Cristina

Tohatsu m40d2 hot start problems

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Posted (edited)

I'm having issues hot starting this engine. I was wondering if anyone could shed some light on how to fix this issue. 

Today, I dropped the boat in the water and engine started up within a few seconds. I drove around for a good 30 minutes as the weather was awesome and everything ran smoothly. I went back to the ramp, turned off the engine and tried to turn it back on but was having issues. It would crank but wouldn't turn over. I towed it home and tried to start it with the muffs but still had issues. Engine would turn over abit but die.  I disconnected the fuel line, cranked it some more with the choke on and it eventually started. It almost seems like the engine was flooded. 

History: I just recently purchased my first boat. Have been towed back twice due to engine starting issues. Got the engine serviced and had spark plugs changed, new thermal stat, water pump, gear oil and cleaned stock fuel filter. In relation to the fuel line, I changed both fuel connectors on either end, replace fuel vent and added an inline fuel filter. The fuel Bulb and hose weren't replaced but seems to be in good nick. I went on the boat with the mechanic but it ran fine. He didn't try starting it while it was hot so this issue wasn't identified.

If anyone has any suggestions, I would greatly appreciate it. I don't have or know a reliable mechanic and looking for someone trustworthy in this industry as a female is very difficult. I've already been burnt way too many times. Please help!

 

Edited by Cristina

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8 hours ago, Cristina said:

I went on the boat with the mechanic but it ran fine. He didn't try starting it while it was hot so this issue wasn't identified.

That's the key to diagnosing the issue, replicating the conditions in which this happens.

They have a few more electronic systems on them compared to smaller 2 strokes like the CD ignition system so hard to say.

Is it auto choke? maybe its not turning off when hot??

Id be taking back to the Mech & get it checked over again, maybe run it at home for a while before taking it in!

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Hi Cristina, as @kingie chaser said, the key to solving this is to be able to replicate the problem. My gut feel from what you have described is that its ignition related.

Are you able to run it on the muffs long enough to get the engine hot so that the hot restart problem surfaces?

If so, while hot and when it wont start, the first thing I'd do is pull out the spark plugs, and check them for spark when you crank the engine. If there's no spark then you can start working back in the ignition circuit. It sounds like something expands when its hot and you lose the start ignition spark, but when cold the gap closes and you have a complete circuit - it could be a crack in the CD circuit board for instance. 

If you are getting spark at the spark plugs then retrace the fuel path - bulb etc.

Cheers Zoran

BTW, you can browse the following site to get a sense of what components are in your engine - may help you when you talk to your mechanic.

https://www.boats.net/catalog/tohatsu/2005/m40d2-2-stroke-tohatsu

 

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3 hours ago, kingie chaser said:

 

Is it auto choke? maybe its not turning off when hot??

Id be taking back to the Mech & get it checked over again, maybe run it at home for a while before taking it in!

There is no auto choke. There is one under remote controls, where there ignition is and one on the engine. However when the cowling is off, they both move different components. So not sure what the go is.

I cant take it back to that mechanic because he is not responding to any of my messages. I've been burnt by mechanics in the past so i'm really hesitant to look one up without a recommendation.

17 minutes ago, zmk1962 said:

Are you able to run it on the muffs long enough to get the engine hot so that the hot restart problem surfaces?

If so, while hot and when it wont start, the first thing I'd do is pull out the spark plugs, and check them for spark when you crank the engine. If there's no spark then you can start working back in the ignition circuit. It sounds like something expands when its hot and you lose the start ignition spark, but when cold the gap closes and you have a complete circuit - it could be a crack in the CD circuit board for instance. 

If you are getting spark at the spark plugs then retrace the fuel path - bulb etc.

