Anyone seen this before? Tohatsu 50B

[jlh29]

I have a 2006 50 TLDI that won't idle and fouls the plugs immediately on start up. I chased a possible fuel/air problem at first but found everything working normally on that end. I tested the TPS, it failed, I replaced it and reset it - no change. Plenty of voltage to the coils. I'm now looking at the rectifier which failed the resistance test and the motor runs normally when I take it out of the system. I'm pretty sure I have it solved but was wondering if anyone had run across this? These motors are a challenge.

 

[pvanv]

Re: Anyone seen this before? Tohatsu 50B

I must admit that you have an unusual symptom/result. Did you test the rectifier with a good analog ohmmeter? Typically with an idle fouling problem, after going through all the routine stuff, such as TPS (most common issue) and crank position sensor, if the pressures and leakage on the air and fuel rails are OK, you would then be looking at the ECU.

BUT... since the rectifier tests bad (is it charging?), that could throw off the whole 12v supply, which in turn could possibly cause the ECU to malfunction. The rectifier is a 4-diode bridge, and a single (only) dead diode could conceivably cause the charging system to put some nasty interference into the 12v supply... which could in turn cause the ECU to do all sorts of odd things. Remember that on these DFI motors (of any brand), the ECU power connections are critical, so also VERIFY all connections.

 

[jlh29]

Re: Anyone seen this before? Tohatsu 50B

Thanks Paul, I really appreciate your input. It was charging the battery, that's what was making me doubt. I replaced the rectifier, no change.. I'm thinking it must have to do with voltage because it will run with the rectifier unplugged. I guess I need to look at the stator, figure out how to measure the voltage. I was only getting 3 volts measuring to ground. Maybe measure between the yellow wires because that's how the resistance test is done? It passed the resistance test but, no, I only have a digital meter. I didn't realize until now that I needed an analog meter for these motors.

 

[TOHATSU GURU]

Re: Anyone seen this before? Tohatsu 50B

It would make it a lot easier if you used the engine's onboard diagnostic computer to tell you what is wrong

 

[jlh29]

Re: Anyone seen this before? Tohatsu 50B

Thanks, I've been using the self diagnostics right along.

 

[pvanv]

Re: Anyone seen this before? Tohatsu 50B

Thanks, I've been using the self diagnostics right along.

Are you getting any codes?

 

[jlh29]

Re: Anyone seen this before? Tohatsu 50B

I had the common low voltage codes along with TPS codes. After I reset the ECU and TPS they wouldn't come back until I cranked the motor trying to get it to start. Being able to run the motor with the rectifier unplugged I realized #2 was dead at idle but would cut in off idle. Did a BDC leak down test and it came out of the throttle body, pulled the intake, missing half of a reed valve in # 2. I'm still a little unclear as to why it will run on 2 cylinders with the rectifier unplugged but not with it plugged in..... I might have 2 problems, or is it stealing voltage or grounding?

 

[TOHATSU GURU]

Re: Anyone seen this before? Tohatsu 50B

I think I would fix the reed issue before doing anything else.

 

[jlh29]

Re: Anyone seen this before? Tohatsu 50B

Well yeah, , I should have my parts tomorrow. Hoping the rectifier is a coincidence but still wondering.

 

[jlh29]

Re: Anyone seen this before? Tohatsu 50B

Well I fixed the reed and it's running great. Learned a lot on this one. It will run on two cylinders with the rectifier unplugged. The symptoms sent me all over the map.