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2005 Tohatsu TLDI 50 MD50b2

Xiphias82

New member
Hey

My motor as above is currently not running - It turns over and fires - but doesnt "catch" and continue to run. It has intermittently run for short periods although last time i tested couldn't even get this to run.

Currently being investigated by mechanic - apparently high pressure fuel pump is not making pressure - They have tested with good "regulators" so these are not the issue. I've been advised that first step would be to replace the whole pump assembly at over 1000 dollars locally for parts alone (unsure on labour to replace). I was under the understanding that the pump could be rebuilt much cheaper and can see online non-OEM fuel pump assemblys for a couple of hundred bucks.

Just wanted to get opinions on options here - given the value of the motor, it sort of starts to become questionable whether its worth repairing when repairs are 1000's of dollars.

Second - hes also advised when removing a regulator for the air system that there was metal on it - which he said will be coming from the air pump which may also require replacement and cost quoted was substantial - just unable to fully diagnose due to the fuel pump issue. He did say this may be fine and this may just be from extended cranking (this was me doing this, not the mchanic) with limited lubrication while troubleshooting the fuel pump issue.

happy to get ant thoughts and suggestions

thanks

Matt
 
If the FFP is bad, the OEM replacement is
T5043100MFFP ASSY, D40/50/70/90B (GSC434)$697.30

I would test it. It could be stuck or burned out, or the signal from the ECU could be bad.
The fuel regulator is just 10 psi above air pressure, so if no air, no fuel.
Is the air regulator working? "Metal on it"? Never heard of that. What do you mean?
 
Hi

Thanks for your reply.

They have suggested testing a known working pump if I can get hold of another motor. I do have an acquaintance with the same outboard but still seeing if he will make his outboard available to assist with troubleshooting. I believe they have tested the pressure and advised it's low. They aren't just going off the warning lights etc.

They swapped in a known working air and fuel regulator and no change to the issue.

They just told me when they removed the air regulator there.was metal on it and that this could indicate a fault with the air pump. They were implying when it runs without enough lubrication it can wear excessively and this would occur. The implication was that cranking the engine excessively without it starting can cause this. I did crank it a.fairnamount whilst trying to troubleshoot.

re the third party fuel pump replacements available a good option, or is it better to change the complete assembly as advised

Thanks for.your.assistance
 
What raw pressure did they get from the air pump?
You can use shop air as a replacement for the motor's compressor. You need about 100 psi. The fuel regulator should raire the fuel rail about 10 pounds.
The air pump should be lubricated by the oiling system, even at cranking. It's a pistopn pump. Where would this "metal" come from?
I use OEM parts, so to save a few hundred, I would go OEM.
 
Thanks, the shop working on it are going to be testing with a known working fuel pump Tommorrow so I will know more then. Once I know more I'll look at options for the fuel pump, being in Australia, some of the parts prices.seem.to.be much higher. What are your.thoughts on replacing the whole pump assembly vs just the pump itself?

I'm not sure of the fuel pressure reading they are getting, just that they said it was low. Also, I'm curious if the air pressure should be able to be checked.when the engine only cranks and won't start. It was implied to me that it's not posaible.
 
I forgot to ask, can the pressure only be checked with the OEM Tohatsu pressure gauge? Or is there a generic tool I could use for this to doy own troubleshooting?
 
You could certainly swap a complete vst with pump if your pump tests bad.
Any gauge for A/C or something that goes a little over 100 psi would be fine.
Yes, you need both air and fuel pressures.
 
So latest update is that they swapped fuel pump in from working motor - no change. They then swapped the air compressor in from working motor which fixed the issue. apparently It ran nicely with the alternate air compressor.

So now I'm waiting on a new air compressor to arrive and be installed. They also checked oil feed to the air compressor in case there was an issue there which caused it but apparently this was working fine.

Any suggestions on what i can do to prevent future compressor issues? Ive heard a few people say that TLDI's are a little prone to this if there is any obstruction to the tell tale. I did here someone mention there being a "choke point" where the tell tale was prone to blockage and Im wondering whether anythign can be done to address this (drilling out, changing fittings etc.). The only time i can recall an issue with the telltale was test running it recently whilst running on earmuffs and the telltale didn't initially flow for maybe a minute or so? I stopped the motor and cleaned the telltale out with wire as soon as i noticed and it then started and run. Could this cause an issue? I also generally flush the motor at home on muffs and the water pressure is pretty low at our place, also wondering if that could be a problem.

The motor is getting towards 900 hours and maybe it was just the compressor reaching the end of its life and not any other issue.

thanks
Matt
 
Remember that the fuel pressure is always regulated at about 10 psi above air. You can always use shop air if you have 100 psi for testing.
The compressor is water cooled, but failures are rare, since the lube oil also cools it. Early TLDIs did not have the water cooling feature.
As long as you get a good flow to the muffs, the motor's water pump should be sufficient.
At 900 hours, anything might have worn, but most common is lack of oiling. Be sure to run DFI oil.
 
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