A-4 dies at higher RPMs and smokes

[pearsontriton28]

I have an A-4 in my 1961 Pearson Triton 28. As far as I know, its the original engine. All though it has no modern upgrades, with exception to the fuel/water separator, it has been meticulously maintained.

After installing the fuel/water separator and regular weekly use without any problems, I thought my fuel issues were over, until last week.
Here's what I have going on:

-Engine starts easily

-Idles nicely, no "missing" , idles smoothly

- As I throttle a little above idle, the engine looses power as though it is fuel starved. I have no tachometer to indicate at what RPM this starts at.

- I notice it smokes a slight gasoline smelling white smoke out the exhaust as the RPMs raise. very similar to what you smell when you first start a lawnmower.

- I can get the engine to rev significantly and smoothly if I advance the choke a bit.

- I notice the white smoke increases as I throttle it up with the choke advanced.

- I have not noticed a change in oil pressure or level.

With that info in mind, what do you think is happening and how do I fix it?
Do you think the smoke is related to my carb/ fuel issue? thanks in advance.
Edit: I do have a polishing filter in line.

[tenders]

I’d recommend adding a polishing filter and an inline fuel pressure gauge between the fuel pump and the carburetor.

The filter is just good practice and the gauge will tell you whether what you’re experiencing now is a fuel pump problem or a carburetor problem. It could be either, but I’d guess it’s the latter, so while you’re waiting for the filter and gauge t arrive I’d take off the carb and clean it out thoroughly, as described many times here.

[pearsontriton28]

Thanks for answering, I need to edit my original post as I do have an inline polishing filter. I will check into a fuel pressure gage and clean the carb.

[ndutton]

The choke effect speaks strongly to the mixture leaning out at higher RPM. I think if it were a lack of fuel supply (pump, filter) the choke wouldn't make a difference. If it were a vacuum leak I think the idle would be affected too which it is not. The typical problem is a clogged or partially clogged main jet so count me in on Tenders' advice for a thorough carburetor cleaning. If debris is found or if cleaning solves the symptom it will then be time to find out where it came from.

Also, just because it is affected by RPM too, lube the distributor advance flyweights. There's no downside and you'll be sure it's not contributing to the symptom. If at all possible, please do it with the distributor in situ. We don't need to introduce timing issues to the mix.

[JOHN COOKSON]

, I thought my fuel issues(?) were over, until last week.
Here's what I have going on:
- I can get the engine to rev significantly and smoothly if I advance the choke a bit.
.

What were the "fuel issues"? Are they still ongoing or new ones?
With the choke closed a bit the engine revs up in gear or out of gear normally?

TRUE GRIT

[pearsontriton28]

Fuel issues refers to the water accumulation in the tank. I use better gas, start tron additive and I installed a fuel/water separator. I can advance the throttle without it stalling if I have the choke closed a bit. Doesn’t matter if I have it in gear or not. Acts normal with the choke slightly closed.

[capnward]

I agree with the diagnosis of a clogged main jet. In my experience, cleaning the carb and jets, and replacing inline filters, usually fixes the problem. We A4 owners eventually become proficient at this. I have gotten the process down to three hours. I sometimes do it before starting the engine in the spring, to be pro-active. If by 'better gas' you mean non-ethanol, I agree with that, too. Ethanol makes the water in your tank mix with the gas, and degrades the rubber parts of your fuel system, IMO. An enzyme fuel additive like star tron is good, to keep the water in your tank from growing things that clog your fuel filters and carb. I also use MMO, as I think do most of us, to keep the fuel pump and valves lubricated. A water separator is essential. The fuel pressure gauge tells you if there is a restriction in the flow. You may want to consider an adjustable main jet. I have read here of a problem like yours being solved by turning the adjustable jet in all the way to the seat, and then backing it out 1.5 or 2 turns. This apparently clears the jet opening, but it also must send the crud into the carburetor, to possibly clog the idle jet or obstruct the float valve.

[pearsontriton28]

Yes, I use non- ethanol gasoline. I’m going to clean the carb and main jet as you and others have suggested. I will start using MMO as stuggested as well. Do you think the white smoke issue is related or it coinsedence that the carb issue is happening at the same time?

[Dave Neptune]

RE the white smoke, are you sure it is not just steam? Various atmospheric conditions can create steam "showing" in the exhaust. It is always there but may not condense for visibility.

How old is the exhaust? A plugged exhaust can create the symptoms you describe too. This is usually a steady progressive performance issue. Not often sudden unless an exhaust hose collapses on the inside.

Dave Neptune

[pearsontriton28]

You raise good points. It could be steam, but it seems to linger and dissipate like smoke. Last season, I had very little of it. This season, it seems like I have noticeably more. I’m not sure how old the exhaust is. It looks to be in good shape to me. With steam / smoke , I start thinking of the possibility of a bad head gasket or cracked head. Really would like to put those concerns to rest.

[ndutton]

The two concerns you mention can be tested easily with a cooling system pressure test (lots of info on the forum).

[pearsontriton28]

update

thanks everyone who responded to my post. I wanted to give you an update and an opportunity to further comment if you would like.

I pulled the carb and tore it down. heres what I found so far:

- some surface rust on the bottom of the fuel bowl.

- main jet was turn out 6 turns, I removed and flushed flakes of crusty particulate out of the jet orifice. the PO and now, I am running an inline polishing filter so I doubt the rust came from my fuel tank. I'm thinking it formed inside the carb surfaces as a result of having water in my fuel in the past.

- the main jet itself was dirty - I cleaned and replaced it back out 2 1/2 turns

- the idle needle valve was out 1 turn and was clean. I replaced it back 1 full turn out.

[ndutton]

Very interesting

- some surface rust on the bottom of the fuel bowl - flakes of crusty particulate out of the jet orifice - the main jet itself was dirty -

and the coup de grace

I use non- ethanol gasoline

You mean this wasn't the fault of the oft assumed go-to boogeyman ETHANOL?

[pearsontriton28]

and the coup de graceYou mean this wasn't the fault of the oft assumed go-to boogeyman ETHANOL?

Honestly can’t believe the motor ran with that much particulate in the jet. So the whole ethanol thing came to light in early June when the carb on my lawn mower took a dump on me, mean while, I was having issues with moisture in the A4. The guy at the lawn mower shop schooled me on ethanol and it’s evils. $150.00 down on the counter, a new carb on the mower and he was telling me to use marine gas for the lawnmower because it contained no ethanol, thus drastically cutting down on moisture issues. Ethanol apparently is corrosive to the delicate parts of a small engine carb also. I had an epiphany at that service counter. I was using pump gas in the boat at the time and had no separator because the previous owner didn’t use one- I was sabotaging myself with pump gas which led to water in the gas and ultimately rust in the carb. I have been using non-ethanol gas. . I was too slow a learn on this one I guess. Anyway, I just got back from reinstalling the carb. I’m happy to report that the old A4 runs great and revs nicely. I have significantly less smoke also. Thanks again.

[sastanley]

Hello, I decided to comment on your post because it seems that your lawn mower guy assumes that if you buy gas at a marina, it is ethanol free. In the mid-Chesapeake Bay where I am, I have found ZERO marinas with E-0 gas. There are a few non-marina places (like restaurants with a fuel dock) that do sell E-0, but I generally source my E-o gas from a land based fuel company via jerry cans.

If you really want to make sure you are running E-0 gas, I have found this site pretty reliable.

https://www.pure-gas.org/

Neil and I and others on the forum have gone round and round with E-0 vs. E-10..all good discussion. I prefer to lug E-0 to my boat in jerry cans.

Let's hope the junk in the jet was the issue!