[Mgs] Intermittent Fuel Starvation

PaulHunt73 paulhunt73 at virginmedia.com
Mon Apr 24 06:40:03 MDT 2017


Normally I don't get them at all!
  ----- Original Message ----- 
  From: Charley & Peggy Robinson via Mgs 
  To: 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? 




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