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2015 Tohatsu Bulb going soft and stalls

T

the riddler

New member
Hello all. New guy here with an issue of stalling out and ball goes south. I can keep it going by staying on the ball and pump it up every 5 minutes. Just started happening the last few trips out. Always drain gas between trips if won't be using in a week. I replaced fuel filter, spark plug, checked for leaks, checked for obstruction or debris in the fuel tank fittings and tube and everything seems to be fine.

I ran the motor, took the hose off the suction side of the fuel pump and nothing at all. No suction that I can feel. Put the hoses back on, pumped up the bulb, started her up, took the top hose off to see if there is a stream of gas, there was a little and then it stopped. Photo below is the hose off with the motor running.

tohatsu.jpg

I'm just an amateur, but it appears to be a fuel pump problem. I would think the gas should be coming out of the top but not sure how the fuel system operates.

I'm under warranty but just want to make sure I have an understanding of the cause before I go to warranty it. Doesn't appear to be a carb problem, but just want to check here first.

Thanks again for a great Forum!
 
For the heck of it I cleaned the carbs. Problem still exits. I took a video of the fuel pump and have no suction but gas will come out the inlet. It's looking like the fuel pump but not quite sure.

 
1. Always specify exact model when describing a service issue. Year is irrelevant.
2. Based on the pix and your description, I assume you have an MFS4/5/6C; since you are talking about a primer bulb, probably the 5 or 6. If you have a fuel shutoff lever on the port side of the motor, what position is it set to? On a dual-tank setup, that valve closes off the integral tank. If that valve is open, and the integral tank is empty, the motor will run out of gas when the air from the integral tank gets into the lines, even if the external tank is full.
3. The primer bulb is on the suction side of the pump, so if it's a long vertical rise to the motor, or if there is restriction in the tank (clogged strainer or vent) or leaky quick-connect o-ring, the bulb will normally go soft. The better the pump draws, the softer the bulb will become if there is a restriction -- it can actually suck flat in an extreme case.
4. What method did you use to clean the carburetor, and why did you do that?
5. Why did you change the fuel filter?
6. When the carb bowl is full, no fuel will flow, so looking at the suction side of the pump when the motor is running may not mean much. However, if you have a running motor, and disconnect the pressure side of the pump, it should squirt in pulses at camshaft speed.

Since you are under warranty, I would recommend you see your dealer for a diagnosis and repair.
 
pvanv said:
1. Always specify exact model when describing a service issue. Year is irrelevant.
2. Based on the pix and your description, I assume you have an MFS4/5/6C; since you are talking about a primer bulb, probably the 5 or 6. If you have a fuel shutoff lever on the port side of the motor, what position is it set to? On a dual-tank setup, that valve closes off the integral tank. If that valve is open, and the integral tank is empty, the motor will run out of gas when the air from the integral tank gets into the lines, even if the external tank is full.
3. The primer bulb is on the suction side of the pump, so if it's a long vertical rise to the motor, or if there is restriction in the tank (clogged strainer or vent) or leaky quick-connect o-ring, the bulb will normally go soft. The better the pump draws, the softer the bulb will become if there is a restriction -- it can actually suck flat in an extreme case.
4. What method did you use to clean the carburetor, and why did you do that?
5. Why did you change the fuel filter?
6. When the carb bowl is full, no fuel will flow, so looking at the suction side of the pump when the motor is running may not mean much. However, if you have a running motor, and disconnect the pressure side of the pump, it should squirt in pulses at camshaft speed.

Since you are under warranty, I would recommend you see your dealer for a diagnosis and repair.
Click to expand...


Thank you Paul. I changed the filter and cleaned the carb because I was on the road with no service center other than a west marine. Had to finish my trip, that was the best I could do.

Good point on the fuel pump. It sputters gas out of top and then stops and won't continue. There is no suction on the other side.
 
If you didn't completely disassemble the carb and soak all non-rubber parts in real carb dip for at least 4 hours, you did not clean the carb. If you sprayed generic carb spray through the throat, all that happened was that the venturi got shiny.

If the pump does not develop either a suction on the in side and pressure on the out side, you may have a bad valve in the pump. If so, in our shop, under warranty, we would change the pump and the o-ring where it mates to the block. If the pump does in fact push fuel out the pressure side with every second cycle of the crankshaft, it is probably working OK.

West Marine services Mercury, which means they can service Tohatsu motors (since the small Mercs are actually Tohatsus), but it would not be a free in-warranty repair.
 



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Went to the dealer and they are looking at a two week turn around for warranty work. Can't wait that long in New England while the Striped Bass are roaming.
Figured it out. Put clear tubing on the outlet of the fuel pump and another after the filter. Primed her and started her up and you could clearly see no flow. It would run only if the primer bulb was pumped. Confirmed no vacuum leaks or check valve issues. Pulled the pump apart and inside the diaphragm I saw a bunch of gummed up ethanol marks looking like varnish or residue. I cleaned everything up with sea foam and carb cleaner and soaked all parts for 3 hours. Put it all together and fired her up and bam it worked.



https://vimeo.com/172486264


I followed the suggestions of emptying the carb If going over a week in between trips. I used additives and always fresh gas. Still the pump apparently got gummed up.

Im gonna hit up the marina and the non ethanol fuel for now and stick with the additives.


Thank you Paul for the help. Appreciate it!


Jeff

Boston , MA

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