MGB GT starting problems

MGB GT starting problems

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Magog

Original Poster:

2,652 posts

188 months

Thursday 14th October 2010
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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?





wildoliver

8,766 posts

215 months

Friday 15th October 2010
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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?

Magog

Original Poster:

2,652 posts

188 months

Friday 15th October 2010
quotequote all
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.


chormy

635 posts

195 months

Saturday 16th October 2010
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Check the connection on the starter solinoid, also the old braided earth straps tend to go after a time.
if by hotwiring the switch it does the same Its not that. Fuses ok not corroded. If he solinoid is working then its low voltage or poor earth. Have you measured the voltage at the starter when you turn the key. (both solinoid and main cable to stater.)

SB - Nigel

7,898 posts

233 months

Saturday 16th October 2010
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I'd go with connection somewhere (possibly earth)

The position, remoteness and the fact that there are two batteries mean these can cause problems and neglect, I read you changed the battery(?), good clean and secure connections are required from these

For this and previous (and to prevent future) problems

Clean and make secure (copperease/vaseline where required)
Batteries
batteries' terminals
batteries terminals connections on batteries connecting leads
main earth lead to body and connetions
engine earth lead and connections
soloniod to starter lead and connections
starter motor fixing
coil connections and leads
coil to dissy HT lead and connections
plug to alterator

always a good idea whether it's anything to do with this problem or not - change dissy cap and rotor arm for good quality - http://www.distributordoctor.com/red-rotor-arms.ht...

It's just a matter of tracking down the problems (clean and securing the above will help at least for the future even if not for this problem so is worth doing)

but Sod' Law says which eever end you start the problem will be at the other so best to start at the batteries and earth connections then test to see if the car will start, then continue even if it does start

That way you'll know where the problem was and be preventing future problems

EFFF

Edited by SB - Nigel on Saturday 16th October 15:41

wildoliver

8,766 posts

215 months

Saturday 16th October 2010
quotequote all
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.

heebeegeetee

28,591 posts

247 months

Saturday 16th October 2010
quotequote all
The battery(ies) on a B live under the back seat. The earth point is on the battery box, and normally gets totally neglected. This is the main earth point I would check first, and also check that the metal in the surrounding area to the earth point isn't getting rusty. If there's too much rust around then the current will have difficulty in returning to the battery.

Your problems definitely sound like dodgy earths to me. smile

Magog

Original Poster:

2,652 posts

188 months

Saturday 16th October 2010
quotequote all
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.

heebeegeetee

28,591 posts

247 months

Saturday 16th October 2010
quotequote all
Magog said:
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.
Get under the back of that car and tackle that earth connection on the battery box. That's your first job i reckon. smile

SB - Nigel

7,898 posts

233 months

Saturday 16th October 2010
quotequote all
heebeegeetee said:
Get under the back of that car and tackle that earth connection on the battery box. That's your first job i reckon. smile
I'll third that (plus checking and cleaning everything as I said above) - you don't need a multimeter for any of this so save time and money for now and leave that purchace (and if you're like me forget as you'll only confuse yourself)

chormy

635 posts

195 months

Saturday 16th October 2010
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You mentioned that you truned the engine over !! is it that teh engine is turning over and no spark of life from engine or just won't turn over.

Magog

Original Poster:

2,652 posts

188 months

Tuesday 19th October 2010
quotequote all
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.

SB - Nigel

7,898 posts

233 months

Tuesday 19th October 2010
quotequote all
You're doing yourself and the car no favours by carrying on as you are so you'll need to get under the car asap to check things out

disconnect the battery(?) before checking the main wire and connectors

unless someone has found a single 12v battery (a good idea) a 1974 BGT usually has two 6v batteries, mine did

keep going and keep posting, check out all suggested above as it'll be the one bit you miss that'll be the problem it's Sod's Law

chormy

635 posts

195 months

Tuesday 19th October 2010
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I think you need a new starter solinoid, have you tried the old trick of shorting the the solinoid terminal to the starter.

heebeegeetee

28,591 posts

247 months

Wednesday 20th October 2010
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I agree, it's starting to sound like a starter motor problem now.

But Mag, is your battery(ies) under your rear seat, and if so, have you traced where the battery earth connection bolts on to the bodywork, which as if as original is a point on the battery box itself?

And also, not inferring anything or owt wink, if the battery is under the back seat, are you sure about the voltage of the battery, have you got one 12 volt battery or do you have two 6 volt batteries as original?

I'm just wondering if you've checked one battery but may not be aware that there is a second battery also under the back seat on the other side of the transmission tunnel. smile

Magog

Original Poster:

2,652 posts

188 months

Wednesday 20th October 2010
quotequote all
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

Original Poster:

2,652 posts

188 months

Wednesday 20th October 2010
quotequote all
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... frown

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

Original Poster:

2,652 posts

188 months

Wednesday 20th October 2010
quotequote all
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?

heebeegeetee

28,591 posts

247 months

Thursday 21st October 2010
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Hi Mag,

You're doing well, but the very next thing you need to tackle are the earths.

You've got the one in your picture, simply undo each end and give a rub of emery cloth or sandpaper.

But the next one, and the most likely culprit, is the battery earth. If your car is up on four axle stands, with 2 under the rear axle, you may be able to find the earth with a light, it'll be on one of the uprights that make up the battery box (assuming you 12v battery still resides under the rear seat).

If you can't see or get at the earth that way, them remove the rear seat and panel and locate the battery. The positive connection will run down under the bodyshell to travel to the starter solenoid itself. The negative/earth connection will bolt onto the bodyshell somewhere, the original place was on one of the uprights of the battery box as i said.

With the battery being where it is it gets forgotten about, and that one earth connection is possibly the most forgotten item on the car, but it does a vital job. Luckily, its something you only need tackle every 10 years or so providing the bodywork in that area isn't rusting away.

That earth connection has to be clean and sound to allow everything else to work. The starter draws the heaviest current of all, so if the earth point is corroding it will be the starter motor that will play up first. smile

SB - Nigel

7,898 posts

233 months

Thursday 21st October 2010
quotequote all
All this cleaning and checking is very worth while

I'd suggest you get a small ignition wire brush for cleaning up things like the thread connectors on the soloniod

Sorry to be a pain but you need to clean everything on the connections and I always renew screws, bolts, nuts and washers with new as they are clean and not rusty plus you can see what you've done if you need to recheck in the future

The crimped connectors I'd replace if they can't be throughtly cleaned up - you may be able to clean the fur off them by dipping them in a small cup of very hot water and then thoroughly drying them

That earth strap I'd replace with new and have done with it - peace of mind plus you don't have to be under axle stand stands for it next time

you're quite right to be cautious about using axle stands but don't be frighten just set them up correctly

We all keep going on about good earth connections especially from the battery because they are very important to starting the car, and keeping it going

Keep checking the battery is fully charged with all this draining on trying to start - check the 'water' level inside the battery before recharging and recharged out of the car (you know the connections are easy to get on and off)

Just thought of something else it could be, worth just checking -
the HT ignition lead from the dissy cap to coil check that the lead is fully seated properly on the coil, the cover cap can create an air seal that actually lifts the lead out of the coil as you push the cover cap further on, you need to 'burp' it as you push it fully on (like a Tupperware lid)

As I said before above are loads of thingsd to check but stick with battery connections first