Mercruiser 3.0 135hp TKS Hot start problem.

[ollie.thfc]

Hi All,

As above it fires up fine when cold but when its up to temperature i either have to pump the throttle or put the revs up in neutral to get it going again, wasn't an issue last year it just fired up at a flick of the key.

Now iv' recently replaced the distributor cap and rotary arm, iv'e replaced the enrichment module, ive had the carb cleaned twice.

Iv'e recently been sent a mercury service bulletin and followed the procedure to test the TKS Diode, according to my volt metre with the ignition on and off it had 12.6v at the enrichment module terminals with the engine up to temperature must mean the diode is fine?

Im now a bit stumped as to what to try next?
Anyone got knowledge of this TKS carb system?

 

[dpb]

I would first check the temperature sender for the TKS (not for the temp gauge) both located on the thermostat housing, either the sender itself or the wiring / connections to it could be at fault. Suspect that it is not sending the message that the engine is hot!
I also had trouble with the three wires that go to the oil pressure sensor on the starboard side of the engine, low down. The plug made a poor connection with the sensor and after cleaning and even replacing the sender the connections would fail again so I ended up hard wiring the wires to the sender and using conventional connectors a few inches away. No more problems.

 

[ollie.thfc]

Thanks,
Would that be a case of testing with a volt meter or actually replace the temp sensor? I'm having issues ordering parts in the uk too, can only seem to find them in the states.

 

[dpb]

It is a while back since I had this engine so cant remember if the temp sensor was closed hot or closed cold.
Next time the engine is hot, disconnect the sensor and try again, if no joy then short the lead straight to the engine earth and try again, if it starts ok with one of the conditions you have found the problem.
Some parts that are in less demand need ordering through a dealer, from warehouse in europe so you dont find them listed on internet shops.

 

[Stavros]

It may seem a silly suggestion, but if your distributor has a Condenser try changing it, its a cheap fix especially if the engine does not like to start when hot.

 

[spannerman]

Hate to say it but condensors haven't been used for at least the last 20 yrs by Mercruiser, everything is controlled by a module or the ECU depending on injection system.

 

[ollie.thfc]

Thanks,
I think i've found the sensor, ebay item number 282386794269 ?
I might just order it and hope for the best!

 

[B58]

The wax module is the most common failure not the temp sender P?No: 3310-866148

 

[ollie.thfc]

The wax module is the most common failure not the temp sender P?No: 3310-866148

Thanks but already replaced that part.

 

[antonw86]

Thanks but already replaced that part.

Really grasping a straw here but did you ever figure out what was causing your hot start problems? I'm having the same issues with my 5.0 TKS merc and have concluded that the diode is fine...

/Anton