Rear SU float not seating -- fuel overflow

[britlover]

Started the 100 today with the hood open (thankfully) and right away, fuel started spraying out of the top of the rear float bowl. I disassembled it and noticed that there was yet again a little rust inside the bowl. Cleaned everything, including the float needle and seat, re-assembled and it still overflows. Repeated process 2 times, last of which I slightly bent the float lever to ensure it is pushing against the float needle, and it still overflows. The float needle has a rubberized end on it (haven't seen one like that before) and perhaps it is shrunken, or deformed so it won't shut off the fuel?

Any thoughts? Can anyone recommend a good re build kit for the float bowl?

 

[Keoke]

Change the needle or add Crose jets

 

[steveg]

You might google/call Joe Curto in Queens, NY.

He can sell you the parts and will take time to talk to you about the problem. I've found him very helpful in the past.

 

[johnea]

Happened to me too some time ago. It turned out to be a binding float on its stem. It couldn't slide freely up and down due to dirt. Clean the stem and the inside of the tube that runs thrue the float.

 

[Michael Oritt]

After changing the jet and needle (I recommend Grose Jets) you had best deal with the cause of the problem: The debris in your fuel system.

1. Clean and seal or replace the tank.
2. Install a see-through inline fuel filter between tank and SU and carry a spare onboard.
3. Pull a new ground to your tank sender as the fuel line no longer provides it due to the new filter.
3. Remove the small filter baskets in the SU and clean out any debris.

 

[Bob_Spidell]

I've had Grosse (sp?) Jets in my BJ8 for many years and miles and they've been flawless. Bought a pair for the BN2 and one was defective; if you pressed the lower, larger ball the upper ball--the one that actually seals the inlet--would stick in place so didn't use them. I've heard quality has decreased since the company was sold years ago.

 

[EV2239]

I agree with Bob that the Grosse valves work fine. They're not the problem, which is tiny bits of dirt and they're best trapped by a modern fuel filter in the line immediately before the Carbs.

Float needles were always sticking in the old days and my wife always carried a large spanner in her BJ7 back in the sixties to hit the offending float chamber. It usually happened in traffic jams in Central London!

 

[britlover]

I pulled both carbs apart, foats out, and there was a sizeable amount of orange goo in the bottom of each float bowl. After cleaning, I thought to be safe I would order a set of float needles and seats from Moss. I hope they ship quickly because there is a show next weekend that I plan to take the car to.

I've cleaned the tank extensively, but it should probably be coated inside by a professional. The gauze filters were clean, so its possible that the crud in the carbs is from before the tank cleaning.

 

[EV2239]

I probably should have posted this before, but with an inexpensive filter like this in the line, you needn't worry about anything in the tank.

 

[John Turney]

Are your floats floating, or do they have gas in them and are sinking?

 

[tahoe healey]

Just my observation but the filter is best placed just after the fuel pump (and mark the date installed with a Sharpie on the filter). I had frequent vapor lock after runs on hot days. I had a plastic filter mounted under the bonnet just before the carbs. I moved new metal filter and now no more vapor lock (last weekend I drove in Sacramento in temps that reached 106! with no problem) since the relocation. The reason for the move was to replace the flexible cabled hose and found the old one did have a small amount of debris that had not yet reached the filter. The clear filter showed me very little in it while it was installed.
TH

 

[britlover]

Yes, floats are floating and not full of fuel.

As far as adding a fuel filter, my car is almost 100 percent exactly as it left the factory, and I would prefer to keep it that way. The only flexible line I've found is near the left side motor mount with a hard line and banjo bolts at the carbs. I would prefer to pre-filter before the pump, but that area is all hard lines and fittings as well. I guess there is no "easy" way to do it. I'd have to cut some lines somewhere, or change out the current stainless braided line at the front motor mount to 2 shorter ones with a filter between.

