1979 evinrude 35hp fuel problem

[fishon1213]

I have a 1979 evinrude 35hp that I am having some fuel problems with. The motor ran fine all last year and in the late fall suddenly wouldn't start for me. It seemed like it wasn't getting gas so I put it up for the winter and waited till spring. I just pulled it out and rebuild the carb thinking that would fix it, still the same story. The bowl on the carb has gas in it, but it wont even pop off. As soon as I spray ether past the choke plate it fires right up for a second and dies. Any suggestions?

[James R]

First suggestion, never use ether. You will burn up your motor. If you must spray into the carb use the 50:1 mix. The bowl may be full but is it good gas? Pull the fuel line from the "out" side of the fuel pump and squeeze the fuel bulb to check for fuel flow. If that is ok then you have a problem with the carb. If not there is a blockage at or before the fuel pump.

[fishon1213]

Thanks for the suggestions. I am getting fuel to the fuel pump and the gas in the bowl is fresh. I just had the carb apart and both jets are clear. I still think it's a carb problem, any suggestions on what to look for?

[Cofe]

When you worked on your carb, did you put in a new kit? I have taken Welsh plugs (core plugs) out and found lots of stuff in there. The only way to repair a carb is to tear it down, clean it, blow compressed air through all the passages, and install a new kit. Since it is getting fuel to the bowl, I think there is something in the carb somewhere.

[fishon1213]

I installed a new carb kit with a new float, jets, and other stuff. I soaked everything in a parts washer and blew compressed air through everything. It is getting fuel into the bowl but shouldn't it get fuel into the throttle plate chamber when I squeeze the primer bulb? I can hear the bowl fill up but then the primer bulb becomes rock hard. I don't remember a primer bulb ever getting that hard.
Can the brass tube(s) that go from the bowl to the top be removed for cleaning?

Sorry I am probably not using the right names for parts but someday I will learn.

[Cofe]

Do not try remove the brass tubes. As long as we know what you're talking about, proper names are not needed.

[AlTn]

you may also be experiencing a weak spark as the one needed to ignite that ether mix is much less than needed for the fuel mix..your spark should jump a 7/16" air gap as tested with an air gap spark tester available at most auto parts stores for $10 or less...you may also have spark to only 1 plug

[Lion hunter]

Have you tested compression?

[Cofe]

Thought I would mention something that I ran into awhile back. I rebuilt a carb using a Sierra kit. I noticed that the float would need some serious bending of the needle tab in order for it to work. After further investigation, I found the gasket under the needle valve seat was twice the thickness of the old one. I used the old gasket under the needle valve and never had to adjust the float. The float level should be parallel with carb body, with the carb upside down.

[James R]

The motor fired for you so you have spark and compression. We don't know how good but lets go back to your carb. Washing in a parts tank will not do the job. Go get a can of Gunk carb and parts cleaner. Strip the carb and soak it for a couple of hours. Move the parts around to ensure the solvent gets into everything. You can remove the Welch plugs for a better clean . This would be the better way but if you don't have replacements try cleaning with the old ones in place. I have not had a problem doing this. Wash in fresh water and blow clean with compressed air. Reassemble the carb ensuring the the float heights are correct.You have a type two carb so set the heights, with the carb in upside down position the float should be parallel with the body. If not then remove the float and bend the needle actuating tab to get the correct height. With the carb in the upright position measure the float drop. From the body to the lowest part of the float should be 1 1/8 inch min up to 1 1/2. to adjust remove the float and bend the small stop tab on the actuator tab. Insert the idle control screw and screw in until lightly seated then back it out 1 1/2 turns.This is the start point, some slight adjustment may may be necessary when running.
Good luck.

[fishon1213]

Thank you all for the advice.

I believe I have made all the correct adjustments to the carb and still the same problem. I have blown through every passageway I can think of with compressed air, both jets are clear, float and air mixture have been adjusted.

Once the bowl fills up, does the gas get pulled up the brass tube by the intake of the motor? And once the bowl fills up is the primer bulb supposed to get extremely hard? I thought it would just get firm but you could still squeeze it. It just seems like I am not getting gas up past the bowl, even though it is full. I have taken the high idle jet at the bottom of the bowl out, cleaned it, and blown air through it after putting it back in so that should be clear.

I am going to go do compression and spark tests and see what I find out. Then I am going to assume its not a carb problem and look at other options? Then I will dissasemble the carb again.

[bonz_d]

Another check to do. With the carb removed and the float bowl empty and the carb upright try and blow through the fuel inlet. Should be able to pass air through it. If not you have a needle valve that is not opening.

Last spring I was having a problem simular to this after a rebuild. Bowl would fill then the needle would stick closed.

[dew2]

The bulb getting hard is showing the float and check valve are properly working,Gas in the bowl.Something in the carb is not cleaned properly,reread James R post and reclean the carb.It is the problem.
A quick test put about 1/2 teaspoon of mixed fuel in each cylinder,remove the plugs,put mixed fuel in each hole,install the plugs and start,If it runs and dies the carb needs cleaned.Sometimes doing this will create enough suction on the carb it can clear itself.But if it starts runs and dies its lack of fuel from a clogged carb.

Stay away from either and unmixed fuel

[Lion hunter]

This is the series of events:
You prime the carb and the bulb should get hard once the bowl is full and the needle valve shuts off the flow. Once you start the motor fuel is pulled into the cylinder through the low speed jet (brass tube). The amount of fuel pulled in at low speed is regulated by the low speed needle valve (air/fuel mixture valve). A starting point for this valve is 1.5-2.5 turns out from lightly seated. Once a certain rpm is reached fuel is pulled into the cylinder through the high speed jet. The amount of full is then regulated by the size of jet.

Here are a few things to remember:
The engines compression creates the vacuum that pull fuel into the cylinder. A low compression engine may fire if fuel is put directly into the cylinder, that does not mean that it has enough compressionn to pull it in.
A bad float valve will usually not express itself until a higher rpm is reached. Assuming everything else is good, as long as there is fuel getting to the bowl the engine will start and run until it runs out of fuel even with a bad float. It will actually run several minutes on what fuel is in the bowl.
Clogged low speed jets are a nightmare! Whenever I rebuild a carb I replace the filter and all the hoses from the filter to the carb. It takes next to nothing to clog a low speed jet.
And last ....whenever troubleshooting it is best to start with compression, move to spark and then fuel. Reason is that without adequate compression you can't do anything. Once verified it is not very likely to change in the course of troubleshooting and it helps us understand where you at. Next is spark, verify routing of plug wires and presence of good blue spark that will jump the gap on a spark tester. This also can change but is unlikey during the course of trouble shooting. Last is fuel. Clean is never clean enough and any adjustment or speck of dirt can throw a wrench in all your efforts.

[fishon1213]

Thank you all. Lion Hunter, your series of events paragraph helped me understand alot. The boat is at my brothers and after work tonight I will get a chance to go over there and mess with it. I am going to do exactly what you guys are saying and go back to compression and spark just to be sure. Then back to fuel.
If the fuel pump were bad would that cause it not to pull fuel into the engine?

[Lion hunter]

The fuel pump just keeps the bowl full. A bad fuel pump can be "overidden" by pumping the primer bulb when it's running. Here is a animation of 2-stroke operation.
http://science.howstuffworks.com/tra...wo-stroke2.htm

[fishon1213]

Good news! Engine runs great, and smokes like an sob. Carb needed rebuild. I did everything right except prime the engine with gas in the plug holes. Thanks everyone.

FISHON!

[James R]

So what did I tell about cleaning and rebuilding!