Fuel pump relay/socket failure

We have a Yanmar 4BY2-150 with 1400 hrs and have been battling an obvious overheating and relay socket failure at one terminal. The pump draws 8.1 amps which I believe is the spec for that pump. Replaced the socket with a BMW OEM socket and it failed again after 19 hours. The wire feeding it seems very light and wonder if that is causing an overheat at the spade terminal.
Has anyone else run into this and/or solved it ? I see some older posts that looks like there have been similar issues but wonder if they reoccurred? Any advice would be appreciated
Thanks
Tom


Sent from my iPhone using Tapatalk

My 2012 4BY2-180 suffers from the same thing. I have been communicating with Mastry Engine in St. Petersburg, Florida about this issue. They are convinced that the problem stems from high fuel pump current draw caused by fuel filters not being changed. That’s simply not the case in my boat.

An electrical engineering buddy looked over the scorched socket in which the fuel pump relay is inserted. He suggested that an undervoltage situation could cause that relay to overheat. He advised me to try to clean the socket pins. The wiring leading to the socket is also heat distressed.

I have searched for a new socket to no avail. One solution is a whole new wiring new harness from Yanmar at $1600 USD.

Very interesting- thanks for the reply.
The socket is a stock BMW part. I, too, have changed the fuel filters and can’t see it being part of the cause. I looked up the fuel pump part # from an old post and see that it’s run current is 8 amps from the spec which is exactly what this one is running at. I carefully tagged and cut of the old leads at the socket which gave enough wiggle room to splice in new leads on the replacement BMW socket. But still really light gauge wire. As a temporary fix I have a universal socket with 14 gauge wire spliced in and going to have a look how that performs. Only have 5 hours on that set up.


Sent from my iPhone using Tapatalk

2islanders":16l84rve said:

The socket is a stock BMW part.….. I carefully tagged and cut of the old leads at the socket which gave enough wiggle room to splice in new leads on the replacement BMW socket. But still really light gauge wire. As a temporary fix I have a universal socket with 14 gauge wire spliced in and going to have a look how that performs…..

Click to expand...

I went to the local BMW dealer parts desk and inquired about the socket. They were quite eager to help, but only could find the relay and not the socket. Of course, their relay was twice the price of the spare relay from NAPA that I carry on the boat. It even has the BMW logo on it.

Could you please post the part number of the socket? I’d like to make the repair you have made. And posting the part number here would help folks in the future who search the archives when they encounter this problem.

Just a little thinking outside the box. The fuel pump spec is said to be 8 amps and the feed wire is probably 14 ga which is sufficient for 8 amps @ 12V. 10amps 16 gauge is large enough. If the relay has larger wires than the harness wiring that is not really going to help you still have to push the current through the wire harness.

Why is a fuel pump using maximum rated amperage to operate? The first thought would be dirty fuel filter. Replace fuel the filter and the problem still is there. ??? There is much more to a fuel system. There are fuel valves, fuel pick ups, fuel lines, fuel pressure regulator and a pump. There is also voltage drops because of dirty connections causing higher amp draws.

Inspection of the fuel pickup in the tank,
Install a vacuum gauge at the primary filter to confirm there is no suction restriction
Inspect fuel lines, fittings for air leaks

A full inspection of the fuel system should be done before jumping to it strictly being an electrical issue.

Clean all connections and check for voltage drops across electrical connections.

A motor rated to operate to 8 amps should draw 4 to 5 amps while in normal operation (My opinion )

You both may be troubleshooting in the right direction. I thought I would just add that sometimes what seems to be the right fix is not always. Look at fuel flow when dealing with pumps and motors.

Thanks for that input. BB marine. Agreed on your points. Have changed fuel filters , pulled the suction line out of the tank and removed the screen on the bottom of that - all looked good. The wire to the one terminal that has been the problem is fed with what looks to be 18. Agreed the heavier wire on the end doesn’t solve what comes through the harness but the thought is it would hopefully help reduce any heating issue at the connection and provide a bit more mechanical support. Lots of vibration around these relays because of where the ECU is mounted It would be very useful to know what the run current from others pumps in this application run at. It is fused at 15 amps so I would assume the harness wiring should be sized to suit the 8 amp load if that is in fact what they “normally “ operate at. Agreed the connections all need to be solid and clean. I am going to recheck the current draw and voltage at the pins while running again. The final thought is perhaps failing pump running at higher current than “normal”.
NOTE: before you start working on this disconnect all your batteries as it appears there is a power source not isolated by just switching off at the isolation switches. That ECU is a pricey replacement if you short it out.
BMW socket is for a 2002 540 i (sorry don’t have the exact part number but may get it yet)
Relay is SMP RY771 rated at 30 amps (identical to BMW- from Rockauto or local auto supply)
I will update this post after a bit more investigation next couple of days.


Sent from my iPhone using Tapatalk

Re-checked the electrical and now find the pump drawing 9.8 Amps (up from 8.1 about 30 hrs previous running hours). 14.1 volts at terminal. This would indicate to me the cause for the overheat on the relay socket and also either there is an increasing fuel restriction or quickly failing pump. I have ordered a Pierburg pump as the delivery times are quite long and can't back to work on further until June when I will check fuel vacuum. Got two spare sockets from local BMW auto wrecker-- comes with wire leads and spade terminals complete in perfect condition-- easy solution to splice in replacement. BMW dealer couldn't give me the part number but said if I brought it in he could match it up.

Just a final update on this problem (I hope)-- received a new Pierburg replacement pump (Amazon) which was an identical replacement for the original. Also ran a vacuum test on the pump prior to swapping out the new one.
There was less than 1" of vacuum on the suction the old pump ( almost undetectable) which was running near 10 amps last check, Installed the new pump and bench tested the relays- the relay coil takes about 0.20 amps. The new pump ( and original) spec out at 8.0 amps. Once the new pump was installed the total current draw on the input of the relay seems pretty steady at 7.8 amps- which would mean the pump is drawing 7.6 amps. So from this I believe the Yanmar system must have designed to run the 8.0 Amp pump and it was the old pump over current that was causing the relay sockets to melt down. New sockets installed, with spare sockets and relays on board. I guess time will tell. So for those that are experiencing relay/ socket issues I would suggest you a have a good look at your current draw. If anyone else has come up with a different cause/ solution I would be most interested. Thanks BB marine for your insights for troubleshooting as well.

Hi 2islanders, Say, I noticed that you are from Duncan, and probably moor in Cowichan Bay. My wife and I are planning an lower island trip in early September and I am wondering if the bay in Cowichan is usually open for chinook fishing in early September? Best regards, Howard on a C28 'the Corinthian', Comox.

Correct- that’s where we are. The “bay” area 18-8 is extremely unlikely but other parts of 18 close by usually does. ( and can be good fishing). If you would like more area info send me an email to ttodd15@shaw.ca
Tom.


Sent from my iPhone using Tapatalk