De-winterized! Carb Issue

[edwardc]

Well, I just couldn't stand it any longer and went and de-winterized the boat's A4 and started her up this weekend. More than a month earlier than ever before!

Swapped out the old fuel filter and poured out the gas in it. Clear, with no trace of water. From the very bottom, I got a tiny amount of brownish "dust" that did not clump together.

After getting the new fuel filter primed with fuel (the facett pump had no problems with the air), I got the engine to start after 4 or 5 tries. Once all the MMO and fogging oil burned off, she ran great at all RPMs, in neutral and in gear (tied to the dock), with one tiny problem.

I had to maintain full choke the whole time, even after she warmed up. Reducing the choke, even slightly, caused her to start bogging and stumbling, and restoring the choke usually resulted in a stall.

I am virtually certain the carb is crudded up and will need cleaning. Last spring, I found the float bowl full of a gelatinous tan sludge, and hardened crud on the needle valve seat, after just two seasons of use. Once I had disassembled and cleaned everything, she would start instantly on the first try. But over the course of the summer, I noted that it was slowly getting harder and harder to start her when cold, and required the choke a little longer. By the end of the summer, I was up to three tries to get her to start, with choke time increasing from 30 seconds to several minutes. And my low end idle was getting a little rough and would occasionally stall. So I suspected even then that the carb would need cleaning.

As an attempt at a "quick fix" yesterday, I tried screwing the adjustable main jet all the way closed to make sure it was clear, and then reset it to the same spot it was. Made no difference whatsoever.

So this evening I'm going up to the boat after work to pull the carb off and take it home for a cleaning. I'll keep you all posted on what I find.

[Mo]

Couple of ideas

Ed, try something for me. Turn you mixture screw in one turn and see what happens...you may be leaned out too much.

....if no change there...sounds like you may have an air leak Ed. Running OK with choke and then bogs down and dies when choke pushed in. I'd check the bolts securing to the manifold also and see how it runs. If that doesn't solve it and you have to take the carb off you may as well pull it apart and blow out the jets and check gaskets

I started mine again today and put water through also....ran it for 1/2 hour however, it started to bog down about 5 minutes in...then came back steady on it's own...I figured she burned a bit of gasline antifreeze and water...all good after that. Doesn`t take much to foul and good working fuel delivery system.

[dvd]

Ed do you have a polishing filter? Why would you be getting crud into your fuel system. You may need to check out your tank because it sounds like it may be filled with stuff you dont want in your fuel system. My experience is that these are great little motors but they dont tolerate dirty fuel as you described.

DVD

[Mo]

good thinking.

That's a very good point there DVD. I hadn't though about fuel filter plugged...and if it was plugged good enough it wouldn't require load until starting to die. Good thinking.

[ArtJ]

Hi Mo

I had a similar scenario a few years back. Don Moyer suggested removing the
main jet and flushing out.Sometimes pieces of crude get into the idle jet per
Don

Best Regards.

[Dave Neptune]

Question?

Ed, seeing a few problems with sitting tanks and krud has got me a wondering. I have almost no fuel issues however I do use the engine quite a bit motoring to the island on calm mornings so my fuel stays pretty fresh.
What I am wondering is if some of the additives being used are actually adding to the problem. Perhaps the E-fuel is causing some of the additives to break down when the fuel "STARTS" to turn.
I use nothing in my fuel unless I am burning up some old outboard fuel which I do at the start of every season. Sometimes I have 10~15 gallons (50:1 mix) and others just a couple gallons in the dinghy jug. I also burn up fuel that some friends want to dump from their dinghies and I'll burn it up to. However as far as I know I am just burning 2-stroke oil and maybe a bit of stabil KRAP as well. But I am burning it up when it goes in and not letting it sit.
I just started my beastie sunday after completing some off season engine wiring. She started a bit hard as there had been oil sprayed into the cylinders when I shut her down in October, and after a few minutes she settled into a nice idle. I then put her in gear to work the dock lines at about 1/4 throttle for a while and no hic-ups at all.
Perhaps some who have no fuel issues could chime in on their practice's and results. I'm beginning to think that some of the problem may be in the additives.

Dave Neptune

[Newenglandah]

I don't know about anyone else, but sometimes I clean my carb for something to do. The fuel filter too, its just so cheap to do and I feel like I did something. Another thing I've run into with old fuel systems is rubber lines that aren't rated for ethanol. They tend to swell and break down, a 1/4" id line will end up 1/8" with walls coated in goo you can scrape out with a slotted driver. Newer fuel lines are more resiliant.

[edwardc]

Post number 500!

Ed, try something for me. Turn you mixture screw in one turn and see what happens...you may be leaned out too much.
....if no change there...sounds like you may have an air leak Ed.

Mo,

Too late. Already pulled the carb last night. Anyway, my idle screw is already down to between 3/4 and 1 turn to compensate for the extra air the PCV valve lets in.

But I think you're on the right track. Although there was not (and never has been) any odor of gasoline in the engine compartment, I found the area around the carb flange gasket coated with a brown oily sheen. So there must be some amount of leakage there. Of course, everything will get new gaskets when I reassemble.

I got the fancy Cyberdyne mixture gauge & oxygen sensor that Hanley uses, and am going to install it this spring so I'll know if the mix is rich or lean!

Ed do you have a polishing filter? Why would you be getting crud into your fuel system. You may need to check out your tank because it sounds like it may be filled with stuff you dont want in your fuel system

DVD,

No, no polishing filter, just the big water-separating Sierra before the pump. As I said, the gas from the old one was clear, no water, and just a bit of fine particles in the dregs from the filter. It's doing its job.

