mht
Club Retro Rides Member
Posts: 123
Club RR Member Number: 185
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May 10, 2020 22:51:40 GMT
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I'll start this off by saying that despite cars being probably my biggest interest, and RR being one of my most visited sites, I have absolutely no experience in anything remotely technical / mechanical but I do want to do something about that. I've got an MGB which I've had for many years and normally if anything isn't right it goes to the garage to get sorted. I went to drive the car this week and it didn't start and I thought that it was about time I tried learning by doing and try and solve the issue. Fault - the car doesn't attempt to start and either stays silent when I turn the key, or makes the clicking sound associated with a flat battery. It has done this occasionally before, but normally just turn it again and it starts. So far - I charged the battery and the issue remains, I the tried jumping it just in case and still nothing. I've bought a multimeter to help diagnose the problem but also have no experience of that either. I did manage to turn enough dials today to get it to show voltage of 12.6v which suggests that the battery isn't the issue. So after a bit of reading online I've got some possibles faults to start with - ignition switch, ignition relay, starter relay, starter, starter solenoid. I've found a wiring diagram (page 25) www.advanceautowire.com/mgb.pdf to help work through some things. On turning the key to position one there is a clicking (relay?!), the alternator light comes on and the radio comes but turning the key any more doesn't do anything which to me suggests the ignition switch is working. There is a way to start the engine from the engine bay (https://www.youtube.com/watch?v=jVxIW_pImjw&t=321s) which I tried today without success, theory being that if it starts it isn't the starter, but the wires are white/red and white/brown and being red/brown colour blind I'm not 100% sure I was doing it right Can anyone suggest a logical way to go about testing? All I ned to do then is figure out how I use the multimeter Any pointers are appreciated!
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Mark
1977 MG B 1992 Lexus LS400 1998 VW Golf VR6 1999 BMW 740i
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ChasR
RR Helper
motivation
Posts: 10,191
Club RR Member Number: 170
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May 10, 2020 23:23:02 GMT
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How clean are your battery connections? If they are corroded or the wire on the terminals is, it can cause a non starting condition.
Has the car ever had a clutch change in your time? How long have you had it? I've had an MG Midget and a Stag break the solenoid wire due to the lazy mechanics not bothering to undo the cabling from the starter motor and instead letting the weight of the starter hand off the cables. This is a tricky area to photo on an MGB, but it may be worth doing, as starters are not an easy job to change on a 'B.
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May 10, 2020 23:26:56 GMT
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mht, Hello. Sounds like a simple issue...poor ground. Check the cable from battery to chassis; remove the machine screw or nut and wire brush the rust away. Then paint with dielectric grease and reattach cable. There might also be a cable from engine to chassis; check the connections on that, also. Finally, look at the connections on the starter solenoid; the posts for the battery and for the start switch are very close together; make sure there are no stray wire 'hairs' making a connection between the two. Also, the terminal lug on the battery cable to the starter solenoid cannot be too close to the starter switch post - it can jump across.
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What happens if you put twelve volts directly across the starter motor? If it cranks over fine then it'll most likely be a bad connection somewhere as others have explained.
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Never having had any sort of mg, what type of starter motor is it? Ie is the solenoid on top of the starter, or is it separate and mounted on the inner wing/ bulkhead?
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mht
Club Retro Rides Member
Posts: 123
Club RR Member Number: 185
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How clean are your battery connections? If they are corroded or the wire on the terminals is, it can cause a non starting condition. Has the car ever had a clutch change in your time? How long have you had it? I've had an MG Midget and a Stag break the solenoid wire due to the lazy mechanics not bothering to undo the cabling from the starter motor and instead letting the weight of the starter hand off the cables. This is a tricky area to photo on an MGB, but it may be worth doing, as starters are not an easy job to change on a 'B. The battery connections are probably at least a bit corroded so sounds like a good place to start, and not too technical. I bought it when I was at school - thinking back now you've asked I think I've had it 17 years now, it's a bit like painting the San Francisco bridge by this stage as all the things I did years ago are starting to need sorting again. I think maybe after 17 years it is due a reader's ride thread. The clutch was done about 10 years ago. The starter solenoid from memory was changed about four years ago by an MGB specialist so I'd hope it was done right, but I wouldn't know for sure. mht , Hello. Sounds like a simple issue...poor ground. Check the cable from battery to chassis; remove the machine screw or nut and wire brush the rust away. Then paint with dielectric grease and reattach cable. There might also be a cable from engine to chassis; check the connections on that, also. Finally, look at the connections on the starter solenoid; the posts for the battery and for the start switch are very close together; make sure there are no stray wire 'hairs' making a connection between the two. Also, the terminal lug on the battery cable to the starter solenoid cannot be too close to the starter switch post - it can jump across. Thanks, I will get hold of some dielectric grease. What happens if you put twelve volts directly across the starter motor? If it cranks over fine then it'll most likely be a bad connection somewhere as others have explained. I haven't tried that, I will give it a go. Never having had any sort of mg, what type of starter motor is it? Ie is the solenoid on top of the starter, or is it separate and mounted on the inner wing/ bulkhead? It is on top of the starter. So it sounds like best place to start is cleaning / checking the battery and earth connections. I will get onto that first, thanks for the help!
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Mark
1977 MG B 1992 Lexus LS400 1998 VW Golf VR6 1999 BMW 740i
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ferny
Club Retro Rides Member
Posts: 983
Club RR Member Number: 13
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May 11, 2020 10:43:08 GMT
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Dielectric grease is only needed in areas you'll get arcing. The arc creates carbon which gives a route for electricity to go where you don't want. If it's not somewhere which will arc then it doesn't need to be dielectric.
