Excessive fuel tank vacuum 99 6.5L diesel - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**DeadheadNM** · 08-07-2023, 12:55 PM

The fuel tank in my K2500 6.5L 99 Suburban builds up a good vacuum during use and has so since I acquired it. I've replaced the cap twice with no impact (one was an AC Delco piece with correct p/n the other a locking Stant supposedly correct for the application). To cope, I release the cap after driving or drive with the cap not fully seated. I'd like to finally correct the issue.

Any ideas where to look first? Were it a 72 I'd know where to start but unsure on a 99 diesel. The truck has 44k miles but the tank was replaced according to the Fire Chief of the station that used it. Is it possible there's a vent line that's not properly connected?

I've done some research and similar issues have been correct with replacement caps but as I've tried two already I'm skeptical this is the issue.

**Ol Blue K20** · 08-08-2023, 12:06 PM

Maybe they kinked the vent line when they installed the tank.

**DeadheadNM** · 08-08-2023, 08:21 PM

I’ll root around and check for anything obvious. Im unsure if diesel tanks were unique or used any sort of an evap/vent system.

08-07-2023, 12:55 PM	#1
DeadheadNM Carpe manana Join Date: Dec 2010 Location: Eau Claire, WI Posts: 12,311	Excessive fuel tank vacuum 99 6.5L diesel The fuel tank in my K2500 6.5L 99 Suburban builds up a good vacuum during use and has so since I acquired it. I've replaced the cap twice with no impact (one was an AC Delco piece with correct p/n the other a locking Stant supposedly correct for the application). To cope, I release the cap after driving or drive with the cap not fully seated. I'd like to finally correct the issue. Any ideas where to look first? Were it a 72 I'd know where to start but unsure on a 99 diesel. The truck has 44k miles but the tank was replaced according to the Fire Chief of the station that used it. Is it possible there's a vent line that's not properly connected? I've done some research and similar issues have been correct with replacement caps but as I've tried two already I'm skeptical this is the issue. Attached Images __________________ 1972 K5 CST Highlander Blazer: http://67-72chevytrucks.com/vboard/s...d.php?t=708547 1972 K20 Cheyenne Super: http://67-72chevytrucks.com/vboard/s...d.php?t=528308 Members met: ORANGBLAZ, 2003 silverado, MikeCofield, BB72CHEVKT, Duncan&Son, Sameyrasmea72, THENEWMEXICAN, HotRod C/10, brianthelion02, Sport/Truck, ryanroo, michael bustamante, Dirt's72, Already Gone, WestButteTruck, 57taskforce, Moreyel, painterljp, AASmedic, SoCoC10, Lumaestas, carbuff382, Chevyland

08-08-2023, 12:06 PM	#2
Ol Blue K20 Proprietor of Dale's Corner Join Date: Nov 2012 Location: Vacaville , CA Posts: 15,875	Re: Excessive fuel tank vacuum 99 6.5L diesel Maybe they kinked the vent line when they installed the tank. __________________ "Some Days Chickens And Some Days Feathers" Dale XNGH ECV Sam Brannan 1004 R.I.P. 67ChevyRedneck R.I.P. Grumpy Old Man

08-08-2023, 08:21 PM	#3
DeadheadNM Carpe manana Join Date: Dec 2010 Location: Eau Claire, WI Posts: 12,311	Re: Excessive fuel tank vacuum 99 6.5L diesel I’ll root around and check for anything obvious. Im unsure if diesel tanks were unique or used any sort of an evap/vent system. __________________ 1972 K5 CST Highlander Blazer: http://67-72chevytrucks.com/vboard/s...d.php?t=708547 1972 K20 Cheyenne Super: http://67-72chevytrucks.com/vboard/s...d.php?t=528308 Members met: ORANGBLAZ, 2003 silverado, MikeCofield, BB72CHEVKT, Duncan&Son, Sameyrasmea72, THENEWMEXICAN, HotRod C/10, brianthelion02, Sport/Truck, ryanroo, michael bustamante, Dirt's72, Already Gone, WestButteTruck, 57taskforce, Moreyel, painterljp, AASmedic, SoCoC10, Lumaestas, carbuff382, Chevyland



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