Early glass dome fuel pump running pressure - Page 2

mocambique-amazone · Jul 7th, 2017, 19:05

Quote:

Originally Posted by 123GT-AMAZON

Hi ya Gary ,

At the fuel pump where it's mounted on the side of the engine does it have a backerlite thick shim ? If not fit one that will cure your issue all being well buddy

that shim will reduce the pump pressure going to the Su carbs naturally if all is ok at the su's I would check for that shim .

If the shim is in place I would then check the flow on both carbs are balanced and work on mixture and maybe pop it when not leaking on a emmison meter to see what it's doing to get the best optimum fuel setup see how you get on but keep us updated

Kind regards

Robert.w

sorry Robert, the fuel pressure is not related to the thickness of this isolator (shim) or the gaskets. And neither influenced by the two valves inside the pump.
regards, Kay

123GT-AMAZON · Jul 7th, 2017, 22:14

Quote:

Originally Posted by mocambique-amazone

sorry Robert, the fuel pressure is not related to the thickness of this isolator (shim) or the gaskets. And neither influenced by the two valves inside the pump.
regards, Kay

If you say so , but by shimming that out in effect it makes the pump work less which then in turn gives less fuel and pressure on each stroke I will let you do the maths...

But moving the pump outwards by shimming your taking it further away from the lobe on the camshaft correct ? Hopefully I have put this into lay men's terms .

Kind regards
Robert.w

mocambique-amazone · Jul 8th, 2017, 07:01

If you use a thicker shim or add gaskets you will only reduce one part of fuel delivery: The volume.
The pressure is only given by one part of the mechanical pump:
The spring behind the membran. Nothing else.
Never try to modify the one-way valves, and I wouldn't even reduce the volume. The risk to damage the engine by getting lean at high revs is high, too high.
His prob is not volume related. And I even think not by the pump. Till now I never seen a pump where the pressure is gone high by getting older or used.
Without a proper check of the fuel pressure nobody is able to help him really.

regards, Kay on the way in the workshop

Jul 8th, 2017, 07:01	#13
mocambique-amazone Master Member Last Online: Jan 24th, 2022 17:08 Join Date: Nov 2008 Location: small village in the north of Germany	If you use a thicker shim or add gaskets you will only reduce one part of fuel delivery: The volume. The pressure is only given by one part of the mechanical pump: The spring behind the membran. Nothing else. Never try to modify the one-way valves, and I wouldn't even reduce the volume. The risk to damage the engine by getting lean at high revs is high, too high. His prob is not volume related. And I even think not by the pump. Till now I never seen a pump where the pressure is gone high by getting older or used. Without a proper check of the fuel pressure nobody is able to help him really. regards, Kay on the way in the workshop

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