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Quote:
Originally Posted by john walker's workshop View Post
I can't remember what year the car was, but I remember one like that, where someone put a single terminal bulb in the double terminal brake light socket and until the brake pedal was released, the car wouldn't shut off. Through some weird wiring scenario, the crossed terminals fed back and kept the ignition on.
This, apparently, may not be so surprising. At first I thought it was just kinda funny, (John W's posts are entertaining and most often enlightening), but after reviewing some coincidental reports here in the forums it seems that a diode failure can have similar symptoms because of back feed with reversed current flow through an alternative pathway. Similar cases are reported with headlights.



In that case, where are the diode holders in a 77 911S?
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Old 03-25-2017, 01:05 PM
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Check the 3 way fuse holder in the engine bay with a meter, If the middle and lower terminals are bridged this can prevent the car from switching off.

This can happen if someone fits a later fuse block from a 3.2 Carrera. The parts look the same from the front but the later block has all three terminals bridged on the back.
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Old 03-25-2017, 01:24 PM
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Just thought I would comment on this problem you have, since a 1987 944 I worked on had this problem. While I am not an expert, I seriously would consider what John Walker said earlier.

Why?

Well, in my case, the 87 944 I worked on had four (4) distinct problems:
1) Ignition switch
2) Light switch
3) Right rear turn signal unit (entire replacement needed w/new equipment)
4) The Fuse panel (problem with grounds being missed through-out car as well as butchered wiring).

The latter relates to the fact that within the fuse panel someone had hot wires (# 30 on the electrical diagrams) wired directly to the fuel pump; it would NOT shut off which is very dangerous IMHO. Especially since the car would continue to run. ( Think accident were one cannot get out of the car and fuel hits the hot engine.)

Now, the 87 944 is a Motronic system with ECU/DME so it is not the same as your car.

However, I thought that this information would help you with your troubleshooting since some, as John Walker and others, suggested this being an electrical problem.

Good luck ! I do hope you resolve this issue soon.
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Old 03-25-2017, 02:08 PM
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Short term pop the clutch. Long term find the power to the ignition and swap it to a circuit that is switched thru the ignition.
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Old 03-25-2017, 02:11 PM
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Quote:
Originally Posted by TibetanT View Post
Just thought I would comment on this problem you have, since a 1987 944 I worked on had this problem. While I am not an expert, I seriously would consider what John Walker said earlier.

Why?

Well, in my case, the 87 944 I worked on had four (4) distinct problems:
1) Ignition switch
2) Light switch
3) Right rear turn signal unit (entire replacement needed w/new equipment)
4) The Fuse panel (problem with grounds being missed through-out car as well as butchered wiring).

The latter relates to the fact that within the fuse panel someone had hot wires (# 30 on the electrical diagrams) wired directly to the fuel pump; it would NOT shut off which is very dangerous IMHO. Especially since the car would continue to run. ( Think accident were one cannot get out of the car and fuel hits the hot engine.)

Now, the 87 944 is a Motronic system with ECU/DME so it is not the same as your car.

However, I thought that this information would help you with your troubleshooting since some, as John Walker and others, suggested this being an electrical problem.

Agreed it seems electrical. My taillights are currently absent, (thanks PO), so there doesn't appear to be a bulb problem like John W had but there are similarities. And I've made rudimentary efforts to ensure that the associated wires are not shorting so I feel the problem lies elsewhere.

And as mentioned in your case, my fuel pump also remains somehow powered until I remove the relay. It's a clue and a problem.

By the way, the common term is "engine over run" meaning that it continues to run with the key removed and ignition in the off position.
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Old 03-25-2017, 05:19 PM
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Originally Posted by T77911S View Post
i would think there would be a battery drain with the car off.
with it off, listen to see if you hear the CD unit on. just curious.

that's kind of what I was thinking, maybe ignition switch bad or miss wired but if there has been a lot of jury rigging in the wiring I would look for the CD to be wired hot all the time.

I don't have a 77 diagram so not sure of this.
power from the ign sw also goes to the fuse block in the engine bay to power the WUR and AAR.
if they hot wired the Wur on that would keep the CD unit on



Ok, life got in the way...


Got out to the storage and started to get my bearings, what little there are.
Here's the dealio.

1977 911 S, won't shut off when I turn off the key.
Battery drain? You betcha. I don't dare leave the battery connected as you can hear something running near the front of the car the instant you connect the negative terminal. That is why the PO installed a battery shut off kluge dangling from the dash.

Anyway, it looks to me like the fuel pump runs continuously. It stops if I pull the red relay that seems to be associated. I thought the relay might be bad but that doesn't explain the run on with the key switched off. Also, I switched relays and got the same thing anyway so I don't think it's just the fuel pump circuit. I'd say that both spark and fuel remain on anytime the battery is connected with or without the key in the "on" position. Does that point to the electronic component of the ignition switch?

