SM gripen fuel problem
03-05-2006, 04:15 PM
#1
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Location: huntingdon, , UNITED KINGDOM
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SM gripen fuel problem
any ideas on this one.....
skymaster gripen...3 fuel tanks all plumbed as per manual...also using a UAT.....pump near engine and UAT....about 400mm from tanks, vent nozzle is about 1.25mm diameter....when engine starts up it doesn't pull the fuel though...almost feels that there is back pressure stopping it...increased pump volatge (recommendation is 0.25v...went up to 1.00v but still didin't pull....when the whole fuel tank/lines are disconnected, introduce small tank near pump etc...it works.....engine fires up on fuel etc...using tygon to 4mm clear tube on tanks with festo 4mm Tee's.
engine...behote66...(nothing wrong with engine)...runs great....
any clues to why the skymaster set up doesn't work?
cheers
dave
skymaster gripen...3 fuel tanks all plumbed as per manual...also using a UAT.....pump near engine and UAT....about 400mm from tanks, vent nozzle is about 1.25mm diameter....when engine starts up it doesn't pull the fuel though...almost feels that there is back pressure stopping it...increased pump volatge (recommendation is 0.25v...went up to 1.00v but still didin't pull....when the whole fuel tank/lines are disconnected, introduce small tank near pump etc...it works.....engine fires up on fuel etc...using tygon to 4mm clear tube on tanks with festo 4mm Tee's.
engine...behote66...(nothing wrong with engine)...runs great....
any clues to why the skymaster set up doesn't work?
cheers
dave
03-05-2006, 05:01 PM
#2
Join Date: Oct 2002
Location: Leeds, UNITED KINGDOM
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RE: SM gripen fuel problem
Well I think you are right the first time. A 1.25mm dia breather pipe can't be any use. I use 6mm pipe for my breathers, and this ends in a 6mm festo straight coupler for my overflow tank, facing forward. This ensures positive pressurisation of the tanks and works great. You cannot be getting air in fast enough. Change the breather pipe for something way bigger.
Regards,
John
Regards,
John
03-05-2006, 05:14 PM
#3
RE: SM gripen fuel problem
Like John said, use a bigger vent line for sure, also be sure there are no lines kinked, with the tanks empty, blow into the vent line, you should be able to feel air coming out of the fuel line (to the pump) with no problems. (of course, if there is fuel in the tanks or lines you're gonna blow that out)
As I recall with my gripen, the bottom tank (center) was easy to kink the lines on if you didn't make sure they cleared the former correctly so double check that as well.
As I recall with my gripen, the bottom tank (center) was easy to kink the lines on if you didn't make sure they cleared the former correctly so double check that as well.
