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MG MGB Technical - Engine not turning over.
|Hope someone may be able to help!|
I've had my MG for about 10 years and have not encountered this problem before.
When I turn the key, I hear a 'chock' sound from the engine bay but the engine will not turn over at all.
The batteries are definitely charged to the maximum, the ignition light comes on when I turn the key to 'on' and the light remains on when I turn the key to 'start' which suggests that there is charge going around the system. The two fuses are still intact and all wires appear to be where they should.
Would love to hear your thoughts!
Thanks in advance,
|By the way, it is a 1966 MGB!|
|Darren, first possibility is a bad connection. Check the battery ground and the engine ground (use jumper cable to substitue grounds) Then use jumper to bypass the starter solenoid.|
|Darren. First question is will the engine rotate when the car is put in gear and pushed, or when you use a wrench on the crankshaft pulley nut? If not, the engine has seized. If it will turn, there is a problem in the starting circuit. |
It has been quite a while since I looked at a Mark I MGB and I have never owned one. Hence, most of this if from memory and ownership of a Mark II Sprite and a couple of MGAs.
The starting circuit consists of the batteries, the cable from the positive terminal of one battery to the chassis, the cable from the negative terminal of one battery to the starter solenoid, the starter solenoid, the cable from the starter solenoid to the starter, the starter itself, and the means of activation of the starter solenoid. (Do not remember if this latter is a pull system like the MGA and Sprite or whether an electric switch, activated by a push button was used.)
Your problem lies in one of these areas. First test is to hook a volt meter up to the ground terminal of the battery system and to the terminal attaching the cable going to the starter solenoid. Then, measure the voltage when cranking. If it goes below 11.5 volts, you have a battery or battery terminal problem. If 12.0 or more, you have a good battery system with good connections. Move forwards to the starter solenoid and test the voltage at the input side of the solenoid, then the voltage through the solenoid when it is activated. If still 11.5 volts, or more, test the battery voltage at the starter connection. If it, too, is at least 11.5 volts, it is probably a bad starter and you will need to remove the starter and have it professionally tested. If you find a low voltage condition prior to the starter, correct the condition and keep trouble shooting forwards, towards the starter, until you find out where the problem is.
|First, you should see if you can get the engine to crank over by pushing the rubber button on the starter solenoid, mounted on the fender above the starter motor. If it doesn't crank over, you have a hung starter drive, bad ground or a poor connection in your starter's wiring. The older starters were notorious for jamming the pinion gear in the flywheel and there is a cap, on the distributor end of the starter, that houses a square head. If you turn this you will free up the jammed starter pinion, from the flywheel, if this is indeed your problem. I've owned my '67 for 39 years and it does this on rare occasions. RAY|
|Thanks so much everyone, invaluable information. I will try tonight when I get home from work and let you know what it was. Thanks!|
|Hello all, thanks for your help.|
Reconnected terminals (checked they were clean too) and tried to key start but all I got was the 'chock' sound from the engine bay.
Tried to start car by pressing rubber button on starter solenoid but nothing happened.
Placed car in 4th and rolled car forward and back to release possible pinion gear jam. Tried key starting again and just got the 'chock' sound. Volt meter shows full charge.
Car roll started first go so that eliminated seized engine. When I returned from a quick 2 minute drive (volt meter showing 13+ volts), I turned off the car and tried to key start. I was met with a mournful sound of the starter trying to turn the car over for a split second then nothing. Turning the key a second time, I was met with the now familiar 'chock' sound again.
Having eliminated most possibilities, I believe I have myself a dead starter motor...
|Try your voltmeter on the starter terminal !!|
|If the ignition warning light is dimming right down when you get the noise then the starter is being energised but is not able to turn.|
This can be from a bad battery or bad connections anywhere through the starter circuit. Measure the voltage between an earthing point on the engine and the cable that goes from the solenoid to the motor. With good battery and connections this should be about 10v, but that would be with the engine cranking. If the motor is physically stalled it will be less than that.
If the light dims quite a bit, then the connections (with the exception of the engine earth strap) are probably OK, but the motor is still being energised but is stalled. You seem to have eliminated the pinion being jammed as a cause.
If the lights dims barely or not at all the motor isn't being energised, so you need to track the voltage through the solenoid and onto the motor terminal, and also measure the voltage on the engine with respect to the body, which will test the earth strap. If you have 12v right through to the starter terminal, and almost zero volts on the engine, then the motor is at fault, possibly worn brushes. Any sudden drop in voltage testing to the motor shows a bad connection. If the engine shows several volts with respect to the body the engine earth strap is bad.
All these voltage measurements need to be with the key turned to crank.
because the starter motor sound changed after a short run my bet is on a dead battery.
Charge it for a while and try again. Better still, roll start and take it for a good long blast...
Even if it starts after a charge it may not after standing for a while. That's when a new battery or two are needed.
PS. ten years from a lead acid battery is very good....
|Try a jump start from another car's battery.|
Firstly, thanks so much for your time and effort in responding, it is truly appreciated!
Geoff - My voltmeter is one of the Smiths dials on the dash so I am unable to run your suggested test - will try to see if the neighbours have one / buy one tonight.
Paul - When I get my hands on a voltmeter (hopefully tonight), I will run the tests you suggested. The ignition light stays bright when turning the key. The voltmeter on the dash is reading 12+ volts when car is off and also when I get the car running from a roll-start. The batteries are definitely at full charge as I charged them with my battery charger two nights ago. The charger indicated that night they were at full charge, and they are still at full charge now as I just retested.
M McAndrew - I would love if I got ten years out of the batteries! The 2 x 6 volt batteries i currently have are 6 months old. I have charged them completely and also went for a good 30 minute drive last night once I roll started the car - after that I checked the charge in the batteries with the battery charger and they were fully charged. When I turned the key I still had the same 'chock' sound from under the bonnet.
Art - Will try that tonight as well.
Thanks again everyone and I will try those tests hopefully tonight if I can get my hands on a voltmeter.
|OK, the ignition light staying bright when the key is turned to crank means no power is going through the starter, i.e. it's not the battery or its connections. Voltage checks between the motor terminal and body earth on the one hand, and motor terminal and engine earth on the other, should tell you whether it is a solenoid, motor or engine earth strap problem.|
I'm fairly new into my 3rd set of twin 6v in 22 years. How long they (and single 12v in my V8) last seems largely dependant on small drains either from electronic equipment of faults, or if the car is unused for several months at a time without a conditioning charger being used. The charger isn't essential, I don't have one, personally I'd rather run mine for a minimum of 20 minutes per month if I can't use them, with the battery cut off when they are parked up.
|Tests complete, faulty starter motor!|
Thanks to everyone for their wonderful assistance - when I'm in the UK next year I will be sure to shout you a beer at the pub!
This thread was discussed between 22/08/2011 and 26/08/2011
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