Tohatsu 40HP 40 TLDI Wont Run Below 2000 RPM and Requires Half Throttle To Start

rustnrot

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I have a 2004 Nissan 40 HP TLDI tiller model. It will not start and continue to run with the throttle all the way closed. With the throttle left on the closed or START position it will sputter and die after catching within a second or so. If I turn the throttle half way open or more, I can get it to start and continue running. However, I cannot get it to run below 2000 rpm (I connected a tach). If I try to ease the throttle down even after a good warmup below 2000 rpm it dies.

I reset the TPS according to the service manual and replaced the 3 spark plugs with correct (expensive) type. I also ran the diagnostic.

Diagnostic shows 1000 rpm on Tach with the center and right two warning lights steady ON. When this is looked up, it means engine hours are between 95-149 hours. It does not correspond to any component failure in the service manual that I can see.

Fuel is brand new fresh and in a brand new fuel tank as well.

BTW, the tach I am using is a Teleflex and the switch on the back is set to the 2 pole position. Is this correct?

Any ideas?
 

TOHATSU GURU

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Re: Tohatsu 40HP 40 TLDI Wont Run Below 2000 RPM and Requires Half Throttle To Start

Nope. You have to have the Tohatsu tach for the diagnostic to run.
 

rustnrot

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Re: Tohatsu 40HP 40 TLDI Wont Run Below 2000 RPM and Requires Half Throttle To Start

OK I will have to get one then. I was duped by this from tach manufacturer: "TLDI engines also require addition of warning light panel ..." I felt I would be OK as the tiller handle has these warning lights on it. So while the tach reads the rpms it won't work with the diagnostics.
 

TOHATSU GURU

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Re: Tohatsu 40HP 40 TLDI Wont Run Below 2000 RPM and Requires Half Throttle To Start

Actually I'm surprised that the tach isn't screwing up the engine itself. Aftermarket tachs can sometimes leak signal back to the engine's ignition system.
 

rustnrot

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Re: Tohatsu 40HP 40 TLDI Wont Run Below 2000 RPM and Requires Half Throttle To Start

Actually I never had the tach hooked up permanently. I had one laying around and hooked it up for troubleshooting purposes only after the motor malfunctioned. I will admit I was not putting the engine into diagnostic "Mode 3" correctly yesterday so I never got a good reading there. Also unfortunately, I cleared the codes before accessing that valuable information.

However, I did a test today. I ran the engine (greater than 2000 rpm by necessity) and unplugged, one by one, the fuel injectors. As expected, the rpms decreased (the same amount) when each one in turn was disconnected. Then I did a diagnostic analysis. The Teleflex tach displayed each of the 3 injectors as having "trouble" perfectly. I cleared the codes then ran the motor again.

With the motor still running the same and everything connected back up, I looked for codes. None are found. No lights and no tach readings when in Mode 3. Tach or no tach, no lights means it is not displaying any codes at all or am I missing something?

Assuming for a moment that there are no codes thrown, what does anyone suppose is happening here? Before I take this to a dealer, does Tohatsu have any kind of telephone technical support?
 

TOHATSU GURU

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Re: Tohatsu 40HP 40 TLDI Wont Run Below 2000 RPM and Requires Half Throttle To Start

No support for individuals, only to dealers. Until it get's hooked up to a TLDI tach you are spinning your wheels.
 

rustnrot

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Re: Tohatsu 40HP 40 TLDI Wont Run Below 2000 RPM and Requires Half Throttle To Start

OK thanks, it is frustrating how it "appears" the Teleflex tach displays correctly. I will get a TLDI tach and report back afterwards.

It appears there are two types of TLDI tachs, one with the 3 lights on it and one without. Can I get the TLDI tach with no lights (I hate redundancy and it is cheaper) since the 3 lights are already on the tiller handle?
 

TOHATSU GURU

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Re: Tohatsu 40HP 40 TLDI Wont Run Below 2000 RPM and Requires Half Throttle To Start

I only know of one TLDI tach type...Available in two different colors. It's not just the probability of the Teleflex tach giving you a less than accurate reading...There is also that possibility of it providing feedback into the engines ignition system and, of course, it's diagnostic functions.
 

rustnrot

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Re: Tohatsu 40HP 40 TLDI Wont Run Below 2000 RPM and Requires Half Throttle To Start

Good points. At least we know the Teleflex tach is not causing the problem itself as it was not connected prior to this problem. It also does not matter if it is connected or not to the engine, it runs the same. It did, however, provide accurate readings for the fuel injector faults or so it appeared.

