Engine only runs at idle with full choke

[GMcK106]

Got the engine running at idle with full choke only. Engine will stall or run rough when I try to advance the throttle.

Dis-assembled the carb and cleaned everything out with carb cleaner. left the idle jet in as idle seemed to work. Working in the boat so no compressed air to blow it out. Second attempt to run, same result. Took the carb home for a full Moyer kit rebuild and a chemical soak for the carb body. On second dis-assembly I noticed the main jet had some tan gunk in it that almost closed the jet. This stuff isn't coming out with carb cleaner either.

Also noticed that the rubber tip on the float needle was ragged, like something was eating it. Does anyone know if this was a problem with alcohol fuel or carb cleaner? I assume the carb was rebuild in 2004 when the engine was rebuild at Moyer.

Will report back on my progress.

[Dave Neptune]

106, are you using a carb spray when cleaning? If so I have not run across much that it will not desolve and remove!! Since ther is KRAP in the carb there is also KRAP in the lines and filters if so equiped.
If you have the carb apart again use a thin wire (copper prefered) to poke around the small holes then stick the "tube" from the spray can right against all orfices and give a good shot! Keep something over your eyes as spray will shoot out other passages in the circuit too.
IMPORTANT~when you hook up the cleaned carb be sure to have a fresh piece of hose on the carb and a NEW polishing inline filter at the end to hook back into the boats fuel system. This will possibly save you from just pumping more KRAP back into the carb.
I doubt that any chemicals in and around the fuel would eat at the tip of the needle. If the needle does not look almost perfect replace the needle and seat!
Another problem with the series 68 Zenith carbs is the manifold that feeds the needle and seat! There is more that one way to attach the fuel fitting and the cavity should have the plugs and fitting removed to be flushed out. Suprising the stuff I have removed from this area over the years on many carbs.

Dave Neptune

[CalebD]

Hi,

Were you able to sort out if your fuel tank has crud in it?
This is what the bottom of my fuel tank looked like.
The A4 does not like this kind of fuel at all since all the black crap is water with crap in it.

I am wondering if a head gasket replacement would help with your compression numbers?

[Sony2000]

The float needle stickyness is from varnish (carb cleaner), or deterioration of the rubber surface (1200 sandpaper). It's your call, when to change it.

[GMcK106]

Engine only runs at idle with full choke

Previous owner had repaired the gas tank and installed the fuel filter. Boat was laid up for bottom barrier coating until I bought it. Whatever this stuff was it coated only the main jet. Almost looked like a tan ceramic. Gumout carb cleaner wouldn't cut it. Chipped off with a sewing needle.

Everything is soaking in Chem-clean now. I'll put new jets in.

I dumped the contents of the fuel filter into a glass. Looked like clear, fresh gas. All the hoses were changed out with the filter install. I installed a new element. There was stabilizer in the gas.

[edwardc]

...I doubt that any chemicals in and around the fuel would eat at the tip of the needle. If the needle does not look almost perfect replace the needle and seat! ...

Well, something eats the tip of the needle! This is what I found the first time I disassembled our carb after purchasing the boat:



The rubber tip was completely gone! And the seat was almost closed off by a hard tan substance similar to what you describe.

Never did find out what the PO had used to cuse this, but since I replaced the needle & seat, it's been perfect every time I've checked.

[GMcK106]

All Cleaned!

Chem-Clean from Berryman worked great. Cleaned off all left over gunk everywhere. Brass parts are shiny again. Even cleaned brown parts around choke. This is a drop in and let soak product. Compressed air finished the job.

I'll re-assemble with new parts and see if it fixed it.

Wish I had this stuff when I was playing with the SU carbs on the Austin-Healey!

[GMcK106]

Running!

Carb re-jet and chem clean did the trick! Running smooth now.

I think I will now remove the carb for the winter and clean and store it off the boat.

[Mo]

Good for you...change all your filter elements now as well. If you have more trouble after that...lets say in the near future, you will need to clean your tank.

Have a good season.

[tartansailboat]

A question for the carb mavens out there. I put a new carb on my A4 11 years ago when I bought my boat. It has worked super all these years but reading from the group that they clean their carbs often, I am thinking I should clean it out. I dont want to disassemble it at all since it is running great. Can I just remove it from the engine and dunk it in this Chem-clean can or are there any non metallic parts that will be harmed?

[GMcK106]

Chem-Clean

The only caution on the can is that it will eat rubber, so the float needle needs to come out. I replaced all of the jets to renew gaskets and start new.

Unlike many carbs, the main jet is on the very bottom of tbe carb. Anything that finds its way there is going thru the main jet if it can. If not, the engine will only run with choke on at reduced power.

[GMcK106]

Mo, thanks. I replaced the filter element and siphoned off gas from the tank. Previous owner had tank repaired, so gas was good and tank was clean. Not sure where the crud came from as even the float bowl was clean. Seemed like it only plated out on the inside of the main jet.

[Mo]

A question for the carb mavens out there. I put a new carb on my A4 11 years ago when I bought my boat. It has worked super all these years but reading from the group that they clean their carbs often, I am thinking I should clean it out. I dont want to disassemble it at all since it is running great. Can I just remove it from the engine and dunk it in this Chem-clean can or are there any non metallic parts that will be harmed?

OK,
When you clean a carb take it apart and clean it up...not a dunk in some cleaner. Not hard to do and it will work just as well as it is now. If you take it off the boat and clean it up once a year I think you are golden. If the engine is used often (I thinking using 5 to 6 gallons per month) your gas should be pretty clean and a tank that has frequent used stays clean as well

[tartansailboat]

Mo, is there a simple way to clean the carb with it still installed on the engine? Say by removing the flame arrestor and squirting carb cleaner into the intake. If I do remove the carb, so I just separate the two halves and then use the carb cleaner or does more of the carb have to be removed. I assume a new gasket is called for when reassembling.

[ndutton]

Based on the questions I encourage you to get the video. It will walk you through the process step by step. It's exactly why the videos exist.