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Tartu56

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Tartu56

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I have a 2007 4.3 litre mercruiser with the TKS ignition that has continuously caused me grief when after starting right up cold will not restart when engine has run for a while and is hot. It will turn over but not fire like carb is flooded. If I leave it until next day it starts immediately when engine cold but same problems after I run out to fishing grounds and shut motor off. I have replaced cool, distributor, plugs but still same problem. Anyone ever run into this that can give me advice?
 
Sounds like leaking injectors or a slow flooding carb--you didn't mention which one you have. If it's a carb, a quick fix is to install a fuel shut off valve before the carb and turn it off just before ****ting down. If it's injected, a deliberate fuel leak around the pressure regulator valve will dump the fuel pressure automatically when you shut down--had to do that to a car I once owned. A hole drilled someplace or a circuit around the regulator (with a needle valve) accomplishes the deliberate leak.

Then again, you could get the carb professionally rebuilt/ or the injectors cleaned.

Jeff
 
Jeff, sorry on the post, it is a carb model and I had new carb installed last year. Problems did not disappear as once engine hot I would get some diesiling before engine shut down. Boat woul restart again after a few hours of cooling down. This past week engine would not start after running hot. I could try a fuel shut off before the carb though.
 
TKS Starting Characteristics
On 3.0 L models - If the engine has not run for a long period of time, it might require a
couple of attempts while the fuel bowl refills. Once the engine has started, it will idle at
700-900 RPM.
On 4.3 L, 5.0 L, and 5.7L models - If the engine has not run for a long period of time, it
might require a couple of attempts while the fuel bowl refills. Once the engine is started, it
will idle around 650 to 700 RPM in idle stabilization mode. If the idle exceeds 700 RPM,
the ECM adds spark, thinking that the operator is trying to accelerate, which could cause
the engine to idle at 700-900 RPM. After the TKS module has shut off the enrichment circuit,
the carburetor will function like a standard carburetor. If the engine is out of idle stabilization
mode, (engine below 700 RPM), you will hear and feel a slight drop in RPM. After the TKS
module has shut off the enrichment passage, the carburetor will function like a standard
carburetor.
 
90-866202 DECEMBER 2004 Page 1C-5
5. If engine still does not start, refer to "Engine Does Not Start."
HARD START - HOT
If the engine does not start when the engine is hot, the probable cause of hard hot-restarts
associated with the TKS carburetor will be the inadvertent opening of the additional fuel
flow path. The temperature switch was added to the system to keep power to the TKS
module to prevent the additional fuel flow path from opening during hot re-starts.
1. Check coolant temperature.
2. If the coolanttemperature is above 43º ± 3º C (110º ±8º F):
a. Verify that 12 Volts Positive (+) and ground (-) are getting to the TKS module. See
Section 4G for details.
b. Operation of the TKS module can be confirmed by placing your finger on the end
of the plastic TKS housing in the center and feeling that the electric heater is
getting warm. A warm TKS module after engine has run for 6 to 10 minutes
confirms that TKS is functioning electrically. See Section 4G for details.
3. Verify that the TKS Module is functioning normally. Follow procedure in Section 4G.
ENGINE DOES NOT START
The possible root causes of the fuel path not functioning include:
• The TKS Module failed in the closed position. See Section 4G and Section 5G.
• The fuel has varnished. See Section 5B.
• There is debris in the fuel path. See Section 5B.
• The float level is out of specification. See Section 5B.
If the engine does not start, check the following:
1. Check that float bowl is full of fuel.
2. Check that the mechanical fuel pump is working. Attach a fuel pressure gauge to the
mechanical fuel pump to verify it is working correctly.
3. Check the enrichment jet emulsion tube, TKS enrichment jet, and the main jets for
damage or debris.
ENGINE DOES NOT IDLE CORRECTLY
If the engine does not idle correctly after starting, verify that the enrichment cycle is fully
closed before adjusting checking the following:
1. The engine idle RPM has been set correctly with a warm engine.
2. Verify the timing of the engine in the base timing mode.
3. Verify there is voltage on the Packard connector attached to the TKS heater.
4. Check the enrichment jet, emulsion tube, and the main jets for damage or debris.
HISSING NOISE
There is a small enrichment air passage for the TKS system in the throat of the carburetor.
Air is drawn through this passage when TKS is in starting mode and does create a slight
whistle or hissing noise. After 6 to 10 minutes when engine has warmed and TKS system
has closed the noise will quit and will only occur again after a cold engine start. If this noise
continues after 10 minutes, this could indicate a problem with the TKS module. See Section
5B.
 
The easiest first check... is the wire to the TKS module attached and is there +12 on the connector pins when the engine is hot and ignition is on ? This wire provides power to the TKS circuit that will EVENTUALLY ( AFTER engine gets warm, above about 130F) shut off the enrichment circuit, i.e. the "choke" function. If this wire is not attached or the temp switch defective, then the TKS carb, will on a hot restart, be very "rich".
 
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