40HP TLDI Problems

[OzzyTLDI]

Hello, I have a 40HP TLDI (MD40B2), I run the correct spark plugs, correct battery, recommended oil and fresh fuel, this engine is fantastic when running a speed / high RPM, however when trolling it runs for period of time (approx. 20mins) then just stops. I have replaced spark plugs, batteries, had it at the dealers who can't replicate the issue in the shop and its not showing any fault codes, noting that this engine has done this from new and it appears that this maybe a common issue after reviewing a few forums online, however I have not been able to find an fixes for this issue? Any feedback would be appreciated, so frustrating!

 

[pvanv]

Does it restart right away? What speed (RPM) are you trolling? What maintenance has been done? What fuel are you running? How many hours are on the motor? Are you running synthetic oil? Are you running IZFR6Q plugs? Did the shop reset the TPS initial setting? What size (CCA) battery are you running? Is your serial number between 003989AX~044507AX?

 

[OzzyTLDI]

Thanks for your response. Yes the engine starts straight away every time, I'm trolling between 700rpm - 900rpm as per the key settings on the control allow me. The engine has 107 hours, serviced as per the service manual and the serial number is 024648AB. I am also running the synthetic oil (DFI), the correct plus (which have now been changed 4 x times) and a 1000 CCA battery, brand new / fully charged last outing. The Tohatsu dealer assures me he has reset the TPS and they are as frustrated with the problem as I am and also noting the engine does has altitude kit fitted and the engine does not stop at idle only when trolling.

 

[pvanv]

You have a tough one, Ozzy. One issue any shop will have is that if it doesn't break for them, they can't diagnose it. Slow trolling could foul plugs -- especially if you were not running synthetic oil, so the faster troll is better, but that does not seem to be your issue. Are you so high up that you need the high altitude kit? So odd that it only happens in gear. I wonder whether you might have a bad wire in the RC cord or control. Or a problem at the ECU.

 

[OzzyTLDI]

I have read online that this particular problem ha seen rectified by cleaning the air rail? What are your thoughts on this? Why would cleaning the air rail resolve the issue?

 

[pvanv]

If I had this one in my shop, I would verify fuel and air pressures. I can't imagine a problem that needs the air rail to be cleaned -- never seen that, but I suppose it can't hurt. Of course, check injectors also, but since it did it since new, they are probably not the issue. However, if a pressure regulator is off, that could cause some weirdness. On the MD40A and B, the pressures should be 80 psi air, and 90 psi fuel. For the B2, the pressures are a bit higher, 94 and 104. Always 10 psi differential. If the pressures are too high, check the regulator, or look for a bypass restriction. If too low, check the air or fuel systems for a restriction, leak, or lack of production. If BOTH pressures are low, it's usually an air problem -- if only the fuel pressure is low, it's typically a fuel problem.

 

[TOHATSU GURU]

Hint: Look at fuel delivery from tank to engine. No fault code on the engine is a good indicator that the engine itself is not the issue.