Yanmar starter relay

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DickTuschick
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Yanmar starter relay

Post by DickTuschick »

As our engines grow older the starter relay is failing on many engines. It is a simple and not very expensive ($179 to $350 depending on where you shop) part that you should have on board as a spare.
Replacing it is not easy due to its difficult to access location just under the starter motor. Many owners have opted to move the relay to a location on the side of the hull next to the engine so that if it fails, the replacement is an easy operation. See attached photo.
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Starter relay
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Re: Yanmar starter relay

Post by deising »

Good advice, Dick.

The starter relay in our port engine failed in 2015 and the mechanic wisely moved the new relay to the outboard hull for easy access. I have since had to re-work the terminal ends of those wires, so it was great to be able to do so easily.

Since it is only a simple relay and Yanmar parts were not available in our situation, the mechanic used a relay he had in stock that did the job. I think the relay cost was less than $20.
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Re: Yanmar starter relay

Post by duetto »

duane,

by chance do you have a make or part # on the relay?
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Re: Yanmar starter relay

Post by AMCarter3 »

What are the typical symptoms of this relay starting to fail? Or is it simply a Go or No Go kind of device?

I started experiencing a fairly consistent pattern of my port engine being hard to start. It went from always starting after ONE second of cranking to suddenly 3 weeks ago not starting after multiple rounds of 3-4 seconds of cranking. My diesel mechanic suspected a fuel line air leak or bad fuel (we are on a 4 week trip in the British Columbia "Broughtons" where it is possible to get bad fuel). When I opened and inspected the port Racor filter, (new last Dec), it was only mildly dirty BUT the small O-ring that should be on the threaded part that screws the lid onto the body of the filter container was missing. My mechanic said that O-ring was essential and was likely the source of the start issue. I put in a new filter and O-ring and, Voila, the engine started immediately. I also checked and tightened every fuel hose clamp I could see. I thought that issue was solved. Not so...

After a few days of no start issues on the Port engine, we again started having the same difficulty starting that engine. Not consistently though. About every 2nd or 3rd day, I would have to crank the starter several times for 2-3 seconds and it might start. Or might not. If not, I then pushed several times on the pump at the top of the secondary fuel filter (attached to the engine), it would start. That my status now. Each day when we anchor, I don't know IF the port engine will start in the morning. Some days it starts immediately (warm or cold engine). Other days, it is difficult to start, but eventually I get it started. This is a bit nerve racking as you can imagine.

Any suggestions or diagnostic thoughts about this issue? Could it be the starter relay or something else?
Mac Carter
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Re: Yanmar starter relay

Post by deising »

John, sorry I do not have any numbers. It is just a 12V relay, so almost anything will work, but get a better opinion before committing.

Mac, if the relay is failing, it is likely going to be a no-crank situation. Sometimes it will crank and sometimes not. If the starter is turning and the engine is slow to start, that is not a relay issue. The voltage at the starter could be low due to the battery, cabling, or connections. Or the engine itself could be aging with low compression or other issues.

As with anything electrical, failure could be simply a poor connection or corrosion issue.
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Re: Yanmar starter relay

Post by duetto »

hi mac,

years ago our port engine started to have starting problems, but they were related to turning the key and nothing happening. used voltmeter and traced to bad start relay. based on your description, it sounds like a fuel problem or more likely air leak in fuel system.
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Re: Yanmar starter relay

Post by AMCarter3 »

So far, I'm buying into the "Air Leak" theory as the cause of my intermittent start issue. The battery is strong. It cranks (strongly) on turning the key to START. The only other speculation someone suggested is the fuel "lift" pump. I don't know anything about that pump (it's below and behind the engine fuel filter. Anyone else think that might be the issue?
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Re: Yanmar starter relay

Post by duetto »

mac,

if i'm not mistaken the lift pump is built into the injection pump and this makes it a problem to replace or bypass to test.
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Re: Yanmar starter relay

Post by duetto »

hi mac,

i gave this some more thought. another possibility could be a sticking fuel valve. it's the valve that opens on cranking and shuts when you hit the stop button. it starves the engine of fuel and it stops. if the fuel valve closes enough to starve the engine but not completely closes it will allow fuel to drain from the injector pump and then need to refill on next start which takes time. the valves are very precise and can be prone to getting a spec of grit which can cause them to bind.

just a thought. we have a genset with that very problem.

good luck.
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Re: Yanmar starter relay

Post by AMCarter3 »

Thatks a very interesting possibility, John. The engine started normally for the last 4 days (we have not started up yet today). I did find one more hidden fuel hose clamp yesterday that allowed more tightening than the others. We’ll be back in port on Wed and I plan to meet with our diesel tech guy on Thursday. I’ll pass along your thought. Much appreciated!
Mac Carter
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Re: Yanmar starter relay

Post by duetto »

hi mac,

did you ever get to the bottom of your starting problem?
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Re: Yanmar starter relay

Post by AMCarter3 »

Thanks for asking. No, after 7 weeks, the intermittent start issue is still happening. We are still pursuing it. We have tested and ruled out the ignition circuit. There could still be a chance of an air leak, but we have done a lot to reduce that possibility. Our target now is the injectors. We plan to replace them next week.
Mac Carter
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Home Port: Bellingham WA 98229
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Re: Yanmar starter relay

Post by Charlie Monroe »

I realize it’s Summer time, but have you tried turning the key counter clockwise and holding it 10-15 seconds to preheat the cylinder? This won’t be a final solution to the problem, but it might open another path of investigation.
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Re: Yanmar starter relay

Post by scgck »

Just a shot in the dark.
The next time it doesn’t start try priming it with the pump on the fuel filter housing.
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Re: Yanmar starter relay

Post by AMCarter3 »

Priming via the fuel filter pump as well as advancing the throttle have been standard “tricks” we have tried routinely since the first day of this saga. Early on both seemed to help. But for the last few weeks, nether trick seems to work.

My diesel maintence guy is very experienced and I’ve had 2 boating friends with professional engineering background advising on this issue for the last 2 months we’ve been troubleshooting this. The latter 2 strongly believe the pattern of symptoms suggest a bad fuel pump solenoid valve.
So, on Tuesday, we’re bringing in a diesel technician from our local Yanmar diesel shop to replace the solenoid valve. We’re hoping a fresh set of eyes may help solve this issue.
Mac Carter
2006 34' PDQ PowerCat "All Heart"; MV 98; twin 100 HP Yanmars
Home Port: Bellingham WA 98229
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