tohatsu 30hp ecu

[Michawilden]

Hi,

I got a 2006 mfs30 tohatsu, 3 cylinder tiller hand start. It is a new to me engine. Sat for a year and the previous owner cound't get it to start over the winter.
The problem with the motor is that it wont start ( no fuel in cylinders) If I put some fuel in the top cylinder it will run for a second and die.

Some diagnostics that I did:
1. Checked for spark, it has spark
2. No fuel pressure, if i remove the valve on the fuel rail, no fuel will come out when I try to start the engine. If I put 12 volts directly on the pump it pumps like mad so no voltage to the fuel pump when I try to start it. With the 12 v directly from a battery, I tried to start the engine but still no go.
3. No trigger signal to the injectors. If I remove the injectors and try to start it ( with the 12 v from the battery on the fuel pump) No fuel is injected / sprays from the injectors. Also, when I put 12 volts directly to it, It opens up and sprays fuel.
The weird thing is that if I check the readings on the wires to the injectors, it gives a reading up to 13.5 v.

Naturally I suspect the ECU. The question is, Is that 100 % the case? Or am I missing someting?

It the ignition works the stator provides power to the ECU. Is that the same power source for the fuel system or can I have a problem with the power supply? Is there a fuse somewhere? Or some trigger sensor that can be faulty?

As I said, the engine is new to me. The only thing I know how to start the engine is to put the lanyard in place. Or is there a hidden switch?

 

[pvanv]

You need a Factory service manual. Either the ECU is bad, or it is not getting power.

 

[Michawilden]

My ignition works. That is also controlled from the ECU. Is that is also powered by the same power source as the fuel injection? If it is the same power source I can conclude that the ECU is bad.

I found a manual. It has an exciter coil, a ECU/ charge coil and a charge coil ( goes to a rectifier). Both the exciter coil and the ECU charge coil wires go to the ECU. I hope the fuel part is powered by the charge coil and the ignition with the exciter coil and that I need a new stator instead of the ECU. In the manual I found the values so I can do some tests.


Here the wiring diagram:

Tohatsu MFS 30 Схема электропроводки онлайн [65/67]

Tohatsu MFS 30 Подвесной Лодочный Мотор Схема электропроводки онлайн Страница: 65

mcgrp.ru

 

[Michawilden]

Oke. Got the motor running. For future owners with the same problems:

With the service manual I started to measure all the sensors on the big plug to the ECU. Exciter coil & charge coil wires gave a correct reading. This motor has two pulser coils. One of those gave an infinitive resistance. Measuring on the plugs of the sensor it gave the correct reading and with the 2 plugs back in place I got the correct reading again on the ECU plug. Cleaned it up but I think it was already slightly lose. Tried to start the engine without any battery voltage on the fuel pump, still no go.

When I put 12 V on the fuel pump. The engine started right up! So still no power to the fuel pump. On the wiring diagram the injectors and fuel pump share the same 12 V supply with a blue wire. The ECU ground the injectors on the right moment in order to inject fuel. Those where working so the 12 V supply had to be good ( or had a broken wire to the fuel pump but a resistance reading gave almost no resistance) So the ground had to be bad. resistance on the negative wire from the fuel pump was also zero the the plug so no broken wires.
The only thing the ECU does ( I think and hope) Is continiously ground the negative wire ( blue / black) for the fuel pump to run. But it doesn't do that.

If I ground the negative from the fuel pump to the engine casing the pump will run continiously when you start the engine. So my work around is to ground the negative wire ( blue / black) from the fuel pump direct instead of trough the ECU.

So, yeah. The ECU is bad but 1500 euro for a new ECU or 50 cents for a new ground wire is an easy answer.

Hope this might help someone in the future.

Thanks for the reply PvanV

 

[Oceanblue]

Michawilden Thanks for the tip. My 2006 Tohatsu 30hp had similar problems & now has the same work around and runs fine.​