Cat 3126 Start system.

dtfeld

dtfeld

Water Contrails
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Jun 5, 2016
5,551
Milton, GA
Boat Info
410 Sundancer
2001
12" Axiom and 9" Axiom+ MFD
Engines
Cat 3126 V-Drives
I have been chasing an intermittent problem. Occasionally while cruising, I experience a sudden loss of thrust on the starboard side. The RPM gauge maxes out, the sync gauge points to the starboard side. Occasionally, it’s a quick blip and right back to normal. Other times I pulled the power back, and the starboard engine is dead.

Lately I have noticed that when I go to start the starboard engine, I have to wiggle the start switch in the middle on position to get the engine solenoids to engage.

Bad start run switch? Originally thought transmission might be slipping.
 
In checking out the start circuit...found a loose wire in the starboard CAT control box. I think this is the glow plugs? Obviously this was disconnected on purpose, so wondering if there was a problem somewhere or is this related to the start/run issues.

Is there a schematic available?

20180712_142454.jpg
20180712_142504.jpg
 
Maybe this will help you sort out the problem.

The 3126 doesn't have glow plugs

The 3126 does have an intake heater in the plenum......I uses a lot of current so if the engines start and run normally, that disconnected heavy gauge wire could be where the previous owner disconnected the intake heater. The intake heaters are typically not needed in Southern climates so finding one disconnected in a Southern boat isn't unusual. Check the port control box and see if there is a similar wire disconnected. Physically trace the wire and see where it terminates.

I am pretty sure your intermittant stop issue has nothing to do with the disconnected wire but is instead a lost connection to the fuel supply solenoid that turns off the fuel flow. If it is momentary, then the engine will hiccup but continue to run; but, if the fuel flow is interrupted for long enough for 4 or more culinders to starve, then the engine has to be restarted. The cause could be the bad ignition switch or the fuel supply relay in the control box or a loose connection somewhere between the ignition switch and the fuel supply solenoid.
 
Frank. Again, Thank You!!

Ah yes, the air intake heaters. I knew that, sorry 30 years of VW diesel ownership had me thinking glow plugs!

I think the start switch/wiring/fuel solenoid is the issue. I ordered 2 new start switched and will replace those first as it seems like it is the likely suspect since I can get that failure mode sitting at the dock.

The top picture is the starboard with disconnected heater, the bottom, the port with them still connected. I looked last night in my documentation. I could not find anything referencing the control boxes. Is there any documentation on those boxes? If the dash switch isn't the issue, I'll have to dig deeper into this.

Dave
 
That little bosch relay (as Frank mentions) in the box operates the fuel solenoid; they do fail and sometimes intermittently. Most carry spares. Cheap $15 item you can get at NAPA.
 
Jus the two of us said:
My 3116s had all the info in the box it self, wiring schematic . I think its two sheets of paper. Not in the sea ray book, It all come from Cat.
Click to expand...

Neither of mine have that. I looked through the CAT documentation that came with the boat, not there either. There is a part # label on each lid. Any chance to get a copy emailed to me??
 
ttmott said:
That little bosch relay (as Frank mentions) in the box operates the fuel solenoid; they do fail and sometimes intermittently. Most carry spares. Cheap $15 item you can get at NAPA.
Click to expand...

Thanks ttmott. I'll pick up a set for the spares box. Like I said, I'll try the ignition switches first. Doesn't look complicated, but beyond the start/run switch, I'd love to get my hands on the CAT documentation before I start poking around in there. I assume the documentation has part #'s for the solenoids/relays?

20180712_142510.jpg
 
Well found a schematic. Is there anything else in the documents that would be benefitial?

CAT Control Box.PNG
CAT Control Box Parts.PNG
 
That is the box construction. There should have been a wiring schematic for the engine in a plastic bag inside of that box. Check the other box.
 
According to layout, that is the starting motor solenoid that is disconnected. The black switch lower left is the motor starter solenoid with orange wiring. The air heaters are the metal solenoid on the bracket with yellow/red wiring.

Am I reading this correctly?
 
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ttmott said:
That is the box construction. There should have been a wiring schematic for the engine in a plastic bag inside of that box. Check the other box.
Click to expand...

Checked that yesterday, nothing in either box, but I did compare one side to the other for reference. Are there differing versions of this box?

Hmmm.
 
Dave,
Since you mentioned that you have to wiggle the start/run switch sometimes to get it started then it sounds like that’s where the problem is.
Is it possible that your engine cutting out could be because the switch gets jostled and turns the engine off?
I might start by cleaning up or replacing the connections on the switch, or swapping it out with the port switch to see if the problem moves over.
 
JVM225 said:
Dave,
Since you mentioned that you have to wiggle the start/run switch sometimes to get it started then it sounds like that’s where the problem is.
Is it possible that your engine cutting out could be because the switch gets jostled and turns the engine off?
I might start by cleaning up or replacing the connections on the switch, or swapping it out with the port switch to see if the problem moves over.
Click to expand...

For $30 to replace both, not worth the trouble. I've found other switches moved/disconnected, so its a high probability play. The biggest expense is time to drive up and work on it.

The more difficult thing is figuring out what several PO's had removed/deactivated and why.
 
Received 2 new start switched. Ill install this week and see where I am with this.
 
Prosideus

Flounder Pounder is my source...fpmarine.com.

The switches are Carling and there are 2 parts to each switch, a body (the electrical switch part) and the actuator, so you have to order the correct part. Here is a shot from my parts manual...the body is Sea ray part # 670521.

switch.PNG


Converting to Carling Part #'s...

VM4J-1 VM4J-1 Carling OFF/ON/(ON) double pole rocker switch w/jumper no lamps - Ignition switch , SR part# 670521 old #647974 VM4J-1

These are pretty common as stop/run/start switches, but there are different versions, so check your parts manual, or pull the switch and get the Carling #.

024C994A-8965-4F3C-B844-796649E8AA07.jpeg




Dave
 
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