That said, assuming for a minute that it is accurate -- does anyone want to speculate, swag, wild guess, etc. as to the problem while I get a Tohatsu TLDI tach?

It's possible (I hope that doesn't happen though) I will get the same results with the Tohatsu TLDI tach. At least we'll know and I'll document it here. It will be a good test.
 

TOHATSU GURU

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Re: Tohatsu 40HP 40 TLDI Wont Run Below 2000 RPM and Requires Half Throttle To Start

Just for giggles. How old is your battery and how many CCA's is it?
 

pvanv

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Re: Tohatsu 40HP 40 TLDI Wont Run Below 2000 RPM and Requires Half Throttle To Start

Interesting that the TAC parts catalog 00221049-3 shows that both the 3GL726470M TLDI tach (with indicator lights) and also the 3AC726400M 4-stroke tach are supposed to be compatible with the MD40B. I wonder whether they were suggesting you could use the 3AC... tach for tiller models (which have the LED's on the tiller)?

So, maybe... IF the Teleflex tach isn't feeding signal back to the ECU... it might work acceptably.

Yes, I would definitely check and VERIFY the battery condition/rating/age, the battery connections, and get a precise voltmeter reading at the motor while running.

I would also verify that you are running oil that is rated for DFI engines.

If the fuel rail and air rail pressures are correct, you may have an electrical/electronic issue, so verify all grounds 100%.
 

rustnrot

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Re: Tohatsu 40HP 40 TLDI Wont Run Below 2000 RPM and Requires Half Throttle To Start

I've already tried it on two large batteries (the CCA's escape me at the moment) using no more than the length of battery cable supplied with the engine. I did make a quick voltage check while connected to one of the batteries and the outboard was charging it at about 14.4 volts at 2000 rpms (at the battery -- I will check at the motor).

I also intend on unplugging all of the connectors on the ECU and verifying that no pins are receded or bent. I will of course check all grounds...to my favor the engine has never been in saltwater and is pristine looking so in theory there should be no corrosion.

Thanks for posting the types of tachs. I knew there was a type without the lights on it. You can now see my "logic" behind at least trying the Teleflex tach since it was handy and I already had it.

I'll brush up on how to check the fuel/air pressures. I expect a tire gauge will check the air pressure but I'm not sure it is suitable to measure the fuel pressure. Of course a cylinder compression test is also warranted.
 

TOHATSU GURU

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Re: Tohatsu 40HP 40 TLDI Wont Run Below 2000 RPM and Requires Half Throttle To Start

My concern about battery size is related to the available amps for initalizing the ignition system. You need to make sure the battery has the CCA's do to the job or you will wind up with a engine that starts, but will not run correctly. Probably not the problem for your engine based on it's symptom, but you may have more than one problem.
 

rustnrot

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Extremely Low Compression 75-80 psi All Cylinders

Extremely Low Compression 75-80 psi All Cylinders

Finally got back on this today. Obviously should have measured compression earlier. 75 - 80 psi on all 3 cylinders. Gauge is known good.

Does the air injection affect the compression in any way? I'm pretty certain this is a real number but does it add or subtract to the number or does it need to be disabled somehow to get a super accurate reading?
 

pvanv

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Re: Extremely Low Compression 75-80 psi All Cylinders

Re: Extremely Low Compression 75-80 psi All Cylinders

That's the correct method, but... unplug the connectors for both fuel and air injectors. Should be 120 psi. Perhaps non-DFI oil was run, leading to premature ring/cylinder wear.
 

rustnrot

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Re: Tohatsu 40HP 40 TLDI Wont Run Below 2000 RPM and Requires Half Throttle To Start

Finally, after many months, I looked at this motor again. For the record, with the connectors disconnected to the fuel injection nozzles and the air compressor nozzles, I get 115 psi compression on each of the 3 cylinders. Obviously, electrically disconnect these items before checking compression on a TLDI! I did find out that leaving the fuel injection nozzles connected I still get the 115 psi. It is the air compressor nozzles that have the effect of lowering the compression to about 75 psi when they are connected and running a compression test.

