Lost Power - not firing on 2 cylinders

[henryb]

Well my arch nemesis strikes again! It seems I've had a bit of a run of bad luck... Today coming in from a morning cruise, I lost almost all power. Speed dropped from 40MPH to 10 in one moment. I thought I hit a huge clump of weeds or something? So I idled into doc. Checked the impeller, sure enough it was jammed with weeds, but our bay is quite weedy!

Cleared the weeds about an hour or so later and tried again, still not running right, low on power, barely holding an idle? I remember Dr Honda suggesting to someone else to check for a cylinder that is not firing by touching the spark plug after running engine for a short time... If plug was firing, it would be warm to touch. But I noticed that the lower 2 cylinders on the drivers side were cold, were all of the others were warm.

I'm guessing it is a coil pack or something like that, if I recall correctly this engine has 3 ignition coils that control 2 cylinders each? Or am I out in left field?

 

[henryb]

I have a 2000 Challenger 1800 with a 210HP carbed engine.

 

[Dr Honda]

There's a pack on each plug.... but I will have to double check on the trigger system for the carb engine. (be back shortly)

 

[Dr Honda]

OK... I was right. (Unfortunately)

The #3 and #5 coils don't share a trigger, or carburation... so... it's a strange situation. They do share a switch box... but if it went bad... #1 would be cold too. AND, It's highly unlikely that 2 coils went bad. SO... here's my list....


1) Make sure your plugs aren't fouled.
2) Check the compression on all cyl's.
3) Check for spark on all cyl's.

 

[henryb]

I changed out the plugs on the cylinders that were cold... No difference.

For compression test and spark tests I have dropped it at my mechanic for further checks. Will keep you updated.

 

[henryb]

To tell you the truth, cylinder #1 was not all that warm either, but it was not as cold as #3 and #5... So maybe it points to that switch box?

 

[Dr Honda]

To tell you the truth, cylinder #1 was not all that warm either, but it was not as cold as #3 and #5... So maybe it points to that switch box?

It could. But... the spark, and compression test will tell us more.

 

[henryb]

Just got a voice message from my mechanic, not a ton of details on the tests that he did... But he said that the problem was a switch box.

 

[Dr Honda]

Well.... that's much cheaper than a new engine. (lol)

 

[henryb]

Hey... You know, you are absolutely right! I never looked at it that way until just now! $400 for a switch box and a few hours labour is definitely much easier to swallow then a new engine! OMG, I'm glad I didn't think that was a possibility! Somehow, you have made me feel a lot better! LOL

 

[henryb]

FYI, for anyone that has 3 cylinders not firing, one bank or the other! There's a good chance it's a switch box that has failed. There are 2 of these switch boxes, both are mounted on the starboard side (drivers side) of the engine, one on top of the other. The one that is easiest to get to is the one for cylinders 2,4,6 (port side bank), the other one that is under the bracket (much harder to get to), is for cylinders 1,3,5 (starboard bank). Fairly straight forward install... Just 3 screws and a pile of wires (mostly with push-on connectors).

 

[henryb]

Well, I'm not sure if this is common or not, but the same problem occurred again today. But it appears that it is the other switch-box! As cylinders 2,4,6 are cold after a 10 minute run where the engine would only get up to 4000 rpms and 25 mph. Even though, it appears that it is the switch-box, might it be something else?

IF in fact it is the switch-box, is there anything to watch out for when purchasing those units online?

 

[henryb]

Duplicate...

 

[Dr Honda]

It's not common for them to fail together... but I guess it could happen since they both have the same amount of time on them.


Nothing really to watch for. Buy the OEM parts, and they will last. Buy used, or aftermarket, and it's a crap shoot.

 

[henryb]

Does it do any harm running the engine on 3 cylinders, as I have about a 20 min run to get to the boat ramp? I can imagine there is still gas going into those cylinders that are not firing.

 

[henryb]

Any feedback on running the engine on 3 cylinders? Does it do any harm? I need to get to the boat ramp... Or should I get it towed?

 

[Dr Honda]

Sorry.... I was tired up for a couple days.


