Cat 3126 problem

[Mr P]

After a good sunny weekend away we were returning to Pwllheli in our Azimut 42. When we were approaching the marina entrance the port engine cut out / stopped. We have Cat 3126 engines. This is the second time this has happened after a day out!
We call an engineer who had a look round, restarted the engine and could not see any obvious visual issues. He said it could be a duff sensor but it would be difficult diagnose and expensive too. He also mentioned that he could not plug PC in for diagnostics

I do know there is a low pressure safety cutout but we are not loosing any engine oil.
Has anyone experience with CAT 3126 engines. Where do I start to look for an intermittent fault?
Wife has lost all confidence in the boat so I need rectify ASAP

Is there any common issue with these CATs?

Thank you

 

[Portofino]

You may be better joining this forum
YachtForums: We Know Big Boats!

They have an engine section and CAT s seem populate it a lot .

Engines | YachtForums: We Know Big Boats!

 

[Deleted User YDKXO]

Are your engine start batteries in good condition? I had both the MAN engines in my boat cut out whilst backing into my berth recently. It turned out that 2 of the 4 engine start batteries were dead and that when I used the thrusters, which are connected to those batteries, they pulled the voltage down so far on the battery bank that the engine electronic control system simply cut the engines

Just an idea. Otherwise it might be worth calling the UK Cat dealer, Finnings, to see whether they can help or at least recommend an authorised Cat service dealer local to you

 

[MapisM]

Has anyone experience with CAT 3126 engines. Where do I start to look for an intermittent fault?

I used to own a 3116 powered boat. Not exactly the same engine, but yours were derived from the 3116, sort of.
I did experience an unwanted engine shut down, only once during 17 years of ownership overall.
So, don't take this as a suggestion that your problem is likely to be the same, also because I'm not sure if the 3126 and the 3116 share the same component.
But FWIW in my case, out of the blue while cruising, the shutdown solenoid decided on its own to do what it's there for, i.e. shut the engine down.
Upon every following attempt to turn the engine on, it appeared to start normally, but it turned off immediately, because after a split second the solenoid turned it off again.
What is really weird is that it's a solenoid that has to be energized to shut down, not the other way round.
So, while it took some time to understand that the solenoid was the culprit (while cruising the Croatian coast, in a hot engine room and with my Cat mechanic on the phone!), the solution was dead easy.
I disconnected the solenoid, and the engine started and ran perfectly.
The only drawback being that I had to go down the e/r and push its red button manually to turn the engine off, once done with it.
But what is even more weird is that the following day I tried reconnecting the solenoid, and the defect disappeared - and never surfaced again to these days...

 

[Mr P]

Are your engine start batteries in good condition? I had both the MAN engines in my boat cut out whilst backing into my berth recently. It turned out that 2 of the 4 engine start batteries were dead and that when I used the thrusters, which are connected to those batteries, they pulled the voltage down so far on the battery bank that the engine electronic control system simply cut the engines

Just an idea. Otherwise it might be worth calling the UK Cat dealer, Finnings, to see whether they can help or at least recommend an authorised Cat service dealer local to you

Thank for your suggestion. I will phone Finnings
I don't think it's the battery's as I had all new last year. One for each engine and on service battery which also powers the thruster and the windless !

 

[Mr P]

You may be better joining this forum
YachtForums: We Know Big Boats!

They have an engine section and CAT s seem populate it a lot .

Engines | YachtForums: We Know Big Boats!