Gotta learn to read wiring charts and the ones specific to 1977 are a bit elusive.
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Old 10-08-2017, 10:45 AM
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Hi..have you checked what Johny H suggested?
I had a client`s 911 1976 once, which acted exactly like yours and it was the rear fuse box wiring..at the engine compartment.

Ivan
Old 10-08-2017, 11:01 AM
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Hi..have you checked what Johny H suggested?
I had a client`s 911 1976 once, which acted exactly like yours and it was the rear fuse box wiring..at the engine compartment.

Ivan
I didn't but maybe I should. Seems like the fuel pump up by the gas tank wouldn't be powered from the fuse box in the engine compartment but I'll give it a shot.
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Old 10-08-2017, 12:28 PM
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The 77 cars had CIS that has been removed correct? If this is the case there's a connector that went to the fuel air measuring sensor plate. When started this plate breaks a ground circuit to the fuel pump relay and closes the circuit thus providing power to the pump. Find the harness it has a blue connector near the center of the firewall you should jumper those two wires. This will fix your continuing fuel pump not your engine run on though.
Old 10-08-2017, 12:44 PM
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Yes, it was continuous injection system converted to pmo's installed by a reputable Builder. I don't know if the run on problem coincided with that same time but tend to doubt if given his reputation. Also, as you pointed out it doesn't answer the question of engine run on so I'm looking for something that might do both.
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Old 10-08-2017, 01:38 PM
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Here's the rear fuse panel. This is what you are referring to I believe.







And...it's upside down. I usually don't store my car upside down but apparently that day I did.

I could probably start with a good cleaning.
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Old 10-08-2017, 02:13 PM
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Quote:
Originally Posted by Jonny H View Post
Check the 3 way fuse holder in the engine bay with a meter, If the middle and lower terminals are bridged this can prevent the car from switching off.

This can happen if someone fits a later fuse block from a 3.2 Carrera. The parts look the same from the front but the later block has all three terminals bridged on the back.


Right then. Don't know why someone would have done that but it seems like an easy enough thing to check. Not that it's up my alley of experience but shouldn't be able to do too much damage.

Here is a glimpse of the solution they came up with interrupting the negative terminal at the battery. It looks like a pair of jumper cables split and running from the battery to the dashboard vent.

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Old 10-08-2017, 02:31 PM
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Not very sophisticated but maybe they were at their limit and couldn't find the problem.




And the dangling participle.


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Old 10-08-2017, 02:39 PM
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Engine run on

Old 10-08-2017, 02:51 PM
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Quote:
Originally Posted by rbogh901 View Post
Here's the rear fuse panel. This is what you are referring to I believe.







And...it's upside down. I usually don't store my car upside down but apparently that day I did.

I could probably start with a good cleaning.

The non standard lower red wire on the left of the fuse panel looks like it could be powering the MSD box. That is permanently live which is why your car doesn't switch off. It should come from an ignition switched live.

P.s. The fuse panel is the correct way up (with numbers upside down!)
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Last edited by Jonny H; 10-08-2017 at 02:58 PM..
Old 10-08-2017, 02:55 PM
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Quote:
Originally Posted by Jonny H View Post
The non standard lower red wire on the left of the fuse panel looks like it could be powering the MSD box. That is permanently live which is why your car doesn't switch off. It should come from an ignition switched live.

P.s. The fuse panel is the correct way up (with numbers upside down!)

Good eye there mate. The numbers give it away and I hadn't noticed. Takes a guy 5 billion miles away to clue me in. Meanwhile, when you say lower left would that be the number two fuse then?
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Old 10-08-2017, 03:37 PM
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Or, actually as I look at it maybe you mean the number one fuse with the extra wire traveling behind. I will trace it and see if it Powers the MSD box. The number 3 fuse is unused here.
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Old 10-08-2017, 03:38 PM
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Could this power the fuel pump also then?
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Old 10-08-2017, 03:39 PM
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Quote:
Originally Posted by rbogh901 View Post
Yes, it was continuous injection system converted to pmo's installed by a reputable Builder. I don't know if the run on problem coincided with that same time but tend to doubt if given his reputation. Also, as you pointed out it doesn't answer the question of engine run on so I'm looking for something that might do both.
You might want to start with the continuous fuel pump running then proceed from there.
Old 10-08-2017, 04:37 PM
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Or, actually as I look at it maybe you mean the number one fuse with the extra wire traveling behind. I will trace it and see if it Powers the MSD box. The number 3 fuse is unused here.
Yes, number 1, the lowest one with the extra wire.

As a simple test, why not pull that wire with the engine running?
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Old 10-09-2017, 12:52 AM
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