MGB GT starting problems

[Magog]

I'm having ongoing trouble with getting my MG (1974 BGT) to start, and it's getting exceptionally frustrating

I'll try not to bore you with all the details as it has turned into a bit of an ongoing saga, but basically after completing a 100 mile drive in exceptionally wet conditions the car wouldn't start the following day. (i'm starting to think the rain might have something to do with this)

Recovery guy identified that the alternator wasn't charging the battery properly, and that the battery probably wasn't holding charge. Both these were replaced and seemed to solve the problem for a short while. Though I now suspect that this work might have been unnecessary.
(the coil was also replaced as it seemed like it might well be overheating).

All seemed to be well for a week or so but problems re-emerged, it was possible to jump start the car, but only with increasing difficulty, revving the other car quite significantly and leaving it to charge for some time.

A few times, trying to start the car has produced the symptoms of a flat battery.

-clicking relay, but starter not engaging
-other slightly odd noises that I can't quite identify
-occasional smell of burning plastic after trying the ignition for some time
- some of the metal trim on the dash seems to get extremely warm after trying the ignition for some time.

several times it's started effortlessly with some slight manipulation of the wires at the back of the ignition.

This led me to believe that the ignition switch might be at fault, but now I'm not so sure as removing the brown and the red & white wires from the switch and bringing them into contact produces the same symptoms as trying the ignition did before.

My conclusions are either that the starter is for some reason drawing a massive amount of power, or that there's some intermittent problem with the relay/solenoid, or there is/isn't an earth connection where there should/shouldn't be.

The thing that's baffling me is why slightly manipulating the back of the ignition would allow the car to start perfectly normally if the problem was the starter drawing massive amounts of power.

At all times it's been perfectly possible to push start the car without any great difficulty.

So has anybody got any ideas as to what to do other than take it to a garage?

[Magog]

wildoliver said:

Absolute classic bad earth symptoms.

You have totally baffled me regarding the ignition issue however. You need to either rig up a temporary earth strap (jump lead) and try it or stick some new earth straps on the engine and box it's a simple job.

Can you explain your ignition problem a bit clearer?

I found that by tilting the wires/switch at the back of the ignition a bit the car would start without difficulty - this was a very hit and miss process though. It was as if by tilting the switch a loose connection was being made good (or possibly the opposite, if you see what I mean)

That led me to believe that I had isolated the problem to the ignition switch, and that there was a bad connection somewhere inside the switch so I tried to hotwire the car, but that simply produced the same symptoms as before.

I'm not sure if that makes it much clearer to be honest. It just seemed odd that a bit of tinkering under the dash solved the problem, if only temporarily.

I'll have a go at improvising an earth strap and see how I get on, thanks for all your help.

[Magog]

wildoliver said:

Am I right in thinking the result of this faulty switch (ign) is that you have to churn the engine over and over? If so that's your reason for melted bits and hot bits (combined with bad earth) they aren't designed to be churned over for long periods.

Yeah, I have churned it over quite a bit more than I should have done. I suspect there's a good chance I might have done some further damage to the relay/solenoid or the ignition switch. I sometimes wonder if I have the right personality type for running a classic car.

Anyway looks like I'm going to have to invest in a multimeter, and spend a busy day tomorrow chasing all these faults ans cleaning a lot of connections and getting the car up on axle stands to poke at the starter at least. Cheers for all your help guys and I'll let you know how I get on.

[Magog]

Well I recharged the battery, cleaned up all the connections at the battery and put some copper-eaze on them. Not much joy, similar symptoms to before.

Disassembled the ignition and there seemed to be a bit more life in the car trying to hotwire it.

Decided to give the starter some short sharp smacks with a breaker bar and that seemed to do the trick, started no trouble what so ever.

So I took the car out for a drive for about ten miles. Stopped off at the motor-factors to try and get a replacement for the small screw that holds the ignition switch into the barrel.

Realised I didn't have any money so got back in and tried to start the car and got it seemed like the car was dead... it then gradually emerged into life over a couple of seconds, from clicking relay to slow grinding to starting up... almost like it was working itself up to it.

Anyway drove it home and switched it off, tried to turn it back on and no joy whatsoever.

Went inside and left it for a few hours, came back out and tried it, and it started first time, no trouble what so ever.

