engine dies after long idle

[SimonP]

Hello all,
I have a 'good old boat', with an atomic 4. New carb in 04. It might have 250 hours on it. I had to leave the boat for 3 months - unfortunately the agreed two-weekly engine run didn't happen during that time. 10 days ago, coming back, first thing I did was to replace fuel filter- a screw-on disposable type. Its an old monel tank and the filter usually has a fair bit of white/pale green dust in it- but no obvious water.

Engine exhibited expected roughness (a sticky valve that frees up after a minute or so) , but also what seem to be fuel problems. It would idle, but would starve/die on throttle. It would hunt (correct word?) ie : not stay at steady revs, but oscillate in a range ie 1200-1500.

I left it for a while, tried again, it ran fine for 30 minutes or more. Revved it up and down, ran it in gear etc, no problems.

Today, it started and did a bit of unsteady oscillating then ran increasingly smoothly for about 20 minutes, then it just died. It seems to have plenty of battery and spark, electric fuel pump seem to be working well. I'm guessing that the 3 months sitting dry has let deposits somewhere in the carb. I'm willing to do a carb rebuild if neccessary, but I think all it needs in a clean, if in fact its a carb problem.

1. any suggestions whether the symptoms suggest carb?
2. if carb- is there a quick and dirty approach to cleaning that may be worth a try without removing the carb?
3. if I remove the carb, is it necessary to replace gaskets, or anything else - assuming they're not worn?
4. If its not carb - I can only think its a blockage upstream of the fuel filter...any suggestions ?
thanks to anyone who has any suggestions,
Simon

[Don Moyer]

It's unlikely that anything bad happened to your carburetor while it just sat there for three months. Most of your reported symptoms could be accounted for by a bit of air moving through your fuel system in the aftermath of your filter change. Before doing anything more difficult or expensive, I suggest you remove the main passage plug from the bottom of the carburetor and pump at least a couple pints of fuel through the system while checking for air, or anything else that might come out with the fuel. If you have a rubber priming bulb in your system as suggested in our second tech tip at moyermarine.com in "Fuel-Related Engine Shutdowns" you might pressurize your system and check for leaks. You may not have gotten your filter back together completely tight.

Don

[SimonP]

thanks for the tips

Don
thanks for your quick and useful response.

I 'did' have a priming bulb between my fuel filter and fuel pump (this is the advised location isn't it?) I took it out a few days ago when I realised one of its valves was not working and so it wasn't pumping - the sound of bubbles rising in the fuel tank tipped me off to this .
Maybe I introduced air then? I guess I'll go grab another bulb and then I'll try the suggested test, thanks.

What test can I do to test the electric fuel pump? Or should I not bother? I imagine disconnecting the fuel line down stream and hot wiring the pump wouldn't be a safe procedure (joking).

Is there a strainer in the fuel pump I can and should clean?

Some people talk about a 'polishing' filter. Do you advise it? What kind of filter would one use - something like an automotive in line fuel filter?

thanks again for a great service
Simon

[SimonP]

some answers found

a little time poking around the older lists was well spent ,ie :

The priming bulb mounts between the fuel tank and the RACOR filter.

The inline (secondary or polishing) installs between the fuel pump and carburetor.

polishing filter :
(FPMP_07.1_473)**Fuel filter, inline secondary (polishing filter)

SP

[sastanley]

I had a priming bulb initially when I replaced the entire fuel system this winter. I had it just on the tank side of the Racor. It worked great for priming the new/dry fuel system, and it did reveal a leak (improperly mounted fuel bowl on mechanical pump).

After some other problems (which I initially thought were fuel related) I began removing some of the stuff I'd added. One of those was the 'squeezy bulb'. If I were to keep it in the system, I would consider this $10 part to be an annual maintenance item for the exact reason you noted...the $3 check valves inside the $10 rubber bulb seem to fail regularly. Incidentally, when I removed the priming bulb, I had forgotten to open the petcock at the fuel tank..I put the fuel lines back on, and the A-4 fired right up and ran great for about 10 minutes, and proceeded to shut down after it drained the line & Racor filter. I cranked and cranked with no luck. After I realized this bonehead move and opened the petcock, my mech. fuel pump had no problem priming the system again after about 20 seconds of cranking...even pulling it thru the Racor filter.

[ghaegele]

I have my priming bulb inline between the Racor filter and the engine and have noticed that sometimes it doesn't work and I have to shake it around a bit to get it to pressurize. (I don't think it matters much if it's before or after the main filter.) But I can't see this as an annual maintenance issue. If it stops working it doesn't shut down your engine, it's just not useful. So go for a sail. Then, after you've checked the whipping on all of your lines and touched up your varnish and are looking for another job, buy a new one and replace it.

