[T3] Dieseling (run-on) again

[Jim Adney]

On 24 Aug 2013 at 23:14, Jacob Adam Schroeder wrote:

> I just tested now (on my car in the garage, cold) and I hear the two clicks
> as normal if I just turn the key to ON.
> 
> If I turn the key to ON and then OFF right away, I hear the second click as
> soon as the key goes OFF.

Okay, that sounds normal, but I understand that this is an 
intermittent problem. I suggest you get in the habit of grabbing the 
pump relay every time you shut the engine off, in order to try to 
catch it when it runs on.

> The next time I experience the run-on, I will try this simple check and see
> if I notice anything different.  This would indicate that the fuel pump
> relay is sticking, correct?

If the main relay sticks, that delay will cascade down to the pump 
relay, too. So checking the pump relay checks the whole chain. If 
it's just the pump relay that's sticking, then that would keep the 
pump running, but with the main power off the injectors will stop, so 
the engine should stop.

IF you have a leaking injector, that could keep the engine running 
(sort of) even with all the relays off.

> Any way to check the main power relay?

The test above does that.

> Also, what kind of things could be miswired to cause this problem?

It would have to be something that fed power to the FI even with the 
main power relay off. That would have to be either at the main relay 
or where the 2 wires at the far LF corner of the engine compartment 
join the 2 white wires in the FI wiring harness. (That's where the 
power from the relay gets into the FI system.)

Other symptoms that might lend a hint to the problem would be poor 
gas mileage or a battery that seems to run down quickly while parked.

-- 
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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