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1982 Johnson 15 HP - won't start, Carb problem?

poida said:
Have you replaced fuel pump, it can leak into the bottom cylinder causing it to run like crap and cut out.
Rig up a bottle of fuel gravity feeding directly into the carb and see how it goes.
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No, but I have previously rebuilt the fuel pump. I'm considering replacing it just to eliminate this.

However, would a fuel pump problem be intermittent as I am witnessing?


CMOS
 
When engine shuts off after 10 minutes or so, What do the plugs look like,black,wet,dry? Have you checked for spark when she dies asap?
 
johnnygjr said:
When engine shuts off after 10 minutes or so, What do the plugs look like,black,wet,dry? Have you checked for spark when she dies asap?
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It doesn't die "ASAP". The idle speed gets very low and then eventually the motor stops. I will pull a plug during my next test, but lately (since I readjusted the down position of the float) I don't see or smell excess fuel.


CMOS
 
What about a leak down test?Also, I just had a strange problem that left me sit with my 85' 20hp.Running good then dead.Lost spark.Ended up being the ground wire that is coming off CDI unit.May have explained some odd running issues I was working on.May have had a weak spark all along?
 
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newyota said:
What about a leak down test?Also, I just had a strange problem that left me sit with my 85' 20hp.Running good then dead.Lost spark.Ended up being the ground wire that is coming off CDI unit.May have explained some odd running issues I was working on.May have had a weak spark all along?
Click to expand...

This got me thinking. Since the low idle happens and corrects so quickly, I may have a cylinder dropping out. I'm going to pull the plug wires one at a time on my next test. This could be electrical.


CMOS
 
I just read your entire post today,again and there's no mention of an open air gap spark test ever being performed, troubleshooting 101, Compression, spark,and fuel tests.check all grounds on engine electronics for corrosion and security
 
CMOS said:
No, but I have previously rebuilt the fuel pump. I'm considering replacing it just to eliminate this.

However, would a fuel pump problem be intermittent as I am witnessing?


CMOS
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Mine was, so yes they can be intermittant. When the engine heats up/rev's are working the pump harder the fuel can leak into the bottom cylinder.
It wont cost you a thing to gravity feed the carb.
 
johnnygjr said:
I just read your entire post today,again and there's no mention of an open air gap spark test ever being performed, troubleshooting 101, Compression, spark,and fuel tests.check all grounds on engine electronics for corrosion and security
Click to expand...

Good points - did all of this previously.

CMOS
 
Forty posts and that thing is not running properly yet? If you have compression, spark that will jump a 7/16" Gap, and fuel, with a properly adjusted carburetor, it's got to run unless you have a sheared flywheel key.

The spark (with s/plugs removed) should jump a 7/16" air gap with a strong blue lightning like flame... a real SNAP! Does it?

I've read where you say you've got 120/120 psi compression per cylinder. Frankly I've never seen a 15hp with compression that high. However, with proper spark and compression, that leaves a fuel problem.

NOTE: When all is well, you should be able to pump the fuel primer bulb up to where it is hard.... then you should be able to grip that bulb and try to compress it further to no avail... that is the engine's fuel pump isn't leaking through the diaphragm and the carburetor is in proper condition (no hoses leaking, etc). If you can continue to pump that bulb (pumping fuel), either the incoming valve of that bulb is faulty OR a problem exists at the engine such as "Carburetor idle N/Valve out of adjustment." or "fuel pump diaphragm split/broken" or "leaking hoses" something of that nature.

Spark plugs should be Champion QL77JC4 plugs, gapped at .040 (strong flame) or .030 (long life).

(Carburetor Float Setting)
(J. Reeves)

With the carburetor body held upside down, the float being viewed from the side, adjust the float so that the free end of the float (the end opposite the hinge pin) is ever so slightly higher (just ever so slightly off level) than the other end. And when viewed from the end, make sure it is not cocked.

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.
 
Joe,

Yessir I have done all of the above, with the exception of pulling the fuel pump to check for leaks on the back side. I will do that this weekend.

