Mercruiser 3.0 TKS - Hard to start when semi-cold

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Jonatande

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Mercruiser 3.0 TKS is hard to start when it first has been running, then have been off for 2-3 hours.

My suspicion is that the TKS system gets confused when the engine is quite cold, yet have ample of fuel in the carburetor so it applies the wrong amount of air-fuel mixture.

It will always eventually start, and noticed there is less issue when I just make a small "pump" forward with the throttle, reversing back to neutral and then start.

However, I would like this problem to disappear. Any ideas?
 
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cyclops222

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My 2002 5.0 TKS always does a start with just turning the key. Hot or cold. When I had to due the PUMP action. My choke needed repair.
 
alldodge

alldodge

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I'm a bit confused with your first statement so I take it the motor has no problem starting up cold, it's only when it's been off for 2 to 3 hours.

Another issue may be your starting procedure

When cold the TKS module is retracted so when motor is cranked more fuel is drawn in. Once running the module slowly extends allowing more air and less fuel

When motor is shut off after warmed up, the Temp switch keeps power on TKS module so it stats retracted. When motor cools down power is removed and TKS extends once again slowly

noticed there is less issue when I just make a small "pump"
Click to expand...
You should not need to pump the throttle

Tell us how you start it each time when warm?
 
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cyclops222

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My TKS was really odd. It had a normal Thermostatic coiled spring in the black plastic housing. That was adjusted to SLIGHTLY too much pressure on the carburetor Choke Valve on a cold enough day.
The really weird part was how the choke slowly warmed up over time. NOT with engine heat. It has a series of heating resistor steps inside of the choke housing. If the heat power is always ON MAXIMUM ? You would need to do the PUMP ACTION. That SQUIRTS some gasoline into the engine every time you move from IDLE to anything above idle.
The SQUIRT in a Rochester 2 BBL carb I have. Will help with hot and cold weather throttle smoothness.
 
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cyclops222

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Old brain just remembered a real hot weather oddity. If engine was NOT NOT run for several HOT days............ The carburetor FLOAT CHAMBER would evaporate lots of gasoline in it . I cured that by turning the key to ON. wait about 5 seconds for fuel pump to fill the carburetor correctly. Go to STARTER POSITION. Instant start every time. no need to try PUMPING the throttle lever.
 
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cyclops222

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Mine is a 5.0 TKS Could be a different Rochester carb as standard in 2002 ? Mine is the Anodized Brass / Bronze finish.
 
alldodge

alldodge

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A TKS, is a TKS , is a TKS
only "differences are" jet size inside the carb
Edit above
 
Last edited:
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Jonatande

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alldodge said:
I'm a bit confused with your first statement so I take it the motor has no problem starting up cold, it's only when it's been off for 2 to 3 hours.

Another issue may be your starting procedure

When cold the TKS module is extended so when motor is cranked more fuel is drawn in. Once running the module slowly retracts allowing more air and less fuel

When motor is shut off after warmed up, the Temp switch keeps power on TKS module so it stats retracted. When motor cools down power is removed and TKS extends once again slowly


You should not need to pump the throttle

Tell us how you start it each time when warm?
Click to expand...

Yea, so the engine starts fine hot and cold (say the first start of the day). BUT the second start (like after you start it again after engine been off for 2-3 hours) is much harder.

My starting procedure is always Neutral position, cold semi-hot or hot.

Your comment makes sense from my understanding of the TKS module, it could be that the module is in a bit off-sync with the temprature?

Basically, if I pump one time forward, then go back to neutral and then starts - it is a lot easier.
 
J

Jonatande

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May 19, 2022
Messages
34
Jonatande said:
Yea, so the engine starts fine hot and cold (say the first start of the day). BUT the second start (like after you start it again after engine been off for 2-3 hours) is much harder.

My starting procedure is always Neutral position, cold semi-hot or hot.

Your comment makes sense from my understanding of the TKS module, it could be that the module is in a bit off-sync with the temprature?

Basically, if I pump one time forward, then go back to neutral and then starts - it is a lot easier.
Click to expand...

cyclops222 said:
My TKS was really odd. It had a normal Thermostatic coiled spring in the black plastic housing. That was adjusted to SLIGHTLY too much pressure on the carburetor Choke Valve on a cold enough day.
The really weird part was how the choke slowly warmed up over time. NOT with engine heat. It has a series of heating resistor steps inside of the choke housing. If the heat power is always ON MAXIMUM ? You would need to do the PUMP ACTION. That SQUIRTS some gasoline into the engine every time you move from IDLE to anything above idle.
The SQUIRT in a Rochester 2 BBL carb I have. Will help with hot and cold weather throttle smoothness.
Click to expand...
Weird thing is that my boat starts really good completly cold, so seems like some functionality of the TKS is indeed working and heat power is not on max.
 
alldodge

alldodge

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Should not need to pump when hot/warm
Could bench test the TKS
Oh and I said it backwards above, retracted cold and extended hot (did edit and fix)
TKS Bench Test.jpg
 
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