'87 Evinrude 4hp OB - cleaned carb but still won't start

[djletin1]

Cleaned the carb and used carb re-build kit I got from Sierra but 1987 4hp Evinrude still won't start. Get good spark and confirmed fuel getting to carb. Get it to run a couple of seconds when spray fuel mix in Carb throat, seems like it starved for fuel but confirmed fuel getting through lines
to carb. This one has remote fuel tank. Not sure if I seat Idle Needle correctly upon re-install - don't know if that's the problem.

 

[JDusza]

Re: '87 Evinrude 4hp OB - cleaned carb but still won't start

Sounds like you need to go back into the carburetor. You have fuel going to the carb, but none from the carb to the cylinders.
The fact that it runs if fuel is forced into the intake is actually a good thing. You know it can run and wants to run. Don't give up!

Before you tear down the carburetor again, try these couple things together; the goal here is to remove the low speed jets and low speed adjustments from the "potential cause list".

1 Ensure your ignition is advanced: make sure the throttle is up past the start position, between start and full throttle.
2 Give it all the fuel allowed by the system and remove the low speed jets and adjustments from the scenario: manually open the carburetor the rest of the way to wide open throttle by holding down the throttle cam follower with a finger or screwdriver. Be very careful of the flywheel.
3 Give it full choke.
4 Now try to start the engine; 2 - 6 pulls. If it starts, it's really going to take off for you are holding the throttle wide open. Be ready to drop the speed at the throttle cam so you don't throw a rod. You may have to juggle between the throttle cam and the choke to keep it running.

Note: this is quite the "hand-dance", I realize. If the engine starts you'll have to drop the throttle cam some, drop the starter cord and grab the choke, then balance the throttle cam and the choke to keep it running. Very busy with your fingers! You may want to practice this before you actually pull the starter cord so you get an idea of the logistics and accessibility. Watch out for the flywheel. It can scrub you with its gear teeth.

If it starts and runs, you have a low speed fuel delivery problem; low speed path. If it doesn't start, you flat out aren't getting fuel to the cylinders; main jet path. In either event you'll have to go over the carburetor again, but, at least you'll know which direction to head.

Hope this helps.
J

 

[Rick.]

Re: '87 Evinrude 4hp OB - cleaned carb but still won't start

Did you genttly seat the slow speed needle and then open it 1 1/2 turns? By getting it to run with pre-mix spray it would indicated it isn't getting fuel from the carb. Best of luck.

 

[djletin1]

Re: '87 Evinrude 4hp OB - cleaned carb but still won't start

Thanks for reply. Not sure about re-install of slow speed needle. When I removed it, there was a plastic-like flat o-ring and a rubber grommet/bushing. The rubber grommet was just about disintegrated but it doesn't look like a replacement came with the kit. Do you know if it would and would it still be rubber? Also, I did not remove the Welch plug during cleaning.

 

[JDusza]

Re: '87 Evinrude 4hp OB - cleaned carb but still won't start

Three things required to run: spark, compression and fuel. You have spark. Have you done a compression test? You should be 80 psi or higher. Ideally, the cylinders should be within 10 percent of each other.

With the carburetor rebuild, did you clean out the low speed jets with a piece of wire accessing them through the main venturi inside of the throttle butterfly plate? If you didnt replace the welch plug, you didn't clean them from the top. The other way to clean them is to remove the welch plug and clear the jets from the top, then replace the welch plug.

Did you replace the main jet or re-use the old one? When looking through the jet with light behind it, a clogged jet could still "look" alright by nature of a round hole, but that hole can be clogged uniformly with old gas crud. You need to be sure the round hole is the right diameter. I have seen jets that "look" good, but when a jet cleaning tool or wire is run through, the old gas crusty stuff comes right out and the diameter gets a lot bigger. The result is "holy cow, that was really blocked!"

A new grommet will be fuel resistant plastic. If the flat o-ring and grommet are not air tight, the carb will leak air messing up the proper combustion mix. Even with good compression and spark you may not get a good robust explosion in the cylinder.

There's two paths fuel can take in the carb, the low speed path or the high speed path. This is why I try to separate high speed running from low speed running. If the engine won't start at high speed, you have something blocking fuel through the high speed section of the carb and you'll probably have no chance of starting at low speed. If it runs at high speed and won't at low, then you have a blockage in the low speed section of the carb.

If you are sure the carb is clean all around, then you may have to go deeper into the intake manifold looking for blockage or stuck reed valves.

What is the history of this engine with you? Has it ever run for you or is it a new acquisition?
Dumber question: is the tank vent open?

Good luck.
J

 

[djletin1]

Re: '87 Evinrude 4hp OB - cleaned carb but still won't start

I have used engine for last 9 summers. Over that time, I've replaced, fuel pump, starter spring and replace plugs every other summer including this past summer. Engine has worked fine, except past couple of summers it did take a hit of starting fluid to get it going but then ran fine.

Except for removing Welch plug, I removed and cleaned every orifice with solvent, carb cleaner, wire thru holes, rinsed wi water and dried w/compressed air. I cleaned and re-installed main jet since it did not come w/ re-build kit. I confirmed gas tank vent cap open and that fuel was flowing freely to carb, but not apparently thru it. When I spray fuel mix directly in carb throat, it runs for few minutes then characteristically revs as it becomes starved for fuel.

I'll order new flat o-ring and plastic grommet since old rubber bushing had deteriorated (can a suitably sized o-ring substitute for the plastic grommet?). I'll remover Welch plug and clean in there if you think necessary. I'll have to replace stating cord since that broke late last night when I was working on it.

Thanks again for your assistance, appreciate your expertise.