1985 xj6 series III Disconnected battery terminal resistance 2.7 ohm

Hi Jag lovers…

There was an article how to bypass the main relay and fuel pump relay long time ago, that help me troubleshoot my 85xj6 series III. It helped me 2 times when my 85xj6 shut down while driving. And by following the “bypass the main and pump” I always got home…

Since I had the issue long time ago I thought I still remember the connections, and recently my car just die while driving again. I tried to redo this without my instructions in-front of me how to bypass the main and pump relays.

This sad thing happened… Unfortunately I connected the positive and negative of the main relay sockets (relay not connected). Now my car will only start and run for less than 4 seconds and it will shut down. (towed my car home)

I checked the disconnected battery terminal resistance and it showed 2.8 ohms without the car key in the ignition…

Could you please help me how I can check what is faulty in the car?

Thanks in advance!


I assume you shorted the main relay socket white to its black, Nony? If so, with ign ‘on’, it shorts ign key, through inertia switch and fuel changeover switch, to ground…

However, if the engine cranks and starts, permanent damage is unlikely - and the brief run has other causes.

Blindly bypassing both main and fuel relay is not ‘best practice’ - the two has different functions and should be tested one at a time, if suspected…

First step; remove air filter and prop the AFM flap open - the fuel pump should now run whenever the ign is turned ‘on’. Does it…?

The main relay has nothing to do with the fuel pump, but if the fuel pump does not run; try shorting the fuel relay socket white to white/green. The fuel pump should run, and if so; try starting the engine…

If the engine still dies after 4 seconds; report back for more tests…:slight_smile:

As an aside; it’s unclear how bypassing both relays helped you twice; did you drive home with both relays bypassed - and then what…?

xj6 85 Sov Europe (UK/NZ)