90hp V4 cylinders firing at different rates

[emmo1210]

Hi all,

Having some ignition issues with rebuilt V4 90hp 1990 motor. I hooked up a test light to check each of the 4 cylinders for spark. They all fire, however I have noticed that #2 cylinder fires much quicker than the other 3 cylinders. I changed the coil on #2 and same still happened.

Was wondering does anyone know of any issues that can cause something like this? Perhaps a power pack problem or magnet problem? or any tests i ca carry out?

Welcome any suggestions, thanks

Emmett

 

[boobie]

Re: 90hp V4 cylinders firing at different rates

Power pack or timer base. Fix it before you run it anymore. Or otherwise you might be rebuilding it again.

 

[emmo1210]

Re: 90hp V4 cylinders firing at different rates

Thanks for input. Any suggestions on how to figure out which one is at fault?

 

[emdsapmgr]

Re: 90hp V4 cylinders firing at different rates

Not sure just what you mean by firing "quicker." Do you mean it is firing in advance of where it should? You can check the timing on both #1 and #2 cyls. There are marks on the flywheel to time each. Check the firing on both and compare them with each other. Timing needs to be set/adjusted for the lower timing between the two cyls.

 

[emmo1210]

Re: 90hp V4 cylinders firing at different rates

I was using a strobe type induction timing light and i could see that the rate of flashing light was noticeably faster on the #2. I done the link and sink using the number #1 cylinder (as per manual) just previously. Using the timing light over all 4 cylinders #2 appears to flash quicker than the other 3?

 

[emmo1210]

Re: 90hp V4 cylinders firing at different rates

so for example #1,3 and 4 may flash every 0.5 second, #2 may flash every 0.1 second

 

[Silvertip]

Re: 90hp V4 cylinders firing at different rates

Are the plug wires in good shape. Bad wires can cause cross-firing where an adjacent plug wire fires into the other wire.

 

[BonairII]

Re: 90hp V4 cylinders firing at different rates

Bad wires can cause cross-firing where an adjacent plug wire fires into the other wire.

If possible, fire up the motor at night(or in a dark garage)....any arcing should be easily visible in the dark.

 

[emdsapmgr]

Re: 90hp V4 cylinders firing at different rates

How does the engine run when under load in the water? Does it make hp? If you test run it what rpms does it make? Holeshot ok?

 

[emmo1210]

Re: 90hp V4 cylinders firing at different rates

I will check on this and reply, cheers

 

[emmo1210]

Re: 90hp V4 cylinders firing at different rates

Haven't tested it under load in the water, didn't want to take it out in case of damage. Not sure what holeshot is?

 

[emdsapmgr]

Re: 90hp V4 cylinders firing at different rates

My concern is that you may have one spark plug firing normally and 3 that are intermittent. When that happens the engine won't make any power.

 

[boobie]

Re: 90hp V4 cylinders firing at different rates

My concern was that if you have a pack that went ape and advances the timing on one cyl it could burn a piston. Seen it happen.

 

[emmo1210]

Re: 90hp V4 cylinders firing at different rates

Hello gents,

Thanks for helpful advice, have since found a fault with the test light. It seems strange that the fault only occurred on 1 cylinder but i think it was the way the test light clamp was positioned on that particular lead, also being close to the bottom coil on that side, it started inducting that signal as well, so all is well thankfully.

Regards
Emmett