1988 Force 50 HP weird issue. Running on only one cylinder but....

[fmt2bx]

Hello,

I have an issue with a 1988 Force 50HP (single carb). It runs on 1 cyl only. Unable to get WOT rpm.


The weird thing is the following:

Motor starts fine. If I unplug Bottom cyl (#2) plug, the motor quits. This would tend to show that Top Cyl (#1) isn't firing.

However if I unplug #2 spark plug wire, the motor starts and runs on the top #1 cyl. (?)

So, with motor started, I unplug #1 plug and motor keeps running at same rpm not any rougher.
Motor started, I unplug #2 plug and motot quits immediately , cal#1 not firing.
Motor off, I unplug #2 plug and motor starts and runs with Only #1 plug.

Seems, that it isn't a fuel issue as I can get both cylinder to run but independently.


Here is what I have done so far:


Compression =130 on both cyl
Replaced spark plugs
squirt fuel mixture in carb and makes it worth, (too rich I presume)
There is spark on both plugs when tested and both are bright blue. (Changed the plugs any way but no changes)
Carb cleaned up.
Fuel pump replaced.

Any ideas? CDI box? Coils? seems like an electrical issue where when both plugs are on only one cal fires.

Thank you.

Fred


1

 

[jerryjerry05]

The pack has a blocking diode that could be bad?
There usually isn't a way to check the pack other than replace it.
outboardignitiondotcom has test procedures for your motor.
Some test can be done with a regular analog meter.
The more advanced need a DVA or peak reading volt meter.

The fuel pump could be part or all of the problem, take it apart and check for holes in the diaphragm.

 

[fmt2bx]

Thanks Jerry. I'll check the fuel pump diaphragm again. 1

 

[fmt2bx]

Quick update:

Checked fuel pump ----Good
Checked stator and trigger resistance and GND as per CDI---all good
Checked Coils--- all good primary and sec
Replaced battery
Borescoped reeds----all good
Swapped coils
Squirted fuel mix directly in carb

Same issue. Showing sparks on #1 and #2 when testing. Engines quits when unplugging #2 but with #2 unplugged motor starts on #1 only. This is maddening ....

So I guess I am going to swap the CDI box and will see.

Will update next week with status.

Thanks
Fred 1

 

[jerryjerry05]

Sounds like that's all that's left to do?
You try unhooking the regulator?

 

[fmt2bx]

No I haven't unplugged the Regulator. I should have. Thanks
The other thing I haven't done is check the DVA. Can't find my DVA adapter. A CDI replacement is on its way. S/b here next week.

Thanks again. 1

 

[fmt2bx]

Qick update:

Problem resolved!!!

It turns out that the #2 Cyl trigger wires had been connected backwards to the CDI.
My guess is that over the years the wire's coloring has changed and whom ever connected the CDI was confused.

Running great now.

Thanks for your help. 1

 

[jerryjerry05]

Been on here since 2008.
Diagnosing a wire that someone's hooked up backwards??
THAT'S A TOUGH ONE

Glad it's better.

 

[fmt2bx]

Yeah, it is a tough one but I should have known better and check all the wiring from the get go. Turns out that by doing so, some of the connectors just broke off too. Definitively time to check all the electrical connections when you buy a motor this old.

Cheers. 1

 

[jerryjerry05]

My 1988/85's
Port motor would miss at idle and then when warmed up it ran great.
UNTIL one day then the miss just wouldn't go away.

It was the trigger leads.
They were breaking under the shrink wrap at the connector.
You could even pull on the wire and it wouldn't come loose.
I replaced ALL the connectors on both motors, even on the pack and stator.