Need Full choke to hold idle, dies above idle

[aelxon]

I just got a boat with an A-4, and it started and ran poorly when I bought the boat...now it starts and runs very poorly. The engine needs full->nearly full choke just to idle, and anywhere from half->full throttle just to idle. Engine will not go above idle currently.

I've changed the coil, and changed back to the old coil, with minimal effect. I just took the carb off and opened it up, and sprayed wd-40 through the jets I could access without removing floats. I put the carb back on, then hooked up an outboard tank with clean fuel directly to the carb(bypassing the older electric fuel pump), and using a squeeze bulb and gravity to keep pressure in the line...no difference, the A-4 still runs as it did, prior to these changes.

After initially replacing the coil, I did notice that the fuel pump wasn't getting power, and I wired it to the coil, then experimented with wiring the pump directly to the battery. With the engine shut off, but power applied, the pump would tick continuously, and if I squeezed the fuel bulb, the pump would speed up a little...but no fuel was dripping out of the carb, or pooling near the choke valve.

I'm going to try installing a new electric fuel pump(Facet, 3-4.5 psi. Box shaped, instead of canister shaped like the weathered one I removed) tomorrow, but it seems I'm throwing good money after bad possibly...any suggestions?

Note: what I could see inside the carb, looked very clean...no gunk coming out when I cleared jets with the wd-40, clean gun-metal look to all the interior surfaces, the floats had a nice weathered bronzy hue...it looked clean.

[Marian Claire]

Two things come to mind. Not enough gas or way to much air. The carb is suspect until it is completely disassembled and cleaned. Using carb cleaner and a small wire to clean out the passageways. Have you tried to adjust the idle mixture adjustment?
Dan S/V Marian Claire

[tenders]

You’ve pretty much ruled out the fuel pump as the source of the problem, I wouldn’t bother replacing it. But a fuel pressure gauge would be a useful $20 addition between the pump and carb.

The symptoms sound like a carb that is getting increasingly clogged (the WD-40 having proved or helped nothing - the main passage is not the issue), or compression getting worse (sticking valves), or bad timing.

[Dave Neptune]

If your carb has idle trouble and won't run past idle without the choke points to fuel delivery. Unless you know you have fuel pressure and not just clicking get a gage to check!!!

WD-40 is worthless as a carb cleaner other than it has a bit of pressure to "blow" something out or wedge it in tighter as it will not "cut/dilute" gummy fuel or moisture deposits.

Leave the ignition alone as well as the carb until you replace the pump or get a gage. If the confirmed fuel pressure does not get it to run time to actually clean the carb.

How old is the fuel?

I somewhat suspect the carb as the squeeze bulb should of worked.

Fire up the pump and then shut it down so you can open the "main jet plug" to confirm that fuel is getting into the bowl. If it is get a carb kit and some carb or brake cleaner. Some small wire will be needed to be sure the both idle ports are clear, a common place to plug up.

Dave Neptune

[ndutton]

I would add . . .

. . . and get the carburetor video from Moyer Marine. IMO it's the best money you can spend right now.

[aelxon]

Gas is new gas-station 87, and in a clean outboard tank. I used a fuel pressure gauge on the old pump, and it wouldn't go above 1 psi(I could blow over 1.5). It looked like trapped air might have been affecting the reading though.

I put in a Facet/Seachoice 20341 fuel pump(3-4.5 psi), and it hasn't made any difference...still barely holding idle, and only with full choke, and moving the throttle from about 1/4->full doesn't change the speed(but dropping the throttle to it's idle position kills the engine).

I'll probably pull the carb off tomorrow and give it a better cleaning. I don't want to buy a video on how to do this, but maybe I'll look around on U-tube. I'm reluctant to make any intentional, or accidental adjustments to the carburetor, before ruling out that it is just dirty, or that there is some other problem...I don't want to compound the mystery.

It looks like I have an electronic ignition system, under the distributor cap. Also, the negative side of the coil reads positive voltage when the ignition key is turned on, the same voltage as the positive coil terminal...I wouldn't have expected this, but both the old and the new coil act the same, so I'd guess this isn't significant?

[JOHN COOKSON]

(A)I'll probably pull the carb off tomorrow and give it a better cleaning. I don't want to buy a video on how to do this, but maybe I'll look around on U-tube. I'm reluctant to make any intentional, or accidental adjustments to the carburetor, before ruling out that it is just dirty, or that there is some other problem...I don't want to compound the mystery.

