Yanmar starter intermittently won't engage

Hi all,

I have a Yanmar 6phm-the and as the title states sometimes the starter just won't "fire". I can hear the solenoid getting energized, but nothing else happens. The starter is pretty new so I don't think it's the starter itself. I found some pretty weird wiring going on and cleaned all that up so it's getting healthy power. If I keep trying the key it eventually does fire the starter, but it's always slightly alarming when it happens and I'm just waiting for the time it decides it's not going to start at all.

Hoping someone more experienced (so anyone) will have ran into this before.

Thanks!
Branden S

The solenoid being energized doesn't mean it's engaging. I had this issue on an older engine with very low hours, and would hit the start button repeatedly before it would fire up. It seemed to be more of an issue once the engine was warm and seldom happened when cold. I suspected it was the solenoid, and simply replaced the starter and my issue went away, it starts flawlessly since.

I did buy a replacement solenoid ($140 Yanmar, name branded) and replaced the bad solenoid on my other starter. There are worse things than having a spare, and I carry spare pumps, impellers, alternator, and external voltage regulator anyway.

If the starter turns sometimes then it's not the starter but is either the solenoid or wiring. Solenoids have heavy contacts that contact a dusk when the starter is energized. Each time the starter is used, the disk rotates a little to spread wear. The contacts and disk can become pitted and cause the starter to fail in some disk positions. Usually the contacts get so pitted the starter doesn't get enough amps to turn over. Rarely the heat caused by the poor connection from pitted contacts will cause the disk to weld itself to the contacts and the starter won't stop.
Either change the solenoid or take it apart and file the contacts and disk smooth. Easy on most solenoids.

The other cause could be bad connections. Not just in the cable to the starter but check the ground, too.
Less common is the key circuit or the ignition switch.
Also I've seen auto (non-marine) cables corrode deep under the insulation and fail to carry enough current.

Some older Yanmar engines also had a known issue with one of the wires to the solenoid being undersized, the fix was to replace with heavier gauge wire. Because mine had always started fine and was 1999 install I assumed solenoid (it was).

AKDoug said:

Some older Yanmar engines also had a known issue with one of the wires to the solenoid being undersized, the fix was to replace with heavier gauge wire. Because mine had always started fine and was 1999 install I assumed solenoid (it was).

Click to expand...

This is absolutely true had it happen on ours we ran new cable has worked fine since.

Thanks all. This gives me a good starting point of things to look into.

Ok I may be having a similar issue with a 2-cyl Yanmar engine for my genset. After having the boat on the hard for bottom work, I pressed the start button. There was a bit of a click and nothing. My start battery was really old so I figured it had finally given up. Replaced it and "click" nothing. So I arced the solenoid contacts, got spark, got some starter spin but no engagement. I took it to a motor shop. I told them the problem and the fact that bypassing the solenoid only spun the motor, no engagement. He showed me a connection that he said needed to be engergized to get engagement. It had one wire attached by a single screw. I marked it for reassembly. They rebuilt it, I put it in and "click" nothing. It had been working fine for over 3 years. So next I expect to try to get into the control box and see if I can see something wrong with the switch. Any other suggestions?

I'm not sure I entirely understand the issue you're having, but if it helps at all my plan is to go ahead and replace all my "large" conductors and go from there. In my situation, I know my main conductors coming from the battery and going to the starter and battery/house negative are original and welding cable. I think it's likely they aren't constantly passing enough current, especially once the engine room has warmed up. Anyway that's my first step in troubleshooting this so once I get the order in and make all the new cables up (as I am going to do all my battery connections and DC panel and returns as well) I will let you know if that resolves anything.

This was the route that a few people on the forums mentioned, and also a Marine Systems instructor at a local college suggested as a first step.

I think that understanding how the starter is meant to work will help with the diagnostics. Lepke posted (post #3) an excellent view of the internals of a "pre-engaging" type starter. I am assuming that your starter is of this type (and not the "inertial engaging" style which depends on the acceleration of the starter motor to throw the pinion (little gear) into engagement with the flywheel teeth).

Briefly it works as follows:
When you push the starter button power goes to relay (solenoid) mounted close to the starter assembly (not shown in this diagram). This solenoid in turn sends power to the engager solenoid (1) and causes the plunger (2) to move to the left. This rotates the lever arm (3) which pushes the pinion (4) to the right, into engagement with the teeth on the flywheel (5).
When the plunger of the solenoid reaches its full travel the pinion is already meshed with the flywheel and the copper disc (6) then meets the contacts (7), allowing the current to flow from the battery (+) to the main starter motor (8). The starter now initiates turning the flywheel.