More to come as I now am taking the time to work on this again.
 

pvanv

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Re: Tohatsu 40HP 40 TLDI Wont Run Below 2000 RPM and Requires Half Throttle To Start

Finally, after many months, I looked at this motor again. For the record, with the connectors disconnected to the fuel injection nozzles and the air compressor nozzles, I get 115 psi compression on each of the 3 cylinders. Obviously, electrically disconnect these items before checking compression on a TLDI! I did find out that leaving the fuel injection nozzles connected I still get the 115 psi. It is the air compressor nozzles that have the effect of lowering the compression to about 75 psi when they are connected and running a compression test.

More to come as I now am taking the time to work on this again.

At this point, I would disconnect/clean/check each and every wiring connection, especially the ones to the ECU, and pay special attention to every ground connection. Are you using the Factory service manual as a guide? If you have an MD40B, the correct manual is Part# 003-21050-2, $40.00. If it's an A model, you would use Part# 003-21050-1, $27.58. These are available from any dealer, including me.
 

rustnrot

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Re: Tohatsu 40HP 40 TLDI Wont Run Below 2000 RPM and Requires Half Throttle To Start

Engine runs! Then doesn't run...here's the scoop.

A couple of months ago on the advice of a Mercury dealer who has Optimax experience recommended I take apart and clean all fuel related items to include replacing high pressure fuel filter, vapor canister and FFP box, etc. I did all that and then proceeded to check the compression right after I did this stuff. With the 75 psi readings I didn't even bother at the time to put gas back in and try it since the compression was so low. I let the motor sit thinking I would have to rebuild the block in the spring...

Fast forward to yesterday when I found out I was doing the compression test wrong and really had good compression after all. Today I decided to go ahead and put gas in and try it. As you can imagine it took awhile for everything to "prime" but I had what appeared to be a good running engine, one that idled good and throttled up good and restarted on demand good (all on an engine stand not on a boat). It would not, however, change idle speed by depressing the ignition key like I thought it was supposed to (maybe this function does not work in neutral)?

There were alot of codes stored (due to many disconnected connectors for checking the compression) so I first reset the TPS. Then I tried -- no start, just a short rev of about a second each time the key switch is turned to start position. Checking codes now I have some relating to both #1 and #2 TPS. I have cleaned and checked all connections to computer and TPS, etc. Maybe I have an intermittent TPS.

My next step will be to insure all codes are cleared and attempt a clean start again. Failing that, it may be in my best interest to replace the TPS.

I have been using Part# 003-21050-1 service manual for my 40B engine.
 

rustnrot

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Re: Tohatsu 40HP 40 TLDI Wont Run Below 2000 RPM and Requires Half Throttle To Start

Update: I had the connectors for TPS #1 and #2 Reversed! After I put the connectors to the proper TPS, and cleared the codes, they stayed clear. Until I tried to start and run it. Now it runs but does not run well below about 1200 rpm or so and is hard to start. After several attempts at running and subsequent code clearing, there is one code (and only this one) that keeps popping up and I think it is the CPS (Crank Position Sensor).

Note: Why it ran so good earlier with the two TPS connectors reversed is beyond me.

Please take a look at the attached table. At a tach reading of 5000, I have only the rightmost LED lit up. Does this suggest the CPS is at fault? OR -- is this an impossible combination? I don't understand the logic of the table and need help. For a faulty CPS, must the tach be at 5000 (it is), the first LED unlit (it is), the second LED lit (it isn't) and the third LED lit (it is)?? OR does the table suggest that for a bad CPS the tach must be at 5000, and either of the two right LED's can be lit to flag this??
 

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rustnrot

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Re: Tohatsu 40HP 40 TLDI Wont Run Below 2000 RPM and Requires Half Throttle To Start

I found another version of the table I referenced above in one of the manuals. Here is a screen shot from a page in it. The way I understand it now is the CPS is intermittent, not a hard fail. Sounds like I need to get a new CPS after verification that the wiring to the CPU is ok.
 

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