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Help on a bad problem, electrical, fuel?

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100DashSix

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So, it figures. Just after I get done saying how well my MG is running, it develops the following problem:

While driving the revs will abruptly plummet and the ignition warning light will come on (sometimes it doesn't), and the car will coast. It then comes back to life while coasting in gear, or after a few turns of the starter if idle.

My first thought was that it was electrical, as the tach would drop but the warning light sometimes stays off--I no longer think so, as the drop in revs is accompanied by the feeling one would get if they switched the ignition off. Also, the starter can be cranked at will, so power is getting to it.

So, where do I start? Is this symptomatic of a fuel pump failure? It's an old SU pump that likely hasn't been touched in a while. I have limited tools and only the jack I keep in the boot. Can I check the points on the pump or replace it, if this is the case?

Appreciate the help...using this car as my main transport, and can't take it 2 hours home as it is now.

Edit: Ah, and the points on the distributer are more or less correctly gapped, with no pitting. (Set with a matchbook.) Dizzy is rebuilt, rotor, cap, wires, plugs new w/ less than 1,500 miles on them.
 
Hi
I have to think that this may be an ignition switch problem. You stated the ign light was sometimes on and other times not.This sounds as if the ign is not making contact properly and is cutting power to the car. The part of the switch which supplies power to the starter is different from that which powers the running (ignition) so the car can be restarted even though it stopped on the road. Try turning the switch to the on position, and moving it gently to see if the ign light goes on and off. You can pull the wires off the switch and bypass it to get home. First try the switch and I'll be here. If this is the problem, we'll talk further to get you home
Dave
 
Alright, good call.. I'll start at the switch under the steering cowl and trace it back to the connections I've made (replaced the electrical part of this switch, though was quite careful and used soldered bullet connectors).
 
Hmm... All the connections seemed fine, and the car didn't have the problem driving around the parking lot. What was interesting, however, was when I parked it and wiggled the switch. There is a definite notch that the on position is supposed to fit into, and it stays there well enough. What I was able to do, however, is move it a few cm towards the off and the engine would die, the warning light turn off, and the other electrical things stay on, as it was on the brink of clicking into the first position. It seems this is easier to do than it should be, but it's not so easy that little bumps on the key would cause it; it required deliberate nudging. This is a 5 month old replacement ignition switch from Moss motors.

It seems somewhat plausible that the bumps in the road cause the key to turn into the other position, and the intermittent behavior of the problem might indicate that this is happening..

I'll first try removing the key from my keychain and wiggling it should it happen again; rigging a simple switch won't be a problem--I used the car with one for months when the last ignition switch gave out.

Thanks for the advice, Dave; I hope it's as simple as this.

Should this fail, however, what are some other possibilities?
 
Hi
I would then check connections at the dist. Also at the coil, as these have been known to give the odd (?) test of your patience. I hope this has been good advice, I'll be here for a while yet so keep on. Good luck Dave
 
I had the same problem with my B and found a loose terminal at the coil. Fixed that and haven't had the trouble return.
 
I had a similar problem but the car would just die and then sometime later just as if there was no problem the car would start and act normal. It turned out to be the high tension wire on the distributor. Cheap fix to replace it.
 
There was a loose low tension wire connected to the coil--the ground, I believe. I'll try to get it on there more securely and buy a new female spade connector for it. I wonder if you can solder connections with a lighter...

I wouldn't expect it to be the high tension wire (just a few months old), though I'll check that over to be sure.

Hopefully I can drive home today...I'll let you know of the progress.
 
This morning I got the spade to have a tighter fit on the coil terminal; the car has behaved well on two short commutes to school and back..now I set out across the Virginian mountains! Thanks greatly for the help.
 
Make sure you check the low tension lead in the distributor. That's the small, fabric covered wire leading from the coil input to the points. They break easily, and create the exact symptoms you describe.
Jeff
 
I had my distributer rebuilt by Jeff from AdvancedDistributors, and that wire is now a nice new one. The driving yesterday went without a problem, I'm happy to report.
 
Glad to see you've apparently got the problem licked. I say "apparently", only because I've been around these things for a <u>LONG</u> time! /bcforum/images/%%GRAEMLIN_URL%%/grin.gif /bcforum/images/%%GRAEMLIN_URL%%/hammer.gif
Jeff
 
Glad you made it hime and as of now it performs as per schedule. I'm usually close to my comp. so I'll be around if you need help or just want to vent Dave
 
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