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-   -   fuel not getting through the carb... (https://www.moyermarineforum.com/forums/showthread.php?t=5026)

sailhog 03-11-2011 06:19 PM

fuel not getting through the carb...
 
Hi all,
I'm having fuel starvation problems.... I can't get the old girl started, as I'm not getting fuel to the combustion chambers. The electric fuel pump works fine. I've replaced the fuel line, cleaned both the racor and polishing filters, permatexed the fittings, cleaned the carb, replaced the float valve and the floats, replaced the carb gaskets... I have a new priming bulb, which is rock hard once fully primed.... still no fuel to the chambers.... I've got good compression, good spark....

The only things left to check, it seems, is the oil pressure safety switch and the manifold gasket...

Any hints from the learned panel?

roadnsky 03-11-2011 06:45 PM

Does the electric fuel pump "click"?
Go ahead and bypass the oil safety switch to check it.
If you disconnect the fuel line downstream of the fuel pump is there flow?

sailhog 03-11-2011 06:54 PM

Jerry,
Should I bypass the oil pressure safety switch by attaching a wire to its positive lead and attaching that to the positive lead of the fuel pump?

ndutton 03-11-2011 07:04 PM

Jumper the two terminals on the switch to bypass it. Can you confirm fuel in the carburetor bowl?

sailhog 03-11-2011 07:20 PM

Neil,
There has been fuel in the carb bowl when I've taken the carb apart to clean it. Not a lot.... but a few tablespoons comes pouring out of the carb...

ndutton 03-11-2011 07:39 PM

I'm wondering how the fuel got into the carb bowl, fuel pump or squeezie bulb? How did you determine the fuel pump was working properly? Jerry's oil pressure switch bypass should help answer that question.

With fuel in the bowl I also wonder about the status of the choke.

sailhog 03-11-2011 07:55 PM

Neil,
I determined the fuel pump was moving fuel a couple of weeks ago by removing the fuel line from the carb and then turning the engine over with a screwdriver on the starter leads. The pump seemed to produce plenty of fuel. The choke cable is in-op as the housing is corroded to the cable itself. When trying to start the engine, I've secured the choke in the closed position with the cable adjustment screw.

roadnsky 03-11-2011 07:57 PM

Quote:

Originally Posted by ndutton (Post 34311)
...With fuel in the bowl I also wonder about the status of the choke.

Excellent point!
Is your choke closing properly? ie. All the way?

sailhog 03-11-2011 08:00 PM

I THINK so. I need to confirm this.

hanleyclifford 03-11-2011 09:14 PM

OK, so you know you are getting fuel into the bowl and you are going to make sure that choke is closing all the way. Do you see any evidence of fuel puddling in the carb intake? After attempts to start there should be some. If not maybe the fuel is not getting past the main jet?

ndutton 03-11-2011 10:32 PM

Don't forget the standard admonition:

Be sure to keep the thru-hull closed until the issue is resolved.

sailhog 03-11-2011 10:48 PM

I removed the impeller so as not to damage it.... Is the main jet the one with the big removable nut on it? If so, that one is completely clear. I think ALL the smaller jets are clear, but it's difficult to be completely certain....

Seaspot 03-12-2011 03:10 AM

Does the electric fuel pump have enough pressure? That's one of the first things I'd check.

You could run a straight line from the pump to the carb to check if there is any obstruction between the tank and the carb.

Dave Neptune 03-12-2011 11:13 AM

Fuel ?
 
Sailhog, might I suggest a fuel preassure gage in front of the carb to confirm furl preassure, it will eliminate a lot of futzing around now and possibly in the future. Also do make sure that the choke is FULLY closed as otherwise an updraft carburated engie as the A-4 is hard to start at best.

One more idea an hopefully and a moot point. You stated you used permatex on the fittings. It is not necessarily a good idea to use it on fuel fittings especially at the carb. If you installed the seat and or the carb's hose bib with it you may have a glob of it holding the needle shut or in a fuel jet or worse yet a passage.

Dave Neptune:cool:

chiron 03-12-2011 12:01 PM

I chased around a fuel related problem such as yours for over a month and thinking that I had good spark I ignored the distributor cap and rotor. I eventually out of frustration replaced both and low and behold what I had thought was good spark had not been adequate enough. New cap rotor plugs and coil fixed my fuel starvation problems, and I got new fuel lines pump and rebuilt carb out of the deal. Just a thought from a newbie.

Chad

domenic 03-12-2011 09:59 PM

I have no idea how the electric fuel pump works...but, if it is like the manual fuel pump here is how I fixed the problem;
The manual pump, does not suck fuel, it pushes fuel into the carb. If there is air in the fuel line, the manual pump will not push the fuel.
Disconnect the fuel line between the pump, and the carb. Clear the fuel line of air between the tank, and the filter with a hand pump bulb. connect the pump to the carb, and start your A4.

MM should know if the electric pump is a sucker, or pusher.

Domenic

Up date The manual fuel pump does suck from the tank, and push to the carb. I have cleard all fuel from the tank to the pump. Have cleared all fuel in the pump. Hit the starter, and within seconds the engine is running. Air in the line does not stop the manual pump from sucking fuel from the tank. The fuel line from the tank to the pump is over six feet. If the electric pump has the same sucking power, you should have fuel in the carb.

