Old engine electrics problem
Discussion
righty, 1975 MG midget (wiring diagram, goggle 1978 mg midget, AFAIK they're the same)
The number of times I come on here to piss and moan about my car I should probably
a) give it a name out of courtesy
b) get the mods to stiky it!!
Anyway, for the last few months its been a none starter, well sometimes anyway. Turn key ignition light comes on (i.e. everything working, but alternator not spinning yet), turn one notch further, light goes out, but nothing else happens
Assume that it's a dodgy solenoid (it's only intermittent), so I check it this morning, starts first time, "ahh well" says I, I've got the part now, I'll be done in time to get to the shops to buy some bacon for a lunchtime sarnie.
Does it work now, does it f***!!! Ignition light now comes on, and stays on through the entire process. Checked all the connections, checked there's a voltage getting to the solenoid, there's a voltage through the solenoid, there's even a voltage at the coil where (AFAIK) the starter solenoid earth's itself (oddly, onto the +ve terminal, presumably this is +ve when the engine is running and as a results makes sure the solenoid is firmly shut).
Grrrrrrrrrrrrrrrrrrr, can't figure it out. Must have nudged something with my elbow while fitting the new solenoid, most likely somewhere between the solenoid and its earth, but can for the life of me figure out what.
Can anyone figure out what the normal route to earth is from the solenoid? I've a feeling it goes through some other stuff that normally +ve when the engines running to ensure that even if you had a short circuit in the ignition switch, you cant engage the solenoid/starter motor. I'll try and find a link to wiring diagram and post it up if anyone could help me figure this out
The number of times I come on here to piss and moan about my car I should probably
a) give it a name out of courtesy
b) get the mods to stiky it!!
Anyway, for the last few months its been a none starter, well sometimes anyway. Turn key ignition light comes on (i.e. everything working, but alternator not spinning yet), turn one notch further, light goes out, but nothing else happens
Assume that it's a dodgy solenoid (it's only intermittent), so I check it this morning, starts first time, "ahh well" says I, I've got the part now, I'll be done in time to get to the shops to buy some bacon for a lunchtime sarnie.
Does it work now, does it f***!!! Ignition light now comes on, and stays on through the entire process. Checked all the connections, checked there's a voltage getting to the solenoid, there's a voltage through the solenoid, there's even a voltage at the coil where (AFAIK) the starter solenoid earth's itself (oddly, onto the +ve terminal, presumably this is +ve when the engine is running and as a results makes sure the solenoid is firmly shut).
Grrrrrrrrrrrrrrrrrrr, can't figure it out. Must have nudged something with my elbow while fitting the new solenoid, most likely somewhere between the solenoid and its earth, but can for the life of me figure out what.
Can anyone figure out what the normal route to earth is from the solenoid? I've a feeling it goes through some other stuff that normally +ve when the engines running to ensure that even if you had a short circuit in the ignition switch, you cant engage the solenoid/starter motor. I'll try and find a link to wiring diagram and post it up if anyone could help me figure this out
what does rocking it prove?
Fairly confident it's not the starter, when its all working the engine jumps into life instantly, even form freezing cold after being left for weeks.
There's no click or anything form the solenoid this time though.
Just found another of my mistakes, the body of the solenoid is earth, the cold start connection is just a straight through from the ignition starter wire, hence why it's the same brightness. Now thinking the new solenoid might not be getting a good earth to the car, seems impossible, but it is simply held in place by two rusty screws, so could be. I'll go clean off the screws and report back.
Fairly confident it's not the starter, when its all working the engine jumps into life instantly, even form freezing cold after being left for weeks.
There's no click or anything form the solenoid this time though.
Just found another of my mistakes, the body of the solenoid is earth, the cold start connection is just a straight through from the ignition starter wire, hence why it's the same brightness. Now thinking the new solenoid might not be getting a good earth to the car, seems impossible, but it is simply held in place by two rusty screws, so could be. I'll go clean off the screws and report back.
Edited by thisisnotaspoon on Sunday 21st February 22:05
Edited by thisisnotaspoon on Sunday 21st February 22:09
easy to check for a bad earth with a volt meter. connect between the negative of the battery and the solenoid body. when the key is turned there should be no volts. a bad earth will show up a voltage on the meter, the higher the reading the worse the earth is.
if you have voltage to the solenoid feed wire (use a test light for this test as a volt meter can be too sensative for this test. 12volts doesn't mean it has a good feed) then short the two large terminals with a screwdriver (make sure the car is out of gear first and DO NOT short to earth) the starter should turn. if it does the solenoid must be faulty.
if you have voltage to the solenoid feed wire (use a test light for this test as a volt meter can be too sensative for this test. 12volts doesn't mean it has a good feed) then short the two large terminals with a screwdriver (make sure the car is out of gear first and DO NOT short to earth) the starter should turn. if it does the solenoid must be faulty.
