2001 Mercury 240 EFI not firing all the cylinders

[eugene69]

Before I even attempted to disassemble the VST, I did check the pressure at the VST and it showed 36 Psi !!!
And when I turn the key to "on", I can actually hear the pump. What a waste of time at that marina (time and money). But the thing is that after I left it with the Marina, the engine now would NOT start at all. If before it would start normally, but would stall after 4-5 minutes of running, now it wouldn't even start on idle. Starter is spinning, all sparks get voltage, but engine wouldn't start. Did try starting it on maximum throttle and only then the engine would start. Put the boat on the water and could run it on different speeds for couple of hours. It does smoke a bit, but I am hearing it is normal for 2 stroke. But my understanding is that all major components are working (fuel lines, electrical etc.). Am I correct in that statement? For example, if any of the 3 fuel pumps wouldn't work, I shouldn't be able to run the boat for 3 hours. Correct? Does it need tuning? Any other reasons for the engine not to start on idle, but on high throttle only? And, by the way, after running it for 5-10 minutes, I could start it on idle too.. Just not consistent. One time it would start on idle and next time wouldn't. Obviously something is still wrong.

 

[rsatina2002]

I think you have to check your TPS voltage... You can check it with manual instructions on proper TPS testing, you can purchase the wire connector to be more easier to check the TPS voltage.... it has the specs on the manual..... If it still has no problem then maybe your fuel injector... Check it out for your TPS, it is very expensive if it fails but you can buy some pre-own working one... around $500 or more for brand new...

 

[eugene69]

I finally got DDT scanner and it shows actually the following :"THROTTLE POS V 4.09" - is this possible? The book says that it should be between 0.2 and 0.3. Is it that much off? Is it even possible? I did not attempt adjusting it yet since I want to make sure I read it right. Anyone witnessed numbers in that range?
Also, my fuel pressure is just a bit over 36 PSI - something like 36.4.. And as soon as I start the engine it complains about high pressure. As per the video below. Any ideas if these two are related or am I looking at two different issues?

 

[Tim75]

Before I even attempted to disassemble the VST, I did check the pressure at the VST and it showed 36 Psi !!!
And when I turn the key to "on", I can actually hear the pump. What a waste of time at that marina (time and money). But the thing is that after I left it with the Marina, the engine now would NOT start at all. If before it would start normally, but would stall after 4-5 minutes of running, now it wouldn't even start on idle. Starter is spinning, all sparks get voltage, but engine wouldn't start. Did try starting it on maximum throttle and only then the engine would start. Put the boat on the water and could run it on different speeds for couple of hours. It does smoke a bit, but I am hearing it is normal for 2 stroke. But my understanding is that all major components are working (fuel lines, electrical etc.). Am I correct in that statement? For example, if any of the 3 fuel pumps wouldn't work, I shouldn't be able to run the boat for 3 hours. Correct? Does it need tuning? Any other reasons for the engine not to start on idle, but on high throttle only? And, by the way, after running it for 5-10 minutes, I could start it on idle too.. Just not consistent. One time it would start on idle and next time wouldn't. Obviously something is still wrong.

Starting at WOT is a huge mistake. Especially out of the water. No load engine may hit 9000 rpm, then grenade. All in about 1 second.
Don't do it.

Open the vst drain screw. Drain into a container. How much came out? Does it look like there was enough to fill the vst to the gasket line? No? Inlet float needle is suspect. May be stuck.

Oil pump arm should be at 9:00 at idle.

