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Fuel is leaking from both fuel bowls; well it’s more like dripping. I’m new to SU carburetors and could use some guidance. Got this 63 PV544 this spring and the engine ran well with no carburetor fuel leak.
Looking for any recommendations or references.
Background:
Gas tank was in very bad shape with a very minor leak. I believe the PO (previous owner) ran the engine after putting gas in the old rusty tank last fall after the vehicle has been sitting for a very long time. So, there may be dirt in the fuel bowl.
The PO had loosened off the fuel pump for some reason, resulting in oil dripping under the car, but the engine ran fine without any fuel leaks.
I tightened the fuel pump bolts, but oil still leaked. Later discovered the inner gasket behind the fuel pump spacer was damaged.
One of the fuel bowls started leaking, I believe, after tightening the fuel pump bolts.
Made fuel pump gaskets from material that was somewhat thinner than the original and reinstalled the fuel pump with gasket on both sides of the spacer. I also mounted a pressure gauge after the fuel pump. I believe I read somewhere that the pressure should be between 2 and 3 PSI.
After starting the engine, had a fuel leak from both fuel bowls. The fuel pressure was difficult to read off the gauge as the needle was fluctuating wildly. The gauge full scale is 100 inches of water (27.7 inch of water = 1 PSI). I estimate the pressure (due to needle vibrations) somewhere around 3 PSI.
Took the three screws off of the fuel bowl to check the needle and seat valve, but the cover is stuck in place. I do not have a spare gasket set, so decided at this time not to pry off the cover and put the screws back. I will get back at it later when I have a set of gaskets. Any recommendations on the best way to pull off the fuel bowl cap?
What should the fuel pressure be for these carbs? I was thinking of adding more gaskets to the fuel pump in an effort to reduce pressure to the fuel bowl.
Other than a leaky fuel bowl, could high pressure cause any additional damage to any component of the carb?
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After reading your other comments in regards to your ongoing project with the Gas Tank, I have come to the conclusion that you are more than likely a Masochist or - at the least - a flagellant.
Now I see that you are attempting to repair carburetors with common household materials. It has been a long, long time since I attempted to make a gasket out of a Cherrios box.
Should you ever weaken and resign yourself to using garden variety, off the shelf OEM parts, you might want to look at the Victoria British catalog for SU parts (our beloved Carburettor is common to both the MGC and the Triumph TR6) and Victoria British (located in suburban Kansas City) maintains a substantial inventory of component parts and repair kits/gaskets/Jets/etc.
http://www.victoriabritish.com/icatalog/mg/full.aspx?Page=109
You should also look at the rubber hose that runs between the float bowls as a source of leakage. This tends to loose it's elasticity with age and "weeping" of fuel results.
Best of luck, but as a matter of providing unsolicited advice... responsibly recycle that Gas Tank. From all accounts, it appears to be shot.
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Problems solved. … Root cause… faulty needle valve in front fuel bowl and excessive dirt in the bottom of the bowl.
Disconnected hoses and wanted to remove fuel bowl, but that does not seem possible without removing the carburetor due to the fuel bowls being mounted between the carbs. Noticed on other vehicles, they have the fuel bowl the opposite end to that of the PVs.
So, I removed the jet assembly and opened up both fuel bowls. After draining the fuel, used a shop vacuum with a rubber hose to suck out some more gunk. Then proceeded to scrape away the hardened stuff and vacuum out. Then cleaned the bowl with mineral spirit and blew it clean and dry with compressed air.
Since the front fuel bowl needle was sticky, I picked up a needle and gasket kit at BMC in Smithville, ON, a town down the road from me ( BMC sells mini and MG parts). [Oh, btw Suppo176, the gaskets I made in the past were always from gasket material, and it’s usually much quicker than having it shipped from all over the planet.]
Since I was also concerned with high fuel pressure, also added a few more gaskets to the fuel pump. With fuel pressure gauge mounted it was indicating around 2 psi. Also after turning off the engine, the fuel pressure held at 2 PSI. So fuel delivery is ok for now… on to the next problem.
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Hello,
Where is the fuel coming from?
If the fuel is coming from the vent hole in the float bowl cover, your valves are not shutting off which can be bad or sticking valves or bad floats.
If the fuel is coming from underside the float bowls, the jet tube seals are leaking or the jet tube hose is damaged.
--
Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
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The fuel bowl is wet on the top, so it’s probably the vent hole, except I did not notice the hole. I think the PO allowed dirty gas into the fuel bowl by using the old tank without a fuel filter. I’ll take a closer look when I get home tonight.
I am currently using a jerry tank and fuel filter to run the engine.
I think I would like to remove both fuel bowls and clean them out. Anything to watch out for during removal?
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"The fuel bowl is wet on the top, so it’s probably the vent hole, except I did not notice the hole"
The vent holes are located just below the inlet tube--and if original should have a small metal cover hanging from the inlet tube which shields but doesn't close the vent hole.
Others have pretty much answered your questions--SU's require very little fuel pressure--it doesn't take much to overwhelm the needle valves--proper float level is important--the "o" ring where the jet fuel line enters the float chamber is a source of leakage--there should be a tiny metal washer between the "o" ring and fuel line fitting. -- Dave
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I would not remove them.
Take the covers off, carefully remove the floats and float valves, clean them valves.
Re-assemble, then test by blowing through the incoming lines, both right side up (valves open), and upside down (valves closed. Don't worry about the gaskets for now. They are easily replaced later, but there is no pressure in the bowls, so they won't leak unless you drive over bumps and slosh the fuel about.
Always carry a fire extinguisher.
If you remove the entire floats, you will most likely end up having to replace the jets and their now leaky tubes.
--
-Matt I ♥ my ♂
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Yes, I always carry one of these
http://www.jegs.com/p/H3R-Performance/H3R-Performance-HalGuard-Clean-Agent-Fire-Extinguishers/761128/10002/-1
I'm a little biased. I caught my PV on fire once and my house was hit by lightning and caught fire. one of these little babies saved the farm! not to mention we thoroughly impressed the fire department who had never seen anyone put out a house fire with such a small extinguisher. "we did good" And yes, a lightning strike is considered an electrical fire since the 50,000V or whatever finds a path to ground through the wiring, coax cable and/or phone lines in your house. So, dosing water on live wires? uhm probably not a good idea
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Matt,
You state that there is no pressure in the bowls but if the fuel pressure is too high it will flood the bowls and you will see seepage from the vent hole. I have a fuel regulator on my line and if I set it to go above 3psi, I will get seepage. 1 1/2-2psi works fine.
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Any pressure at all in the float bowl will cause spillover. All fuel pump pressure needs to stop at the needle valve. As you say, it's not capable of handling much more than 2psi.
--
67 144, 85 740T, 86 740T, 91 945SE, BMW R69S, R60/2
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