Personally... I would NEVER run a 2-stroke engine when it's known to be not firing on all cyl's. If fuel isn't flowing... it could kill it. Not to mention, it will put extra load on the one's doing the work.


I would have it towed to the ramp.

 

[henryb]

Stranger things have happened I'm sure... But this past weekend (Thanksgiving in Canada)... I went up to the cottage to lift the boats out, winterized and shut things down for the year. I put stabilizer into the gas tank and decided to run it for a minute to get the stabler into the carbs and so on. I was curious and felt the engine for heat and sure enough all 6 cylinders were warm! Took it out for a run on the lake and it was running great? So I guess those switch boxes can have an intermittent problem? Drove it a few times for about 30 each time and the engine ran very smooth! Amazing!

 

[henryb]

Well it appears that the intermittent problem that began last fall has reared its ugly head this summer (again).

This past week, I have noticed that every now and again, I would loose power... RPMs drop to 4000, and speed would drop off. So I idle back to the dock and let it cool down to check if 3 cylinders are not firing... However every time I go back out... It is working fine again! But before I get back to the dock the same problem kicks in again.

This morning was the last straw... About 10 miles from my cottage, it happened again... So this was a long idle back in! So I pulled it up on the trailer and took it into the marina for a look over.


Sent from my iPhone using Tapatalk

 

[Dr Honda]

I'm thinking you just need a new switch box. or CDI.


Did you figure out if you are loosing 3 cyl's... or is it just above a certain RPM?

 

[henryb]

Unfortunately I was not able to figure out if it was 3 cylinders not firing, as every time I came down to test the engine cold... it would start working again! :-|

No, the problem seemed to occur at different rpm's... Sometimes at idle, other times at mid-throttle, other times at higher speeds. So there didn't seem to be any pattern?

One other note, I also started noticing that the volt meter was reading very high on occasion this past week... around 16+ volts? It didn't seem to be directly tied to when I would loose power, but I thought it was worth mentioning? Eventually in all cases the meter would return to its normal 14 volts while engine was running.


Sent from my iPhone using Tapatalk

 

[Dr Honda]

High(er) voltage, can cause the electronics to fail... and as you know... when we get a bad regulator in a seadoo PWC... the CDI's do crazy things. SO... I would say to replace the regulator. AND... as a test... and assuming you have a good battery... disconnect the wire from the regulator, to the battery. Yes, you will eventually drain the battery... but if the problem doesn't come back... then you know where the issue is. (I recommend bringing a jump pack or extra battery to do that test)

now.... knowing it's 3 cyl's... you may be in luck. Also... you mentioned it was "One bank" as I recall. There are 2 switch boxes. One is for 1, 3, 5. and the other is 2, 4, 6. So... I would say that you need the switch box that corresponds with the "Dead Bank".


If it was above a certain RPM... that would lead me to believe you have a bad stator. AND... if it wasn't "A bank"... then I would say you have a bad trigger.

 

[henryb]

Boat has been in the shop for almost 2 weeks, they can't seem to find the problem... With it being intermittent it has only happened once for them on 4 trips out on the water!

I suggested to start by replacing the voltage regulator and go from there.


Sent from my iPhone using Tapatalk

 

[henryb]

I heard an interesting piece of advise from another local Merc mechanic. He had 2 past customers come in with the same type of intermittent electrical power cutting issues. And they had replaced one of their switch boxes the year before!!! Sounds exactly the same as my issue!

As it turns out in both of those cases, one of the push in round pin connectors did not go into the middle of the matching female connector... The female connector had been squished flat and the male end went on the outside of the connector and although it made connection initially, it was not very tight and eventually came loose and caused the intermittent nature of the power cutting out!

So I called the marina, told them this story and they are going to check the connectors from the switch box they installed last summer and see what they find!


Sent from my iPhone using Tapatalk

 

[Dr Honda]

That's a place I always start. Even if the connector isn't damaged... they do build corrosion since there is water and heat. SO... I take plugs apart, and put them back together.


Heck... I got my Polaris Genesis for almost nothing because it simply had a few bad connections, and the local shop didn't want to deal with it.