Thank you I'll have a look

 

[Mr P]

I used to own a 3116 powered boat. Not exactly the same engine, but yours were derived from the 3116, sort of.
I did experience an unwanted engine shut down, only once during 17 years of ownership overall.
So, don't take this as a suggestion that your problem is likely to be the same, also because I'm not sure if the 3126 and the 3116 share the same component.
But FWIW in my case, out of the blue while cruising, the shutdown solenoid decided on its own to do what it's there for, i.e. shut the engine down.
Upon every following attempt to turn the engine on, it appeared to start normally, but it turned off immediately, because after a split second the solenoid turned it off again.
What is really weird is that it's a solenoid that has to be energized to shut down, not the other way round.
So, while it took some time to understand that the solenoid was the culprit (while cruising the Croatian coast, in a hot engine room and with my Cat mechanic on the phone!), the solution was dead easy.
I disconnected the solenoid, and the engine started and ran perfectly.
The only drawback being that I had to go down the e/r and push its red button manually to turn the engine off, once done with it.
But what is even more weird is that the following day I tried reconnecting the solenoid, and the defect disappeared - and never surfaced again to these days...

.
.
Thank you it's given me something to look at. I'll look for a engine fuel shutdown solenoid … If I have one .

 

[Spare Thyme]

As long as yours are not the 3126b the only thing that will shut these engines down is the shutdown solenoid, (there is no auto shutdown on temp / low oil, only an alarm) if it’s like my Azi 39 they are energised to stop, with no power they run. your Azi will have the same red Rubbery buttons at the helms to shutdown, check they are OK, they have fiddly screw terminals behind that are very close Easy for a loose one to allow it touch the other and shutdown.

also check the terminal panel in the guest bedroom on the wall, this is where the cables from the helms meet the engine looms, also very tight with close quarter wiring and a bizarre current shunt (for the ammeter) buried in the loom that gets warm, worth checking this isn’t melting wires and causing a short

 

[rafiki_]

I had an Azi 39 with 3126 DiT’s. These are non electronic, so no engine ECU or diagnostics. Mine never let me down, always started even after a lay off, and performed brilliantly. I don’t think even if you had a battery problem like Deleted User this would stop the engine as they are mechanically fuel injected. So it looks like MapisM and Spare Thyme have the best suggestion with the solenoid cut-off. Finnings have always been very helpful, but Spare Thyme is always the best source of info on the Azi and Cats.

 

[MapisM]

Thank you it's given me something to look at. I'll look for a engine fuel shutdown solenoid … If I have one .

Here's how it looks like on the 3116.
I guess it's neither much different nor far from that placement also in the 3126, but I can't be positive about that.
The red button on the right side of the cylinder is the manual stop, btw.

 

[Spare Thyme]

Here's how it looks like on the 3116.
I guess it's neither much different nor far from that placement also in the 3126, but I can't be positive about that.
The red button on the right side of the cylinder is the manual stop, btw.

I can confirm its identical on the 3126

 

[volvopaul]

No edc or electronics of any kind on this engine .
Now was the shut down when you went from forward to astern ?
Is it on ZF Mather controls ?
do you have a sea fire system that’s connected into the engine stop system ?

 

[Mr P]

No edc or electronics of any kind on this engine .
Now was the shut down when you went from forward to astern ?
Is it on ZF Mather controls ?
do you have a sea fire system that’s connected into the engine stop system ?

Just to confirm that the 3126 has no engine electronic control system!! I didn't know that! … so less to go wrong !
The shutdown occurred when I had been at 2000rpm for about an hour, then I went to tick over - not out of gear (for putting the fenders out) and it stopped
I have phone Finnings and they suggested new fuel filters. Also someone else suggested the same so I changed them yesterday. I have not been able to take her out yet due to the weather but when I do I'll report back.

Is it on ZF Mather controls ? I don't know ...
do you have a sea fire system that’s connected into the engine stop system ? I don't know … I do have a fire system in the engine room

 

[Mr P]

Here's how it looks like on the 3116.
I guess it's neither much different nor far from that placement also in the 3126, but I can't be positive about that.
The red button on the right side of the cylinder is the manual stop, btw.

