Fuel Problem '78 Evinrude, 35hp

[martysauer]

Thanks in advance - I have a '78 Evinrude, 35 hp. It starts when I pour a little gas into the carb directly, and then will usually start drawing from the portable tank once I do so. New fuel pump,(plugs too - great spark), tried two tanks (portable), tried two fuel lines, both new, same problem. Am I looking at a carb rebuild? Thanks, Marty.

 

[F_R]

Re: Fuel Problem '78 Evinrude, 35hp

Are you saying it will continue to run good at all speeds after you once get it started? If so, the carb is probably OK. Hard initial start is generally caused by a choke problem, or possibly sitting for an extended time where the fuel has evporated out of the carb bowl and left just oil behind.

On the other hand, if it doesn't continue to run well once you get it started then yes you are looking at a carb rebuild.

 

[martysauer]

Re: Fuel Problem '78 Evinrude, 35hp

When the problem first occurred last summer, it wouldn't start even by pouring straight gas into the carb. Then I got annoyed and didn't look at it for a week and once again I poured some gas down the carb, it started. I took it over to the lake, started it the traditional way (with the key, and no pouring of gas directly) and it ran fine for 2 hours. Then I let it sit for a couple weeks, and went to start it up, and had the same problem, and was able to get it running again by pouring gas into the carb. So I winterized it, and haven't thought about it since. Thanks...

 

[martysauer]

Re: Fuel Problem '78 Evinrude, 35hp

I'll add one more thing: tell me if this is a crazy thought, but I have a theory that I may have a clogged jet, which seems to open up under vacuum, but won't let any fuel out of the float chamber otherwise. Do jets clog the way arteries do - like a sludgy buildup that makes the hole narrower and narrower until there is no hole at all, or do my symptoms of having a great running boat once it starts mean that the jets are ok?

 

[Silvertip]

Re: Fuel Problem '78 Evinrude, 35hp

Sounds to me like you have a choke problem. And yes, jets can get covered or clogged with debris. First make sure the choke is working properly and that your starting procedure is correct. If you are not pumping up the primer bulb after long periods of non-use, that may be the problem. Once the fuel is pumped up to the carb and float bowl is full it appears to run ok.

 

[martysauer]

Re: Fuel Problem '78 Evinrude, 35hp

Thanks for the reply, and yes, I've been a pumping like crazy, and still no luck. How would I diagnose a choke problem? I can see the choke with the cover off and it isn't stuck or anything - it seems to do what it's supposed to do when I turn the key as far as I can tell - would there be a calibration or something?

 

[martysauer]

Re: Fuel Problem '78 Evinrude, 35hp

I just read something on another posting about the manual choke lever, versus the electric choke. Would you think that maybe the dumb owner (me) set that lever to the wrong position - could that cause this type of problem?

 

[F_R]

Re: Fuel Problem '78 Evinrude, 35hp

If the choke is closing when you work the switch, and opens when you get off the switch, it is OK.

Yes, jets clog. The high speed jet is a brass orfice plug with a small calibrated hole in it. It is in the very bottom of the carburetor where dirt and gum can get in it very easy. If it is clogged, the motor won't run right, or not at all. You may have to disassemble the carb and clean it. Buy a repair kit first so you will have the necessary parts to put it back together. They have the kits here at iboats.

 

[martysauer]

Re: Fuel Problem '78 Evinrude, 35hp

thanks f_r - I appreciate it. Is the consensus that it is more of a carb problem than a choke problem? Anyone else care to weight in?

 

[ezeke]

Re: Fuel Problem '78 Evinrude, 35hp

Have you tried closing the choke manually while you run the starter? No one can see what you are doing from out here.