 

[tahoe healey]

If the filter clogs or slow due to crud from the tank before the pump it will put strain on the pump. No strain on the pump after the fuel has gone through the pump. You can cut a 5 inch section from the tube with a plumbers pipe cuter and fit the filter with a couple of pieces of "fuel" hose. It will never show if you don't remove the wheel.
I am not familiar with your car as I have a BJ8. Mine has a hard pipe running up the engine side of the front wheel fender. A braided SS fuel line goes from the pipe to the carbs. The PO fit a fuel filter in the braided line. Talk about obvious and subject to engine heat.

 

[Michael Oritt]

If the filter clogs or slow due to crud from the tank before the pump it will put strain on the pump. No strain on the pump after the fuel has gone through the pump.

Running unfiltered fuel through the SU and having it clog up will certainly put a LOT of "strain" on the pump. The filter baskets in the SU are extremely small and easily clogged whereas a decent inline filter mounted in the hard line between the tank and pump will hold many times more trash before creating a flow problem. Just remember to pull a new ground to the tank sender.

Re the comments that mounting an inline filter before the pump will increase the chance of vapor lock--I fail to understand this advice and would appreciate an explanation.

 

[Bob_Spidell]

My experiences are different. I've never run a fuel filter--besides the stock screens--in my BJ8 and in 120K miles never had a problem with fuel (except for a bit of vapor lock right after starting on a hot day with a hot engine, which I attribute to ethanol blended gas). No crud in either set of screens (pump and carburettors) and nothing in the float bowls. Before I sold my '96 Ranger to my dad at 110K miles I pulled the (original) fuel filter, cut it open and examined the filter media and other contents. There was only a few tiny black flakes, which I suspect were shed by the black plastic fuel tank. No dirt, sand or anything besides the black flakes, and there was just a few of them (they would be a problem in a FI engine). I have to wonder why so many Healey owners are getting so much crud in their fuel lines. Note I live in California and most, if not all service stations have had to change out their underground tanks in the last 15-20 years or so to prevent leaking into the groundwater (it put quite a few stations out of business). Maybe that's it (although I do travel throughout the western states and Canada).

Regarding the original topic--overflow--I've found the float needles have to be 'just so.' If the levers that close the needles are allowed to drop too much--the center tang on the lever at the pivot pin sets this--the needle can be jammed in its barrel. This would cause severe flooding. Also, I've had one of the rubber-tipped needles stick in its barrel, cutting off fuel to that carb completely. Grosse jets work great, if you can find two (or three) that aren't defective (the upper, small ball can stick in its opening).

 

[steveg]

Re the comments that mounting an inline filter before the pump will increase the chance of vapor lock--I fail to understand this advice and would appreciate an explanation.

FWIW - Facet pumps use a filter on the input side.

 

[Dandare]

Su fuel pumps and inline fuel filters.

https://homepages.donobi.net/sufuelpumps/Fuel_Pumps/SU_Fuel_Pumps_Facts_and_Myths.pdf

Danny

 

[Michael Oritt]

While I can see Dave Dubois' point regarding an SU pump burning up should a "high efficiency" filter mounted upstream of it become clogged I have always regarded this filter as a maintenance item which should be checked frequently enough so that it can if necessary be replaced before a total clog takes place. I also agree that a filter is not a solution for a filthy tank.

BTW I have never had to change a filter except when I got some Hylomar in the tank while attempting to seal up the sender (I should have simply used a new cork gasket which works just fine). And with all due respect to DD--who rebuilt the SU double header that I have installed in my 100--I will keep my filter in place.

 

[tahoe healey]

Michael, please re-read my post. The plastic filter was before the carbs under the bonnet.

 

[britlover]

OK. I'm at my wits end here. I have replaced needles and seats, and the rear carb overflows anyway. Everything is clean and in order. For some reason the Viton tipped needle will not stop the flow of fuel. When I take the top of the bowl off, I can move the float lever up, blow on the inlet, and air does not leak. I'm supposed to load the car on a trailer right now for a show 4 hours away, and I can't get the F$$%^&^ carb to stop overflowing!

Any ideas?