Service manual states low speed needle backed out 7/8 turn, not 1.5. When I first got this running I barely had to move that mixture screw off the 7/8 to get a good idle. Subsequently the low/rough idle issue developed.

So my next course of action is to re-check the fuel pump, and then pull the plug wires one at a time when the low/rough idle is witnessed. I may have a cylinder dropping out intermittently.

For the record, I have your entire post above cut-and-pasted into a document from another post almost a year ago. As always, thanks for your input. I'm close to getting this on the lake.

I'll post my results after my next testing opportunity.

CMOS
 
Update 7-2-17

I replaced the fuel pump today and got the same results. She starts and runs smooth as glass for about 3-4 minutes then the idle RMP drops very low and eventually dies.

I pulled the plugs right after this happens to inspect. Top cylinder is fine. Bottom is fouled with what believe to be WATER. I even cleaned both plugs, re-ran this same test and again - ran for a couple minutes fine then low, rough idle, - bottom cylinder plug is fouled with WATER.

How does this happen? Help.

CMOS
DSCN7302.jpg
 
siphon your fuel tank into a five gallon bucket be sure and tilt the tank and put the hose at the lowest point of the fuel tank. Once the tank is completely empty just pour the fuel in the bucket back into the tank you will see the water in the bottom of the bucket if there is water in the tank. Then pull the plug off of the float bowl and pump the primer until fresh fuel comes out the carb. Put the plug back in the float bowl and fire it up.
 
kimcrwbr1,

I use this same fuel tank for my 1966 Johnson 9.5 which runs just fine all day long, so I'm confident the fuel is good.


CMOS
 
kimcrwbr1 said:
216-240 inch lbs or 18-20 foot lbs. Use a center out torque pattern
Click to expand...

It is a new head gasket. I replaced it when I changed the T-stat, but I did not check the head surface for flatness at that time. Is this the primary way that water gets into the bottom cylinder?


CMOS
 
start there pull the head and on a glass table with 220 grit paper swirl it in a figure 8 pattern until it all shines the same then torque it down slow in a center out pattern in at least three steps to 20 ft lbs. If you used sealer on the head gasket it needs replaced.
 
Unless I'm missing something I don't see how I can properly tighten those lower Head bolts without pulling the Power Head. Is this a correct statement?

I had a heck of time with those lower bolts when I re-installed the Head the first time.


CMOS
 
I tightened up the Head bolts as best as I could, with no positive results. The bottom cylinder is still getting fouled with water.

CMOS
 
Water entry points to either cylinder (or both) are normally via the head gasket and the exhaust baffle plate assembly.

If it were me, I'd be pulling the powerhead, checking both areas for warpage, installing new gaskets, and possible replacement of the inner exhaust baffle plate (pin holes). This would, by necessity, make replacement of the powerhead base gasket mandatory.... covering all bases.
 
joereeves said:
Water entry points to either cylinder (or both) are normally via the head gasket and the exhaust baffle plate assembly.

If it were me, I'd be pulling the powerhead, checking both areas for warpage, installing new gaskets, and possible replacement of the inner exhaust baffle plate (pin holes). This would, by necessity, make replacement of the powerhead base gasket mandatory.... covering all bases.
Click to expand...

Thanks Joe. This is getting over my head so I'll need to find someone I can trust to look at this.


CMOS
 
Nothing to lose! Most of the components etc can be left on the powerhead.

Remove the manual starter handle, hold on to the cord and tie it up on the powerhead somewhere
 
Joe,

How and where do I disconnect the throttle linkage before I pull the PH?

CMOS



joereeves said:
Nothing to lose! Most of the components etc can be left on the powerhead.

Remove the manual starter handle, hold on to the cord and tie it up on the powerhead somewhere
Click to expand...
 
I am wondering about your fuel line. Have you tried a completely different line from the tank to engine? I have experienced this myself recently with a 72 6hp. The hose worked good on my 25 but not on the 6.
 
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