Yanmar Starter

[Mark Thurlow]

I have a 4JH3 DT on my Moody.

The starter motor is spinning but there is no engine turnover. Ignition circuit is fine, with 12+v and I get the same results using the ignition circuit or jumping the solenoid.

I can here the solenoid firing.

I have tried to remove the starter but as yet cannot shift the bolts. I have used a little heat and penetrating spray ; iris now soaking.

So two questions please.

Q1 without removing the starter is there anything I can do to release what I presume is a stuck bendix; I have given it some light taps?

Q2 . Other that more spray and a lot more heat how can I free off the bolts. I have standard ring/open spanners.

Mark

[mikeo16]

Using an impact wrench should loosen those bolts quickly. It is the impacts along with the torque that makes a big difference especially with rusty frozen fixtures. The cordless Milwaukee impact wrench delivers 1,400 pounds of torque

[Tin Tin]

Disconnect and clean all electric terminals, to eliminate possibility of weak amps. Spray with plenty of WD40 or similar. Try spinning the starter and spraying WD 40 inside at same time. Try spinning starter and decent taps with a hammer on the starter motor.
Having soaked bolts in penetrating fluid or PB blaster etc, if you only have a ring spanner, try tapping ring spanner near the bolt head in the correct direction. Keep tapping, if it looks like the spanner teeth are slipping don't press it any more.


That is what I would do with a limited tool set far from port.

[Wotname]

Originally Posted by Mark Thurlow

......

So two questions please.

Q1 without removing the starter is there anything I can do to release what I presume is a stuck bendix; I have given it some light taps?

Q2 . Other that more spray and a lot more heat how can I free off the bolts. I have standard ring/open spanners.

Mark

Q1. Some heavier taps but still taps, not heavy blows.

Q2. More heat and then spray to quickly cool, repeat and repeat. Use ring end only (if possible) and extend leverage by using pipe (if available) or another ring end on the first open end.

Try tightening the nuts (bolts?) ever so slightly. This sometimes helps to break the bond.

[Excalibur5]

At least on my 3GM30, the control panel and start switches are known to be problematic, as the wires were a bit undersized. The end result is that enough amps would get from the start button to the start circuit on the starter, making the solenoid click, but not actually turning over the starter itself.

After verifying all the connections to the battery are clean and good, the next step in troubleshooting would be jumping the starter using a screwdriver. Directly connect the start circuit to the hot incoming wire, but be sure not to touch anything else. Note it will spark - this is normal. If the engine turns over, you have the same issue I did.

You can then replace the wire and possibly the switch itsself, or frankly the easier way to do it is to wire in a 12v automotive relay like this one into the start circuit.

https://www.amazon.com/Bosch-0332019...29E1FCC7AFD950

[a64pilot]

He already did the screwdriver trick, but it’s still possible to be a dirty connection.
Once that is eliminated, he’s got to get it out I believe.
Try to find a 6 point socket or box end wrench and not 12 point ones. 6 point of course is far less likely to slip.

[Wotname]

Also measure the voltage across the starter motor while it is spinning; be sure to measure the starter motor only, not the solenoid contacts as well. It should be comfortably over 10V.

[Mark Thurlow]

Thanks some good ideas. Not enough room for anything other than ring spanners; sadly. Both bolts are not really accessible despite stripping back the loom.

Regarding the lack of power some have discussed could this be an issue? The starter turns fast and fine just no engagement?

[Wotname]

Originally Posted by Mark Thurlow

.......

Regarding the lack of power some have discussed could this be an issue? The starter turns fast and fine just no engagement?

Unlikely but possible. It is worth checking IME.

[roverhi]

If the mount bolts are frozen sounds like the starter motor has seen some salt water. If that's the case the Bendix may have rusted and stuck in retracted position. Spraying the hell out of it with penetrating oil and tapping the starter with a large hammer starter at the end that engages the ring gear on the engine may loosen it up. If that doesn't work, starter will have to pulled and Bendix free'd up or replaced.

I had to do that much of the winter with my MGA in college. Starter would whirr away but not engage. Had to get the wire wheel hammer out and whack the starter a few times and Bob's your uncle.

[Dockhead]

You're sure the starter motor is spinning? Definitely?


Because it is an extremely common, almost universal problem on these Yanmars for the solenoid not to get enough power to engage. You can hear it click, but it doesn't get the starter going. To check for this, give power from another source (fused!) to the + terminal of the solenoid, of the trigger circuit, and see what happens.


Most of us have installed relays to solve this problem.

[Group9]

Our 4JH did this once. The easy fix (described to me over the phone by a diesel mechanic at the time) was to take the starter off, polish the bendix shaft with an Emory cloth, grease it, and put it back on the motor. It worked fine ever after that.

Later we had the not enough juice to the solenoid problem and installed a $10 relay from auto zone that fixed that problem.

But, if you can hear the starter motor spinning, but not engaging the flywheel, try the first suggestion.

[a64pilot]

Originally Posted by Dockhead

You're sure the starter motor is spinning? Definitely?


Because it is an extremely common, almost universal problem on these Yanmars for the solenoid not to get enough power to engage. You can hear it click, but it doesn't get the starter going. To check for this, give power from another source (fused!) to the + terminal of the solenoid, of the trigger circuit, and see what happens.


Most of us have installed relays to solve this problem.

He did the screwdriver trick which bypasses the problem wiring etc.

[Dymaxion]

You may be able to remove the solenoid alone and give it a servicing to free it up. Access to it may not be possible, I don't know your engines layout.

[Captain Bill]

Originally Posted by a64pilot

He did the screwdriver trick which bypasses the problem wiring etc.

Not necessarily. I once had an issue with a starter on one of my Yanmars. The screwdriver test only bypasses the positive wiring, not the ground. Yanmar puts put the starter directly below the exhaust elbow which are notorious for leaking (at least the standard stainless steel ones) which then drip on the starter. Even worse the ground wire is also located directly under the elbow, at least on my engine. The ground wire on mine was corroded and not making good contact and though the solenoid would close it did not have enough current to spin the starter fast enough to engage. I clean the ground lug and engine block and all was good. There was enough contact for some current to flow but not enough to drive the starter properly. If the op's mounting bolts are rusted I'll bet the ground lug is rusted too.