Cheers Zoran

BTW, you can browse the following site to get a sense of what components are in your engine - may help you when you talk to your mechanic.

https://www.boats.net/catalog/tohatsu/2005/m40d2-2-stroke-tohatsu

 

I'll have to try to run it with muffs tomorrow but I'm pretty sure it will do the same thing. If it fails to start after 15 minutes of running, I'll check the spark plugs. As mention in the first post, I've been towed back twice and each time was when the engine was still hot. Usually I manage to get it going again at the ramp when I disconnect the fuel line.  Thank you for the link, I'll definitely check out the engine breakdowns.

So I took a video when I arrived home about 25 minutes from the ramp if this helps.

https://www.youtube.com/watch?v=X7sR-qQIrc4

When I stopped recording, I disconnected the fuel line, had the choke on, turned the key for about 20 seconds and it started.

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18 minutes ago, Cristina said:

When I stopped recording, I disconnected the fuel line, had the choke on, turned the key for about 20 seconds and it started.

So if I read this correctly,  the motor started when it was hot but the fuel line was disconnected. So starts to point that you are getting spark and that its a fuel delivery issue.

I just had a quick look at the video. I don't use inline filters so don't have direct experience with them, but I think they should be full of fuel ... I don't think there should be vapour in there as I see at 0:20 in your video. Maybe you are getting a vapour lock in the line. That would explain why when you disconnect the fuel line, and open the throttle it may clear the vapour lock and the motor starts on the residual fuel that still in the carbie. 

So what could be causing a vapour lock after a long run?

I see an orange fuel tank to the left of the video - can you confirm you are opening the vent on the petrol tank? If the vent is closed the motor will have trouble sucking fuel especially after a long run which would have used up any built up pressure in the tank that helped move the fuel at the start of the run.  

The primer bulb. Please confirm it goes hard during priming- if not, the non return valve inside has failed and is allowing fuel to run back to the tank - could explain the vapour we see in the inline filter.

image.png.297d65229431514e067eff3b6625770a.png

Cheers Z

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Posted (edited)
32 minutes ago, zmk1962 said:

So if I read this correctly,  the motor started when it was hot but the fuel line was disconnected. So starts to point that you are getting spark and that its a fuel delivery issue.

I just had a quick look at the video. I don't use inline filters so don't have direct experience with them, but I think they should be full of fuel ... I don't think there should be vapour in there as I see at 0:20 in your video. Maybe you are getting a vapour lock in the line. That would explain why when you disconnect the fuel line, and open the throttle it may clear the vapour lock and the motor starts on the residual fuel that still in the carbie. 

So what could be causing a vapour lock after a long run?

I see an orange fuel tank to the left of the video - can you confirm you are opening the vent on the petrol tank? If the vent is closed the motor will have trouble sucking fuel especially after a long run which would have used up any built up pressure in the tank that helped move the fuel at the start of the run.  

The primer bulb. Please confirm it goes hard during priming- if not, the non return valve inside has failed and is allowing fuel to run back to the tank - could explain the vapour we see in the inline filter.

image.png.297d65229431514e067eff3b6625770a.png

Cheers Z

I had hot starting issues even before installing the filter.. At the time of installation, I started up the motor fine without it. Installed the filter and started it up again with no issues. Engine was cold though.

I have replaced the fuel vent on the fuel tank as it was corroded shut. I made sure it was open when trying to start the motor. Primer bulb will go solid after a few pumps and the air remains in the filter as shown in the video. I had a thought that if I didn't have a glass cylinder in the line that you wouldn't even know or see there was air or vapour. Once turning the ignition a few times, the bulb will soften up within minutes and the fuel in the inline filter empties and gets sucked into the engine. I'll try bleeding the fuel line and remove all air/vapour.

After the second time getting towed back, I speculated that there was a fuel delivery issue. I replaced the fuel vent and fuel connectors on the tank side and engine side. The vent was corroded shut and I found a tiny leak on the tank side as I saw air bubbles coming out of the connector. Primer bulb was also struggling to get solid. I thought replacing these components would fix the hot start issue but obviously not. I'm not sure how long the bulb is meant to stay hard for as I have nothing to compare it to and my only other experience of boats was when I was a child/teenager. 