It looks like I have an electronic ignition system, under the distributor cap. Also, the negative side of the coil reads positive voltage when the ignition key is turned on, the same voltage as the positive coil terminal...I wouldn't have expected this, but both the old and the new coil act the same, so I'd guess this isn't significant?

(A) You are correct. You need to establish that sufficient gasoline is getting to the carburetor. Dave N. touched on this in post #4. Do you have a fuel pressure gauge? If you don't the only other way I can think of is to activate the fuel pump and catch the fuel in a container. After you have established sufficient gas is making it to the carburetor then you will know if the carburetor has a problem. Have you tried adjusting the idle?

(B) Electricity is brought to the coil at the + terminal flows through coil primary winding then out of the coil at the - terminal to the points or EI where the circuit to ground is opened and closed. The coil - terminal is not a ground. The coil can be suspended in mid air, not grounded, and work normally.

TRUE GRIT

[tac]

Both sides of the coil, (+) and (-), will read +12V (or so) to ground when the points (or electronic switch in the case of electronic ignition) are open. The (-) side of the coil is generally connected to the distributor points (or electronic ‘switch’), not to ground. With the points open, there is an open circuit, and no current can flow through the coil. If no current is flowing, there is no voltage drop (the voltage drop across the coil, from (+) to (-), is V = IR. If I = 0, then V = 0).

To see this, measure the voltage drop across the coil (+ to -), rather than (+) to ground and (-) to ground. With the points open you should read 0. With the meter still connected, rotate the engine until the points close, and the meter will read +12V or so.

With electronic ignition, depending on the type, you might not see this. These types may require the distributor rotor to be in motion for its switch to open.

[ndutton]

I'll probably pull the carb off tomorrow and give it a better cleaning. I don't want to buy a video on how to do this

??? OK, your boat, your choice.

[roadnsky]

I'll probably pull the carb off tomorrow and give it a better cleaning.

If you're gonna pull the carb, why not really clean it by REBUILDING it?

I don't want to buy a video on how to do this, but maybe I'll look around on U-tube.

And, why would you not want to buy a $12 video from our host that will teach you one of the key maintenance items on these engines from the master??
You'd rather trust a You-Tube "mechanic"?
Trust us, you're gonna spend more than that in aggravation...

[CamaroMan]

diy it

the carbs on these are SUPER easy to work on. Assume the prev owner set it up right.

Dont bend anything - yes u can learn alot on utube. I dont quite see the need for a dvd for a carb as simple as this.

My wife made a new gasket last week using a cheapo harbor freight punch set (i taught her and now she insists!) - carb is running beautifully.

Once u have the carb separated - in the top pretty much between the 2 large bores sits the idle jet, its usually the jet that blocks 99% of all carbs as its the smallest.

Get some copper wire and run it thru (this might now even be necessary).. sometimes the crust just sits on top and u can brush it off with a soft metal brush.

Spray thru all holes u can possibly find with brake/carb cleaner. Esp the ones that sit right next to the brass butterflies (round plates). To verify these arent blocked I usually puddle some spray there and u can watch the holes open up as they drain the carb fluid.. other than sonic cleaning / compressor theres no other real way of telling theyre clean.

if this is your first carb - just take it slow, take pics, write things down, sometimes a short video also helps seeing exactly where things were.

Once uve done it ull do every carb thereafter (or try at least!).

[JOHN COOKSON]

Maybe this will help. Follow the exploded parts diagram as you disassemble the carburetor.

TRUE GRIT

[ndutton]

Don't bend anything - yes u can learn a lot on Utube. I don't quite see the need for a dvd for a carb as simple as this

Don Moyer is the foremost authority on Atomic 4's so you can bet any how-to video produced by MMI will be the best information you can find - and considering the quality of the information, at a very reasonable price.

Our goal here is a successful result by any means possible and the MMI carb video is a direct path for someone new to carb maintenance and repair. That's why it's been recommended more than once in this thread.

[Boat]

Don Moyer is the foremost authority on Atomic 4's so you can bet any how-to video produced by MMI will be the best information you can find - and considering the quality of the information, at a very reasonable price.

Our goal here is a successful result by any means possible and the MMI carb video is a direct path for someone new to carb maintenance and repair. That's why it's been recommended more than once in this thread.

AND........ why not kick 12 bucks to the site sponsor that host the very site you went for help to begin with???????????

Did you get help from the site??????

***? buy a video!!!