 

[eugene69]

Thanks, Tim. After multiple manipulations (adjusting TPS being the latest) I can now start at idle. I still believe I will need tune-up. And when I opened that plug i got enough to fill the VST, so I think it is OK. With the only exception that my pressure is a bit over 36 PSI (36.4 or so). How bad is it? What do you think? And another important question for me - when I first checked my TPS, the voltage showed 4.6V or so (way over suggested 0.2-03), but when I started adjusting TPS using DDT, it would go down to 0.03 (TPS all the way clockwise), but when I turned it counter-clockwise as slow as I only could,- it would stay at 0.03 for a bit and then would jump to 1.4 or so. I could catch couple of times 0.7, but as soon as I started putting back screws, it would either switch to 0.03 or back to 1+... Left it at 0.03 (but close to the spot where it is ready to jump over 1V) and the engine now starts in idle. Is this normal behavior for TPS? How "sensitive" should it be? And is 4+V normal voltage? What is the range I should expect? Or is it my TPS that needs to be replaced now?

 

[cbjustDOOit]

did you have the temp sensor unlugged when you adjusted the TPS?

 

[eugene69]

No, but the manual somehow suggests to do so when using multi-meter and I used DDT... I thought that I might need to unplug, but decided to follow the procedure as per the book Do you think I need to unplug it while using DDT also? Let me try that and I will let you know if it made any difference.

 

[eugene69]

Need to finish this topic - the engine runs great right now! I did not try it in the water yet, but I am sure everything will be OK. After all that ordeal with multiple money-grabbing marinas (what a bunch of crooks), I finally found one individual who knows what he is doing and is very reasonable in pricing. Nothing needed to be replaced (I already fixed all the broken pieces myself) - he just tuned the engine to the specs and it now fires fine and runs on idle with the RPMs expected. Here is what he did. I did tune TPS myself with the DDT, but he used the harness and multimeter and confirmed that it is between 0.2 and 0.4 V (instead of 4.6V before). By the way, he confirmed that 4.6 V is possible, because the range is 0-5.0 V indeed. Also idle timing was at 20 BTDC and he adjusted it to 9. WOT idle timing was changed from 24 to 26 BTDC and that is what fixed my issue. He also checked compression on all the cylinders and it turned out to be 125 on 1,2,4 and 6. And 130 on 3 and 5. The local marina gave me totally wrong numbers and claimed that I need a new fuel pump that will cost me 1200 with 4 hours (another 500) to replace. Also suggested to get rid of my boat !?!?! Now I get it. They are selling new boats and were probably hoping that I would ask them to trade my in for a new one. Hate it! Left them negative review on Google and hope it will pay back for my $200+ lost on their "service"... Wish you, guys, all the best and thanks for helping me with my issue!

 

[cbjustDOOit]

Did you pay the CROOKS with Plastic???? if so.. call your card company, and tell them to stop payment... or get it back. Thanks for sharing the experience, it WILL save some of us money down the road.

 

[nenikol23]

Thanks, Tim. After multiple manipulations (adjusting TPS being the latest) I can now start at idle. I still believe I will need tune-up. And when I opened that plug i got enough to fill the VST, so I think it is OK. With the only exception that my pressure is a bit over 36 PSI (36.4 or so). How bad is it? What do you think? And another important question for me - when I first checked my TPS, the voltage showed 4.6V or so (way over suggested 0.2-03), but when I started adjusting TPS using DDT, it would go down to 0.03 (TPS all the way clockwise), but when I turned it counter-clockwise as slow as I only could,- it would stay at 0.03 for a bit and then would jump to 1.4 or so. I could catch couple of times 0.7, but as soon as I started putting back screws, it would either switch to 0.03 or back to 1+... Left it at 0.03 (but close to the spot where it is ready to jump over 1V) and the engine now starts in idle. Is this normal behavior for TPS? How "sensitive" should it be? And is 4+V normal voltage? What is the range I should expect? Or is it my TPS that needs to be replaced now?

@eugene69 , I am experiencing the same problem as you with the TPS. When I slowly rotate it counterclockwise to obtain 0.250 Volts, it will get to 0.130 volts then immediately jump to 1.2 volts. So what was different when the guy did it for you with the harness. The harness simply allows you to splice into the wiring without litterally shaving wires and poking the multimeter probes thru it. Therefore I do not see a difference between using the multimeter or the specialty harness other than convenience.