Mercury 40hp 1980-40 runs only when carb cleaner sprayed in carbs

[jayard78]

I have a 1980 2 cylinder 2 stroke outboard that I just mounted on my boat. At first there was problems with how the previous owner set up the ignition but it would start up fine. Now after rewiring the ignition the engine will only start and run when carb cleaner is sprayed directly into the choke.

This happened originally and then we hooked the fuel line back to the original tank and it fired up fine. Even though we are still using that original tank now, it won't fire.

I suspect somehow air is getting into the fuel line but I don't know where b/c we replaced all the lines going from the tank to the motor (did not replace the small lines off the fuel pump) and we also held the new line submerged in the tank itself to troubleshoot the valve on the tank. The primer bulb feels like it is taking air into the line after pumping it a few times because it does not stay completely hard unless u keep pumping it.

NOTE1: There is fuel dripping directly in front of the carbs but I did not think this was related to my issue.
NOTE2: The motor is backfiring here and there when it is trying to start and occasionally when running off of carb spray. It was not doing this before.

Any advice?

 

[JB]

Re: Mercury 40hp 1980-40 runs only when carb cleaner sprayed in carbs

1. NEVER spray carb cleaner or ether (starter spray) into a 2 stroke engine. They contain no lubricant and will cause engine damage.

2. Go to the Engine FAQs Forum and do "Outboard won't start".

I am pretty sure your fuel delivery system is fouled, but do the troubleshooting to determine where.

Good luck, and let us know what you find.

 

[jayard78]

Re: Mercury 40hp 1980-40 runs only when carb cleaner sprayed in carbs

Curious, could I already have done some damage to the pistons/engine but running it with carb cleaner for a 2 to 3 minutes on possibly 5 to 6 instances?

 

[dennyb123]

Re: Mercury 40hp 1980-40 runs only when carb cleaner sprayed in carbs

Sounds like the engine is getting fuel fine, since fuel is dripping from carb. Carb probally needs a rebuild.

 

[jayard78]

Re: Mercury 40hp 1980-40 runs only when carb cleaner sprayed in carbs

The weird thing though is that the motor was running loud and strong until just recently, in fact we could not get it to shut off until we rewired the ignition except by putting the throttle in nuetral. Is the carb something that needs rebuilt often? Would this just happen all of a sudden?

 

[Laddies]

Re: Mercury 40hp 1980-40 runs only when carb cleaner sprayed in carbs

I doubt if you have done any damage but it's certainly not a good idea to run the engine on car cleaner except to see if it will fire. You might check the fuel pump diaphram and see if it's damaged

 

[JB]

Re: Mercury 40hp 1980-40 runs only when carb cleaner sprayed in carbs

Do the troubleshooting. Tell us what you find.

 

[jayard78]

Re: Mercury 40hp 1980-40 runs only when carb cleaner sprayed in carbs

Ok Im going to work on it more tomorrow night so watch for my post Tuesday night and Wed. morning. U guys rock.

 

[jayard78]

Re: Mercury 40hp 1980-40 runs only when carb cleaner sprayed in carbs

Ok here is what I got so far.

I have the motor to the point where it starts off the fuel but dies out in 1 to 3 seconds. The primer bulb always feels as if its pulling air from somewhere but I have no idea where. I have looked at all of the hoses coming out of the fuel pump and around the fuel pump itself and it is dry as a bone. There is a lot of fuel dripping from inside the carb itself (which is normal I have been told) and on the bottom of the carbs is this 1 inch nipple that is dripping gas. The nipple is hard to explain but I'll try. It is a medal part of the carborator that points directly downwards and is located directly underneath the carb. The fuel is not coming out of this very much but i do see a drop of fuel on it usually. (He said nipple )

Ok so other than that I have primed the bulb and then squeezed the holy hell out of it to see if I could see any fuel escaping and on one occasion I saw a spurt of gas shoot directly out of the starboard side of the motor toward the front. I saw this happen the other day too, but only once and shrugged it off. I don't see how this could be coming from the carb that is dripping gas constantly. There is a hose coming from the fuel pump to the carb (i believe) but it is located behind the starter and is very hard to see, but this is the location of where the spurt of fuel may have come, but as much as i can see the line is dry.

To troubleshoot my fuel and tank, I took a brand new tank I had and put 3 gallons of fresh gas in mixed perfectly 1:50 and connected a new piece of hose and new nozzle to the tank. Since I have now replaced all of the hose going from the tank to the pump and the bulb and the tank and the nozzle I really feel that I'm pulling air into the system from somewhere on the motor and not the delivery system.

Anyone know how big of a pain it is to take that starter off b/c I dunno where else to look except behind it?

I assume that if the primer bulb never stays completely primed then I am sucking air and if there is air in the line then the motor will do precisely what it is doing. Can anyone confirm my logic?

Thanks in advance.

 

[hkeiner]

Re: Mercury 40hp 1980-40 runs only when carb cleaner sprayed in carbs

It is not clear if you tried a different squeeze bulb when you connected the trial remote tank or if you used the same bulb. I ask because it is possible that the squeee bulb check valves are not working OK. Also, to confirm if you are sucking air somewhere in the fuel line, you can connect a short piece of clear hose inline at various points and see if you can see any air bubbles.

Just my thoughts...

 

[tashasdaddy]

Re: Mercury 40hp 1980-40 runs only when carb cleaner sprayed in carbs

there should be nothing dripping fuel anywhere. if it is the carb float needle is not seating properly, and closing off fuel flow. if you are using an aftermarket fuel line and bulb, there is an arrow on the bulb, point the arrow to the sky, they work better in that position. then the bulb should get hard, if it does not, either the check valve in bulb is bad, or gas is going some where it should not, like overflowing carbs. it being a 1980, it sounds like it may be time to change all the fuel lines to the new alcohol resistant lines, the ethanol in the fuel, deteriorates the inside of the old lines, causing carb problems.

 

[jayard78]

Re: Mercury 40hp 1980-40 runs only when carb cleaner sprayed in carbs

I bought a new bulb and am planning on installing all new lines tomorrow. Hopefully this will help the issue. I am not quite sure what a float needle is but I will look and see if anything looks out of sort.

 

[jayard78]

Re: Mercury 40hp 1980-40 runs only when carb cleaner sprayed in carbs

Ok I found the fuel line leak in the line behind the starter, but now I have found that the wires in my switch box or fdd up. I'm going to start a new Thread regarding this Called "Mercury 40hp 1980 Switch Box is Bad"