Chicagoland MG Club: Tech Tips

Chicagoland MG Club

Chicagoland MG Club

General Tips

MGA Tips


Midget Tips

MGT Tips

MMM Tips

Tech Session
Photo Archives

  Chicagoland MG Club:Tech Tips

MGB Tries to Self-Start

Recently I had parked my 1974 MGB in the local shopping center parking lot. Upon returning I noticed the car had moved slightly forward up against a concrete barricade. Strange! When I pressed in the clutch pedal to start the car, it moved back and the engine turned over, all before I turned the key!

Puzzled, I tried to start the car, but nothing happened-no starter operation. Popping open the bonnet I could detect the faint smell of smoked electrical wiring! After getting the 'B push-started and arriving home, I started trouble-shooting. I disconnected the small white wire to the starter solenoid and rigged up a wire so I could see if the solenoid was getting 12 volts when I turned the key.

My multi-meter showed 12 volts to the starter solenoid even without the key in the ignition! I then disconnected the solenoid wire at the starter relay end, thinking that maybe the relay had an internal short. Still 12 volts at the solenoid end of the wire, which was now disconnected from anything at both ends!! About this time, before climbing under the jack-stands, I disconnected the battery.

Really puzzled, I started unwrapping the wire bundle into which the solenoid wire disappeared, from the solenoid end. About an inch into the bundle, I found chaffing on both the solenoid wire and one of the 12 volt lines that taps off the starter and that is live at all times. The culprit was the mounting bracket for the clutch hydraulic line. The wire bundle was resting against this bracket, and even though the wire bundle wrapping material appeared only slightly frayed, the insulation had completely worn off the wires inside.

The fix was easy-I clipped off the frayed wires, and re-spliced them with some butt connectors. Then I wrapped the area with electrical tape, bought some plastic wire bundle stuff at the hardware store and routed the bundle away from the clutch line bracket. The starter was in fact fried, so a rebuilt one was installed.

The lesson is scary. I had been under this car several times in the past few weeks, changing brakes, oil filter, and other routine maintenance. If I had bumped the wire bundle I could have activated the short. I normally place the car in gear, brakes on, with chocks under a rear wheel when jacking. The car still could have jumped forward off the jackstands with me underneath. Usually I do not disconnect the battery since that causes my radio to zero and I have to reprogram my favorite stations and reset the radio's clock!

Next time you are under your MGB, after either disconnecting the battery or at least putting gear shift in neutral, unwrap a few inches of this wire bundle and check for chaffing at the point adjacent to the bracket where the clutch hydraulic line is attached.

Back to MGB Tech Tips

©1999, 2001 Chicagoland MG Club, All rights reserved.