Draining passengers side fuel tank
Thread Starter
Racer
Joined: Aug 2019
Posts: 289
Likes: 64
From: Edinburgh, Scotland
Draining passengers side fuel tank
1999 coupe. I need to get on with changing the electric fuel pump I now have. I’m hoping, and don’t think there’s too much fuel in the car. This being my project C5 that’s not ran in 8+ years.
I’m a little confused about the way the tanks work (I’ve a rough general idea but am slightly lost on which tank empties first and how the gauge works and so forth). My gauge was erratically showing 1/8 or so full so it’s hopefully not too full. Putting that aside I simply want to drain fuel from the passenger tank as well as letting loose my fuel from the drivers tank when I remove the pump/sender.
Will removing a pipe from the passenger side tank/pump drain fuel relatively well? I’d obviously fill up with good gas if leaving some old gas in. If I can avoid it I don’t really want to remove the passengers side pump incase re sealing is an issue. I guess it’s either this (removing a pipe) or run my new electric pump to drain the tanks from the fuel rail. This was the original plan until I discovered the electric pump was defunct!
Any advice as to what seems my best plan appreciated. Thanks
I’m a little confused about the way the tanks work (I’ve a rough general idea but am slightly lost on which tank empties first and how the gauge works and so forth). My gauge was erratically showing 1/8 or so full so it’s hopefully not too full. Putting that aside I simply want to drain fuel from the passenger tank as well as letting loose my fuel from the drivers tank when I remove the pump/sender.
Will removing a pipe from the passenger side tank/pump drain fuel relatively well? I’d obviously fill up with good gas if leaving some old gas in. If I can avoid it I don’t really want to remove the passengers side pump incase re sealing is an issue. I guess it’s either this (removing a pipe) or run my new electric pump to drain the tanks from the fuel rail. This was the original plan until I discovered the electric pump was defunct!
Any advice as to what seems my best plan appreciated. Thanks
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,564
Likes: 4,034
From: Cape Coral, Florida
Hi !!...WOW !!...not run in 8+ years...now how do you know the pump is bad ??...now the pump will run for 2 seconds when the key is turned on..have you given the pump a few good taps because after sitting all that time it may have just bound up a little ??...do you think you can run a 50 yard dash at full speed after laying motionless for 8 years in bed...LOL !!...basically the left fuel pump supplies fuel to the right tank siphon jet pump so the fuel will transfer from the right to the left tank and then into the engine...I would disconnect the electrical harness at the pump and jump power and a ground (earth) to it and see if it runs...I would attempt this before pulling the pump !!...BTW, I'd have your injectors removed and either professionally cleaned or replaced because dollars to donuts the first time the engine is started it will either not start or run poorly...and then you'll be back here on the Forum !!...cleaning all the external body grounds as well as the battery terminals at BOTH ends wouldn't hurt either !!
Thread Starter
Racer
Joined: Aug 2019
Posts: 289
Likes: 64
From: Edinburgh, Scotland
Hey, the pump definitely bad. Thoroughly checked including re-earthing it. I’ve also now been over quite a lot of earthing points and re done a few. Despite penetrating fluid over days, the nut in the earth pin bolts seem prone to seizing solid hence unavoidably broke. Cue making new earthing points.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,564
Likes: 4,034
From: Cape Coral, Florida
Any of the grounding points I would drill a new hole in the frame rail and secure with a sheetmetal screw or if you have enough room tap and secure with a new stud !!
Thread Starter
Racer
Joined: Aug 2019
Posts: 289
Likes: 64
From: Edinburgh, Scotland
I’ve done just that. Ground and smoothed frame rail and inserted large self tapping screw. Decided to use small steel ‘L’ brackets for good earth to rail contact, then earth points bolted on to the small bracket.
Tech Contributor
Joined: Oct 1999
Posts: 41,044
Likes: 9,808
From: Charlotte, NC (formerly Endicott, NY)
To answer your one question the passenger side tank empties first. The driver's side fuel pump provides a stream of fuel to the siphon pump in the passenger side tank and that pulls fuel out of that tank. If you are 1/8 full that means you have about a quarter of tank of gas in the driver's side tank. There may be some residual in the passenger side tank but after 8 years it might be sticky goop.
Bill
Bill
Thread Starter
Racer
Joined: Aug 2019
Posts: 289
Likes: 64
From: Edinburgh, Scotland
To answer your one question the passenger side tank empties first. The driver's side fuel pump provides a stream of fuel to the siphon pump in the passenger side tank and that pulls fuel out of that tank. If you are 1/8 full that means you have about a quarter of tank of gas in the driver's side tank. There may be some residual in the passenger side tank but after 8 years it might be sticky goop.
Bill
Bill
Safety Car
Joined: Mar 2017
Posts: 3,768
Likes: 940
From: Orlando Florida
I'm pretty sure that without a siphon break fuel levels out between the two tanks when the key is off, similar to how a water level works.Just thinking that both tanks will have similar amounts of residual fluid, whether that be gas or goop.
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Thread Starter
Racer
Joined: Aug 2019
Posts: 289
Likes: 64
From: Edinburgh, Scotland
Thanks for your reply. There are obviously differences of opinion. Before posting I had read conflicting opinion too!
The pump system obviously constantly runs fuel from the passenger side to the drivers side tank, constantly topping up the drivers. I’d tend to go with the passengers side emptying first for that reason but as per why I posted, I’m not certain..
The pump system obviously constantly runs fuel from the passenger side to the drivers side tank, constantly topping up the drivers. I’d tend to go with the passengers side emptying first for that reason but as per why I posted, I’m not certain..
Safety Car
Joined: Mar 2017
Posts: 3,768
Likes: 940
From: Orlando Florida
Well, that's probably because I seem to have been wrong. Again. I was basing my thoughts on what I've observed with my '99 and use of water levels and fluid dynamics in other applications. Looking for a system description I find that -- for 03's and 04's at any rate -- there is a definitive siphon break in the transfer line, so unless the pump feed line is acting as a siphon, unlikely, it's a one way trip from right to left. So sorry I was wrong, but glad for the opportunity to learn something new.