Merc 240 efi won't re-start

[reeyou]

Hi guys, I have a similar situation where the engine won't start when hot.

2001 islandia, 240 EFI

I've used it only once since putting in new spark plugs (and fuel filter) late last week. Started fine off the launch. Pulled the kids around for a short while but after the 4th shutdown-restart, it wouldn't start anymore. Had to get towed back to the launch. Didn't start there either... But it started in the driveway an hour later.

I've read in other threads about the EFI's finickiness for clean air and I have to admit that I wasn't using the bilge fan long enough. I also haven't checked the injector pressure yet (as this thread recommends); I will do that soon.

Out of curiosity, I checked the spark plugs today. All 3 on port side are nice and clean. The 3 on starboard are black. I was told that compression test results are 125 on all 6, but I haven't seen the actual test being done so I can't confirm.
Shouldn't all 6 plugs look the same?

 

[LesPaul]

I am not a boat engine mechanic, but I think ideally you would want all the plugs to look the same. It would seem to me that something is going on with the starboard side. (Captain Obvious, I know)You said that the compression was good, so we can probably rule that out. Next I think I would look at the ignition. Either not firing or firing intermittently. Not sure why one side would be good and the other not. In a car engine I would say that the starboard side is not firing or has low compression causing the plugs to foul. But, it's unlikely that all 3 cylinders are low just on one side. I know my reply probably wasn't any help.

 

[reeyou]

Bad fuel injectors maybe?

 

[LesPaul]

Thanks Reeyou. I guess it's possible. I put the new air temp sensor in this morning and took her to the bayou. Ran like a champ for the better part of 2 1/2 hrs. Perfect. Great day with the wife. Got back to the launch, shut her down and the same thing. It just will not re-start once it gets hot. I tested the port temp sensor and it seemed to test fine with the ohm meter. I disconnected it at the launch still no start. I ran the bilge fan the whole time we were out. I'm out of ideas. Has to be something simple. If the injectors were bad I don't think it would run like a champ all day, until you shut it off.

****EDIT****
Just hooked water hose to it in the driveway, fired right up. It had been sitting for about 30 minutes (including ride home from the launch).

 

[Djs]

Do you have a spark tester or even another spark plug you could use to verify if there is spark when this situation occurs.

 

[LesPaul]

Thanks Djs. I do not have a spark tester, but suppose I can go get one. Seem to be pretty cheap at HF

 

[LesPaul]

So today I set the idle a little higher (1300 rpm) just because. Took it to the canal ran it for about 30 min and `went back to the launch. Shut it off and low and behold it started. Repeated that a few times and each time it re-started. I don't know if my problem was to low of an idle or not, but it did start. Fingers crossed. I will have to did it a few more times before I regain my confidence in this thing so not to leave me stranded.

The downside is that with the higher idle it wants to go forward so there is no "neutral".

 

[Djs]

Positive result and I try to keep diagnostics simple e.g an healthy engine (good compression) needs air, fuel and spark to run, it's a process of elimination if it occurs again.

 

[reeyou]

So today I set the idle a little higher (1300 rpm) just because. Took it to the canal ran it for about 30 min and `went back to the launch. Shut it off and low and behold it started. ...

Some threads mentioned that turning the steering wheel to the end will give it more gas when starting up (I can't remember what that feature is called). Maybe lowering the idle a little and using the wheel trick can help you start the engine and still manage to keep some semblance of neutral?

 

[LesPaul]

I read that on a different thread too. I tried it before I adjusted the idle (didn't work). It definitely is worth trying again. Lower it and find a happy medium because the boat leaving the dock without me is not an option. lol

 

[Dr Honda]

It should be able to idle around 1000 rpm. But to help it from moving... you can lower your bucket a little more. (adjust the shift cable in the neutral position)

 

[LesPaul]

Well, apparently that was NOT my problem. Ran it today hard for about 30 min. Got back to the bock and it wouldn't restart. Waited about 20 min and it finally did start. Ran it hard again and could not replicated the problem. I put a spark tester in but couldn't tell if it was sparking or not. Probably a POS $20.00 tester. Couldn't see from the helm. If it was getting fire the tester wasn't very bright. Going to get afriend to go next time so we can see the tester better.

I am just really frustrated with it right now. Wouldn't mind if it sank.

 

[Djs]

We can all feel frustrated by diagnostics and remember keep it simple. If you have good spark you could also remove the spark plugs and observe if any or all are very wet with fuel or normal. If you thought you had an over fuel situation (wet spark plugs) with all park plugs removed crank the engine over a few times to evacuate the cylinders and if you had a fresh set of plugs install them or make sure the original set are clean and dry, refit them and try again.

 

[LesPaul]

While still trying to track down my hot start issue I found this. These wires are from the trigger. They were stowed under a metal clip and obviously have been chaffing for some time and/or just worn out.