I'll have a look and come back to you ….. thank you for photo

 

[Spare Thyme]

Is it on ZF Mather controls ? I don't know ...
do you have a sea fire system that’s connected into the engine stop system ? I don't know … I do have a fire system in the engine room

if you have a little button on the throttles you have to press to make that throttle control then it’s most likely Mathers microcommanders, however malfunction of this system will not stop an engine, the belts in early ones fail and slip preventing you starting occasionally, fiddly but easy to replace the belts, defiantly will not shut down a running engine

The fuel primer can be tricky, you have to be careful the little selector knob is in the run position otherwise it can limit fuel flow, sometimes the knob slips and you loose position. If when you prime with the pump you get drips of diesel then the primer pump seals have gone, if the selector is not fully in the run position this can pull air in, however when that happens the engine is a pain to start, I don’t think this is your issue

one final favourite of Azimuth is the electrical solenoid on the fuel line from the tank, you will see these close to the big fuel shut of valve on the tank, these are energised when you turn the battery master on but the wires can get knocked off, there is a manual override knob on the solenoid, work this a few times just in case there is any crud in there, they do get warm when energised.

if you have an auto shutdown system there will be a small panel with a green light and a “run - override“ switch on it, they are not standard fit but a worthwhile safety feature, there will also be an electrical cable attached to the extinguisher bottle

suggestions

1 check your fuel primer pump switch, for priming the indicator should point to the pump, for running it should point to the filter
2 tank solenoids manually override these temporarily to eliminate them
3 if you have shutdown system put it in override temporarily
4 as the engine shutdown solenoid needs power to shutdown, put a 100mA (very small) automotive fuse across the terminals (in parallel with the solenoid), remember if you push the stop button this fuse will blow, then go for a run. If the engine shuts down by itself again pull the fuse, if it’s blown there is a wiring issue causing power to go to the solenoid

the other more radical is swap the port and starboard shutdown solenoids over, you can the eliminate the shutdown solenoid if the same engine self shuts down

 

[Mr P]

if you have a little button on the throttles you have to press to make that throttle control then it’s most likely Mathers microcommanders, however malfunction of this system will not stop an engine, the belts in early ones fail and slip preventing you starting occasionally, fiddly but easy to replace the belts, defiantly will not shut down a running engine

The fuel primer can be tricky, you have to be careful the little selector knob is in the run position otherwise it can limit fuel flow, sometimes the knob slips and you loose position. If when you prime with the pump you get drips of diesel then the primer pump seals have gone, if the selector is not fully in the run position this can pull air in, however when that happens the engine is a pain to start, I don’t think this is your issue

one final favourite of Azimuth is the electrical solenoid on the fuel line from the tank, you will see these close to the big fuel shut of valve on the tank, these are energised when you turn the battery master on but the wires can get knocked off, there is a manual override knob on the solenoid, work this a few times just in case there is any crud in there, they do get warm when energised.

if you have an auto shutdown system there will be a small panel with a green light and a “run - override“ switch on it, they are not standard fit but a worthwhile safety feature, there will also be an electrical cable attached to the extinguisher bottle

suggestions

1 check your fuel primer pump switch, for priming the indicator should point to the pump, for running it should point to the filter
2 tank solenoids manually override these temporarily to eliminate them
3 if you have shutdown system put it in override temporarily
4 as the engine shutdown solenoid needs power to shutdown, put a 100mA (very small) automotive fuse across the terminals (in parallel with the solenoid), remember if you push the stop button this fuse will blow, then go for a run. If the engine shuts down by itself again pull the fuse, if it’s blown there is a wiring issue causing power to go to the solenoid

the other more radical is swap the port and starboard shutdown solenoids over, you can the eliminate the shutdown solenoid if the same engine self shuts down

Thank you Spare Thyme
I will have a look at your suggestions next week and come back to you

 

[Mr P]

Thank you for all your suggestions. I have replaced all the fuel filters and been out twice

No cutout problems to report! …….....

Let hope it was as simple as that !!

I'll return to the forum and post if I have future problems . thank you

 

[rafiki_]

Good result. It is usually a simple problem. Best to check those things first.