Johnson 15HP 1997...continuing problems

[bigfish55]

I posted here about a couple problems I've had during reassembly of this motor (my first rebuild). Thanks for the imput everyone. I knew other issues would arise before it was complete, and of course they have. The first one was a leaking fuel pump. It didn't leak before, so I couldn't understand why it would after a careful rebuild. I took it apart and reassembled it several times, and I could see it was the O ring. So ordered new O rings and cap, and instant fix. Somewhere along the line a different cap was installed, because the new one was noticeably thicker.

So did the tank test yesterday and it started on the third pull. Idled pretty well too. OEM called for break-in to run first 20 minutes at 1500 RPM in gear. Anyway it died after 10 min and it was late so I went at it again this morning in much better light. It didn't want to start, but after playing around with it, I got it running. The motor sounded very healthy, compared to before the rebuild.

Anyway, I noticed some water leaking out from behind the thermostat, looked like it was coming from the head gasket. So I doubled the RPM and water was squirting out from the HG a couple of inches. I double checked the torque, but that was OK, so I pulled the head off and noticed a depression about 3/8" wide X almost the thickness of the powerhead case right above the top cylinder. This is clearly the problem. I prepped the damaged spot and filled it in with some JB weld.

I also noticed some type of tan colored "patching" on the PH just forward of the damage. I thought the machine shop put it on because I got it back sandblasted and it was painted when I sent it to them. I called them and they said they don't do that. They "repair" engine parts. So maybe it was under the paint and hidden, but it looks like it was clamped wrong. Either way, that water leak was never there before, and I know I didn't damage it when I re-installed the head.

I'm just wondering if that JB weld is a legitimate repair choice for a machined surface like that after it is smoothed flush? The head will be bolted over the repair, so I would like to think it will be OK? Machine shop said the pressure in the water jacket is about 16 PSI...I have no idea. The beat goes on...

 

[Willyclay]

I also noticed some type of tan colored "patching" on the PH just forward of the damage.

A picture or two of this damage would sure help me and I believe other forum members as well with our input.

 

[bigfish55]

I'll try tomorrow, but the PH is repainted now. I did file away some of the excess and it appears to be grey...I guess the sandblasting caused the apparent color difference.

Also, I forgot to mention that the damaged spot is probably .005 -.010 deep...so not that much. I'll check back on here tomorrow. I don't have a computer at home.

 

[bigfish55]

Well the patch job worked fine, no more water leak. The problem I'm having now is keeping the thing running. It starts normally the first time: pump ball, choke out, 2 pulls and starts, choke back in when it sputters, give it a little throttle and it runs OK for about 20 seconds or so and then wants to die. If I give it more gas it will keep running but then die anyway after about another 10 seconds. At this point I don't want to over rev it...I'm trying to follow the break in procedure.

When I try restarting, the only way I can get it started is with half throttle in neutral...but then it just dies pretty much right away when I reduce the RPM. After it cools for a half hour or so, I can repeat as above...but I'm pretty sure it never got close to operating temperature.

 

[thatone123]

Sounds like it needs a carb clean. Spray carb cleaner - Berriman's Dip - hydrosonic dip with Pine sol - spray carb cleaner again. This is best but if not available, just Spray carb cleaner, but does not do the greatest job many times if clogged up in the small passages.

 

[bigfish55]

It does act like a fuel delivery problem, but I did a complete carb rebuild including multiple solvent applications/air blowouts and the carb sat in my office for 2 months, and didn't see any fuel until a week ago. I may have to take it apart again just to double check.

 

[heypawpaw]

Did you try pumping the primer bulb when it cuts out to see if that would help?

 

[Joe Reeves]

Did you try pumping the primer bulb when it cuts out to see if that would help?

Interested in the reply to that question. If pumping that bulb (acting as a manual fuel pump) allows the engine to run on... suspect a faulty fuel pump, or air entering the fuel line at some point which should also cause a fuel leak at the same point,

If a fuel restriction exists, that should cause the bulb to have a tendency to collapse.

 

[bigfish55]

Pumping the primer bulb doesn't help...still dies. The carb is full of fuel and when I disconnected the fuel line from the carb and pulled the starter rope, fuel shot out of the line. BTW the fuel pump has been completely rebuilt just a few weeks ago. The bulb stays very firm throughout this start/die cycle I doubt that the motor is even using all of the fuel in the carb before it dies...but not sure. Anyone know how long would it run at half throttle with just the fuel in the carb bowl?

 

[Joe Reeves]

Pumping the primer bulb doesn't help...still dies. The carb is full of fuel and when I disconnected the fuel line from the carb and pulled the starter rope, fuel shot out of the line. BTW the fuel pump has been completely rebuilt just a few weeks ago. The bulb stays very firm throughout this start/die cycle I doubt that the motor is even using all of the fuel in the carb before it dies...but not sure. Anyone know how long would it run at half throttle with just the fuel in the carb bowl?

I'm aware that the fuel pump was rebuilt... several times, but it needed to be questioned.

