I have just replaced the Coil in my '91 Formula Mach 1. My sled is finally getting spark, but when I start it is back fires and shuts off. Any Ideas on what could be wrong with the sled.

I have just replaced the Coil in my '91 Formula Mach 1. My sled is finally getting spark, but when I start it is back fires and shuts off. Any Ideas on what could be wrong with the sled.[/b]

does it abckfire everytime? then shut off? or does it sometimes jsut shut off? does it stay running if you hold the thorottle? give us details.. or we can't help you.

welcome to the site.

does it abckfire everytime? then shut off? or does it sometimes jsut shut off? does it stay running if you hold the thorottle? give us details.. or we can't help you.

welcome to the site.[/b]

The initial problem was that I was sledding and was having some trouble, so I parked the sled and when I went to start it again, it would not start (there was no spark). Then I replaced the coil and it is getting spark now, but when it starts, it idles for a few seconds, backfires, and shuts off. I put new plugs in the sled 3 times and I still have the same problem. I have no idea what could be wrong. :crazy:

The initial problem was that I was sledding and was having some trouble, so I parked the sled and when I went to start it again, it would not start (there was no spark). Then I replaced the coil and it is getting spark now, but when it starts, it idles for a few seconds, backfires, and shuts off. I put new plugs in the sled 3 times and I still have the same problem. I have no idea what could be wrong. :crazy:[/b]

what kind of trouble were you having when you had it running? did you check to make sure the coil was correctly put in and it was the right one? i'd have to say its something you did when you changed the coil. go over everything to be sure. then repost with information.

what kind of trouble were you having when you had it running? did you check to make sure the coil was correctly put in and it was the right one? i'd have to say its something you did when you changed the coil. go over everything to be sure. then repost with information.[/b]

I wasn't having any trouble with the sled until the coil gave out. I have already double checked the coil and it is in correctly and I have plenty of spark now. When I prime the sled it will run for about 5-10 seconds and then shut off. Then when I try to re-start it again, it REALLY backfires (a ball of flame comes o ut and hits the ground). Then a few mins later I have to prime it to start it again. Seems like it's geting too much gas, but the needle valves and everything looks fine and the carbs are clean... any more ideas???

have you ran a compression check on the sled before?

I have just replaced the Coil in my '91 Formula Mach 1. My sled is finally getting spark, but when I start it is back fires and shuts off. Any Ideas on what could be wrong with the sled.[/b]
I know what the problem is right now! You told me you just replaced the coil. The reason your coil went is probably due to the fact that you were running extra lean on that cylinder causing the coil to overheat and go open circuit due to the extra voltage needed to produce the spark to jump the spark plug gap. Another reason I believe the sled is running lean is because you told me the sled backfires and then shuts off. If you take away fuel from a cylinder, more air will be present causing a big bang which is the backfiring. Take a look at your plugs and I will bet you that one is super clean and extra white. That is your problem cylinder. This usually happens because of the carburetors varnishing and guming up due to the fuel getting old and breaking down. A good carburetor cleaning will fix this problem. Not just spraying cleaner in the venturi but taking the carburetor apart and cleaning all the parts. Clean your carburetors. Hope this helped you out.