Bad Positive earth???? (Super Major)

skateboss · Post by **skateboss** » Tue Mar 10, 2009 11:07 pm

Hi again everyone,

I have just got to the point where I have fitted the wiring loom and clocks after shot blasting and painting everything....

when i turn the key on i get clock lights etc, if i touch a jump lead on the terminal on the back of the starter motor and connect the other one to the positive lead on the super major, it spins really quick... if i do it with the starter engaged with the flywheel it spins the engine over very slowly, the battery is a massive lorry battery which is fully charged...

another scenario is if i link a normal size battery in series with my lorry battery and touch a jump lead from the negative pole on the lorry battery to the starter and engage it with the flywheel it spins over like crazy... but as soon as i try to use it linked in the normal way neither battery will throw it round as it should. Bad positive earth or solinoid? Solinoid seems fairly new though.

I had a bit of smoke from the switch on top of the starter earlier, now it doesnt seem to work, so i will pull it apart tommorow and have a look, if faulty i will change it for another one that i have got.

Sorry if you have to read this several times to understand it as it is'nt brilliantly worded.

Many thanks Chris

Grani · Post by **Grani** » Wed Mar 11, 2009 7:56 am

The bad connection can be anywhere in the thick cables or in the solenoid or in the starter. Try to start for i while and then feel with your hand if any connection becomes hot. The hot spot is the problem.

Meanderer · Post by **Meanderer** » Wed Mar 11, 2009 10:43 am

Hi Chris,

A couple of things confused me in your summary.
You said you used a Jumper Lead to connect POSITIVE of Battery to the terminal on the back of the starter? Didn't you say it was Positive Earth System??? You also tried two different capacity batteries (both 12V) in series making it a 24 volt on the system??? I have heard of 24V being used to start high compression Hot Rods etc., but I don't know what else they incorporate into the system.

Back to the system. My starter has two connections on the back of the starter. The cable is connected to the top one and nothing connected to the bottom. (from your other post) My Earth cable is connected to the body where the Fuel tank mounts. I don't know if that is the original position or no. Make sure that the connection to the chassis is bare metal and clean. Not painted. (Although a month ago I did take an earth strap from a DB990 that's about 30 yr old and it has never been removed before and was a painted surface other than the bolt thread and spring washer!)

Grani is right about feeling the connections with fingers to see if any get hot.
However, it could also be the internal contacts of the Solenoid. To test that, you can very carefully use a good Jumper lead to bridge the two main terminals on the solenoid. Caution is required because it will be a large spark initially. When you do it, you need to give a sure and positive jab and hold it on while starting. If you are hesitant it will spark all the more and melt the nut/threads. Without going to look at mine, I think there is a bit of a plastic divider between the terminals. You can use something like a larger pair of (old) pliers as the jumper. Rest one jaw firmly against a terminal, go around the divider and jab the other jaw firmly against the second.

If it still cranks the engine slowly, then it could be the starter motor itself. Just because it spins quickly without load only means that it isn't burnt out. The Brushes and or bushes could be badly worn. I couldn't say if the 24V you tried was just cheating to overcome bad brushes or bushes.

CAUTION: Do not cause any sparks near the battery. Batteries give off hydrogen and can exploded very easily!

Reading your post a couple of times and I'm not 100% sure I've interpreted correctly.

Ps>>> answering your other post. Name is same as the main part showing in address line and P-word is nickname for Dorothy 5 letters d***y

skateboss · Post by **skateboss** » Wed Mar 11, 2009 6:22 pm

hi thanks for your answers,

if batterys are wired in series ar'nt they still 12 volts??
i thought that the original system use to use 2 batterys wired in this way.

the positive on one battery was connected to positive earth through the chassis then the negative to positive on the other battery and then negative on other batt to post on starter.... like this

(+ EARTH -> + BATTERY POST) (- BATTERY POST -> + BIG BAT) (- BIG BAT -> STARTER POST)

Many Thanks Chris

Mike Kuscher · Post by **Mike Kuscher** » Wed Mar 11, 2009 6:48 pm

Skateboss wrote:

i thought that the original system used to use 2 batteries

They were originally fitted with 2 6 Volt batteries.
Think of a torch. 2x 1.5 volt batteries, one behind the other.
Connect positive of one battery to negative of another, you maintain current but double the voltage.
That is why the torch has a 3 Volt bulb.

Question:
You say...

the battery is a massive lorry battery which is fully charged...

Most big lorries (trucks) are actually 24 volt systems. Some use 2 x 12 Volt batteries, some use 24 volt batteries. What is the voltage of the first big battery?
Have you put in 12, 24 or even 36 volts?

A tip, learned from bitter experience:
When I first got my Major, the battery was dead and needed replacing.
A friend gave me a spare 12 Volt battery from a lorry, in good condition, which I fitted.
Like yours, it was 'a big un'.
Things were fine for 2 weeks, when I set off on a road run.
Within 1 hour I was stranded on the road side, needing a new dynamo, fan belt and regulator.
The battery was much too big for the system and trying to 'pull' the Amps it required for charging had burnt out the insulation on the regulator coils and overheated the poor old generator that much that it had siezed, taking out the fan belt with it.

So, 12 Volts only, but not too big on capacity (Amp Hours) either. Big is not always beautiful.

Mike

Grani · Post by **Grani** » Wed Mar 11, 2009 6:58 pm

2*6 volt batterys in series is 12 V and 2*12V batterys are 24V. If you connect both batterys in parallel, then you get 12V but with more Amps. I guess the starter is the last thing to burn with a 24 V connection.

skateboss · Post by **skateboss** » Wed Mar 11, 2009 10:15 pm

Hi guys thanks for your help,

I realised that I was talking out of my rear end when I went out and tested it with my multimeter.

That big battery is 12 volts and way too big to fit in the battery tray so I wouldnt be using it when she is up and running anyway.
I was just using it for jump starting.

I have figured out that there is something wrong with the starter as i connected the jump leads from the big battery to the body of the starter motor and the pole on the back of it, and like before when not engaged it flys round, but when i engage the flywheel she barely does a revolution.

Im not really sure how I got away without blowing the dash bulbs but I did so im happy lol.

anyone got any idea of a rough price for reconditioning one?

Thanks for everyones help yet again. Chris

skateboss · Post by **skateboss** » Thu Mar 12, 2009 11:29 pm

Update:

I took the motor to 'Diesel Electro' in Norwich today they are gonna give it a recon for me.... completely rebuilt with new rubber boot on top for £132.00.....

Just thought i would let everyone know just incase anyone had same sort of problem.

Chris

Meanderer · Post by **Meanderer** » Thu Mar 12, 2009 11:33 pm

Did they confirm that your problem was the condition of the Starter?

skateboss · Post by **skateboss** » Fri Mar 13, 2009 8:58 pm

Not yet as they havent done it yet but I got my jump leads which are really heavy duty and put the straight on to the motor and it did the same thing so it has got to be the problem....

When i bought the super major she hadnt been started for 10 years and 2 of the brush springs had got wet and rotted away so i guess it has given up now it hasnt been started for another 8 months during restoration

P.s. i did replace all of the springs lol