I only found that out the other week. 🙂
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mht
Club Retro Rides Member
Posts: 123
Club RR Member Number: 185
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May 11, 2020 10:55:17 GMT
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Dielectric grease is only needed in areas you'll get arcing. The arc creates carbon which gives a route for electricity to go where you don't want. If it's not somewhere which will arc then it doesn't need to be dielectric. I only found that out the other week. 🙂 Thanks. I've found some battery clamp grease so I'll get that
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Mark
1977 MG B 1992 Lexus LS400 1998 VW Golf VR6 1999 BMW 740i
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ChasR
RR Helper
motivation
Posts: 10,191
Club RR Member Number: 170
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May 11, 2020 19:35:33 GMT
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Battery terminal cleaners will be a Godsend here for your battery terminals. They're not alot of money from Amazon either.
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mht
Club Retro Rides Member
Posts: 123
Club RR Member Number: 185
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May 11, 2020 20:49:40 GMT
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Battery terminal cleaners will be a Godsend here for your battery terminals. They're not alot of money from Amazon either. huh, would never even known that was a thing. Arriving on Wednesday
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Mark
1977 MG B 1992 Lexus LS400 1998 VW Golf VR6 1999 BMW 740i
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ChasR
RR Helper
motivation
Posts: 10,191
Club RR Member Number: 170
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May 11, 2020 21:08:47 GMT
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Even if they don't work on this occasion, they can rule out one thing and be handy for the future . On my Mercedes I got caught out big time, with similar symptoms to you. Only one of those tools would take away half of the corrosion. The other half was going onto the battery to cable connection within the terminal! I'd have taken a pic but I was in a rush that day as RetroWarwicK will remember . The same problem came to haunt me on my dad's 535d. That battery I took out of the Merc.
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If your terminals are all white and crusty, a kettle of boiling water will clean them up before you start with the cleaner and grease, but wear eye protection and make sure to wash it off the bodywork afterwards! Had to do this on a mates transit, so much crud you couldn’t see the terminals!
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How old is the battery? Single 12v car, not an earlier 6v converted one?
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ChasR
RR Helper
motivation
Posts: 10,191
Club RR Member Number: 170
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Being a '77, it will be a 12V battery; they only came with one battery 'bin'. I think the two 6Vs stopped in 1975.
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Last Edit: May 19, 2020 5:57:00 GMT by ChasR
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May 19, 2020 10:21:41 GMT
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So come on mht what’s the results? 🤔
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moglite
Part of things
Posts: 815
Club RR Member Number: 144
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May 19, 2020 11:32:45 GMT
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So come on mht what’s the results? 🤔 Absolutely Also try an earth jump lead from battery to engine block. A poor engine earth kept my Volvo off of the road for a couple of weeks, after the garage balls'd up a clutch change. It has the unfortunate effect that the alternator wont charge the battery fully, and a jump pack does nothing.
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1967 Morris Oxford Traveller 1979 Toyota LandCruiser BJ40 1993 Daimler Double Six 2007 Volvo XC70 2.4D
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May 19, 2020 12:00:45 GMT
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So come on mht what’s the results? 🤔 Absolutely Also try an earth jump lead from battery to engine block. A poor engine earth kept my Volvo off of the road for a couple of weeks, after the garage balls'd up a clutch change. It has the unfortunate effect that the alternator wont charge the battery fully, and a jump pack does nothing. I knew when we had an earth fault after a gearbox change with mk1 sons landy The throttle cable turned into a heater element !😳
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mht
Club Retro Rides Member
Posts: 123
Club RR Member Number: 185
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May 19, 2020 14:00:54 GMT
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Sorry for the lack of reply! Yes, it's a 12v. I got all the bits delivered including the battery terminal cleaner.
I took the battery out and the terminals look ok but the clamps have a bit of surface rust. The earth lead is frayed so I think that's probably something to get swapped out. The nut and bolt was absolutely rusted holding it in and I could not for the life of me undo it. I've sprayed some WD40 on it and left it.
I'll get some pictures up and see if the consensus is in agreement. I've got 9 month old twins which doesn't help with getting things done quickly!
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Mark
1977 MG B 1992 Lexus LS400 1998 VW Golf VR6 1999 BMW 740i
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Phil H
Posted a lot
Posts: 1,448
Club RR Member Number: 133
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A frayed earth cable rarely helps..
Word of wisdom - WD40 is certainly better than nothing but there are considerably better releasing fluids out there such as PlusGas or Duck Oil (yes, it's a thing and before you ask I believe the Duck reference is due to its water displacement capabilities). Others have sworn on a mix of Acetone and Automatic Transmission fluid but I find PlusGas (GT40 isn't bad, or AC-90 from Toolstation) much better personally from experience.
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mht
Club Retro Rides Member
Posts: 123
Club RR Member Number: 185
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A frayed earth cable rarely helps.. Word of wisdom - WD40 is certainly better than nothing but there are considerably better releasing fluids out there such as PlusGas or Duck Oil (yes, it's a thing and before you ask I believe the Duck reference is due to its water displacement capabilities). Others have sworn on a mix of Acetone and Automatic Transmission fluid but I find PlusGas (GT40 isn't bad, or AC-90 from Toolstation) much better personally from experience. Thanks for the pointers, if I don't have any luck getting it off I'll grab one of those
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Mark
1977 MG B 1992 Lexus LS400 1998 VW Golf VR6 1999 BMW 740i
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