'78 70hp rude only running on 1 cylinder

[b_ry]

Hi guys, I've been fighting with a 70hp rude it will start and run on the bottom cylinder only. It had a bad coil on the top cylinder that I replaced and both the top cylinders have great spark. I pulled all 3 carbs and cleaned and soaked in Chem dip and blew them out with compressed air. The top 2 plugs are always dry and you can pull the wires right off with no change while it's running. Holding my hand over the top 2 carbs does nothing but if you touch the bottom one it chokes it out quick. I checked compression #1 117 #2 114 #3 115. I shined a light down in the reed cage I didn't see anything wrong not to say there isn't a problem there. Spray bottle with fuel does nothing to the top 2 cylinders, I also ran sea foam through it smoked like crazy but no change.

 

[flyingscott]

Do you get shocked when you pull the wires off of the top 2 plugs.

 

[Joe Reeves]

With "all" spark plugs removed..... The spark should jump a 7/16" air gap with a strong blue lightning like flame... a real SNAP! Does it? The air gap is important, nothing less will do!

(Spark Tester - Home Made)
(J. Reeves)

Most auto part stores have "air gap" spark testers... OR..........

You can use a medium size philips screwdriver (#2 I believe) inserted into the spark plug boot spring connector, then hold the screwdriver shank approximately 7/16" away from the block to check the spark or build the following:

A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.

Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:

..........X1..........X2

.................X..(grd)

..........X3..........X4

The fact that you have compression and with a running engine, spraying a fuel mixture into the carburetors with no response.... that indicates a ignition problem.

 

[b_ry]

I did the first time lol, yeah spark is super strong the top 2 plugs are always dry, I'll make an air gap and give it a shot putting a new plug in the wire and holding it against the head seems to yield good blue spark but I'll try it

 

[b_ry]

Alright Joe Reeves bottom plug snaps like thunder you weren't kidding top 2 dead as a door nail!!! Power pack? I tried uploading a pic of my nail board the file was too big it was super primitive but worked lol

 

[b_ry]

With "all" spark plugs removed..... The spark should jump a 7/16" air gap with a strong blue lightning like flame... a real SNAP! Does it? The air gap is important, nothing less will do!

(Spark Tester - Home Made)
(J. Reeves)

Most auto part stores have "air gap" spark testers... OR..........

You can use a medium size philips screwdriver (#2 I believe) inserted into the spark plug boot spring connector, then hold the screwdriver shank approximately 7/16" away from the block to check the spark or build the following:

A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.

Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:

..........X1..........X2

.................X..(grd)

..........X3..........X4

The fact that you have compression and with a running engine, spraying a fuel mixture into the carburetors with no response.... that indicates a ignition problem.

Alright Joe Reeves bottom plug snaps like thunder you weren't kidding top 2 dead as a door nail!!! Power pack? I tried uploading a pic of my nail board the file was too big it was super primitive but worked lol

 

[Joe Reeves]

Yeah, the pixel width of the pictures needs to be down around 600 to 1000. I use the program ACDSee Photo Manager to do that among other things.

Check the coils by switching the lead from the powerpack that feed the firing coil one by one to the non firing coils. Let us know if they fire as strong during that test. If they fire as they should (7/16" gap).... that leaves the timer sensors in the timer base and the powerpack.

 

[mrcj001]

move the bottom ignition coil to one of the cylinders that are not firing....those power packs usually just go dead. Check the coils.

 

[b_ry]

Ok I will this evening when I get home and I'll report back thanks

 

[b_ry]

I can't get a peep on 7/16 gap board on the top 2 coils, I moved the good coil up each cylinder and they fire perfect. (All 3 wires coming from power pack fire good on the good coil.) I just replaced the top coil I'm wondering if it was doa

 

[mrcj001]

I would replace all three with new ones. ...that way you know what you got!

 

[b_ry]

I would replace all three with new ones. ...that way you know what you got!

I bought the 16.99 one off eBay for the top one I'm wondering if they are crap

 

[mrcj001]

those ignition coils for your engine average $45-$55 ea. I think the ebayer sold you a used one....that wasn't any good

 

[mrcj001]

If the coil came with the spark plug wire not assembled......and you assembled it....make sure that the lead wire in the boots are making contact with the plugs and the male end of the coil......on the plug end it looks like a spring. Make sure it "snaps" on to the spark plug

 

[b_ry]

If the coil came with the spark plug wire not assembled......and you assembled it....make sure that the lead wire in the boots are making contact with the plugs and the male end of the coil......on the plug end it looks like a spring. Make sure it "snaps" on to the spark plug

Yeah I'm not sure, says they've sold hundreds of these ones, probably half of them are crap @ 16.99 lol. I replaced all 3 with cdi electronics ones with new wires that came assembled and low and behold it snaps fire on each plug and runs like a champ. I'm definitely convinced the coils it had on it came from the same manufacturer as the eBay one I bought they both say tiawan.