[Mgs] Intermittent Fuel Starvation

Charley & Peggy Robinson ccrobins at ktc.com
Mon Apr 24 07:08:42 MDT 2017

Sorry about the double post.  I forgot to change the subject. :-(

I managed to get one bowl cover off once while the needle was stuck shut 
& the float had dropped away from it.  Just lightly touching it made the 
needle drop.  There has never been any residue in the bowls but I may 
replace the fuel hoses JIC that they are decomposing internally.  I've 
never been able to detect any deposits on the needle tips though.

Here's another thing; the floats in my carbs are all plastic, not as 
shown in all the exploded views I've seen.  Perhaps I ought to replace 
them with the adjustable plastic/metal ones.  What do you think?


On 4/24/2017 7:40 AM, PaulHunt73 wrote:
> Duplicate?
> Normally I don't get them at all!
>     ----- Original Message -----
>     *From:* Charley & Peggy Robinson via Mgs <mailto:mgs at autox.team.net>
>     *To:* mgs at autox.team.net <mailto:mgs at autox.team.net>
>     *Sent:* Monday, April 24, 2017 12:27 PM
>     *Subject:* [Mgs] Intermittent Fuel Starvation
>     Every now and then the new viton tipped float needles are sticking
>     on one or the other of my HS-4 carbs. When it happens if I tap on
>     the top of the offending carb's float bowl using a screwdriver
>     handle and with the fuel pump energized, the needle valve opens
>     and I can hear the fuel pump fill the bowl. This started happening
>     in the summer of 2016. I replaced the needle & seat assemblies in
>     both carbs with aftermarket units. It didn't cure the problem.
>     Several weeks ago I put in new OEM viton-tipped needle & seat
>     assemblies. Then as I was adjusting the jets both carbs ran dry &
>     the engine stopped. So I tapped on one carb bowl & then the other,
>     heard the pump run while filling them up. The engine then started
>     right back up. Last time it happened I had the engine warming up,
>     running at fast idle when it started running very rough. I Tapped
>     on the front carb bowl whilst it was still running & it smoothed
>     right out. Same thing happened another time but it was the rear carb.
>     The fuel pump is a ~5 year old SU with points. I measured the fuel
>     pressure at the carbs to be 4 psi on the nose and it doesn't leak
>     down much or very fast. It has a new inline fuel filter mounted
>     just before the carbs. The floats are the all-plastic type and
>     they don't show any sign of leakage. The floats are very free on
>     the swivel pins and will drop to the stops.The swivel holes in the
>     floats aren't visually elongated and the swivel pins don't show
>     appreciable wear. The carb's vents are clear and I can blow air
>     through the vent tubes.
>     I thought maybe the 7 month old gas might be a contributor to the
>     problem but we put about 100 miles on the car last Tuesday after
>     putting in fresh mid-grade gas, looking at Hill country
>     wildflowers. The car will maintain 70 mph in hilly country all
>     day. Ran like a swiss watch
>     I'm at my wits end on this. Could pressure somehow be building up
>     in the bowls now and then? How?
>     CR
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