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MG MGB Technical - Car will not start - intermitant

Due to insurance requirements my 71 MGB has a self setting immobiliser fitted which works as follows. A small red flashing light indicates that the immobiliser is armed, by turning the key to the on position the system recognises a chip in the key ring and the red flashing light goes out and the car can be started.
On a few occasions when I have turned the key to start the car nothing has happens, immobiliser light goes out, charge light does not dim, starter solenoid does not throw out and petrol pump does not start. When this first happened I assumed a bad battery connection and I cleaned and reconnected the battery terminals and of course then the car would start. This happened a number of times and I started to suspect another problem as the battery connections were in good condition.
The last few times this has happened I have turned of the key and after a set period (3 minutes) the immobiliser has reset and on the second try the car would start.
The last time this happened the second attempt would not start the car, I turned on the front headlights turned the key to start again nothing happened and the lights did not dim so I assume my battery connection is good. I tried the car again after 4 hours and the car started straight up first time. Assuming the immobiliser is functioning correctly as indicated by the red light and to simplify diagnosis what else can I look at.-
Poor connection in the start switch?
Poor connection at starter?
Starter Relay? (Modern Bosh relay fitted a number of years ago)
Any help, past experiences or checks to carry out when it next happens would be most appreciated.
David Levy

Sounds like the LUCAS immobiliser gremlin strikes again.
I would suspect that addition long before anything else.
On a 1990 Sterling I had the same type problem. With a call to the warranty department in Miami the technician advised me to make certain that all windows including the sunroof were closed. Get out of car and lock all four doors. Wait 30 seconds and get back in and start the car. It never failed to work that way. Later I found out that it had something to do with the sequence of releasing the seat belts, If they were unlocked prior to turning the key off it would send a false signal to the security system and nothing would work until it was re-sequenced.
Sterling never did fix the problem but in March 1993 we had "the no name storm" and it covered the car in 5' sea water.I actualy miss it.
Sandy Sanders
conrad sanders


There is a double bullet connector on the white wire circuit under the bonnet on the right side near the bulkhead. It connects three white wires: from ignition switch; to coil; and to fuel pump. Double bullet connectors disintegrate much faster than the singles. Check it.

Allen Bachelder

Poor connection at the starter (solenoid) should be suspected as well. If your blade connection there is corroded, it will cause intermittant starting. As you'd expect it is easy enough to correct and remove from suspiscion. Not sure what effect the immobilizer would have - but could provide a false scent for diagnosis.

Allen's right about the double connector in the ignition circuit.

Funny enough - my '73 has experienced intermittant starting due to corroded connections at the solenoid, while both my '72 and '73 have had the ignition circuit double connector crumble to dust. The circuit problem caused the cars to stop running, the solenoid connection problem provided the starting problem.

Good luck, and your local conditions may yield different results.
John Z


You brought back fond memories of my Rover 820 in the UK and I liked it so much when it wore out I bought the then flagship of the range 1994 Rover 827 Sterling - it was without doubt the best modern car I have ever owned ... with the exception of my MG ZT-T which we unfortunately had to leave behind in the UK (because of Import restrictions) however it does give us about the only decent reason outside of family & friends to go back to the UK as I couldnt bear to part with it. So we now have it in storage and looked after for us while we are away - then I enjoy blasting the cobwebs off it!!

Paul Barrow

Thanks to all for the responses, I will carry out the checks as recommended this weekend.
Intermitant problems are so much harder to find,
David Levy

This thread was discussed between 29/07/2008 and 30/07/2008

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