Fuel tank foam + sender
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Joined: Apr 2009
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Fuel tank foam + sender
I have a '92 C4 with 130k for 70/30 HPDE/street use (not a DD but is street legal).
Looks like some of the fuel starvation problems in the C4 are due to the fuel pickup not being close enough to the bottom of the tank, and this is fixed with simply bending down the tube closer to the bottom of the tank.
While the tank is apart, I'd like to add some fuel cell foam as both an added safety measure and to prevent excessive slosh.
I've heard that a "tube style" fuel level sender is necessary if foam is in the tank. And to replace the fuel tank lock ring. Summit Racing seems to carry both foam and generic tube senders in their own brand.
A few questions:
Thanks for the tips,
Andy
Looks like some of the fuel starvation problems in the C4 are due to the fuel pickup not being close enough to the bottom of the tank, and this is fixed with simply bending down the tube closer to the bottom of the tank.
While the tank is apart, I'd like to add some fuel cell foam as both an added safety measure and to prevent excessive slosh.
I've heard that a "tube style" fuel level sender is necessary if foam is in the tank. And to replace the fuel tank lock ring. Summit Racing seems to carry both foam and generic tube senders in their own brand.
A few questions:
- How many foam 'bricks' will fill a tank? I guess knowing tank dimensions would help this...I can do the math.
- Beyond the obvious, what happens if you underfill (loose/floating around) or overfill (packed too tight) with foam?
- What length of tube sender would I need? Again, tank dimensions...
- Confirm that the stock sender is a 90-0 ohm?
- Is it worth replacing the Fuel Pump while apart? Or at minimum the sock? What socks work best?
Thanks for the tips,
Andy
Race Director
Joined: Jun 2004
Posts: 13,966
Likes: 710
From: WI
Answered your same post in the race section. Addition, I think it was $250 for foam to fill the huge stock tank. Like I said there it would be better just to use a fuel cell. The stock tank is just so large. To keep cost down, I'd skip the new sender and just check it manually. I looked into the same idea. Interested in other options! 
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
Normally the fuel pump sits an inch or so just above the the bottom of the tank tray and only the fuel strainer (fuel pump sock) actually comes in contact with the bottom. Once the sock is soaked with fuel it is very resistive to sucking air through it. Stock fuel pump socks are elongated on one end intentionally. The longer side of the fuel strain needs to be towards the bottom/back of the tank tray to avoid air entry & low fuel level "slosh" issues.
Additionally, if you've changed the fuel pump or disconnected the electrical connectors on the fuel pump assembly I highly recommmend that you replace the electrical connectors/harness terminals. These connectors are just a few dollars and are available locally a most auto parts stores. I've seen electrical related fuel starvation problems occur on take hard launch/ take off and while making tight turns (will just less than 3/4 of tank) and where the actual fuel sloshing in the tank around was enough to wiggle poor electrical connections/wires on the pump to momentarily stop the pump from running. Surprisingly this does not show up even with a fuel pressure gauge strapped to the windshield but you can feel the car stumble under throttle and see it if you monitor the O2 gauge readings (it will go super lean).
Intermediate
Joined: Feb 2008
Posts: 27
Likes: 2
Answered your same post in the race section. Addition, I think it was $250 for foam to fill the huge stock tank. Like I said there it would be better just to use a fuel cell. The stock tank is just so large. To keep cost down, I'd skip the new sender and just check it manually. I looked into the same idea. Interested in other options!
Race Director
Joined: Jun 2004
Posts: 13,966
Likes: 710
From: WI
Racer
Joined: Jul 2010
Posts: 308
Likes: 2
From: Kansas City MO
Cheapest - I'd sump the stock tank and run an external pump or put the pump in the sump... I know there are universal sump kits out there with a wedge shaped piece of metal and a couple of AN fittings on it that are pretty cheap.
Also - a couple of baffles in the tank can prevent the slosh during turns if you're taking the tank down to the point you can sump it might consider putting in some baffles...
Also - a couple of baffles in the tank can prevent the slosh during turns if you're taking the tank down to the point you can sump it might consider putting in some baffles...
Race Director
Joined: Apr 2003
Posts: 17,700
Likes: 1,667
From: moraga ca
Because of the elongated size and shape of the stock fuel tank, it would be very difficult to fill it with foam. I cut my tank out so I could remove it without removing the bumper and replaced it with a fuel cell. You can see the goofy shape here. Unless your arms are 3' long, you won't be able to reach the ends of the tank. You can also see the small size of the opening. You'll have to mince up the foam.
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