How do you know that the carburetor was still full of fuel when the engine quit?.... Remove the hose at the carburetor and observe while you apply pressure to the fuel primer bulb to make sure that fuel is flowing to the carburetor at that point.

If you have a fuel flow at that point, double check your carburetor work... float level, possible float upside down (it happens),

Double check and carefully clean the high speed jet located horizontally in the bottom center of the float chamber (way in back of the drain screw) with a piece of single strand steel wire as solvent just doesn't do that job properly. Fuel must flow thru that jet before it gains access to any other fuel passageway.

If all is as it should be... if that engine has but one carburetor and it is full of fuel, that is enough fuel to run for at least 30 seconds or so (perhaps longer) as it would still be pulling fuel from the fuel lines and pump.

 

[OptsyEagle]

deleted.

 

[oldboat1]

Unhook the fuel line at the carb (fuel pump to carb) and crank the motor. Insure there is fuel being supplied. Weak supply would likely mean the pump diaphragm needs replacement.

 

[bigfish55]

Thanks Joe.I pulled the carb again to double check everything, removed the drain screw (full of fuel) and shined a light through the opening. All I could see was the float so I removed the bowl and there was a very small brass screw with maybe a 1/64 hole through it. This was screwed into the long aluminum protrusion that the float fits over in the bowl. Is this the high speed jet you spoke of ? If so, it appeared clean, but I ran a wire through it and cleaned in acetone, then blew out the hole it screws into. There is another hole inside there that looks clear.

I'm certain the float was installed correctly originally. I can blow air through the fuel inlet when the carb is right side up, but it seals off when flipped upside down. Fuel flows well to the carb when the ball is squeezed. As far as the carb having fuel the moment the motor dies, I can't be sure. I probably checked the ball for pressure before trying to restart it. If the same problem occurs I will check it then before proceeding.

As an aside, the small brass jet looks identical the the picture of the one for the 9.9HP rope start #0323703. My motor is a 15HP rope start and according to the parts list, it's calling for #0326500. The picture of that is too blurry to tell what it looks like. Model # of my motor J15REUC.

 

[Joe Reeves]

Yes, your explanation indicates that you've located the high speed jet. They all look alike to a degree, however the ID is of course different sizes. The iD is imprinted on the side of the jet.

 

[bigfish55]

Another question...not sure if's related to my problem or not, but just more of a general knowledge question. I've read of "vented" fuel tanks. Mine is a metal 6gal, original OEM I believe. The bulb and lines/connections all seem to work fine, appear to be in good condition, and no leaks anywhere. I can go out into the shop every 2 hours and unscrew the gas cap and there is a very noticeable hissing sound and air escape. Is this normal? To me a 'Vent" is something that releases pressure. Ambient temp here is 45-60F.

 

[Joe Reeves]

If the vent was a two way vent, more or less a hole in the top of the tank so to speak... bouncing around would have fuel dropping all over the place. I'd suspect the vent is a one way vent... to allow air in only.

Some metal tanks has two small pin valves (air & fuel) that the plastic fuel connector pushes in... others may have a screw type valve in the fill cap.

 

[bigfish55]

I finally got this motor running in the barrel at a speed a little over idle, to where it won't die. I'm not trusting the speed settings on the tiller...in fact that control almost seems like part of the problem. I have a question about temperature. I replaced all the parts in the thermostat except for the 2 springs, and it has a very strong stream out of the telltale, but the water coming out is only lukewarm at the warmest. Is that normal? I thought it should reach up to 140 degrees or so.

 

[Joe Reeves]

The water from the water pump is supplied "First" to the exhaust baffle plate area where the fitting is located that supplies the water flow to the telltale..... NOT after the thermostat area. As such, the telltale water flow would be far below the thermostat temperature setting.

 

[oldboat1]

surface temperature on top of the head should normally be between 120-140F (affected a bit by temp of incoming water.) Also, look for an idle needle valve on the top of the carb. As the motor will start and run for you at a fast idle, start it and warm it up, then adjust idle needle (air mix) -- clockwise first. If the motor speeds up, throttle it down and continue needle adjustment. If it stalls or lean sneezes, open the needle slightly to correct.

 

[bigfish55]

Thanks for the info. If I would have followed the schematic for the water path I should have caught that, but the one I have is very hard to follow, due to poor print quality. After still more tinkering, I got the idle down to where I think it should be. That, plus I hadn't completely tightened one of the bolts on the throttle linkage causing the RPM to rev quite high without even increasing it. That made a huge difference obviously, and I had the motor running like a peach in the barrel this AM.

I won't ramble about the details, but due to unforeseen circumstances, I elected to pull the head off to check for damage from possible overheating. I was dismayed to find that the repair I made with the JB weld FAILED. Either the sealant, water, exhaust, or I don't know reacted with it and turned it all rubbery, It's supposed to be good to 500F so I doubt it was heat. I don't thing the motor really overheated anyway.

Any advice on what to use to patch a small ding on the machined crankcase surface where it mates with the head?