2004 TLDI MD90, unable to pull any codes/engine hours and no beep when turning key, cranks up fine

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Hi guys,

Recently bought a used 2004 TLDI MD90 from a friend, he said everything was running well on his boat when he pulled it a few months ago. I got the controls, wiring and gauges from him as well.

Got it installed on my boat yesterday by a local mechanic and took it out for a sea trial today. She fires up instantly and idles fine, an occasional slight rpm surge, but she is running LOUD (maybe normal?) and vibrating alot, pissing water just fine and not overheating but with the noise/vibration I was worried to get too far from the marina

I stuck her back on the trailer and came home to do some more research.

I am trying to check the codes or pull the engine hours via pushing the key in on the ON position for 5 seconds, but it is not doing anything. When I first turn the key to ON, all 3 of the dummy lights do light up and turn off in a second or 2 as expected.

I also noticed I am not getting any chime when I turn the key to on.

The person who installed the motor was not very familiar with TLDIs so not sure if he possibly hooked something up incorrectly to the tach?

Any ideas on why I would not be able to pull the codes, or at least check the engine hours? Also why no chime on key turn?

I am down here in Baja, MX, unfortunately these motors are not distributed here so not many mechanics are familiar with them

 

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the tach did work and show RPMs while in the water

 

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repost

 

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hmmm I am reading about both the battery and throttle position being issues, both of which have changed since we moved the motor to a new boat, I tracked down the MD90 service manual


tomorrow I will buy a new battery and do the throttle cable adjustment procedure to get her dialed in, I will also double check the grounds

Still not sure why that would lock me out the diag mode and eliminate the ON buzzer, so perhaps not related

 

[Sea Rider]

Buy a marine battery factory recommended for that motor, tech specs are in the Owner's Manual...

Happy Boating​

 

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Alrighty, went out and got a brand new batt with 950cca, my buddies was only like 600 and 1/2 dead

still having issues she’s running rough and idling poorly, if I try to give her gas she will rev up and then die

kind of seems like something related to the TPS

i also discovered a wire had pulled out of the back of the Tach remote control harness which explains why I wasn’t getting any codes or feedback from the motor at the start switch, also found my buzzer wire was cut.. fixed both those issues, now I have the buzzer and am able to pull codes, there were none stored, ran the motor for a while, still not throwing any codes, if I pull the TPS when she is running it will throw a code so I know that’s working

Also learned she has about 600 hours on her according to the tach

i am looking over all the wiring now, wiring looks fine at the motor but the wiring up at the controls is a bit suspect

I recorded a video of her running, and me changing gears around, then back to neutral, u Can hear how erratic and loud she is

 

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Can we confirm that these battery cables are hooked up to the right spots? Can’t seem to find that in the service manual

https://imgur.com/w89fQim

and should this air box just be sucking air here or is there a tube it should be connect too

https://imgur.com/A0SYUk1

 

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cleaned up all the wiring, cleaned all the grounds i could find, reset the TPS/ECU, and fired her back up

same problem :-(

let her idle for about 15 mins, still no codes

the way she is jumping all over the place and responding strangely to throttle/dying when we rev her up makes me think its something related to the TPS


I am hunting aroudn town to see if anyone has the particular air/fuel gauges needed to run tests on those systems

 

[MattFL]

Did you check if the TPS is faulty? Watch your meter while you slowly open and close the throttle, the voltage should change smoothly. Any jumps or gaps indicates a problem. If you don't have a meter, this one works great and powers the TPS so you don't even have to have the motor powered up:

Amazon.com

 

[pvanv]

OK, looks like you have an MD90b. Model is critical; year is irrelevant. Yes, the wiring and air filter look OK. What are the air and fuel rail pressures?

 

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OK, looks like you have an MD90b. Model is critical; year is irrelevant. Yes, the wiring and air filter look OK. What are the air and fuel rail pressures?

thanks for the reply, I will get back out there and check on those pressures tomorrow

 

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Got back out there today, found a mechanic in town who had both styles of fuel/air pressure gauges (basically AC gauges) and we pulled the fuel pressure, looked good, pulled the air pressure and it was super low ~30psi, hmmm

removed the air filter, still no pressure

Mechanic said he had worked on Optimax in the past and had seen the gaskets in the air compressor fail, so he started tearing into it, ended up breaking off 2 of the rusted bolts in the pump, bit of drilling and ez-outs later we eventually got it apart down to the piston inside the compressor

found the piston to be very loose in the cylinder, lots of side to side play, not sure if its the cylinder walls, rings, or the piston itself but something seems screwed up and explains why she is not making any air pressure

After a bit of hemming and hawing with the mechanic on what we could do I recalled reading a post by @pvanv that mentioned you could bring in outside air and pump it into the motor, as long is it was within the proper psi specs it should work

So mechanic went to his house and brought over a pancake compressor with variable pressure, we wound it up to around 90psi and cranked her up, she ran great for a few seconds and then started to die as the psi dropped off in the small compressor... hmm we need a bigger tank!

luckily i know a guy in town with just the tool... called up our mobile tire repair guy and he drove on over

he thought it bit a weird when I told him what the hell we were trying to do, but he was game

Unfortunately his compressor was dialed in at 220psi and the knob had long rusted shut, so i had him cut off the compressor motor and i just drained the air from the tank by holding down the nozzle valve, eventually got it down to ~90psi, jammed the spray nozzle down the air hose on the motor and had a buddy crank her up

ran like a friggin top!!

I had him rev it all up and down, all over the place, she finally sounded like a real motor!

problem located!! lots of celebrating all around as at this point pretty much everyone in the town knows about me trying to fix this motor


now... how the hell to replace/fix this Tohatsu air compressor in the middle of nowhere Mexico...

the saga continues but I am just glad to have finally pinpointed the problem

 

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welp I got an entire new to me (ebay used) compressor on there and still have the same problem, I had my buddy with the truck with big air compressor come back over and if we shoot air straight into the hose where the air compressor is going into the air rail, bypassing the compressor, she fires right up and runs great

So either this used compressor is junk as well... or something else crazy going on, any other reason that the compressor wouldnt put out enough air?

the belt looks fine, flywheel looks fine, pulled the air filter off as well to check, no issues there

If I crank the motor to start up with my air pressure gauge attached i can see it only builds about ~30psi and wont fire up, if I give it about 1/2 throttle I can get her to fire up, she revs up to 4000 but she dies if I try to bring the RPMs down below ~2.5K, I assume because the air pump isnt putting out enough psi to keep it running

I pulled the oil send and return lines to the pump and can see oil flowing there, so i assume its ok

 

[pvanv]

check your regulators...

 

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check your regulators...

si amigo, I found the air regulator was busted and full of crud!

New thread here, thanks for your help!!

Tohatsu MD90B TLDI, Running poorly, Fuel pressure lower than air pressure

Figured I would start a new thread since my other issue was resolved. I am still working on getting this MD90B running, previous owner reported it ran well when he pulled it, ~8 months ago. When I got it installed on my boat I could get it to run but it was running very poorly and would die...

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