​Johnson 70 won't start/runs on 1 cylinder

[cferr59]

I have a 1980 Johnson 70 that will not start consistently and if it does start, tends to run on the bottom cylinder.

It has 100psi compression on all cylinders, I rebuilt the carbs (hoping to fix this) and additionally tried swapping in a second set of carbs that I have. The primer primes when activated and doesn't leak fuel otherwise.

I replaced the powerpack and all coils with parts from a blown parts motor. Once I did that, the engine started up and ran fine for about 15 minutes on the hose. I then tried to take it on the water and the same issue occurred where it ran on 1 cylinder and then wouldn't start again.

It seems like the cylinders are getting fuel because the 2 non-running cylinders plugs do get wet if I keep trying to start the engine. It also will not start on starting fluid either.

I tend to think it is an ignition issue. I performed the following ignition tests:

1.) Total output - spark jumps a 1/2 inch gap.

2.) Charge Coil - I'm not sure that the manual I have has the right values for these tests, but here are the results. I have a 3 pin amphenol connector that has 2 wires from the stator and 1 black/yellow kill wire.

a.) Ground check: Pass - A-B leads are not grounded.
b.) Output test: - Manual specified 250 volts or higher between A - B leads when cranking. However, I only read 11 volts. The wiring looks good. But, I'm surprised I would get perfectly good spark if there is a low voltage issue on this coil. Any thoughts on this?

c.) Ohmeter Test: 582 ohms. Manual specified 850 ohms. However, I have a stator from another motor and it also reads 580 ohms. So I'm thinking I may have a different stator than is described in my manual

3.) Sensor Coil
a.) Ground check. No voltage to ground when cranking from any lead
b.) Output test: .250 volts. Manual specifies .3 volts minimum.
c.) Ohmmeter test: ~12 ohms on each lead to timer base. (11+-3 specified in manual)

I have a 10 ohm resistor on order which is necessary to perform the power pack voltage test.

Any other ideas? Anything else I should check? Maybe it isn't the ignition, but I don't know what else it could be.

 

[flyingscott]

Re-do the compression test with a different gauge that is pretty low for one of those

 

[jakedaawg]

What tyope of voltmeter are you useing for your charge coil output??? These tests require a peak reading voltmeter.

Goto cdielectronics . com and down load their trouble shooting guide. Then ask needed questions. It makes it easier and you should not have an issue using it based on what you say you have done. You just might need a different meter or a DVA adaptor.

 

[cferr59]

I'm using a Fluke 115 meter with its MAX voltage mode. Is that basically the same thing as a peak reading voltimeter?

Also, I think my compression gauge reads low. Its a cheapy from Harbor Freight. I'm going to try hooking it up to my compressor to "calibrate" it.

Thanks for the advice on cdi's website. I'm going to take a look and see if it helps.

 

[cferr59]

Actually, I might be doing these tests incorrectly. I have been doing them in DC mode and it looks like the voltages are actually AC. Any idea if the Fluke 115 is an appropriate meter to use for this?

So the CDI manual answered my question: "A Digital multimeter with peak voltage scale cannot be used without the DVA as the meter is expecting a 60 hertz signal where the outboard can have an equivalent frequency of over 1000 hertz"

 

[jakedaawg]

Actually, I might be doing these tests incorrectly. I have been doing them in DC mode and it looks like the voltages are actually AC. Any idea if the Fluke 115 is an appropriate meter to use for this?

I have quite a few fluke meters...none have a DVA. I am not familiar with the MAX setting so...I am no help there. Maybe hook it up on AC and see if the reading makes sense.

I believe CDI sells a DVA adaptor. The problem I have found with a digital peak reding voltmeter is the values fuctuate so fast it is hard to read. An analog peak reading voltmeter has a needle that goes accros a scale. It is smoother and steady. Stevens Instrument Co. made them and that is usually the meter called for in an OEM manual.

 

[jakedaawg]

Many auto parts stores will let you rent a decent compression gauge. Frankly, you can get a snap-on guage for not that much money. Its really only their wrenches that are so darn expensive.

In my experience with this website and the many guys that are using HF tools...the consistency accross the cylinders seems to tell more than the peak number. There was a guy last spring with a HF guage that had even readings in the 60's. I gave up on the thread at that point but some others got him running. Conclusion: guage was both bad and good. It gave wrong values obviously but the consistency along with the fact that he got it running leads me to believe he had good compression just a guage with a scale that was off by half probably. (the motor he had should have read~125.)

 

[cferr59]

The Evinrude manual doesn't specify compression reading and only states that the variation should be less than 15psi. What kind of numbers should I expect from a Johnson 70 assuming the gauge is accurate.

 

[flyingscott]

A motor like yours after a rebuild would read in the 140+ psi. An original like yours I would like to see at least 110+. Your fluke needs a DVA adapter to work correctly. The only voltage that is DC on your motor is the charging voltage after the rectifier and starter motor everything else is AC. I would re-do the compression test with a different gauge because you could be reading high.

 

[cferr59]

It seems like this is some kind of fuel line or fuel connector issue. I swapped the stator, timer, and rectifier with spares from another motor that I had and still had the same issue. Figuring this mostly eliminated the ignition system as the issue (unless my spares were bad), I messed with some of the fuel fittings and was then unable get a prime. However, after doing this, I was able to start the engine without issue. Interestingly, I was never able to start it on starting fluid and there was definitely some fuel in the carburetors (but maybe not as much as they should have).

Regardless, thanks everyone for your help and I am pretty sure I will have it running consistently tomorrow after I replace all of the fuel lines and connectors.

Also, I've ordered a new compression gauge so I can get better readings in the future.