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positive and negative ground
- Thread starter spankyway
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dklawson
Yoda
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As others have said, it's time for some methodical testing. I'd start with a multimeter (volt/ohm meter). Put the black (common) meter lead to the engine block and touch its red test lead to the battery cable connection on the starter solenoid. If you read "negative volts" on a digital meter (or if the needle tries to go below "zero" on an analog meter) then you have indeed got positive ground. If this doesn't happen, (you get a positive reading on a digital meter or the needle swings up on an analog meter) then you have negative ground in spite of what the previous owner told you. This test don't even involve turning on the ignition so it's simplest thing to check.
You said you measured the alternator output at 14.8v. How did you measure this? Where did you connect your meter's leads between?
You said you measured the alternator output at 14.8v. How did you measure this? Where did you connect your meter's leads between?
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I'm betting the Alternator was bench tested. Physically the battery has been hooked up with positive terminal to the ground side of the car (chassis). I believe erroneously due to bad info on the part of the DPO (as evidence I offer the "new battery").
After 1967 there were no positive earth MG cars LH drive, shipped to the US.
After 1967 there were no positive earth MG cars LH drive, shipped to the US.
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Spankyway - This is all good advice. Earlier I said I know what I'd be doing now. I should've added this: I'd be trying the swap after doing some checking. BUT - I've already ordered all the wiring, fuse blocks, etc., to replace my under-hood wiring anyway. Plus I have an uprated alternator waiting to go in. I do NOT recommend this rash approach at all; I never said I had any sense. /ubbthreads/images/graemlins/nonod.gif
This could be tedious, but once you're done you're going to know this stuff really well. If the car is a keeper, you'll always use the info - plus, you'll be the one telling the next guy who's been DPO'd how he can fix the problems he inherited.
Rick
This could be tedious, but once you're done you're going to know this stuff really well. If the car is a keeper, you'll always use the info - plus, you'll be the one telling the next guy who's been DPO'd how he can fix the problems he inherited.
Rick
You may not have to change the wiring, but rather change how it is wired. If possible ask the previous owner why the car was changed to positive earth and what changes were made to components. Does this car have its original motor? The ignition light could be on due to blown diodes in the alternator because of a polarity problem. 14.8 volts seems a bit high, shouldn't it be about 13.5 volts for a properly working alternator?
Turn signals not working-
Not aware of a relay in the turn signal circuit. Green wire supplies power into the hazard switch (pin 7). Then there is a green wire coming out of the hazard switch (pin 8) that goes to the turn signal flasher. You should have continuity across pins #7 and #8 when the hazard switch is in the off position. Even though they look the same, the hazard flasher and the turn signal flasher), don't mix them up. The turn signal flasher has an incoming green wire and an outgoing lightgreen/brown wire which connects to the turnsignal switch. The hazard flasher has an incoming brown wire and an outgoing lightgreen/brown wire which connects to the hazard switch (pin 3).
Does your car have the starter solenoid as part of starter? Look at the following link and let us know which starter yours resembles. https://www.victoriabritish.com/icatalog/mg/0161.html
If there has been no changes made to the fuel pump, tachometer when the car was "converted" to positive ground, changing it to negative ground will be fairly easy. Having negative ground will be advantagous. You would be able to install a modern radio, charge your cell phone, and you will lose the confusion and frustration when purchasing some replacement parts.
I tried the link you supplied ( www.mgcars.org.uk )
It did not connect me to the article(s) that the previous owner supplied to you. I would like to see the article.
Turn signals not working-
Not aware of a relay in the turn signal circuit. Green wire supplies power into the hazard switch (pin 7). Then there is a green wire coming out of the hazard switch (pin 8) that goes to the turn signal flasher. You should have continuity across pins #7 and #8 when the hazard switch is in the off position. Even though they look the same, the hazard flasher and the turn signal flasher), don't mix them up. The turn signal flasher has an incoming green wire and an outgoing lightgreen/brown wire which connects to the turnsignal switch. The hazard flasher has an incoming brown wire and an outgoing lightgreen/brown wire which connects to the hazard switch (pin 3).
