A4 Runs fine for hours then gets rough

[hanleyclifford]

So ethanol and additives are here to stay. And they will foul the carb, it seems. And afaik, they are dissolved so they don't filter out.
So what are we to do?

When dissolved the stuff is not a problem. It simply runs thru the engine with the fuel. It is the junk picked up by the additives than creates the problem because it is not dissolved but remains in suspension until it settles in the jets and crudifies. AFAIK the only thing we can do is filter aggressively and run the engines regularly. Once the tank has been cleaned by the ethanol the problem diminishes. In many cases we have 40 years of accumulated crud in our tanks but once it has been washed out routine changes of filters should keep our carbs clear.

[jkenan]

I filter using a Racor S3228TUL, and also have a secondary filter between the fuel pump and the carb. Also replaced my fuel tank two years ago with a new, welded Aluminum tank. The only place I fuel up is Oriental Harbor which claims to have Ethanol-free gasoline, and at the Beaufort Docks, which I believe has ethanol. The majority of time it is Oriental Harbor.

I'll definitely be checking grounds, terminals, and will take the advice to use a stainless grounding bolt on the transmission case. Will also clean my carb for good measure. I have an adjustable main jet which I'll probably install AFTER I get the engine running smoothly (so as not to complicate the issue with too many variables), as I plan to make some longer trips up and down the ICW this spring and summer and want to optimize fuel consumption, but that will be another conversation.

My fuel pump is a faucet pump from Moyer I installed in 2005, about 9 years old now, and my EI is also from Moyer installed around the same time. They both seem to be working fine, but should either unit be replaced after a period of time as a matter of point? I replace my distributor cap, rotor, and plug wires every year with a new set from Moyer, and my current set is about 6 months old.

[hanleyclifford]

There are not many places on the ICW where you can easily buy a fuel pump or distributor parts without a wait (at a marina) which can cost big bucks. Better to carry a spare distributor (or at least your old points set up). I also have a back up fuel pump. I'm impressed by your changing plug wires every year - overkill even by my standards.

[sousou]

Round #2

As previously reported, I had (have) a similar issue with my A4.

Event

Motored for about an hour at above-cruising RPMs into tide/wind directly on the nose. A4 ran like a dream and performed admirably in the rough conditions. Once back in range of Marina, we killed the motor and sailed around for 10-15 minutes. When I attempted to restart the motor didn't catch at all. After 2-3 tries, I put the throttle lever about 1/2 and it sputtered to to start. I put it in gear and cruised into marina at cruising RPMs, but as soon as I throttled down the motor 'knocked' and sputtered. I had to keep it in neutral at mid-rpms to keep it from ding while I sailed into slip.

I'm RWC in salt water so I run at 140-150. The electronic fuel pump is brand new on a 5amp fuse.

I'm thinking either the coil is overheating after extended motoring or idle jet on carb is gunked up.

[hanleyclifford]

Our Favorite Subjects

Motoring in rough weather can stir up the poo in your tank and deliver it to the carb (jets). Is your coil hot just before the shutdown? Two separate issues here.

[sousou]

Well. I sail in rough choppy water just about every time I go out (SF Bay in the afternoon), so I don't think my fuel was sloshed around any more than normal. The difference this time was I motored for an extended period. Normally I just motor in-and-out of the marina.

I stopped by this afternoon & the A4 ran like a dream at the dock (in neutral & in gear). The correlation of extended motoring and this problem is leading me down the coil path.

It's probably high time I replace mine anyways, so I'll go ahead and grab the 4omh resister that Don sells!

[Dave Neptune]

Gage=eeasy diagnostics

sousou, I think you need a fuel pressure gage and it would tell you of a different path. Most ignition problems other than fouling of the plugs are an off/or on condition. But when the fuel stream gets weak the engine sputters away. If your blessed with a mechanical pump you can operate the priming bale next episode, if not try a gage first IMHO.

Dave Neptune

[ndutton]

I'm thinking the same as Dave but from a different direction. There's certainly no harm in replacing the coil and doing so will put your mind at ease but the symptoms do not fit the typical overheated coil scenario. Installing the fuel pressure gauge a Dave suggested is very low cost and also results in no harm.

There's no downside to either.