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Float needle check

Posted by IlliniBlue 71

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Float needle check #1
IlliniBlue 71 Scott Calhoun Coal Valley, IL, USA	Posted: June 14, 2012 11:37AM Registered: 2 years ago Posts: 5

In an attempt to diagnose a problem with my '71 MGB, I consulted my Haynes manual. As it says in the manual, I removed the inlet pipe at the float chamber and turned on the ignition. The book then says, "if fuel spurts from the end of the pipe, the fault is probably a sticking float needle." My question then is, how much fuel makes up a spurt? Some fuel came out, but I have no idea how much I should have expected? I disconnected the fuel line before it reached the fuel filter, and again turned the ignition. Again, fuel came out (maybe 1/2 ounce) for a 5 second turn of the ignition. Just wondering if the fuel pump is working correctly. I do hear the clicking sound from the pump when the ignition key is turned.
Thanks.
Scott

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Re: Float needle check #2
ddubois Dave DuBois Bremerton, WA, USA	Posted: June 14, 2012 11:44AM Registered: 7 years ago Posts: 4,290

Scott - Direct the fuel line into a quart jar that is marked at the 1 pint level. Turn the ignition on and time how long it takes to pump 1 pint - should be 25 seconds maximum.
Cheers,

Dave DuBois
1953 MGTD
1966 MGB
http://homepages.donobi.net/sufuelpumps/

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SU Fuel Pumps & More SU fuel pump restoration and conversion to solid state. Information and technical articles on SU fuel pumps.

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Re: Float needle check #3
Lee Lee Miller Mburg, PA, USA 1966 MG MGB 1967 MG MGB 1971 MG MGB	Posted: June 14, 2012 11:46AM Registered: 13 years ago Posts: 4,187

What is the problem your trying to diagnose? Sounds right for the fuel line removed with a short burst of power.

Lee Miller

Experience - hobbyist, rotisserie restoration 1967 MGB, welding, bodywork, painting, wiring, interior, suspension, clutch, engine, SU HS4 carburetors, windshield, and installing convertible top.

Website www.myclassicmg.com

1971 MGB
1967 MGB
1966 MGB restoration project

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Re: Float needle check #4
IlliniBlue 71 Scott Calhoun Coal Valley, IL, USA	Posted: June 14, 2012 11:57AM Registered: 2 years ago Posts: 5

Two days ago I took the car out for its initial drive of 2012. About a 1/2 mile into the trip, the car seemed to lose power. Could not generate rpms by depressing the gas pedal. I pulled into a drive, took the car out of gear, and tried to rev the engine. Not much success. The car sputtered and eventually died. After about a five minute wait, I was able to restart the car, but engine was still sputtering. After a 90 minute wait, I was able to start the car, and drive it in first gear back home; however, the last quarter mile was iffy with the car again losing power and sputtering.

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Re: Float needle check #5
IlliniBlue 71 Scott Calhoun Coal Valley, IL, USA	Posted: June 14, 2012 12:01PM Registered: 2 years ago Posts: 5

Thanks, Dave, for the advise. This will give me a much better idea if I'm looking at a fuel pump situation. I'll let you know the results.
Scott

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Re: Float needle check #6
Lee Lee Miller Mburg, PA, USA 1966 MG MGB 1967 MG MGB 1971 MG MGB	Posted: June 14, 2012 12:06PM Registered: 13 years ago Posts: 4,187

Do you still have the evaporation canister? It might be fuel system venting, try removing the gas cap.

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Re: Float needle check #7
IlliniBlue 71 Scott Calhoun Coal Valley, IL, USA	Posted: June 14, 2012 12:28PM Registered: 2 years ago Posts: 5

Dave, just did what you suggested with the quart jar. Took 12 seconds to pump one pint of fuel. Probably not a fuel pump problem? Probably will continue with the sticking float needle diagnosis after lunch.
Thanks, Scott

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Re: Float needle check #8
IlliniBlue 71 Scott Calhoun Coal Valley, IL, USA	Posted: June 14, 2012 01:00PM Registered: 2 years ago Posts: 5

Lee, Is the evaporation canister located on the boot's left side with two hoses attached? If so, yes, i do still have the evaporation canister. Once I reconnect the fuel lines, I'll try running the car with the cap off.
Thanks again.

Scott

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Re: Float needle check #9
dickmoritz Dick Moritz Philly 'burbs, PA, USA	Posted: June 14, 2012 01:22PM Registered: 3 years ago Posts: 7,277

Scott,

Could be water condensation in the fuel. Suggest you repeat the fuel pump test by pumping a couple of inches of fuel into a clear glass jar. Gasoline is lighter than water and will not mix with water, so if there is indeed water in the fuel you'll see obvious stratification of the two liquids in the jar. If it's not obvious, you probably don't have any...

Dick

Edit for typo...

Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

Edited 1 time(s). Last edit at 06/14/2012 01:23PM by dickmoritz.

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Re: Float needle check #10
JimM Jim Martens Gainesville, GA, USA 1974 MG MGB	Posted: June 14, 2012 05:00PM Registered: 2 years ago Posts: 206

Sounds like what's been keeping me off the road. I believe it's garbage in the carb. Cleaned it out once by removing the bottom plate and turning the key to pump some fuel through. Wiped out the inside. Ran great for a 50 mile test dive. Ran fine the next day until I made a short stop. Engine turned but would not start. Pulled choke and pressed pedal to the floor and it started. Checked under the hood and noticed some fuel having exited through the overflow. These are the same symptoms experienced before cleaning the carb.

I've run gas into a jar (without the filter) and there might have been a spec of something (rust?) in there but not a bunch. Then the starter acted funny so I stopped. Need to clean carb again.

I'm going to fill the tank with E-free gas and see if it make a difference.

Never forgot my first vehicle at 17, a 77 B.
30 years later graduated to a 74 chrome bumpered B.

High-torque starter, sports coil, pertronix elect. ignition, SU solid state fuel pump, HIF-4 carbs (rebuilt May 2011).

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Re: Float needle check #11
herkdriver George Pelech Georgia, USA 1963 MG MGB "Maggie"	Posted: June 14, 2012 07:20PM Registered: 7 years ago Posts: 295

Jim, if you have fuel coming out of the overflow tube, you are running with a float level way too high and therefore very rich. Most likely cause is a float needle that won't seat properly (contaminates). I tried a Grose jet but threw it out in short order because it refused to seat. If you don't have a filter back by the fule pump, put one. I alos run a second (clear) filter in the engine compartment near the hard fuel line. This way I can see if there is fuel running to the carbs and I get twince the filtering. Would recommend running at least a quart through the pump into a suitable container before hooking up to properly cleaned carb float bowls.

Scott, are you sure you have a proper fule level in the carbs? if one is not filling, you would probably get the same symptoms. Remove the pistons and peer down the jets with the choke pulled out-you should be able to see the fuel level near the top of the jet. If you can, pull the bowl lids off both carbs and see if the remaining fuel level is equal in both carbs.

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