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2018 MFS20E won't start, No Fire

J

justind1407

New member
Hi Everybody! 👋👋

I'm new to the forum and outboard engines but I'm fairly mechanically inclined.

Recently I purchased a used 2018 Tohatsu MFS20E off Facebook for a great deal to install on my 1540 Jon boat. I assumed there may be an issue with the motor since it was cheap therefore I threw the motor up on a stand to give it a once over before installing on my boat and low and behold I can't get it to start. The motor looks like its never even been ran but I can't tell for sure. It didn't come with a prop and the spark plugs look nearly new so If it was ran it wasn't very long.

First off I disconnected the kill switch and checked continuity with and without the kill lanyard installed and the switch appears to be functioning correctly. Secondly I removed each spark plug 1 at a time and held them to a bolt on the engine block that was unpainted and I don't see any spark. What if anything can I check on these newer EFI motors that may help be do some diagnostics on the ignition circuit. Thanks!
 

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We'll I went and looked at the engine last night again because I wasn't convinced that the ignition system was at fault for my "no start". When I tested the spark plugs for spark a few nights back my wife was manning the pull cord and I guess she wasn't strong enough to cause them to fire. Last night I purchased a spark plug tester and put it inline with the plug and coil wire and could clearly see spark when I was turning the engine over.

Next I will focus my attention over to the fuel side. I sprayed a good shot of starting fluid into the intake and after about 5 pulls it ran for about 2 seconds so I believe I may be on the right track. Someone told me that the fuel rail should be under pressure after priming the hose bulb and I can press the Schrader valve with no release of fuel or air.

Could a replacement fuel pump be next?


pvanv said:
Use the Factory service manual to test the ignition system.
Click to expand...
Do you know if this manual is available to view online anywhere?
 

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@pvanv Is there a way to test the Low pressure pump to rule it out before jumping to the high pressure pump? The fuel inside the engine smelled awful when I got this motor so I assume it has not been ran in years possibly killing the high pressure pump.
 
The low pressure pump is only a few psi, so if you disconnect it at the output, see if any fuel flows. If the FFP is credded up, you might get lucky cleaning it. YMMV. Service manuals are copyrighted, so no online versions.
 
This weekend I tried the B-12 soaking method. Unfortunately I was unsuccessful in getting any fuel to pass thru the pump. Next I dug into the High pressure fuel pump assembly and found a mess. Thick sticky gunk stuck to everything. This unit needs a new pump and filter along with a THOUROUGH cleaning...

@pvanv do you know if there is a better aftermarket fuel pump I should look for or if another OEM Tohatsu pump and sock is the ticket?
 

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Circling beck to this thread. I received the new fuel pump and installed it this week. She fired up and purrs like a kitten. Thanks for the help @pvanv

What is the typical idle RPM for this engine?
 

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I’m back with more problems with this engine. I replaced the high pressure fuel pump and thoroughly cleaned out the VST as well as the fuel filter but I’ve still got some running issues with this outboard.

When the motor is on the stand running with muffs it will run perfect. It idles great and will run fine at all RPM ranges. The problem occurs under load in the lake.

I can launch the boat into the lake and it will idle great for what seems forever. I can cruise around for several minuets at around the 3500 rpm range with no issues. Once I open it up to WOT at 6100 rpm’s (I’m slightly under propped) after about 2 minuets of cruising the motor will start cutting out heavily and jarring. I can slowly bring the boat down back to idle and it will still continue to idle great. I can put the engine in neutral it runs fine. Once I put it in gear again it will do the same thing after about 3500 rpm’s and up. Once the cutting out trend will continue until I let it cool completely back down.

I do have a brand new tank and fuel line/bulb as well and the primer bulb is always hard once running. Any ideas? The red light isn’t coming on during this trend either. I’m stumped. What could be happening once the motor is hot to cause this?

After the first time this happened on the lake I came home and took the VST back apart to reinspect my work and everything there seems fine. I spoke with a Tohatsu support tech and he recommended cutting removing cotton and mesh completely off the internal VST fuel filter just to ensure the motor was getting enough fuel so I did just that. Today i went out to the lake again for more testing and the problem is still there just the same.
 
pvanv said:
Check float height.
Click to expand...
I adjusted the float so that the needle would start filling as soon as the float dropped and took it for a test run. It ran great for a couple hours yesterday. We ran probably 8 miles or so with many periods of WOT as well as multiple startups.

Then all of a sudden after 1 startup the problem was back and continued the same old trend for the duration of the day 😭
 
justind1407 said:
I’m back with more problems with this engine. I replaced the high pressure fuel pump and thoroughly cleaned out the VST as well as the fuel filter but I’ve still got some running issues with this outboard.

When the motor is on the stand running with muffs it will run perfect. It idles great and will run fine at all RPM ranges. The problem occurs under load in the lake.

I can launch the boat into the lake and it will idle great for what seems forever. I can cruise around for several minuets at around the 3500 rpm range with no issues. Once I open it up to WOT at 6100 rpm’s (I’m slightly under propped) after about 2 minuets of cruising the motor will start cutting out heavily and jarring. I can slowly bring the boat down back to idle and it will still continue to idle great. I can put the engine in neutral it runs fine. Once I put it in gear again it will do the same thing after about 3500 rpm’s and up. Once the cutting out trend will continue until I let it cool completely back down.

I do have a brand new tank and fuel line/bulb as well and the primer bulb is always hard once running. Any ideas? The red light isn’t coming on during this trend either. I’m stumped. What could be happening once the motor is hot to cause this?

After the first time this happened on the lake I came home and took the VST back apart to reinspect my work and everything there seems fine. I spoke with a Tohatsu support tech and he recommended cutting removing cotton and mesh completely off the internal VST fuel filter just to ensure the motor was getting enough fuel so I did just that. Today i went out to the lake again for more testing and the problem is still there just the same.
Click to expand...
Last time my motor acted like that I ran some lucas fuel injector cleaner and cleared up eventually that same day of running on th water
 
Final update!!!

The whole cutting out problem ended up being the primer bulb. It was new but broken. I cut it open and one of the check valves was restricting flow. A new primer bulb solved the problem.
 
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