So, if you hear a "click" and nothing starts turning, there are a few possibilities:

1 The first solenoid is defective, making a bit of noise but not completing the circuit to the engager solenoid of the starter.

2 The starter's engager solenoid is defective - not able to complete its travel and complete the circuit to the starter motor. This could be a problem with the disc/contacts of the solenoid or could be that the solenoid is not able to push the pinion into engagement with the flywheel (which would not allow it to complete its travel and close the contacts).

3 Both solenoids do their jobs but the motor is unable to rotate the flywheel. This is usually evident from a louder sound (hum/buzzing) of the motor trying to turn.

Hope this helps!
Nick

Have you put a meter to the starter to see the volts when cranking?

Where are the first and second solenoids? I only seem to have one attached to the outside of the starter.

It is possible that your motor does not have the first solenoid. Here is a link to a good animated graphic of a starter with the ignition switch controlling the engager solenoid directly.


My Lehman120 has both solenoids. I managed to find some images of this on Google - see below. The first solenoid is a regular automotive type solenoid.

In the second photo it ias more difficult to see - it is grey (unpainted).

The third photo is the best view but it is a bit difficult to tell the separate pieces because all are painted bright red. The starter motor itself has the white label. The engager solenoid is directly above the motor with a spiral wrapped wire going to its left hand end. The first solenoid (or relay) is upper right with the yellow wire connecting to it.

Regards,
Nick

I am having a similar problem. Went to start my Yanmar 4LH-HTE today and there was just a very loud spinning sound similar to a vacuum. From reading here it seems like the starter is spinning but not engaging the flywheel.

Here are pics and video. Help appreciated. I’ve read it could be the “Bendix” and the solenoid is bad?

*******I am having a similar problem. Went to start my Yanmar 4LH-HTE today and there was just a very loud spinning sound similar to a vacuum. From reading here it seems like the starter is spinning but not engaging the flywheel.

Here are pics and video. Help appreciated. I’ve read it could be the “Bendix” and the solenoid is bad********




JustOne

No photos or video appeared.

Regardless if the starter motor spins but the engine is not cranking then something is wrong inside the starter motor itself. Pinion gear lost driving connection between itself and the pinion shaft, the pinion gear is stripped, the pivoting arm that pushes the pinion into flywheel engagement has failed or something of a similar nature.
Something is haywire between the starter solenoid and the pinion gear.


Pull the starter off and take it to a starter/alternator rebuild shop for repair.

Back in the day I had an F250 with a 460 in it. It would very occasionally have the same problem. There was a removable cover on the starter with a plunger under it. I would push on the plunger and the starter would engage and the engine would start. I never pulled the starter to get it fixed since it only happened a few times. Someone told me that it was the bendix not engaging. Sounds like a similar thing to your problem. Probably get the starter rebuilt and that will likely fix it.

RickyD said:

Ok I may be having a similar issue with a 2-cyl Yanmar engine for my genset. After having the boat on the hard for bottom work, I pressed the start button. There was a bit of a click and nothing. My start battery was really old so I figured it had finally given up. Replaced it and "click" nothing. So I arced the solenoid contacts, got spark, got some starter spin but no engagement. I took it to a motor shop. I told them the problem and the fact that bypassing the solenoid only spun the motor, no engagement. He showed me a connection that he said needed to be engergized to get engagement. It had one wire attached by a single screw. I marked it for reassembly. They rebuilt it, I put it in and "click" nothing. It had been working fine for over 3 years. So next I expect to try to get into the control box and see if I can see something wrong with the switch. Any other suggestions?

Click to expand...

AS a follow up, I had a repair company come and check it out. They said the circuit board was bad. Got a new circuit board and had them put it in. Pushed start and it just went "Click". More poking around revealed a small 10 amp fuse blown. Replaced the fuse. Started right up. Did I pay over $900 for a fuse?

No, you paid $900 for the knowledge of how to fix it next time…

Comodave said:

No, you paid $900 for the knowledge of how to fix it next time…

Click to expand...

It is entirely possible that the board was bad and the fuse. There is no denying they spent 3.5 hours in two calls. And I had spent money and weeks trying to figure it out myself. Call in the experts and spend the cash. I'm happy it works.

At about similar timing my water maker quit. Popping the breaker. Called the mfg rep and he said the motor almost never goes bad. Took the motor out, big job, had it checked, bad bearings. Put it back in, big job. No go. Called in the experts, needs a new circuit board. $1250 just for the board before labor. Works great. Running as we speak. Boats cost.