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Re: [GMCnet] Fuel system. [message #323686 is a reply to message #323685] Sun, 10 September 2017 04:02 Go to previous messageGo to previous message
USAussie is currently offline  USAussie   United States
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma:
Senior Member
John,

I have pasted all three of your emails below and have interspersed comments in CAPS below for clarity - I'm not shouting.

As you can see from my signature I have two Avions.

Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808

-----Original Message-----
From: Gmclist [mailto:gmclist-bounces@list.gmcnet.org] On Behalf Of John Phillips
Sent: Saturday, September 9, 2017 1:02 PM
To: gmclist@list.gmcnet.org
Subject: [GMCnet] Fuel system.

Hi,

I have a 75 Avion built on a 74 chassis.

BOTH OF MY AVIONS WERE BUILT IN 1974; ONE IN OCTOBER ONE IN NOVEMBER.

The fuel line from the fuel pump to the carburetor has a hose connecting 2 sections of the line. There are about 2 inches of space
between the 2 ends, the ends look like they are factory cuts rather than someone just cut 2
inches out of the line. I have been told there should not be any hose after the pump.

ALL GMC'S NO MATTER THE OUTFITTER (AVION, COACHMAN, MIDAS, ETC) ALL CAME WITH A METAL LINE FROM THE OUTLET OF THE MECHANICAL FUEL
PUMP TO THE CARB. IF IT'S NOT METAL IT'S NOT OEM.

I parked in my driveway 4 days ago with the front wheels about 8 inches higher than the back wheels. The engine has taken several
seconds to start if it has not run for a day or 2. When I took the line apart I was surprised there was no fuel leakage. There is a
clear fuel filter at the pump input with just a little fuel in it.

IT IS POSSIBLE THAT FUEL SIPHONED BACK INTO THE FUEL TANK.

What should keep the fuel from running back into the tank so the fuel pump does not have to charge the line?

NOTHING, THE FUEL CAN'T DRAIN OUT OF THE FUEL BOWL AND ONCE IT STARTS THE FUEL PUMP CHARGES IT IMMEDIATELY.

Did the 74 units come with a solid line from the pump to the carburetor?

YES AS NOTED ABOVE.

One good thing is the oil pump has time to lube the engine before it starts

YEP!

*John Phillips*


-----Original Message-----
From: Gmclist [mailto:gmclist-bounces@list.gmcnet.org] On Behalf Of John Phillips
Sent: Saturday, September 9, 2017 5:59 PM
To: gmclist@list.gmcnet.org
Subject: Re: [GMCnet] Fuel system.

My chassis VIN is TZE064V101164 and the Avion VIN is A26000 and it has an Edelbrock air cleaner.

BOTH MY AVIONS WERE BUILT BEFORE YOURS

The main thing is how do I keep gas in the filters and fuel lines.

DOESN'T MATTER SEE ABOVE.

I do plan on replacing the hose part from the fuel pump to the carb. I would like a pressure tap in there some place.

THE CONNECTION FROM THE FUEL PUMP TO THE Q-JET SHOULD BE A SOLID METAL LINE NOT RUBBER. IF IT'S RUBBER IT'S NOT OEM. I WOULD SUGGEST
YOU REPLACE IT WITH ONE OF THESE AS THEY ARE MUCH EASIER TO REMOVE AND INSTALL THAN THE SOLID METAL LINE.

http://www.appliedgmc.com/prod.itml/icOid/853

IN MY OPINION THERE IS NOTHING TO BE GAINED BY PUTTING A PRESSURE TAP IN. I HAVE PUT 80,000 MILES PLUS ON DOUBLE TROUBLE AND NOT HAD
ANY NEED TO CHECK THE FUEL PRESSURE.

Is there a check valve in the pump?

I DON'T KNOW.

Would an air leak between the carburetor and the pump cause the bleed down?

POSSIBLY BUT IT WOULD PROBABLY LEAK FUEL WHEN THE ENGINE WAS RUNNING.

After I get the fuel bleed down problem fixed I plan on installing a Wix 33161 but I do not want to crank the engine long enough to
fill that large filter.

IF YOU HAVE DROPPED AND CLEANED YOUR FUEL TANKS AND REPLACED THE FUEL LINES WITH ETHANOL COMPATIBLE LINES YOU DON'T NEED A LARGE
FILTER HERE'S WHAT IS INSTALLED IN BOTH MY AVIONS:

http://www.gmcmhphotos.com/photos/aa-miscellaneous-photos/p54750-fuel-pump-inlet-filter.html

*John Phillips*

-----Original Message-----
From: Gmclist [mailto:gmclist-bounces@list.gmcnet.org] On Behalf Of John Phillips
Sent: Sunday, September 10, 2017 1:07 AM
To: gmclist@list.gmcnet.org
Subject: Re: [GMCnet] Fuel system.

If that is case ken how do you explain why they fuel line from the carburetor to pump was empty as well as the fuel filter below the
pump?

DOESN'T MATTER AS THE FUEL CAN'T DRAIN OUT OF THE FUEL BOWLS WHICH IS INDICATED BY YOU NOTING IT ONLY TOO COUPLE OF SECONDS FOR THE
ENGINE TO START, ONCE THE ENGINE STARTS THE FUEL PUMP SUCKS FUEL OUT OF THE TANKS AND REFILLS THE BOWLS.

I parked there Tuesday afternoon and this morning I took the fuel line off.

*John Phillips*


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Regards, Rob M. (USAussie) The Pedantic Mechanic Sydney, Australia '75 Avion - AUS - The Blue Streak TZE365V100428 '75 Avion - USA - Double Trouble TZE365V100426

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