No Power To Fuel Pump or Starter Relays - Yanmar 4BY2-180

[CaspersCruiser]

A friend is cruising the Great Loop. While secured in a lock on the Tennessee-Tombigbee Waterway with the engine running, the Yanmar 4BY2-180 engine in his 2012 R27 abruptly quit. It did not run rough or present any sign of distress. It just stopped running and would not restart. My friend used a 3 HP kicker motor to exit the lock. Before the trip, he designed and built a swim platform mount for the kicker. Luckily, there was a nearby safe anchorage. After two nights in the anchorage, a tow service traveled 49 miles to pull them to a marina.

While waiting for the tow, my friend did extensive troubleshooting. Among many things, he made sure the key switch, the “deadman” switch and the neutral safety switch checked out and that all fuses in the ECU were intact. Once at the marina, mechanics determined that no power is getting to the fuel pump or the starter relays in the ECU. A mechanic suggested that there is a problem internal to the ECU.

My friend returned home to get his trailer and is towing the boat this week to a facility that has competency to troubleshoot the ECU.

I’m posting this in hopes that another 4BY2 Tugnutter has experienced this issue and can share what was the resolution.

 

[4umfreak]

Let's all hope it's not the ECU. I've spent some time looking into it and those things are hard to come by. That's the short version of the story.

I hope your friend finds a competent shop with good connections!

-M

 

[4umfreak]

FYI, I uploaded the Yanmar 4BY2 Troubleshooting manual on the Facebook group, if you / they need it. It will outline the relays and related connections.

https://www.facebook.com/groups/rangertug/files/files

 

[CaspersCruiser]

FYI, I uploaded the Yanmar 4BY2 Troubleshooting manual on the Facebook group, if you / they need it. It will outline the relays and related connections.

https://www.facebook.com/groups/rangertug/files/files

Thanks. I’m pretty sure he has that manual.

I sure hope he can find a resolution because, for my own 4BY2 files, I’d like to know what caused the problem.

 

[ohioan55]

I know this boat and hope they get their issue resolved.

 

[William Sanborn]

Had the same issue Checked the lift pump fuse was of, but the Relay and Holder were burned up.

 

[CaspersCruiser]

Had the same issue Checked the lift pump fuse was of, but the Relay and Holder were burned up.View attachment 26631

The overheated fuel pump relay and scorched socket is a common issue on the 4BY2 and 6BY2 Yanmars. Most mechanics ascribe it to a high current draw caused by obstructions, such as clogged filters, in the fuel delivery system during high fuel flow situations. I don’t think that is always the case. Twice, I’ve had the fuel pump relay fail when throttling back to a low fuel flow. An electrical engineer buddy says relays can overheat because of a low voltage situation. I think it’s entirely possible the failed fuel pump relay issue is a fault in the ECU or an inadequately sized relay.