Engine runs but won't quit.

[retsurv96]

The last time on here I addressed gas tank cleaning for my 73 Squareback . The gas tank has been cleaned and I was able to start the engine, using the original fuel pump. The problem now is that it won't quit. The bugger keeps running with the key shut off. The only way I could stop it was to disconnect the wire from the battery to the ECU power relay. I replaced the relay which didn't help. Then, with the same wire disconnected from the relay I tried starting it and she fired right up. It also shut down normally using the ignition switch. So, does this mean the engine will run without the ECU? Will that situation do any harm?
The other thing is I noticed the odor of exhaust fumes inside the car so it seems there must be a leak in one or more heat exchangers. My repair manual (Bentley) indicates that is usually a rear exchanger. I hope that is the case, for it looks like it will be the easier of the two to remove, maybe without removing the engine. I welcome any comments on both these issues.

[Mike Fisher]

The rubber seals on the hatch & engine lid have to be good to seal out exhaust fumes.
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[KTPhil]

Check if the relays are wired correctly.

Check the connections between the muffler and the large heat exchangers. Leaky or missing seals there will let exhaust, forced out in a jet, to enter the moderately pressurized heat exchange fresh air and give you fumes.

[Bobnotch]

[retsurv96]

Thanks Bob. I've checked the relay wiring several times but I may have missed something. It's worth another look.

[KTPhil]

[retsurv96]

While heeding Bobnotch"s advice I found a wire running from terminal 86 of the fuel pump relay to fuse #11 in the fuse box. The wire shouldn't be there, according to the wiring diagram, and explains why the engine can run without power to the ECU. Thought I'd better run it on the forum before disconnecting the wire. There is a disturbing explanation of this.....maybe that's how the former owner ran the car after the ECU went caput.
As for the fume problem, the seal in the engine lid is in fair shape, but the seal around the rear hatch is missing. So no doubt therein lies the problem.
Have yet to check the connections between the muffler and large heat exchangers.

[KTPhil]

When you are moving, the interior of the car is a vacuum relative to the outside of the car. Lack of the hatch seal is the major source of your fumes, and must be replaced, including the straight separate section at the bottom. These are vital to avoid poisoning yourself!