Perkins T6.3544 Engine Wiring and Thermostart Question

[Turtle Blues]

Replacing worn/corroded relay sockets and this led to question concerning the Thermostart System. Looking at the wiring diagram and operating instructions I have all the engine mounted components and relay but no part labeled Thermostart Push at the panel. The key switches appear to be replacements, on / off only, no additional functions.
Always wondered what that mysterious third relay on the engine harness was for.
Following existing wires and diagram it appears the wire intended for this feature is run to the harness connection block at the panel but is not present on panel side for either engine.
Have had no issues to date but curious if others have this system active.

 

[STB]

Replacing worn/corroded relay sockets and this led to question concerning the Thermostart System. Looking at the wiring diagram and operating instructions I have all the engine mounted components and relay but no part labeled Thermostart Push at the panel. The key switches appear to be replacements, on / off only, no additional functions.
Always wondered what that mysterious third relay on the engine harness was for.
Following existing wires and diagram it appears the wire intended for this feature is run to the harness connection block at the panel but is not present on panel side for either engine.
Have had no issues to date but curious if others have this system active.

I'm not sure I understand the question. If I don't answer, maybe rephrase.

The ThermoStart start system is just a set of electric glow plugs where the glow plugs ignite a small amount of diesel fuel to produce even more heat faster.

Somewhat few marine 6.3544 engines have ThermoStart installed. Even fewer have it working. The engine will usually happily start right up even in pretty cold weather. So most boaters with those engines just never use them and don't maintain them. Of course I'm sure there are folks out there with situations where they need and use them.

They are somewhat more commonly installed and maintained in generator and tractor applications.

 

[Turtle Blues]

Thanks for the reply.
like you say system has probably never been active and operation has been just fine without it.
Like most things British it is just a little different.
The electrical connection is to what I assume is an electric valve set into the elbow of one of the turbo air charge cooler lines. This valve has a fuel line connected from a port on the engine filter distribution block. The size of the connection fitting leads me to think it contains some type of orifice assembly.
Seeing as it hasn't been necessary for thirty plus years it's going to remain that way.

 

[jgwinks]

My 6.354:s don't have preheat and start up just fine without it. If it's really cold (in boating terms, 40-50 F) they might crank a little longer, but they start. Same basic engine in a tractor might be used in sub zero temps and probably would need the system. I never liked the concept of burning fuel in the intake to heat the air, just seems like a bad idea. No problem with electric glow plugs though. As said earlier, the Brits do things a little differently. The system is described in my engine manual, I believe it was activated by turning the key one way then back the other way to start. So if the key switches were changed that would explain the lack of a switch.