73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: 74k20 on July 22, 2014, 04:48:51 pm
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Quick fuel pump sanity question.
New standard mechanical fuel pump on my new sb400. When I hooked up the truck line INTO my fuel pump (carb not on yet), gas started flowing OUT the outlet (gas all over the place) NO biggy, I quickly capped off the outlet (after gas all over the place). But I thought fuel didn’t flow unless it was pumping? No biggy and I ignored it (after cleaning up gas all over the place). Then right before firing up the new motor, I decided to do a double check of the brand new QJ carb to insure there was actually a filter in the carb. YEP…fuel gushes out NON-STOP (gas all over the place). Carb is higher than pump, but gravity seems to be pushing fuel out with some force/pressure. I seem to remember changing filters, lines, ect without this much fuel spilling all over thru the fuel pump.
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Heat may be building pressure, to you have your vent plugged at the charcoal canister?
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74 had no canister that I know of, as I believe all is original. It was a bit warm out tho, so maybe pressure was built up in the tanks??? It flows QUITE well out the lines.
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If 74's don't have vent lines than the gas cap has to be vented. When you remove the gas cap is there pressure behind it?
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^^^^^ X 2
The tank(s) have to be vented to breathe and properly deliver fuel - either through lines plumbed to a vapor canister or via the gas cap(s).
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Take the gas cap off when you open the fuel system. If your tank isn't vented some guys will drill a small vent hole on the inside of the cap to cheat
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Good points guys...both new caps, but I don't know if vented or not. I'll check as that makes sense - thanks
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74 had no canister that I know of, as I believe all is original. It was a bit warm out tho, so maybe pressure was built up in the tanks??? It flows QUITE well out the lines.
My 74 has a charcoal canister. Its down under the left headlight. Check there.