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Old 12-31-2017, 12:40 PM   #16
Vincent Brick
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Quote:
Originally Posted by AndrewBird View Post
I put mine next to the tank just after the pump, not right at the pump. The short distance from it to the pump isn't enough to cause an issue.
Next to the tank? By the fuel filter?
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Old 12-31-2017, 12:58 PM   #17
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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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Old 01-01-2018, 01:22 PM   #18
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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, Cory
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Old 01-01-2018, 02:20 PM   #19
jeffnhiscars
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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 it
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Old 01-01-2018, 10:07 PM   #20
AndrewBird
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Quote:
Originally Posted by Vincent Brick View Post
Next to the tank? By the fuel filter?
Literally on the side of the tank before the filter. There was probably 8" of line from the pump to the check valve.
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Old 01-06-2018, 01:14 PM   #21
Vincent Brick
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Quote:
Originally Posted by cory58 View Post
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, Cory
Pretty sure there is a check valve built into the pump assembly, but that it commonly fails before the pump itself, so these are added to avoid replacing an expensive pump that still mostly works. At least that is what I have gathered, tank side of the fuel system is one of the only things in these cars I haven't messed with much.


Quote:
Originally Posted by AndrewBird View Post
Literally on the side of the tank before the filter. There was probably 8" of line from the pump to the check valve.
I'll have to get underneath and look, about to right now. On my car there is a lot more than 8" of fuel line from the pump to the side of the tank where the fuel filter resides.
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Old 01-21-2018, 04:03 PM   #22
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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.
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Old 01-25-2018, 09:45 AM   #23
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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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