 

[LesPaul]

So I already know I need to replace the trigger assembly due to the condition of the wiring. I also attempted to check the TPS with no luck. I don't have the test harness like the manual outlines, I tried to use the needle through the wire method. I just couldn't get the reading I was supposed to. At this point I'm not ready to trash the TPS as I don't have confidence that I was doing it right. Should be a simple test, but the heat of the day, location of the TPS and being by myself made it difficult. May order the test harness (another $60.00) and try again. What concerns me right now is if I have to have the trigger connected to perform the TPS check. I don't see why but I am getting some really erratic numbers. Which I know is not a good sign. I did disconnect the port temp sensor as required

 

[Dr Honda]

Just disconnect the TPS, and put the meter on the center and one of the outer wires. You should get a smooth resistance transition from one side to the other. As I recall... it should be 10K ohms at full.

I have a spare TPS... I'll go read it on the bench. Give me a few to do that.

As far as the trigger... that's not just chaffed. The covering looks rotted.


*******EDIT******

I put the meter on the new one... and I got 9.9K ohms at one end, and 0 on the other. (smooth in the middle)

 

[LesPaul]

Thank you so much for the help.

I thought I was supposed to be testing for voltage. (.20-.30 volts DC) fully clockwise.
How do I hold the throttle shaft in the closed position? That doesn't make sence to me.
What do you mean on "one end"/
What do you mean "smooth in the middle"?

Sorry for being a noob on some of this. I just want to be completely sure TPS is bad before I order a new one. ($500 bucks)

Yes, the trigger is toast. I know that is one problem. Thinking the TPS might be my other

 

[Dr Honda]

If you use the harness... you are looking for voltage (key on) between the TPS and the ECU. Since you dont' have the harness, it's easier to just read the resistance of the TPS itself. It's not a proper test, but it will tell you if it's bad.

Pop the connector apart at the end of the TPS. Stick your meter in the middle pin, and ether of the outer pins. You will get some reading. It may be high, or low, just depends on what pin you put it on. Then, have a helper slowly move the throttle up. You should have a smooth change in resistance. If you see it jump, or go open... the TPS is bad.

Since yours is still on the engine... you won't see a full reading like I got. (On the bench, I can twist it from stop to stop) In the engine... it won't give you that. The key point is... you just need a smooth change in readings as the throttle is moved.

 

[LesPaul]

Got it. Thank you.

How do I hold the throttle shaft in the closed position?

 

[LesPaul]

OK. Replaced the trigger still no start when hot. Will the TPS keep it from starting when hot? I always thought the TPS was a kind of a "fail safe" and it would start, but run rich or just sh**ty. I'm out of ideas.

Replaced trigger assy, air temp sensor, port temp sensor. Only thing I can think of is a $500.00 TPS.

 

[Dr Honda]

It depends.

When the TPS goes bad... YES... the ECU goes into fail safe, and adds max fuel for the RPM. The TPS and the Port side temp sender is a fuel trim for this system. Normally, the engine will start, but it will be Smokey and stinky. The extra fuel isn't an issue cold... but it makes it harder to start hot, as it could be flooding. This could be made worse if you have poor ventilation , and the compression is low. (on an older engine)

But as you already said... it's crazy expensive... just test it. If it works as I described... it's good.

There was another member this year who had a bad ignition control unit. I've never seen one go bad yet... but as these engines age, I'm guessing we will eventually see every part fail. I don't think there's a way to actually test it, but he was having a bunch of starting issues.

If I was in your position... I would buy the Rinda Scan tool. It's obviously an electrical issue, and that unit may be able to tell you what's going on with "Live" data.

 

[Jmkaufman84]

I found the ignition control was bad, I assume it was causing injector timing issues.

Most recently I’ve found that my TPS was bad as well, really Smokey at idle. I have read that you can modify an older TPS connector and save money. Is this true? If so does anyone have the part number?

 

[LesPaul]

I found the ignition control was bad, I assume it was causing injector timing issues.

Most recently I’ve found that my TPS was bad as well, really Smokey at idle. I have read that you can modify an older TPS connector and save money. Is this true? If so does anyone have the part number?

I also have heard that other TPS will work just have to modify like you said. I hope someone will chime in. Would like to know before I buy one. Most electrical stuff can not be returned.

 

[Dr Honda]

I found the ignition control was bad, I assume it was causing injector timing issues.

Most recently I’ve found that my TPS was bad as well, really Smokey at idle. I have read that you can modify an older TPS connector and save money. Is this true? If so does anyone have the part number?

Yes.... it's true. (I have one) The slightly older outboard version had a round plug, and the newer has the flat plug. It's the same part number, but just remove the suffix at the end.

For a while, you could get them on ebay relatively cheap. But over the last few years, 1) people figured this out and 2) the older parts are drying up.

 

[Tim75]

If you use the harness... you are looking for voltage (key on) between the TPS and the ECU. Since you dont' have the harness, it's easier to just read the resistance of the TPS itself. It's not a proper test, but it will tell you if it's bad.

Pop the connector apart at the end of the TPS. Stick your meter in the middle pin, and ether of the outer pins. You will get some reading. It may be high, or low, just depends on what pin you put it on. Then, have a helper slowly move the throttle up. You should have a smooth change in resistance. If you see it jump, or go open... the TPS is bad.

Since yours is still on the engine... you won't see a full reading like I got. (On the bench, I can twist it from stop to stop) In the engine... it won't give you that. The key point is... you just need a smooth change in readings as the throttle is moved.