Thread: 110 - ISUZU Starter problem

yep..

you have probabley got a resistance across the solenoid contacts.

heres how to check... (assuming you have a multimeter)

read the voltage across the terminals of the battery

measure the voltage drop across the following items while the starter is working (or trying to)

the cable to the relay, the relay, the cable to the throw out solenoid, the throw out solenoid, the cable from the throw out solenoide to the motor.then from the earth of the motor to the earth of the battery

then check the voltage at all of those points again but with the earth of the meter on the earth of the battery.

the sum total voltage drop across all of those items should be less than .5v
90% of the time its a bad connection somewhere along there. Depending on how professionally the starter was checked out if its not one of those then you have either got.

• stuck brush in the motor thats not making a good contact
• interal short or high resistance in the motors fiel/armature windings
• failed/siezed bearing
• jammed reduction gears
• crook battery thats dropping a cell when under load, rare but it can happen

try the bushie fix of hitting it with a big rubber mallet and swearing at it then test it again. if that doesnt work pull it out and see what it does without the load on it.

and the "heavy load" is relevant... whats a heavy load to the startermotor of dads ride on mower isnt a heavy load to the isuzu starter.... at stall with a brilliant set of batteries those things will draw the better part of 750amps.. in normal circumstances expect 400+ amps to get things turning and 200ish to keep it moving.

if its not your voltages dropping, the throw out not throwing or the gears binding post the results and I'll dig out my rebuild bok for em.

Thanks Dave - Saturday's looking like the first chance to do the tests. I'll post the results hopefully with a not a

I have had repeated problems with mine with the solenoid contacts. These were originally caused by a poor earth between the engine and the chassis. (The earth strap across the LH front engine mount is strategically located so it gets bathed in oil from the leaking return oil line on the vacuum pump - a slightly loose bolt and the oil seeps in to insulate it!)

Try the tests that blknight.aus suggested. To turn this engine you need really good connections, and it is likely that either your jumper leads are not heavy enough or they are not making good enough contact. If you don't have a multimeter, a 12v bulb with a pair of leads will show where the voltage is going (or not going). You are not looking for a subtle voltage drop!

John

I'm using 100amp Jump leads with the clips direct to the starter mounting bolt (neg) and the pos clip direct to main supply lead bolt.

Could the fact that I'm using clips with minimal contact points to the stater bolts be the problem. I can make up a proper teminal connectors to go to the two bolts.

The reason I'm using the jump leads is because the engine's just gone back into the chassis and there's no electrics at this stage.

Originally Posted by fid-def

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Could the fact that I'm using clips with minimal contact points to the stater bolts be the problem............

Yes.

John

oh yeah thats going to do it for ya...

Put your battery straps back on and give it a go..

dont worry about the bulb thing, the voltage drop your looking for is way too low to show up on a bulb..


you might get away with 100 amp leads IF they really are 100 amp leads and not Kmart 100 amp leads...

from memory you want at least 12mm diameter copper flex for the start lead on those thats overkill for the duration they need it but worth it for the extra amps they can let you get to.

Id not think of using anything under 8mm flex and thats going to be pushing it.

Originally Posted by Blknight.aus

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dont worry about the bulb thing, the voltage drop your looking for is way too low to show up on a bulb..


......

If the voltage at the starter is two low to turn the engine, I'll bet it is less than six volts (probably a lot less, as the current through the stalled motor will be higher than normal), meaning the drop is also at least six volts - which will show on a 12v bulb. Which is not to say that a meter is not better!

As an aside, I have never managed to turn my engine directly using jumper leads, no matter how good the leads - you have to use the jumper leads to give your "dead" battery sufficient charge to carry at least part of the load.

This is a high compression engine with large individual cylinders, and also a heavy flywheel to get moving.

John

I was talking about the .5 drops with re the bulb check. it doesnt matter how good/bad the batteryis a bulb wont measure a drop across a cable with any accuracy unless the cables really shot.. but for your initial volt probe yep the bulb is a good idea as it can be setup so you can check it from inside the cab

never seen jumpers that will crank your engine directly... you need to come have a look see at mine...

They'll start a leopard off of a fresh set of batts with the master switch off on the leopard... but then Im into that overengineering thing...

ask dirtydawg, hes got a set of winch power leads made from my old light duty jumper leads.

I know whats in the suzi motors Ive rebuiilt em something to do with being a mechanic for the ADF... :P and you think thats a hard motor to start? try the 6 pot diesel in the ATR200m tadano.