Dave Neptune 03-13-2011 11:52 AM

Pump=displcemant
 
Domenic, if your pump is pumping it must be sucking! My mechanical pump has had no trouble priming my system ever. When changing filters I drain the lines once replaced a few strokes on the bail and fuel is in the bowl:rolleyes:.
All pumps suck or they would not displace the volume to push it as you say.
How much the pump is capable of drawing fuel (sucking) is contingent on the condition of the check valves and the volume being displaced. Most pumps have a rating as to how high they will draw or the "suck rating" rated in inches or feet. Some will actually state the amount of draw as a vacuum value which is the draw or "suck" value. Once the pump is primed the pump will draw what it displaces.

The air in the system will be vented by the vent in the carb as the air gets to the carb. there may be a few air pockets left but there most always will be. You can see it in the clear type polishing filters and it has no affect on performance. With fuel injection you need to get the bubbles and air pocket to a minimum for consistant fuel preassure at the injectors.

Dave Neptune:cool:

sailhog 03-14-2011 08:11 PM

Okay.... so I now have fuel moving through the carb. The plugs are damp with fuel, but she's not turning over. She wont' even start with starting fluid. I thought I had the spark problem fixed.... apparently not. Tomorrow I'll be trouble-shooting the coil, distributor, plugs, etc. I'm ready for this engine to start. It's been 75 F here with 15 kt winds out of the SE.... Argh.

Thanks for everyone's help. Still requesting suggestions....

roadnsky 03-14-2011 08:45 PM

1 Attachment(s)
Quote:

Originally Posted by sailhog (Post 34444)
.... Still requesting suggestions....

You may already have this, but here's a checklist from Don you can run while you're troubleshooting...

sailhog 03-14-2011 08:50 PM

Thanks, Jerry. I'll be working through this thing as methodically as I can....

domenic 03-14-2011 10:46 PM

Quote:

Originally Posted by Dave Neptune (Post 34351)
Domenic, if your pump is pumping it must be sucking! My mechanical pump has had no trouble priming my system ever. When changing filters I drain the lines once replaced a few strokes on the bail and fuel is in the bowl:rolleyes:.
All pumps suck or they would not displace the volume to push it as you say.
How much the pump is capable of drawing fuel (sucking) is contingent on the condition of the check valves and the volume being displaced. Most pumps have a rating as to how high they will draw or the "suck rating" rated in inches or feet. Some will actually state the amount of draw as a vacuum value which is the draw or "suck" value. Once the pump is primed the pump will draw what it displaces.

The air in the system will be vented by the vent in the carb as the air gets to the carb. there may be a few air pockets left but there most always will be. You can see it in the clear type polishing filters and it has no affect on performance. With fuel injection you need to get the bubbles and air pocket to a minimum for consistant fuel preassure at the injectors.

Dave Neptune:cool:

With all respect Dave...and I do respect you. I know it sucks, and you know it sucks.
Ken Of Moyer Marine said, "THE PUMP DOES NOT SUCK...IT PUSHES FUEL TO THE CARB. IF AIR IS IN THE FUEL LINE, THE PUMP WILL NOT WORK."

I used a bulb to clear air from my line. A4 fires right up?

I had fuel in the bowl, and the pump would not push fuel to the carb. Took air out of the line, and the stupid system works like a dream. Now don't that suck?

Dave Neptune 03-14-2011 11:23 PM

The bail
 
It may not suck much but I have used the bail to prime my system many times when changing the fuel filter anually and when I do I drain the lines first.
The purpose of the check valves in the diaphram is to create suction on one side to draw in the fuel and then when moved the opposite direction the check valves push the fuel out. If it didn't suck how would the fuel get there?

Dave Neptune:cool:

ndutton 03-14-2011 11:32 PM

I'm wonderin' about the fuel pump itself. The whole point of the bail is for manual operation and decades ago that's exactly how we would prime new installations for testing - with the bail.

We'd pump, it would suck, the bail would stiffen (Stop that!!) and the engine would start.

So why won't yours prime itself? Bad check valve? Gasoline smell in the oil? Something not right here.

Dave Neptune 03-15-2011 09:06 AM

Problems
 
Sailhog, you stated that the plugs are wet with fuel so there must be fuel getting to the combustion chamber. If you tried a bit of "motor crack" and it didn't light one of two things or even both could be the culprit.
First before trying again cnofirm that you have spark at the plugs. you can disconnect one wire and stick a spare plug in the boot and give the beastie a spin. With the plug laying on the block so it is grounded you should see a bit of blue spark jump across the gap. If spark is confirmed and we have fuel and a bit of "motor crack" has been tried my gut tells me it could be timing.
How did the motor run before the present problem showed? If it ran OK and you have not moved the timing by twisting or removing the distributor all should be well. If you moved the plug wires around you will need to make sure they are in the correct order.
If we have all three it should run. Fuel yep it's there, spark(? the timing is correct or close), and compression (a thumb check should be fine) it should lite.
I am concerned about the choke and it functioning properly however motor crack will start almost anything.
Perhaps a historicle senario of how the problem started might help.

Dave Neptune:cool:

sastanley 03-15-2011 10:10 AM

right...what neil & Dave said..I was waiting before jumping on the bandwagon about the fuel pump. mine sucks just fine, and pulled fuel from a new tank, thru new lines and an empty Racor filter no problem using the bail. Vrooom!

Sorry this doesn't help sailhog with his no-start problem. :(


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