 

[chrish]

Re: Fuel Problem '78 Evinrude, 35hp

a week fuel pump might act in that mannor too, needs a priming to get it flowing,
just a thought

 

[Silvertip]

Re: Fuel Problem '78 Evinrude, 35hp

Diagnosing the choke is simple. Its either open (horizontal) for normal running or closed (vertical) when activated, thus closing off the throat of the carb inhibiting the flow of air and causing more fuel to enter the intake. If it's not closing all the way, it's not functional and needs to be adjusted or the parts that are worn and not allowing it to work properly need to be replaced. If the engine runs wide open and idles normally and the only problem you have is cold starts, that says operator error or choke problem. Since wide open throttle is not a problem, the fuel pump is a non-factor. Lastly, does this engine have a primer solenoid rather than a choke butterfly? If you look into the throat of the carb and see two butterflies (one choke and one throttle) it won't have the primer solenoid. That system is entirely different and presents a different diagnostic approach,.

 

[martysauer]

Re: Fuel Problem '78 Evinrude, 35hp

It has two butterflies - one choke, one throttle. I agree that the fuel pump is fine, especially since it's new. The only thing that leads to believe it's not a choke problem, is that I can see it close when I push the key in to start it up. It seems to me that if closes fully.

Would I see this type of behavior if the float were stuck in the up position?

 

[Silvertip]

Re: Fuel Problem '78 Evinrude, 35hp

If the float were stuck in the up position, the engine would run the existing fuel out of the float bowl and it would sputter and die. Since it seems to run fine otherwise, the float bowl would be full of fuel when you shut it off. Unless the float bowl is leaking, there should be fuel in it for a restart. If you tilt the engine up when not being used, the fuel can run out so you would need to pump the primer bulb to refill the carb. If you are not doing that, it takes forever for the fuel pump to draw fuel up to the engine. Have you checked compression on this engine. Low compression can cause poor cold starts. Have you done a spark check. Weak spark can also cause poor cold starts. Spark should exhibit a sharp blue snap not just little flash.

 

[ezeke]

Re: Fuel Problem '78 Evinrude, 35hp

You might want to check the reeds.

The gasket between the manifold and carburetor must be airtight.

The pump mounting gasket behind the fuel pump must be airtight as well.

 

[Saskatoon2005]

Re: Fuel Problem '78 Evinrude, 35hp

I would do a full diagnosis...
1) check compression (it only takes minutes if you have the guage)
2)check spark (pull plugs and check for bright blue spark)
3)check carburetor ( not much trouble to pull and rebuild, and you can visibly check the reeds from there once the carb is off the engine. When was the last time it was done? I had the same rpoblems and I found out it was a weak spark, after I rebuild the carb like three times.....LOL!

 

[martysauer]

Re: Fuel Problem '78 Evinrude, 35hp

Is the intake mainfold gasket included in a typical carb kit? That's an interesting thought about the fuel pump, because I changed the pump, but not the gasket I don't think...thanks a million for the ideas.

 

[F_R]

Re: Fuel Problem '78 Evinrude, 35hp

In the very bottom of the carburetor, facing forward, is a hex head plug with a screwdriver slot in it. Take that out when the motor won't start. Gas should run out if there is any in the carburetor. If there is gas in there, it is not a supply problem.

Deep in the hole where the plug came out is the high speed jet. It is removed with a special screwdriver. Don't try to use a regular one, it will bugger up the jet and you may never get it out.

Use the special driver (see below) and take out the jet. It should be absolutely clean, not even a trace of gum or crud in it. If there is, you might get away with cleaning it, but more than likely need to disassemble the carb and do it right.

You can make your own special screwdriver. Use any cheap Wal-Mart type screwdriver with a 3/16" round shank. #1 Phillips screwdrivers are often ideal. Cut off the business end and grind or file a new flat blade with parallel sides. It is important that the sides be parallel. It is the tapered sides of a regular screwdriver that spread the jet and jam it in the threads.

 

[F_R]

Re: Fuel Problem '78 Evinrude, 35hp

Let's try that picture again

 

[Lubosleftboot]

Re: Fuel Problem '78 Evinrude, 35hp

If as you say the engine was lying idle a varnish gathers on all the carbs interior parts I had the same problem with my 1981 35 hp Evinrude.

I stripped and cleaned out the carb after that no problems starts easily and idles as well....

I did not buy a carb kit either I just cleaned the carb out properly with carb cleaner here in the UK we are not allowed to use sea foam unfortunatly....

LLB