1989 Force 85hp dead cylinder

[alangore]

I am working on a 1989 Force 85 hp. the lowest cylinder is not making power. I have checked the carbs, seemed clean but still blew out all the passages after removing the jets and air bleed. All 3 cylinders have 120psi compression, the spark will jump about 1/2" but it doesnt seem to me as crisp or full as the other 2 cylinders. Is it possible the coil is bad and canno jump the gap while under cylinder pressure? An assistance would be appreciated.

thanks

 

[Jiggz]

The next test to do is called spray test. Using a pint size or even larger sprayer bottle (one that will not melt under gasoline) filled with fuel oil mix, remove the carb's air cover and while the engine is idling (and I know it is idling rough) spray directly into the bottom cylinder carb and watch for the engine rpm reaction. If engine rpm increases, you have fuel related or carburetion problem. If no change in engine RPM, you have either electrical/spark problem or might have broken reeds.

 

[alangore]

I did a similar test with a can of carb cleaner and a mist. It didnt change the rpm at all. thanks, I should have included it in my original post.

 

[Jiggz]

What is a mist? Carb cleaner may be combustible but does not have the same volatility as gasoline. When diagnosing you will need to use the right tool and right technique. Otherwise, you will end up chasing your tail coming up with nothing. With proper tools you can eliminate doubts and suspicions without having to have second thoughts.

Do the spray test and if rpm does not change then assume it is a spark problem. I believe you have the Prestolite ignition system, thus you can switch parts around to see if the problem follows. Start switching with the ignition coils, then followed by CDM.

 

[jerryjerry05]

I do that test with starting fluid.
It WILL make the motor stumble if it's drawing in.
No fuss no muss.
Just don't overdo the spray.

Pull the plugs and see if they are wet?
Possible the carbs float's stuck and not getting fuel???

Now try moving the wires around.
Move the leads to see if the no power affects the other pistons.
Move the packs around and see if that affects anything.

The trigger leads can break under the shrink wrap.
Replace the connectors and see if that helps.
Remove the flywheel and check for worn wires or dark spots.

Outboard ignition . com has test procedures. Might help???.

 

[alangore]

Carb cleaner works great. It works as a fuel for cars. I have filled up carb bowls and drove a car in the bay with an inop fuel pump. Ive also sat on the fender and sprayed it in the throttle body and drove them across the parking lot into the shop. I am swapping coils this evening as the wires are part of the coil assembly. I will also check for broken wires. thanks for the help.

 

[Jiggz]

Another option is to use an in-line spark tester which is readily available at auto stores. Just make sure you do the testing under the shade or in a not so bright environment to see the sparks. After verifying there is no spark then that will be the time to do the parts swapping. In-line spark testers cost less than $10 at HF.

 

[backhandman]

Sounds like the problem I just fixed on mine. Water was getting in the lower cylinder from a blown exhaust gasket and washing out the fuel. Replaced it and now it runs. I checked by putting a piece of paper towel in front of the spark plug hole and craned it over. collecting the liquid. then tried to ignite it. even though it smelled like fuel. it was too diluted with water to ignite.

 

[Jiggz]

Backhandman, that is one great troubleshooting. Usually, that will the last of the diagnostic testing required to isolate the problem.

 

[alangore]

while the engine is running I do see some water leaking out beneath the cylinder on the left. I am curious if it is the same issue. I will try the paper towel if he coil swap doesnt move the dead cylinder. Backhandman, was that gasket dificult to change?

 

[Jiggz]

If there is any water intrusion into any cylinders, this can be easily detected also with spark plug inspections. After running the engine for a little while shut if off and immediately pull the spark plug on the suspected cylinder. If there is water intrusion and the cylinder is not firing, there will be water droplets or wetting on the spark plug. If the cylinder was firing and has water intrusion ( so little it doesn't stop combustion) the spark plug tip will be clean as a whistle due to "steam cleaning".

 

[alangore]

I swapped coils last night and ran it without any water circulating. It still has the same dead cylinder. when I initially pulled the plugs the cylinder not firing was very clean and the other two had some light black soot. I suspect a reed valve issue at this point. Does everyone concur?

 

[Jiggz]

I'm not sure running these motors without any cooling water is a good troubleshooting step regardless of length of time. Anyways, were you able to validate there is spark or maybe there is NO sparks on that dead cylinder using in-line spark tester or using some other methods?

 

[jerryjerry05]

The reeds won't stop it from running on that cylinder.
Like I suggested in the other forum. Swap the packs around.

 

[alangore]

The same cylinder, Lowest, is still dead after swapping coils. How could a reed NOT stop it from working if the reeds are not allowing any fuel into the combustion chamber? I have since done a leakage test and only 7% leakage on the dead cylinder. so far everything I am looking at is leading towards bad reeds.

 

[jerryjerry05]

Reeds are a one way feed.
If broken they still allow fuel in and back out the carb.
You'll get an effect like a miss.
And fuel back out the front of the carb.
Changing coils around only proves the one coil's not bad.
Try swapping the pack around.

Then pull the carbs and check the reeds.

 

[alangore]

I have come to the conclusion it has to do with the reeds. I am going to pull the carbs this weekend. thanks for your help

 

[jerryjerry05]

Let us know what you find?