Does your car have the starter solenoid as part of starter? Look at the following link and let us know which starter yours resembles. https://www.victoriabritish.com/icatalog/mg/0161.html
If there has been no changes made to the fuel pump, tachometer when the car was "converted" to positive ground, changing it to negative ground will be fairly easy. Having negative ground will be advantagous. You would be able to install a modern radio, charge your cell phone, and you will lose the confusion and frustration when purchasing some replacement parts.
I tried the link you supplied ( www.mgcars.org.uk )
It did not connect me to the article(s) that the previous owner supplied to you. I would like to see the article.
Alright, here goes. The car is a negative ground, the previous owner was amiss. I still can't get the turn signals working but thats okay. Right now I have a problem with engine miss at about 3000 rpm no matter what gear. I pulled the distributor and theadvacing mechanism was stuck so I cleaned it up and relubed it so it moves freely. The diaphragm seems to be okay but fairly stiff. The engine has about 21 lbs of vacuum at idle but I don't think it is pulling the advancing mechanism because the diaphragm is so
stiff. I have a dwell angle of 60 degrees and sitting inthe riveway I can rev it all the way to redline with no problems. When I get on the road I can't get it to run smoothly above 3000 rpm.
Any ideas?
stiff. I have a dwell angle of 60 degrees and sitting inthe riveway I can rev it all the way to redline with no problems. When I get on the road I can't get it to run smoothly above 3000 rpm.
Any ideas?
I know that the oil inthe carb leaks out pretty quick so I figure it might need some work. I don't particularly like the SU/Zenith carbs, are they good or should I consider a swap to a Weber?
I also have a couple of the early MGB carbs, they look a little different and it looks like they are from a dual carb set-up. Would it be a bad idea to rebuild one of them and put it on the car or should I just rebuild the SU/Zenith that is already there?
I also have a couple of the early MGB carbs, they look a little different and it looks like they are from a dual carb set-up. Would it be a bad idea to rebuild one of them and put it on the car or should I just rebuild the SU/Zenith that is already there?
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My take on the situation:
If you've got the relevant pieces for the SU retro-fit, THAT would be the way to go. But you need intake and exhaust manifolds, carbs and linkage... the ZS is (IIRC) 1-3/4" throat, the dual SU's are 1-1/2"... too small to use just one. Best bet at this point would be to bench the ZS and go thru it completely to insure its in good nick. The rebuild kits are relatively cheap and once it's all done it'll work fine.
Collect the SU bits as you can and plan the retrofit.
If you've got the relevant pieces for the SU retro-fit, THAT would be the way to go. But you need intake and exhaust manifolds, carbs and linkage... the ZS is (IIRC) 1-3/4" throat, the dual SU's are 1-1/2"... too small to use just one. Best bet at this point would be to bench the ZS and go thru it completely to insure its in good nick. The rebuild kits are relatively cheap and once it's all done it'll work fine.
Collect the SU bits as you can and plan the retrofit.
Online
[ QUOTE ]
I haven't done anything to it. I am coming over from the streetrod world and don't really know about these Britsh cars.
[/ QUOTE ]
/ubbthreads/images/graemlins/rolleyes.gif Oh my, are you in for an education. /ubbthreads/images/graemlins/crazyeyes.gif Once bit though, these cars are hard to get away from. Plus, you get to deal with all the great LBC people who are full of information on just about anything you can ask about these little cars. Some like to play jokes though and along with the seriousness of the business, we have a few laughs, the last being on me. Welcome to the forum /ubbthreads/images/graemlins/savewave.gif and good luck with your new venture. /ubbthreads/images/graemlins/cheers.gif PJ
I haven't done anything to it. I am coming over from the streetrod world and don't really know about these Britsh cars.
