Originally posted by AndrewBird
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Fuel pump drainback check valve? (16 14 9 068 988)
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I would think that no matter your pump setup you'd want the check valve as close to the pick up point for the tank as possible. For me, with an M42, and an in tank single pump it meant putting it less than .75" from the outlet nipple.
After all, the farther you put it from the feed point (with the bad check valve) the more drain back you will get, the longer your time to pressure at the rail will be on startup, and the longer your initial cranking will be.
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If the fuel delivery system is stock and functioning properly, what keeps the fuel from draining back? Is this retrofit being done to avoid replacing an expensive part that functions otherwise (fuel pump, sending unit), but is allowing drain back?
Thanks, Cory1992 325i Cabrio
1988 320i Touring
2000 M5
1977 530i
2015 328i - Euro Delivery/Performance Center Delivery
BMWCCA
E30CCA
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A good check valve should work anywhere along the fuel line and it's not a bad idea...but I thought there was one in one or both fuel pumps ?
Note that check valve says "positive seal at low back pressure or slight vacuum" so it does not matter where you install itLast edited by jeffnhiscars; 01-01-2018, 04:22 PM.Seat Shocks....I have passed the baton to John Christy from Ninestitch. Email John or Garrett at ninestitch1@gmail.com
https://www.r3vlimited.com/board/sho...86#post4944786
Alice the Time Capsule
http://www.r3vlimited.com/board/showthread.php?t=360504
87 Zinno Cabrio barn find 98k and still smells like a barn. Build thread http://www.r3vlimited.com/board/show...20#post3455220
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Originally posted by cory58 View PostIf the fuel delivery system is stock and functioning properly, what keeps the fuel from draining back? Is this retrofit being done to avoid replacing an expensive part that functions otherwise (fuel pump, sending unit), but is allowing drain back?
Thanks, Cory
Originally posted by AndrewBird View PostLiterally on the side of the tank before the filter. There was probably 8" of line from the pump to the check valve.sigpic
1991 325i Sport - Calypsorot Metallic - DAILY DRIVEN
WTB in SoCal: 8"/10" Lukebox, leather Sport steering wheel, 60L MotoMeter fuel gauge, Thule/Yakima roof rack
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Just following up to add that I finally got the check valve installed yesterday, and it seemed to solve both the revving/stalling issue at cold start and the long warm starts (usually requiring two tries). The only place I could find where this particular valve+fittings would fit easily was immediately after the fuel filter, but it does the job despite what would seem like a less-than-optimal position within the fuel system.
Thanks again for the help everyone, no more telling people "nah it's ok, it does this."
UPDATE EDIT:
The check valve actually did not cure my very cold start (only after sitting overnight) revving/missing/stalling, but did fix the warm start issue. Just wanted to state this for any future troubleshooters reading this.Last edited by Vincent Brick; 01-23-2018, 11:17 PM.sigpic
1991 325i Sport - Calypsorot Metallic - DAILY DRIVEN
WTB in SoCal: 8"/10" Lukebox, leather Sport steering wheel, 60L MotoMeter fuel gauge, Thule/Yakima roof rack
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I also added a fuel check valve recently, although at first it seemed to solve my long cranking time when I let my car sit for a while it doesn't help anymore and it seems like my fuel pressure regulator is leaking.
I was able to put the check valve right after the pump in between the two metal fuel lines.
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