 

Edited by Cristina

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Let’s eliminate the tank vent first. Next time you recreate hot start problem remove the tank vent or fill cap. There should be no back suction on fuel line. 

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Hey Cristina, I did some googling and looks like I was on the right path regarding a "vapour lock" being the issue and showing up in your glass fuel filter.  I came across this --

"The TLDI engines have a documented problem with this (it's vapor lock), particularly during hot running conditions. I had a TLDI that did this frequently. I figured out that the solution was to pop the cowling and pump the primer ball, then open the shrader valve on the fuel side of the air/fuel rail with a screw driver or pocket knife and turn the key to on position so the high pressure fuel pump would spin and push the air out of the fuel side of the fuel rail. Once a clean fuel stream was coming out of the fuel rail the engine would start. I love the TLDI engines and I don't think they can be beat for power to weight ratios but this problem is a bit of a pain. The dealers recommend installing an auxiliary, external fuel pump near the tank. The pump gets wired to the engine so that when the engine is keyed on or running the external fuel pump runs and keeps the system primed. If you call a Tohatsu dealership that works on a lot of TLDIs they should be able to recommend a part number for the external fuel pump."

Full article is here: https://www.microskiff.com/threads/fuel-system-not-staying-primed-tohatsu-tldi-40.54290/

BTW, I had a Tohatsu 40hp in the mid-late 80's and the place to call then was Cohoe Marine as the owner was a Tohatsu dealer and used to race them - they may still be the place to call and have a chat ... but I have lost track of Tohatsu since ... hope someone else may be able to advise you on a reputable Tohatsu tech ....

Cheers Zoran

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Unfortunately Warwick from cohoe marine retired years ago his daughter now runs business. I have used tohatsu guy at brooklyn seems ok

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After watching that video, I also believe its a fuel delivery issue,

when cold and running does the fuel filter fill up completely or is it a mixture of air and fuel.

What is it like on full throttle when on the water, does the filter show air bubbles and fuel or just fuel.

Check all connections as they may be letting air in.

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Definitely a fuel problem symptoms are flooded motor. Is the motor a direct injection or carburettor type this will have a major impact on the diagnosis of the problem seems as it is fueling up after motor is turned off. The motor runs fine when restarted it will not be fuel flow problem it will be fuel cut off usually a solenoid possibility of leaking vacuum lines can get technical.

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I really appreciate the replies. As soon as the rain settles down, I will get the cover off the boat and start trying a few suggestions. I'll keep you updated.

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after you checked zorans teats out and if all goood try when not starting when hot .put in neutral and put throttle to full if flooded it should clear even tilt motor up a bit that will help clear flooded motor also cheers dunc333

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Very hard to diagnose but i would do a compression test first, Reason i said that is it could be low on comp when hot expansion of bore piston rings etc then look at fuel spark etc good luck.

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Hey Cristina,

Hope you are making progress with the diagnostics so you can get out on the water again. 

From the video you put up and the tools you were using (volt meter etc) I can see that you are very handy and pretty well know what you are doing - probably more than most. I did a bit more googling and realised that your model Tohatsu is a carbie model - not a direct injection so that vapour lock article I posted previously may not be directly relevant - nevertheless you can still get vapour lock issues with a carbie model.  For now start with the tank vent first as that has caused problems for some folks https://www.cruisersforum.com/forums/f54/tohatsu-5hp-2-stroke-runs-fine-for-20mins-then-quits-and-wont-restart-202569.html

Also, I managed to find a service manual for your Tohatsu. So incase you don't have it you can download from here: https://www.dropbox.com/s/q0ss8sh45lkmcje/Service Manual_3-4 Cylinder 2-Stroke.pdf?dl=0

Just let me know when you no longer need it and I'll take down the link.

Best of luck with it.

Cheers Zoran

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