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Sluggish starter motor

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oscar225 View Drop Down
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    Posted: 21 Mar 2020 at 16:36
Hi in the process of finishing the complete rewire of my 67 V700, had a new loom from Greg Bender along with his relay upgrade also fitted an alternator conversion from Scramnler cycle. Brand new fully charged battery but when i attempt to turn it over it usually clicks and when it does catch is very slughish. I have bench tested the starter and all preforms as it should, i have cleaned the paint from the battery tray to ensure a good earth contact and even swapped the relays although all new without any joy, the only good thing is i have 12 weeks to try and resolve the problem as i am within the at risk group and in lock down, any ideas or suggestions would be welcome.

Thanks Chris
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Richard Hyatt View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richard Hyatt Quote  Post ReplyReply Direct Link To This Post Posted: 21 Mar 2020 at 17:19
Always consider voltage drops.
Use a decent volunteer and put 1 clip on the battery earth negative lug and the other clip ontp the engine. 
When you crank it , you should preferably show 0volts indicating a good earth path.
Any voltage shown will indicate a bad earth connection somewhere along that negative route.
I've always used 0.5v as a max

Do the same process along the positive path starting at the lead battery terminal and other clip on the big terminal on the starter, it is not unknown to lose volts across the solenoid itself built onto the starter.
Again 0.5volts max

As an AA man , the number of times I've diagnosed dirty corroded connections is amazing , crimps and spades can lose lots if filthy or corroded.
The same trick can be applied to the charging side , but of  course you've already checked the earth side out above.
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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 21 Mar 2020 at 17:28
Originally posted by Richard Hyatt Richard Hyatt wrote:

Always consider voltage drops.
Use a decent volunteer and put 1 clip on the battery earth negative lug and the other clip ontp the engine. 

Is this standard AA proceedure?
Brian.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 21 Mar 2020 at 17:33
Are these the pre-engaged starters or the bendix type?

Testing off load is not going to tell you much. There is a guide to testing a starter motor in the FAQ section.

I would put a voltmeter across the battery terminals and check what the voltage drops to when you push the button. Then check the volts across the starter to earth in the same way when you press the button. They should be much the same. If the second reading is rather lower, then you have a bad connection somewhere.

Just another way, and possibly simpler, to do the test Richard suggests.


Edited by Brian UK - 21 Mar 2020 at 17:51
Brian.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richard Hyatt Quote  Post ReplyReply Direct Link To This Post Posted: 21 Mar 2020 at 18:36
Certainly , we always taught in our technical training the principles and usage of volts drops.
I can vividly remember a member , whom i attended ,complaining of flat batteries every few days.
Using this test, i fiscovered only 11 volts reaching the battery , but at the alternator red post , there was a good 14.2v.
Using this test , end to end of the positive side, enabled me to discover that 14 v went into a crimp on the starter post but only 11 came out the same post on the lead to charge the battery .
Bingo , dismantle , clean green corrosion , full volts.
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oscar225 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote oscar225 Quote  Post ReplyReply Direct Link To This Post Posted: 21 Mar 2020 at 18:51
Thanks for the replies will venture into the garage and do some more investigation tomorrow, only issue is my voltmeter is the older needle type rather than digital, but if its a big enough drop ishould see it OK.

Thanks again will keep updating, Chris
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Richard Hyatt View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richard Hyatt Quote  Post ReplyReply Direct Link To This Post Posted: 21 Mar 2020 at 19:27
Needle or analogue meter is fine
Just disconnect the means of sparking though , to make the starters electrical paths 'work's During cranking.
This'll give you enough time to look at the needle
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 21 Mar 2020 at 21:13
Often an analogue meter can be better than a cheap digital. There is a considerable delay in the reading on cheap digital meters, enough to confuse anyway.

But yes. pull the plug caps off so it won't start, gives you a bit more time to read the scale.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 21 Mar 2020 at 21:14
It may be that you find no fault in the wiring, in which case you might find the brushes in the starter motor are worn, or the commutator itself.
Brian.

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Dave P. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Posted: 21 Mar 2020 at 22:50
You could remove the heavy cable from the battery to the starter motor and with your meter check the cable alone for resistance end to end.
I had the same problem on my Laverda GTL as you have. The cable looked fine but when checked as above it registered a high resistance when it should have registered none,or very nearly none. It turned out that there was much corrosion between the copper conductor and the terminal lugs. Suspicion turned to the cable when it was noticed that after repeated attempts to start the engine the cable became quite hot.
The corrosion was not visible until a terminal lug had been removed.

Edited by Dave P. - 21 Mar 2020 at 23:03
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Amboman Quote  Post ReplyReply Direct Link To This Post Posted: 22 Mar 2020 at 14:09
It may be time to service the starter - disassemble, clean, inspect, grease and carefully reassemble. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote oscar225 Quote  Post ReplyReply Direct Link To This Post Posted: 22 Mar 2020 at 14:43
Thanks for all the input everybody, as i feared the wiring connections are all pretty good as i expected them to be with the new loom (Greg Bender) i have tried to contact somebody mentioned in another post Gloucestershire way to see if i can get it refurbed just need to hope the couriers keep going for a bit as i said im in lockdown just awaiting notification from the NHS as to how long!!!!!!
Thanks again all stay safe
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richard Hyatt Quote  Post ReplyReply Direct Link To This Post Posted: 22 Mar 2020 at 16:26
Just before you dismantle everything.
I think an earlier 
Let mentioned battery voltage.
Put your voltmeter across the battery , nothing turned on , should be about 12.4 to 12.6 volts.
Ok?
Leave it on there and turn the ignition on and press the starter button.
Ok it's sluggish , but what do the volgmeter read whilst it is spinning sluggishly ?
You don't want it to go below 10.5 or 10.7 really during cranking.
If it does , how old is the battery?  Give it a good charge?  What's the electrolyte level ? Above the plates ? Assuming it's a lead acid and with screw tops of course? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote red leader one Quote  Post ReplyReply Direct Link To This Post Posted: 22 Mar 2020 at 17:04
Originally posted by oscar225 oscar225 wrote:

Thanks for all the input everybody, as i feared the wiring connections are all pretty good as i expected them to be with the new loom (Greg Bender) i have tried to contact somebody mentioned in another post Gloucestershire way to see if i can get it refurbed just need to hope the couriers keep going for a bit as i said im in lockdown just awaiting notification from the NHS as to how long!!!!!!
Thanks again all stay safe


Are you one of the 1.5 million people who have/are had/getting a letter from the Goberment?
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oscar225 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote oscar225 Quote  Post ReplyReply Direct Link To This Post Posted: 22 Mar 2020 at 17:09
Apparently yes not holding my breath though, work have already arranged to get my van collected next week and off hire it, maybe they know something that i dont?
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