Author Topic: FYI: Fuel pump prob  (Read 7885 times)

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Offline TIPPA

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FYI: Fuel pump prob
« on: June 29, 2005, 04:15:28 PM »
My '78 C3 always had a niggling problem where when left for a while it would usually take 5 to 10 seconds cranking over to finally start. Thought it was either a carbie (tuning) prob or maybe a cracked fuel pump diaphragm allowing the float bowl and line from the pump to the carbie to siphon dry.
Bought a new fuel pump, and could only find one made to suit up to '74 models. It has one less line on the bottom. Realised that the extra(third) fuel line on my original pump was in fact the culprit by design. Seems it, via a tiny orifice, is designed to siphon the fuel in the float bowl and fuel line and return it to the tank when the engine is off- prob for pollution reasons (escaping fuel vapour???).
So on with the new earlier pump and now she fires instantly even after sitting overnight ;)

Offline 77CVT

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FYI: Fuel pump prob
« Reply #1 on: June 29, 2005, 04:22:13 PM »
The 3rd line is the return line to the tank.  Make sure you cap it off.

I wouldn't have thought it would siphon back although my '77 had the same problem.  It was cured with an electric pump after the mech one failed.  

Nothing like starting first crank!

Offline TIPPA

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FYI: Fuel pump prob
« Reply #2 on: June 29, 2005, 07:12:41 PM »
For sure :22 I capped the return line and with a carbie kit put thru the rochester and a new pre-pollution fuel pump its so much better now. Qik run on the dyno tomorrow and she is ready for the brizzy trip  ;)