, that will be a last resort for me.

jbrand540 · 10-19-2007, 08:22 AM

One more item to note on the DME relay is before I changed it out I had power at the coil with the key off. After swapping it I do not. Once the engine is off everything is now off so something is obviously working correctly now with the new relay. I attribute the relay to some chain of events stemming from whatever the beginning problem is.