Middle cylinder sparking but not combusting

[Keith Buchanan]

50 HP 3 CYL ELPTO 1989 Clamshell. Started to lose power today so running it in the bucket idle was irratic. I started with the plug leads and disconnecting all in turn number 2 made no differance, lead sparking to earth okay I thought I had a dead spark plug. Changed plug still no result, clipped an earth on plug and observed a good strong blue spark, replaced plug still no fire from number 2. Compression on all 3 cylinders okay. So after swapping around leads, plugs etc to try and pinpoint this prob still remains. Although number 2 cylinder is not combusting the plug is wet after running and appears to be getting fuel. Number 2 spark plug is definately sparking I just can't get my head around this one.

 

[emckelvy]

Re: Middle cylinder sparking but not combusting

Try putting a timing lite or spark firing indicator on #2 while the motor's running. You may have good spark to ground but it's blown out under compression.<br /><br />If you do have good spark, and considering you see a lot of fuel, maybe that cyl's carb is going overrich.<br /><br />I'm assuming it's got 3 carbs, if not than that theory is out the window.<br /><br />If there is a separate carb for #2, one of the jets could be loose, float needle valve leaking, or some other type of failure that could flood the carb.<br /><br />Or, a problem with the fuel pump could cause too much fuel to be sucked into #2. This would require that the fuel pump's vacuum input comes from #2 cyl.<br /><br />Not overly familiar with this motor so this is just basic stuff, but at least it may give you something to go on.<br /><br />HTH.........ed

 

[Keith Buchanan]

Re: Middle cylinder sparking but not combusting

Only 2 carbs on this model but you have brought up an interesting theory as the fuel pump is run from number 2 cylinder and I have recently replaced the fuel pump kit, could fuel be entering via this route I wonder.

 

[Keith Buchanan]

Re: Middle cylinder sparking but not combusting

Looked at it again this morning.Although I have a healthy looking spark I swapped cyl 1 & 2 coils around to discount ignition probs. What I did notice after starting it for the first time today it was firing on all 3 cylinders but after several seconds middle cylinder started bogging down and then came the smoke from the mostly unburned fuel and oil. Again when this happened removing and grounding the spark plug lead made no differance. Cylinder number 1 is working fine, the plug is a nice burnt cookie colour, no 2 is clean and no 3 is not as brown as no 1.<br /><br />Regards Keith B...

 

[Barnacle_Bill]

Re: Middle cylinder sparking but not combusting

Blown head gasket between cylinder and water jacket??

 

[achris]

Re: Middle cylinder sparking but not combusting

Hi Keith,<br /><br />It does sound a bit like you need to pull the pump off and have another look at it. There is no head gasket on these engines. The head is part of the main casting, so we can elinimate that.<br /><br />As you stated, the 'give-a-way' is the running ok for a few seconds, and the fact that the last thing you did before it went faulty was the pump.<br /><br />Chris........

 

[Keith Buchanan]

Re: Middle cylinder sparking but not combusting

Agreed Chris I will be having the pump apart later this PM, I used to get all heated up with these troubles but with time taken and a little logic and help from you guys I have had some good results recently with various problems, and boy sure learned a lot..Regards Keith..

 

[Keith Buchanan]

Re: Middle cylinder sparking but not combusting

Backtracking to my last step I had the fuel pump apart today, everything looked fine, used the same new diaphrams but made sure it went back together with two new compression gaskets. After having a flashlight down the spark plug hole I noticed that cyl 2 was nice and clean and number 3 wasn't far behind whereas the top cyl' still had residue of burnt oil on the piston crown,(nice). Thinking that water not only is going to blow my spark out it is also a good decarbonizer I am about to renew my exhaust and water cover gaskets just in case. (Pls' see my post about correct torque settings for the bolts). Could somebody pls' tell me if there are waterways in the transfer gasket on the other side that could also be letting vapour into the cylinders.<br /><br />Thanks all....Cheers Keith....B......

 

[achris]

Re: Middle cylinder sparking but not combusting

No water galleries in through the transfer ports.<br /><br />Chris.............

 

[Keith Buchanan]

Re: Middle cylinder sparking but not combusting

Good I,m glad to hear that. Well just finished putting her all back together last night. So far we,ve had new leads and plugs, fuel pump kit, manifold and water cover gaskets, tested switch box and coils, compression test. It,s now 06:25 local time and in about 4 hours Chris I will be finding out if we,ve found the problem. If not it,s time for carb kits. You have a nice evening will post later..Keith B..

 

[achris]

Re: Middle cylinder sparking but not combusting

Good luck Keith.....

 

[Keith Buchanan]

Re: Middle cylinder sparking but not combusting

Well Chris no prob's. Chugged out cautiously with one ear behind and slowly started giving it some, bit hasty with the tide and got bogged down in the mud for five minuits, waited another five for it to flood a little more and I was away into the Wyre Estuary through Fleetwood harbour. Absolutely brilliant, I'm having a beer or two tonight and thanks Chris and the rest of you guy's, boy this has been some learning curve but loved every minuite. Thank you all....<br /><br />Keith B........

 

[achris]

Re: Middle cylinder sparking but not combusting

Keith,<br /><br />Doesn't it feel great when you fix something like that? In the knowledge that you saved a heap on money along the way and you got the job done right!<br /><br />Chris..........

 

[Keith Buchanan]

Re: Middle cylinder sparking but not combusting

Out again today and two words on the subject:......ABSOLUTELY BONZA!!!!!!!

 

[Elmer Fudge]

Re: Middle cylinder sparking but not combusting

Happy boating