Startproblem Tohatsu/Nissan 90 HP, 2 stroke, 1992

[ullandhaug]

I am located in Norway and am struggling with engine starting problems when I should be out on the fjord!

Problem:
The engine is hard to start when it is cold. (The starter motor works well and stop-signal to the CDI box is deactivated). The engine starts easily when warm. It runs well at high rpm but not so well at lower rpm.

Troubleshooting:
I have checked fuel line from tank, hose, pump and cleaned the carburetors. Seems like the spark plugs gets wet by fuel and that the air/fuel rate is correct. (The spark plugs are new and of correct type). I have also tested with the control cable disconnected to eliminate cable errors. Checked that the compression is the same on all 3 cylinders (9 bars - approx. 135 PSI). Have verified that there is spark on all the 3 cylinders when the engine is running and that all are firing. I have checked the choke.

It seams like there is week spark when starting the engine. I have measured the resistance in the exciting coil under the flywheel to eliminate broken coil wire.

How I start the engine:
Fill the tank up with new petrol (95 octane), open the tank vent valve, manual pumping fuel, set the idle speed on full, presses the key to activate the choke and turn key for 30 sec. Then I repeat this for 5-15 times, sometimes with and sometimes without choke, and the engine finally starts. Run it for one minute, and it starts easily after that. (I have also experienced staring problems when warm).

Questions:
1) When I try to start, it seems like the engine fires when I stop cranking. Can there be some issue related to ground of the battery power?
2) How can I find out / measure if the problem is related to ignition coils, CDI, or stator exiting coil?
3) Any other suggestions?

Thank you for any help on my problem!

 

[pvanv]

Re: Startproblem Tohatsu/Nissan 90 HP, 2 stroke, 1992

"Questions:
1) When I try to start, it seems like the engine fires when I stop cranking. Can there be some issue related to ground of the battery power?
2) How can I find out / measure if the problem is related to ignition coils, CDI, or stator exiting coil?
3) Any other suggestions?"

1- You may have a low voltage issue, caused by low battery or a poor connection. OR, and this is rare, but I have seen it... you may have an ignition switch (or wiring) fault, causing the IGN line to go dead during cranking. To prove that out, you can set the switch to "run" and verify power at the ECU, then jumper the starter solenoid manually. If it fires as expected, then you know there is a wiring/switch fault.

2- A service manual would be good to have. Don't bother with the aftermarket doorstop manual, get the real Factory manual from a dealer.

I have had customers who over-choke, and don't throttle up enough at cold start. Wets out the plugs, which then won't fire. The 2-strokes, especially when older multi-carb variety, like the warm-up lever up quite a bit, then crank, and only push-to-choke as needed, in bursts.

 

[ullandhaug]

Re: Startproblem Tohatsu/Nissan 90 HP, 2 stroke, 1992

Thanks for answer.

I have tested with the control cable dissconnected and then jumper the starter solenoid manually. The same problem still. What is ECU and how to verify power on it? (Is it the DCI unit?)

I got at tip that the start-motor may have an error, making it using too much current. And that this can result in loss in voltage to the coils. (Because the engine fires when i stop to crank, not during cranking.)

Can this be the case? How can I verify if this is the problem?

 

[pvanv]

Re: Startproblem Tohatsu/Nissan 90 HP, 2 stroke, 1992

Thanks for answer.

I have tested with the control cable dissconnected and then jumper the starter solenoid manually. The same problem still. What is ECU and how to verify power on it? (Is it the DCI unit?)

I got at tip that the start-motor may have an error, making it using too much current. And that this can result in loss in voltage to the coils. (Because the engine fires when i stop to crank, not during cranking.)

Can this be the case? How can I verify if this is the problem?

Yes, you could have a bad starter, drawing too much current. That could be caused by an electrical fault in the starter, or by bad bearings in it. If the voltage to the ignition coils drops during cranking, that COULD result in a loss of spark. Is the battery a good one, and big enough? Poor batteries sometimes cause problems like this. Are all connections verified clean and tight?

 

[ullandhaug]

Re: Startproblem Tohatsu/Nissan 90 HP, 2 stroke, 1992

Thanks for all help. It seems like the main problem was over-choke. When I start without choke, without pumping the manual fuel pump and with full throttle, it starts much easyer