[/ QUOTE ]
/ubbthreads/images/graemlins/rolleyes.gif Oh my, are you in for an education. /ubbthreads/images/graemlins/crazyeyes.gif Once bit though, these cars are hard to get away from. Plus, you get to deal with all the great LBC people who are full of information on just about anything you can ask about these little cars. Some like to play jokes though and along with the seriousness of the business, we have a few laughs, the last being on me. Welcome to the forum /ubbthreads/images/graemlins/savewave.gif and good luck with your new venture. /ubbthreads/images/graemlins/cheers.gif PJ
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PROFUSE APOLOGIES PAUL!!!!
Good deal for the Haynes manual, Spanky. It'll be the "bible" for whatever you have to do. Sometimes it's a bit "sparse" on detail, but this forum is your "backup" for whatever you find yourself into.... Just had a thought... I'm headed fer th' "Pub"... s'cuse me.
Good deal for the Haynes manual, Spanky. It'll be the "bible" for whatever you have to do. Sometimes it's a bit "sparse" on detail, but this forum is your "backup" for whatever you find yourself into.... Just had a thought... I'm headed fer th' "Pub"... s'cuse me.
I have owned a Triumph before but didn't keep it long. I already enjoy working on the car. I pulled the distributor theother day and went through it. The vacuum advance mechanism was completely frozen up so I cleaned it up and now it moves freely. It is not my daily driver yet so I can afford to spend some down time with it.
Still got the problem? I live in West Cobb near lost mountain and would be glad to come take a look.
ragtopmg@juno.com
ragtopmg@juno.com
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[ QUOTE ]
Alright, here goes. The car is a negative ground, the previous owner was amiss.
Any ideas?
[/ QUOTE ]If a well charged battery was installed backward, there would likely be quick damage to the alternator & possibly some other parts. Basically a short circuit through the alternator diodes. If the battery were not charged when it was installed, it would be possible to permanently charge it backward but it wouldn't have much capacity. Either way, since the PO did this part, you wouldn't know exactly what happened.
If you discovered the reversed battery, & reconnected it properly but it still had some charge in it, there would again be a short circuit through the alternator diodes, & the same problem as the first time. If the reversed battery was dead when you got the car, & you somehow got it running in that condition, the battery &, or alternator are still almost certainly damaged, though it might run for awhile.
I think you probably need to start with a new battery & alternator, connect them correctly, & also look for other parts that may have been damaged during the reversals. If you replace both, I would put a temporary 40 amp fuse in the heavy alternator lead to protect things until the problem is totally solved.
D
Alright, here goes. The car is a negative ground, the previous owner was amiss.
Any ideas?
[/ QUOTE ]If a well charged battery was installed backward, there would likely be quick damage to the alternator & possibly some other parts. Basically a short circuit through the alternator diodes. If the battery were not charged when it was installed, it would be possible to permanently charge it backward but it wouldn't have much capacity. Either way, since the PO did this part, you wouldn't know exactly what happened.
If you discovered the reversed battery, & reconnected it properly but it still had some charge in it, there would again be a short circuit through the alternator diodes, & the same problem as the first time. If the reversed battery was dead when you got the car, & you somehow got it running in that condition, the battery &, or alternator are still almost certainly damaged, though it might run for awhile.
I think you probably need to start with a new battery & alternator, connect them correctly, & also look for other parts that may have been damaged during the reversals. If you replace both, I would put a temporary 40 amp fuse in the heavy alternator lead to protect things until the problem is totally solved.
D
The battery was hooked up correctly, he just had the wrong colored leads and he was adamant about the grounding of the car. I guess I should pay better attention before jumping to conclusions.
I messed around a little more with the car but still cannot get it to run properly. I am going to get a compression gauge to check that but I think I have a weak cylinder.
I got the gap on the points right, I got the dwell right, and I set the dynamic timing at 13 degrees btdc. When I went for a drive it seemed like the car was being held back.
I messed around a little more with the car but still cannot get it to run properly. I am going to get a compression gauge to check that but I think I have a weak cylinder.
I got the gap on the points right, I got the dwell right, and I set the dynamic timing at 13 degrees btdc. When I went for a drive it seemed like the car was being held back.