I suspect, as many of you have suggested that I'm going to have to get under the front of the car at some point and sort out the wiring to the starter and the earth strap on the engine before It's reliable, but I'm due to pop over to a friends this evening so I'll see how I get on with it.

[Magog]

Well surprise surprise... Started no problem whatsoever on my way out, then when it came time to head home again no joy whatsoever, just the clicking of what I presume is the relay. Before I had any chance to fiddle with it though I had 4 burly(ish) guys push starting it for me, so I managed to make it home ok.

So now I'm going to jack the car up and fiddle with things underneath and see how I get on. I'll try and take some photos just to give you a bit clearer picture and see if there's any guidance you can give me on the basis of them..

I've got a suspicion that the earth strap's been moved as when I had trouble with it before about 3 years ago I took it to an auto electricians , and I think he moved the earth strap, I'll try and get a picture of it's current position.

Sorry I meant to mention earlier that it only has one 12V battery as opposed to the two 6Vs. The change was made some years ago before the car was in my ownership as the two 6V batteries were incredibly unreliable I believe.

[Magog]

Well I spent an enjoyable hour or so this afternoon/evening underneath the car. I have a bit of a phobia of getting underneath a car on axle-stands, but once I'm under there I seem to be alright.

So here are the photos...

This is the connections to the solenoid as I found them...



I disassembled them and rubbed them down with emery paper...



And reassembled them with some copper grease...



The one connection I didn't/couldn't sand down was the crimped connector, though I did sand down and apply copper grease to the tab it connects to.

I believe this is the red/white connection from the ignition switch... the crimped connector appeared to be quite corroded/contaminated with a white sort of film on it...



Anyway after it was all reassembled I lowered the car back down and tried it again, and met with exactly the same symptoms as before...

The one thing I didn't check was where the three large wires that are connected to the solenoid lead to, does one of these connect to the starter elsewhere, or have I got this incorrect?

I haven't yet tackled the earth strap on the engine... but I might try that tomorrow.

It's located on an engine mount at the front below the air filters and seems like it's going to be quite hard to get at... It' didn't seem in too bad condition looking at it, but the photos seem to make it look quite a bit worse.





Sorry this is a bit photo heavy, but it seemed like an easier way of showing what I'd done/was going to do.

[Magog]

chormy said:

I think you need a new starter solinoid, have you tried the old trick of shorting the the solinoid terminal to the starter.

Does that involve shorting between these two connections with the nuts on that I've circled here?

[Magog]

Well its back to life!

Thanks for all your help guys, I should have made it clear that the first thing I'd done was clear up and copper-ease the earth to the battery and it's connection to the bodywork.

Anyway, cleaning up the front earth cable and putting copper grease on it seems to have done the trick (trying to rig up an earth with a jump lead hadn't really worked), I also had a little look at the coil and it did seem a bit loose but I don't think that was the root cause of the trouble.

It was a bit easier to get the front earth strap off than I was expecting (once I'd removed the air filter/intakes). The nut holding it onto the engine mount on the engine side was surprisingly loose and the strap connections had certainly suffered some corrosion. I cleaned it up with a wire brush attachment on a dremel and copper eased it at both ends and did the bolts up tight and it seems to have done the trick, started without and great difficulty at all.

The before and after photos of the front earth strap are below;




Anyway thanks for all your help guys, hopefully I'll have at least a few weeks of trouble free motoring, but I'm sure I'll be back for some more advice before too long.

[Magog]

SB - Nigel said:

Well done, now make sure your battery is fully recharged by going on a good long run as soon as possible down some enjoyable B roads

That'll certainly be my plan for the weekend I think.

perdu said:

Magog that earth cable is ferked

I'm glad you did get it sorted though, these starting problems can "do yer 'ead in!"

I'm not sure that the earth cables quite as bad as it looks in the photos, I had a pretty close look at it and I'd say it's probably still 90-95% unbroken, I think the main cause of wear is the rubbing against the engine mount, but I'll certainly try and pick up a new one in the next week or so.

I have to say it's been doing my head in for a month or so, but I'm quite glad of the opportunity it's given me to reacquaint myself with generally working on the car and being around it. It's certainly left me with a long list of other things to do having spent so much time examining it closely.

Hopefully I'll manage to lavish a bit of TLC on it over the next few months than I have been doing recently, and generally smarten it up a bit. Thanks once again for all your input guys.