Set a gas reserve on a floatless, i.e., accurate, fuel sender? (Page 1/1)
imacflier JUN 19, 07:35 PM
Good evening, All,

Well, I have the last parts on order to replace my stock lying fuel level sender with a floatless sender. (Total cost including shipping is about $125, and is just about plug and play with the existing gauge. I will do a build thread once everything arrives!)

I think that means a capacitive sender, at least I am unfamiliar with any other floatless type.

My question for Y'All, is simple: if you really know that empty means empty, would you give yourself a reserve?

Opinions, please, and what reserve, if any, would you set?

TIA,

Larry
pmbrunelle JUN 19, 09:13 PM
I found the stock gauge to be fairly OK, with 4 L remaining between "E" and the engine sputtering to a stop. After running out of fuel, I filled the tank to the brim; with this test I established the volume of fuel that is useable by the engine. Then, on future fill-ups, I recorded the gauge reading and the volume of fuel needed to refill the tank to the brim.



In general, I would make "E" equal to empty. Having a reserve after that means you're blind to the level of fuel. In other words, your gauge has become devoid of useful information when you need it the most.

The exception is if someone else will drive your car... they may expect to drive for a while on E like they do on other cars.

[This message has been edited by pmbrunelle (edited 06-19-2020).]

theogre JUN 20, 01:29 AM
Gauge "Empty" should be close but above Tank "Empty"
Tank "Empty" is where FP will suck air because repeatedly doing this will ruin the FP. Fuel is Coolant and Lube for the FP and injector(s).

That means you often never use Total Tank Capacity Spec in Ads, Owner Book, etc.
Read the tank spec and forget about ~ 1 gal for many cars, not just Fiero.
Often less usable gas when people replace the pump and don't measure OE and New pump install depth to mach sure they match.

IOW 84-86 says 10.3 gal but FP is often sucking air at ~ 9 - 9.5 gal. Later Fiero says 11.9 but often runs out at ~ 10 to 10.5 gal.
And That depends on when you are... Level ground at same speed is different then hit the gas or brakes or going up or down a hill because fuel moves in the tank and baffle(s) only helps a little when tank is near empty. Is why when driving in Hill Country I fill most cars at ¼ not Empty.

Accurate? Most are never accurate to start w/ because 1 issue is Fiero and most other tanks are not simply shapes and depth of fuel often is not = to gallons of fuel.
So any type of sender and whatever gauge are mainly a quessiment for fuel available. Is also why some gauges read quickly at top, bottom or both vs ~ middle ⅓.
Some cars w/ BCM running the gauge may have programing to be more accurate then others including new vehicles w/ "dumb" fuel gauges.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

claude dalpe JUN 20, 08:46 AM

quote
Originally posted by theogre:

Gauge "Empty" should be close but above Tank "Empty"
Tank "Empty" is where FP will suck air because repeatedly doing this will ruin the FP. Fuel is Coolant and Lube for the FP and injector(s).

That means you often never use Total Tank Capacity Spec in Ads, Owner Book, etc.
Read the tank spec and forget about ~ 1 gal for many cars, not just Fiero.
Often less usable gas when people replace the pump and don't measure OE and New pump install depth to mach sure they match.

IOW 84-86 says 10.3 gal but FP is often sucking air at ~ 9 - 9.5 gal. Later Fiero says 11.9 but often runs out at ~ 10 to 10.5 gal.
And That depends on when you are... Level ground at same speed is different then hit the gas or brakes or going up or down a hill because fuel moves in the tank and baffle(s) only helps a little when tank is near empty. Is why when driving in Hill Country I fill most cars at ¼ not Empty.

Accurate? Most are never accurate to start w/ because 1 issue is Fiero and most other tanks are not simply shapes and depth of fuel often is not = to gallons of fuel.
So any type of sender and whatever gauge are mainly a quessiment for fuel available. Is also why some gauges read quickly at top, bottom or both vs ~ middle ⅓.
Some cars w/ BCM running the gauge may have programing to be more accurate then others including new vehicles w/ "dumb" fuel gauges.





I 100% agree with the theogre. If there is one thing to remember from his words it is: Tank "Empty" is where FP will suck air because repeatedly doing this will ruin the FP. Fuel is Coolant and Lube for the FP and injector(s).
darbysan JUN 20, 11:06 AM
FWIW, I have always tried to keep at least 1/4 tanks as my fillup point. Not only does it keep the FP cool and prevents starvation, it also helps to prevent the FP from sucking up the debris that settles in the bottom of the tank. If that debris gets sucked up, it can plugg up your injectors, causing an expensive repair. May be wive's tale, but seems like sound advice.

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'87 GT , '00 3800 Series II SC, 4t65e, Vue Power Steering. (SOLD)

theogre JUN 20, 05:32 PM

quote
Originally posted by darbysan:
FWIW, I have always tried to keep at least 1/4 tanks as my fillup point. Not only does it keep the FP cool and prevents starvation, it also helps to prevent the FP from sucking up the debris that settles in the bottom of the tank. If that debris gets sucked up, it can plugg up your injectors, causing an expensive repair. May be wive's tale, but seems like sound advice.

FP is happy as long as has gas flowing thru it.
Is why many fools put wrong gas regulation in engine swaps then burn out FP's.
Example: many carb setup tries using wrong 2 port regulator w/o a return.
Good return line is a required part of most "older" Pump in Tank systems. Newer 1 gas line to engine just moves the regulator near or in the tank and dumps return gas right back in.

If you have loose crap in the tank, FP will suck it up no mater how much gas in the tank.
The FP "Sock" is first layer of Gas filters to keep out big trash.
Next is obvious gas filter you often replace. The Filters for Fiero and many others trap crap in 2 ways...
1. Heavy crap sinks to bottom of the filter can because because wide slow flow there.
2. Filter Media stops most of the rest, IOW over X particle size.

Most injector can pass crap Under X particle size. Some like 700 TBI injector for 87+ l4 has more filter screens to stop crap trying to plugging them up. These screen get flush and return crap to tank via return line w/ extra gas.