I have a 15 horse twin with CD2 ignition system. I'm trying to get it going for a friend. The motor starts and dies within a few seconds. I've rebuilt the fuel pump beacause the diaphram looked to be in poor shape when I checked it and cleaned the carb twice and put a kit in it. No change. I did find some chaffed wires on the ignition sensor and charge coil wires so I isolated them from grounding out until I repair them. I did resistance checks on these two components and they check out as per the manual. 36 ohms on the sensor and 514 ohms on the charge coil. There is spark but it appears to be weak when checked with an in-line spark checker.
The motor operates like its starving for fuel but I don't know what else I can check on the fuel side. I don't have anything other than a multimeter to check things with so I don't know how to rule out the CDI box. Could the chaffed wires shorting to ground caus the CDI to fail in such a way as to give a weak spark? I don't want to change it only to find out I've overlooked something.
Not likely to be an ignition problem if it starts and then dies. My guess is the ignition is functioning.
There's a few more questions to ask about the fuel system before we leave it.
You have rebuilt the fuel pump. Check. Still stalls.
Look for air leaks in the fuel line; good, reliable connections, cracks in the hoses, start at the fuel tank and check all the way to the carburetor, etc.
When you start it, be sure you have the throttle to the start position to advance the ignition properly.
Can you keep the engine running by choking it?
Did you separate the carburetor functions between low speed operation and high speed operation? There's two routes the fuel can take within the carburetor, low speed path or high speed path. They each have their own troubleshooting routine.
How did you clean out the low speed jets in the carburetor when you used the repair kit?
Did you remove the Welch plug to access the low speed jets? Is the new replacement Welch plug air tight?
Can you keep the engine running by going aside the carburetor and pushing the throttle cam follower to the full throttle position (down)?. Watch out for the flywheel, it'll scrub your knuckles.
Let us know.
Agree that the ignition is functioning, but may not be functioning at optimum performance. Fuel may still be the issue.
The fuel pump lines and connections are good, all checked out, vacuum line to fuel pump replaced. The fuel pump will build preasure to the carb. checked by removing line at carb and pulling the cord to turn the engine over.
When starting, shifter set to neutral, throttle is set to start position, choke on, 2-3 pulls motor starts briefly but will not idle. Adjusting choke setting has no effect, motor dies. I have been able to jam my finger down onto the throttle lever and nurse the motor to higher rpm for short periods but it will not sustain operation when returned to idle. There is a small amount of throttle movement available within the start range and it starts better when set on the high side.
This is all pointing to a low speed idle circuit blockage or air leak, no?
My carb has the plastic mixture block bolted on top of the carb. I had everything apart that comes apart but did not remove any welch plugs and I don't remember seeing any in the kit to replace. I used compressed air and blew out all the passages.
I don't have an air gap spark tester. I have an inline neon bulb type tester that indicates a weak spark when compared with outher outboards in my stable with coil ignition. This is my only CDI. I have not tried the raw fuel in the carb throat yet but I suppose this would confirm that it is a fuel issue if I can keep it going with a few squirts.
I'll have to try that.
My mistake. Wrong carburetor. You do not have Welch plugs.
On yours, the low speed jets are beneath the plastic cover and gasket. They are visible if you look down the carb throat on the intake manifold side of the venturi. You access them by removing the plastic cover. There are three very small holes. Be sure they are clear; compressed air or small wire.
The low speed orfices have definately been cleared. Made double sure of that the second time I took the carb apart! I suppose I could still have an air leak, the gasket has been squeezed a couple of times and is now stretching a bit around a couple of the screw holes.
I guesss I'll try spraying some fuel directly into the carb tonight to try and confirm a fuel delivery problem.
I think you are on the right path with the low speed circuit of the carburetor or air leak.
From your description, the engine wants to run. Your carburetor high speed circuit sounds OK.
How's your low speed needle seat? Vent screen and needle retainer/gasket in place? Air silencer to carb seal/gasket in place?
I'd be surprised if it doesn't fire when fuel is forced to the intake.
Hang in there. It'll come around. Keep us posted.
I managed to get the motor to run when fuel is sprayed directly into the carb. This rules out an ignition issue. I'll have to pull the carb and go through it again but it will have to wait for another day.