By the way, there is a fine screen in the fuel pump that could have gotten crudded-up (let's blame ethanol! though my engine gets winterized with fuel in it for a lot more than 3 months without developing problems). But probably this would blow the fuse first. You can check the pump by jumping a wire from the pump to the positive terminal of the coil, bypassing the oil pressure switch. When the ignition switch goes on you should hear a fast ticking. And yes, you can use the pump to check the flow from your tank. Just catch what should be a heavy flow in a clean bottle. (Gatorade bottles work great!) To clean the screen turn the "nut" on the bottom cap on the filter with a wrench. There's a small element in there that you can blow clean with compressed air.

Good luck! Greg

[SimonP]

fixed, but some mysteries

I blew back into the tank to make sure there was no pickup blockage. I put in the bulb between tank shuttoff and filter, checked lines, and discovered that my tank has good gravity feed, once syphoned over a little rise in the line.
I pulled fuel pump and cleaned it, cleaned my flame arrestor, reassembled.
Don said 'I suggest you remove the main passage plug from the bottom of the carburetor'. I noted that my old carb had a plug on the bottom, but my new one doesn't, so I pulled the main jet plug and pumped a couple of pints - nice and clean. Started the engine, ran it for over an hour with no probs - so I guess its fixed.

But I have some questions about the facet pumps, so I'm starting a new thread
"facet pump mysteries"... see you there?
SP

[rigspelt]

Don said 'I suggest you remove the main passage plug from the bottom of the carburetor'. I noted that my old carb had a plug on the bottom, but my new one doesn't, so I pulled the main jet plug and pumped a couple of pints

I thought the main jet plug was the one his instructions were referring to, but I could well have got that wrong? The plug that was on the bottom of the old carb would have been impossible to get at on my engine, and I can't recall if there is one on the new carb. Is there any downside to doing the autumn or perioidic maintenance fuel-draining using the main jet plug, other than the risk of damaging that difficult-to-find washer/gasket that seals the main jet plug?

[sastanley]

same thing?!?!

I think in this case the 'main passage plug' & 'main jet plug' are the same thing. If there was cruddy fuel hanging out just prior to the main jet, the closest access point (& the removal location for the jet) is the main passage plug as I understand it.

[roadnsky]

I agree. Same animal. You can, however remove the Main PLUG without removing (and potentially damaging) the FIXED MAIN JET.
See attached schematic...

[ghaegele]

There is a drain for the float bowl which is at the bottom of the carb and there is a plug which gains access to the main jet (or passage) at the forward breather end. Either will empty the float bowl but Don's suggestion is to remove the main jet plug and pump a few pints of fuel through in an effort to clear an debris that may be blocking the main jet. By opening the main jet plug the fuel actually flows past the jet increasing your chances of clearing the blockage. (I know this as I was on the phone with him hanging on a hook in Pt. Judith RI as he talked me though this. The procedure was done over a clean basin and I was pretty sure that the procedure removed a fine thread of teflon tape--I now understand this is a no-no--that I had used to seal the threads and could have been my blockage.)

[sastanley]

I agree. Same animal. You can, however remove the Main PLUG without removing (and potentially damaging) the FIXED MAIN JET.
See attached schematic...

When I rebuilt the carb this winter, I could not remove the fixed jet without damage..I chose to leave it alone and sprayed some carb cleaner thru using the main plug hole as an access it to clean it up

[roadnsky]

I thought the main jet plug was the one his instructions were referring to, but I could well have got that wrong? Is there any downside to doing the autumn or perioidic maintenance fuel-draining using the main jet plug, other than the risk of damaging that difficult-to-find washer/gasket that seals the main jet plug?

Rigs-
You're right about the washer!
This from Don...
"Remove the ½" hex-headed main passage plug and drain all of the fuel in the carburetor into a clean glass jar to check for any sign of turbidity in the fuel.
The main passage plug lies horizontally in the bottom of the carburetor with the hex-head pointing directly away from the flywheel end of the engine. The main passageway is the lowest part of the carburetor so any crud that is trying to pass through the carburetor will wash out into your clean glass jar. CAUTION: The main passage plug has fine machine threads and seals with a hard black washer under the hex-head.
Be careful not to drop the washer when removing the plug, and do not over-tighten the plug when reinstalling it or the washer will extrude out from under the hex-head."

[SimonP]

roadnsky:
thanks for the pic, I knew the plug and the jet adjustment were different. I'm glad I did it right - of course I was tho I might have overtightened the main jet plug washer...

BTW: where did you find this nugget from Don?
There is so much solid gold info on this site, but it can be hard to find - isn't there a good argument for an A4 encyclopedia - wit an wisdom of Don Moyer? - attached to this site where we can organise all this info by topic...?

SP

[roadnsky]

BTW: where did you find this nugget from Don?
There is so much solid gold info on this site, but it can be hard to find - isn't there a good argument for an A4 encyclopedia - wit an wisdom of Don Moyer? - attached to this site where we can organise all this info by topic...?

Simon-
Attached is the PDF of the actual document I took the quote from.
I keep everything I find as a PDF or "Screen Shot" in an A4 folder for quick reference.

Good idea though about the encyclopedia. I think Don actually published something like that called "The Moyer Marine Newsletters" available in the catalog...