Just had my starter apart for the first time in 22 years and the s
t inside was incredible. Also, the earth strap was half broken in two at the terminal to the shell and the bolt holding the earth strap to the shell rusty. Now she starts first time every time whereas despite recharging the battery time and again sometimes she would and other times she wouldn't. Still, I guess 22 years and over 80,000 miles ain't that bad really. Just an idea or two for you.
t inside was incredible. Also, the earth strap was half broken in two at the terminal to the shell and the bolt holding the earth strap to the shell rusty. Now she starts first time every time whereas despite recharging the battery time and again sometimes she would and other times she wouldn't. Still, I guess 22 years and over 80,000 miles ain't that bad really. Just an idea or two for you.I felt his arcid brearth last night (smells supprisingly like a mixture of burning grease and plastic), I have been visited by the dark lord himself, Lucas, the prince of darkness.
You'd think they could sell me a f****** soelenoid that f****** worked, no wonder it had the same f****** symptoms before and after replacing the f******* hard to get to f******** thing.
4 days and one very bored girlfriend later there's a very satisfying clunk when I wire up the old solenoid to the egnition wire and earth it against the engine block.
Another hour's spannering and I'm back where I started with a 'working' car, well untill the intermittent fault reveals itself its working anyway. Hopefully it is an intermittently duff solenoid and yet another replacement will cure the problem.
You'd think they could sell me a f****** soelenoid that f****** worked, no wonder it had the same f****** symptoms before and after replacing the f******* hard to get to f******** thing.
4 days and one very bored girlfriend later there's a very satisfying clunk when I wire up the old solenoid to the egnition wire and earth it against the engine block.
Another hour's spannering and I'm back where I started with a 'working' car, well untill the intermittent fault reveals itself its working anyway. Hopefully it is an intermittently duff solenoid and yet another replacement will cure the problem.
Er, might be faulty replacement soloniod, might not be
I usually find replacement MG electric bits OK (Triumph bits in my experience were abysmal)
An intermittent fault that I've found a couple of times on my Midget -
HT lead to coil seems firmly on coil but isn't
The hood/sleeving needs to be burped (like a Tupperware lid) when pushed on to the coil otherwise the trapped air can lift the lead connector slightly out of the coil connector head
Sorry I can't explain it in technical terms but it's worth checking as it will cause intermittent faults
If you want, given a bit more time I can suggest some simple quick actions that might solve your problem but even if not will act as preventative to other potential problems or expose other actual problems - depends if you believe in above or think I haven't got a clue - you decide
I find eyes are sometimes better at finding intermittent problems that an electric tester
I usually find replacement MG electric bits OK (Triumph bits in my experience were abysmal)
An intermittent fault that I've found a couple of times on my Midget -
HT lead to coil seems firmly on coil but isn't
The hood/sleeving needs to be burped (like a Tupperware lid) when pushed on to the coil otherwise the trapped air can lift the lead connector slightly out of the coil connector head
Sorry I can't explain it in technical terms but it's worth checking as it will cause intermittent faults
If you want, given a bit more time I can suggest some simple quick actions that might solve your problem but even if not will act as preventative to other potential problems or expose other actual problems - depends if you believe in above or think I haven't got a clue - you decide
I find eyes are sometimes better at finding intermittent problems that an electric tester
I have faith in anyone with a plan (this regularly gets me it trouble)
The new solenoid is definitely duff, I tested it by attaching it to the white/red ignition wire, and earthing it against the engine block, no joy, (and there was a definite 12V there), old solenoid passed that test with flying colours and a definate clunk.
I don't think its an earthing problem or a starter problem, or an ignition problem, that's stopping it from starting. Its definitely a solenoid problem as I should be able to hear the click of the solenoid but can't.
If it were an earthing problem surely the symptoms would be the same as a flat battery, i.e. the solenoid would engage, but the starter wouldn't start properly, probably clunking into gear then not turning.
The new solenoid is definitely duff, I tested it by attaching it to the white/red ignition wire, and earthing it against the engine block, no joy, (and there was a definite 12V there), old solenoid passed that test with flying colours and a definate clunk.
I don't think its an earthing problem or a starter problem, or an ignition problem, that's stopping it from starting. Its definitely a solenoid problem as I should be able to hear the click of the solenoid but can't.
If it were an earthing problem surely the symptoms would be the same as a flat battery, i.e. the solenoid would engage, but the starter wouldn't start properly, probably clunking into gear then not turning.
thisisnotaspoon said:
I don't think its an earthing problem or a starter problem, or an ignition problem, that's stopping it from starting. Its definitely a solenoid problem as I should be able to hear the click of the solenoid but can't.
If it were an earthing problem surely the symptoms would be the same as a flat battery, i.e. the solenoid would engage, but the starter wouldn't start properly, probably clunking into gear then not turning.
I'm not sure if you're asking or telling, if you already know the answer you've solved the problem, so you'll only need to ask again if your solution hasn't worked, which it may well haveIf it were an earthing problem surely the symptoms would be the same as a flat battery, i.e. the solenoid would engage, but the starter wouldn't start properly, probably clunking into gear then not turning.
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