J40ECCS popping from exhaust

[ChrisinNashville]

Hi all,

Need a little help please. 1988 J40ECCS, been sitting for about 3 years. Fresh carb rebuild, new plugs, wires appear fine.
VRO has been removed, so pre mixing with a standard fuel pump.

If I remove the coil wire from the top cylinder the popping stops. Tried swapping the coils and it stays with the top cylinder.

Trying to narrow it down to a fuel or ignition problem, have a look. https://youtu.be/NK2KTOKzc7E

I'm suspecting the power pack...

Any thoughts appreciated,
Thank you

 

[racerone]

Some will argue.-------But what does a compression test show on this motor ?-------Does the spark jump a gap of 3/8" or more , yes or no ?

 

[ChrisinNashville]

120 on each cylinder. Just used an inline spark test and it is firing. Need different test to test the spark length.

 

[tlewis1]

Do you have access to a mulitmeter with a DVA hook up.....If so CDI has a great troubleshooting guide to help with ignition issues.

http://www.cdielectronics.com/troubleshootingguide/

 

[jakedaawg]

I only heard a little lean pop. But then I have been listening to a 250hz tig welder all morning...

 

[PhrozeN_FisH]

Sounds like a lean pop condition to me. Does it do it just off idle or continue as rpm's increase? Did you remove main jet and insure it was completely open? Float level set to spec?

 

[ChrisinNashville]

It continues as rpms increase. Jets are fixed, the carbs were thoroughly cleaned and floats to spec. I thought lean pop's came back out through the carb?

 

[oldboat1]

backfiring through the carb can indicate reed valve issues. Think you might be leaning out a little on the muffs, or just hearing exhaust noise. Do you notice this when in the lake?

 

[ChrisinNashville]

Havent been on the water yet, engine has been sitting for three years so just trying to get it running right before I take it out.

 

[Keyboardman]

Sounds better than my old Johnson on muffs. Big difference in the water with back pressure.

 

[PhrozeN_FisH]

I was asking about part #19 being removed. If air box is removed you could partially cover carb throat to richen and see if it improves.

 

[PhrozeN_FisH]

sorry, duplicate post. please delete.

 

[Chinewalker]

I wouldn't worry about it too much until you can get in the water. If the popping is still evident when it has some back pressure, then move on to possible carb cleaning and rebuild.

 

[ChrisinNashville]

On mine, part 12 is installed

I was asking about part #19 being removed. If air box is removed you could partially cover carb throat to richen and see if it improves.

 

[PhrozeN_FisH]

CN,

The main jet (#19) I was talking about is screwed into the float bowl behind the plug (#12). If it was not removed or cleaned thoroughly it could be the cause your issue.

 

[ChrisinNashville]

Ok, I didn't remove that but I did pass a carb jet tool through it and into the bowl and made it was clean.