I've inspected the tank as best as I can, and the bottom appears discolored but there is no layer of crud that I can see.

The gas I drained out of the carb float bowl last night also came out clean, clear, and totally crud-free. We'll see what the insides look like tonight. I suspect the gelatinous tan crud is stuff that the ethanol is disolving (hoses, fittings, gaskets, pump seats, whatever) that gells when it sits in the float bowl.

I had a similar scenario a few years back. Don Moyer suggested removing the
main jet and flushing out.Sometimes pieces of crude get into the idle jet per
Don.

Art,

I read this too. I tried screwing the adjustable main jet shut to try and ream out any possible obstruction, and then reset it, but it made no difference. I'll examine the jet tonight.

Ed, seeing a few problems with sitting tanks and krud has got me a wondering. I have almost no fuel issues however I do use the engine quite a bit motoring to the island on calm mornings so my fuel stays pretty fresh.
What I am wondering is if some of the additives being used are actually adding to the problem. Perhaps the E-fuel is causing some of the additives to break down when the fuel "STARTS" to turn.... I'm beginning to think that some of the problem may be in the additives.

Dave Neptune

Dave,

I think that's a very real possibility. I used to add stabil, but now I've only been adding a little MMO because it was the first season on a fresh rebuild.

Another thing I've run into with old fuel systems is rubber lines that aren't rated for ethanol. They tend to swell and break down, a 1/4" id line will end up 1/8" with walls coated in goo you can scrape out with a slotted driver. Newer fuel lines are more resiliant.

All of the lines after the water-separating Sierra filter are new and specifically fuel rated. But I never really trust that they're impervious to alcohol. A superfical exam of the line leading to the carb showed no goo on the inside.



Stay tuned!

[ndutton]

my idle screw is already down to between 3/4 and 1 turn to compensate for the extra air the PCV valve lets in.

Uhh, excuse me but . . . . Oh, never mind

Congrats on post #500 and thanks for making my morning.

[ArtJ]

The main jet needs to be completely removed to clean it. This applies mostly
to the fixed jet, but you may want to do this with the adjustable jet.

[ILikeRust]

Y'know, I added the PCV valve kit, and am running the factory carb (albeit I believe a newer one from Moyer that the PO installed just a couple years ago) - no adjustable main jet or anything - and so far, it seems to run just great. I think I need to tinker a little bit with the idle screw, since I messed with it the other day just to see what would happen (not much). But I haven't seen any indication that the PCV valve has adversely affected the carburetion.

Am I just not noticing it?

[sastanley]

Bill, me too. I know it is a band-aid, but it sure helps with the boat smell & the blue haze.

[edwardc]

Updates on Carb

Well, I opened up the carb and guess what? Clean as a whistle! So it's sure looking like an air leak. The photos below are without so much as a wipedown, just the way I found it when I opened it. Since I had it open, I went ahead and sprayed it down, scrubbed it down, and ran a wire through every opening and jet, and sprayed it some more. Then back together with a brand new gasket.

Tomorrow evening I'll remount it with new flange gaskets and see what happens.

I'm glad I'm not fighting a fuel crud issue.

[Dave Neptune]

Clean

Ed, looks great. Did you check your housings for mating surfaces being paralell? It is easy for the top housing to be pulled out of shape and not give you a good seal on the pick-up tube in the center. That is a critical point if you are concerned about an air leak in the carb.

Dave Neptune

[edwardc]

Nothing's ever simple.

Ed, looks great. Did you check your housings for mating surfaces being paralell? ...

Yes I did. They're good.


Last night, I went back to the boat to reinstall & test the carb.

Neil is going to love this.

I believe I've found the "air leak". It seems to be a failed PCV valve!

Before I reinstalled the carb, I checked the PCV valve and it does not behave at all like this diagram says it should:



Instead, at very low vacuum, it's closed, opening with increasing vacuum, and never closing at high vacuum!

So it looks like a replacement valve is in my future. Part # on the valve is AC Delco "CV 789 C 137". I believe the "137" is some kind of date or batch code, and the actual part no is just "CV 789 C". Amusingly, this shows up as the valve for a 1988 - 1991 Corvette! I will probably also take this opportunity to re-plumb the valve so it is installed in a vertical position.

So I decided to go ahead and test and see if closing off the PCV hose would cure the problem. Reattached the carb, reconnected the choke & throttle cables and the fuel line, and opened the fuel valve. Bypassed the oil-pressure safety switch and ran the pump for a few seconds to get some fuel into the carb. Removed the bypass and tried to start it.

After 3 or four tries without so much as a "pop", I knew something was wrong. Ran back down below to the engine compartment and was immediately greeted by the odor of raw gas! Fuel was dripping out of the carb throat, leaking through the joint where the flame arrestor attaches!

It seems the float valve was stuck open, and the pump was just flooding the carb with gas!

After a frantic cleanup and ventilation, I had to pull it all apart again to open the carb and see what was going on. All the while I'm thinking "Did I forget to put the needle valve in? Or did it fall out unnoticed while I reassembled the float hinge?"

Carb apart, and everything is in-place and looks fine. Maybe the gasket was cocked and interfered with the float??? Is that even possible?

Reassembled carefully, this time verifying the operation of the float valve by blowing gently through the fuel inlet fitting with the carb both normal and inverted (to get the float to close the valve). Works perfectly!

At this point it was late, I reeked of gas, and I still needed a new PCV valve, so I left it all for another day. Probably can't get back to it before Saturday.