Hi again everyone! The 85 has been running like a beast since the spark plug escapades, so I'm working on minor annoyance things now. I have two issues with the fuel tank.
1. It fills normally most of the way, and then I have to baby it to get the tank full. There must be a fume escape vent somewhere and it's plugged? It triggers the fuel fill nozzle to turn off like it's full, but I can generally get another gallon and a half in.
2. The tank won't empty all the way. The gauge must be accurate, because at about the 1/4 tank mark I can generally get about 7 gallons in. However, once I hit 1/4 the car starts running out of gas.
Are there diagrams that would be helpful in helping me figure this out? I'm assuming I'm going to have to drop the tank, which sounds like a pain in the butt. I'd like to be as well-prepared (knowledge-wise) as possible before disabling my DD.
The 85 has a 10 gallon tank. It's generally accepted that only about 8 of that is usable. So, at 1/4 tank, assuming it relates to full capacity, you only have 2.5 gallons remaining.
For 2 of my cars that have bad gauges, I always fill them up and reset the trip odometer. Then I never drive more than 150 miles before filling up again. If you're only realizing 20mpg, that would be about 7.5 gallons of fuel, still less than the 8 gallons available.
I had an 85 4 cylinder that would run out of gas at 1/4 full .Had to get towed once .After that , never let it go below 1/2 full without filling up .Checked on this forum , another common GM screwup .I never fixed it , just warned the next owner .
Fuel tank sizes are 38 litres for 84-86, 45 litres for 87-88. That's a complete fill to the top of the vent, and there's more room above that but it's essentially unusable.
The tank is long and narrow and the fuel pick-up is in the middle. The internal baffling will direct fuel to the pickup when the car accelerates or decelerates but not left to right or steady speed, so it can run out even with fuel in the tank.
[This message has been edited by mender (edited 04-09-2016).]
The 87 and 88 had larger tanks. Nearly 12 gallon, so there would be about 10 gallons of usable fuel. I get varying mileage on my 3 cars. About 24 on the 87 with a 3.4, about 28 on the 86 with a 2.8 and last trip, I got 35 on the 88 Duke. All are 5-speeds. My brother's 86GT automatic is somewhere near 20 mpg. Maybe less.
When I had a working fuel gauge and a 2.8 in my 87, I pushed it to the limit and I recall getting near 300 miles, also. I just don't make it a habit of draining the tank that low. Don't want to burn out an original fuel pump and have to replace it. I've seen lots of folks on here that also say they use the 150 mile limit for fuel.
Originally posted by Chantruese: Hi again everyone! The 85 has been running like a beast since the spark plug escapades, so I'm working on minor annoyance things now. I have two issues with the fuel tank. 1. It fills normally most of the way, and then I have to baby it to get the tank full. There must be a fume escape vent somewhere and it's plugged? It triggers the fuel fill nozzle to turn off like it's full, but I can generally get another gallon and a half in. 2. The tank won't empty all the way. The gauge must be accurate, because at about the 1/4 tank mark I can generally get about 7 gallons in. However, once I hit 1/4 the car starts running out of gas.
Push nozzle into fill port and lift handle up often helps. Keep nozzle fully into the fill port all the time. Letting handle rest to fill often causes problem to many cars, especially w/ fast pumps.
2. Likely: Gauge is off or not reading at bottom of scale. Fuel pump and pickup is set high and can't reach bottom. or Both
By now every Fiero has had at least one fuel pump change. I was careful during the last fuel pump change to empty the tank once it was removed from the car and position the pump as low as I could in the tank without obstructing it, to access as much of the available fuel as possible as well as calibrate the fuel gauge. On a flat surface I recall being able to pump fuel out of the tank with less than a gallon in it and I purposely biased the fuel gauge needle to below "E" for true empty. I can get at least 250 miles hwy to a tank in an 86 SE avg about 27-28 mpg based on round trip fill averages over the same long distance commute ~150 miles requiring 5.5 gal or less at return top off, except for fun filled days which may hit 6 gal.
My three Fieros are running on original pumps and have never had the gas tanks dropped. I guess I've been lucky. I ordered the '84 SE 4 speed in Sep '83, rec'd it in May '84 and it has 371,600 kilometers (230,900 miles) on it. It shares daily driver duty (excluding wet salty conditions) with an '86 2.5L 5 speed that has 130,600 km (81,100miles) on it. The Formula 5 speed only has 30,100 km (18,700 miles) on it.
Edit to add: My gas log shows at last fill-up the '84 has pumped 31,664 litres through 371,544 kilometers over almost 32 years. That's 8.5 L/100km; or 33 MPG imperial; or 27.5 MPG American gallon.
[This message has been edited by David Hambleton (edited 04-10-2016).]
I daily drive, but never on the freeway (I don't commute that far.) I get about 16 MPG, so I go about a max of 110 miles between fill ups. Based on what I'm reading with the pick ups and design, maybe I don't have a real issue, although I would guess that the vent isn't venting as well as it should based on how it acts during fueling. I've done a ton of work on the vacuum issues, checked compression, new coil setup, new plugs, and I went from 14 to 16 mpg. Where else should I focus if I wanted to improve gas mileage?
I'm running new tires, suspension is good, and I always keep an eye on pressure to make sure I'm not running on floppy tires.
Instead of locking the filler nozzle on, try holding it and deliver fuel as slowly as possible. Sometimes I've had the same trouble because of the angle of the filler nozzle. Not just with the Fieros, but even with my truck.
Ive learned the hard way NOT to top off fuel till its full (I call it superfilling). Leave it alone after it shuts off. Ive had a couple of cars I used to fill to the top. It would soak a gasket being submerged in gas to where it leaked and let fuel run up thru emmission lines where it sometime caused the engine to stall from flooding. On 2 of mine, that seal was not replaceable since it was built into the tank. I had to buy 2- $500 gas tanks to learn. You also will never get the last gallon or so out of a tank. Fiero may not be the same since it has a metal tank. Another downfall of superfilling is if you park in the sun it will boil out thru the cap or emissions lines.
Mine was also on the original fuel pump till I did the engine swap a couple year ago. Car was apart at the time and figured might as well change it out (it was a bit noisier then before).
That being said, everything the OP said is "normal".
BTW, no fuel tank on any car will empty all the way, there will always be some left.
[This message has been edited by Mickey_Moose (edited 04-11-2016).]
This has very little to do with the thread but you still might enjoy it: A friend of mine was, decades ago, a fireman on a federal facility in Indiana. His fire chief boss [who also was the nominal fire chief at the Indy 500 for several years] rarely rotated shifts, preferring day shift - rotated just enough to keep his premium pay for odd hours worked. The boss was also commonly [among the fire fighters] known to be a crook, stealing what ever was loose from the base, most often when leaving one of his rare night shifts. So during one cool evening when the guys are lounging around after their evening meal, watching the telly, the boss does his typical thing and sneaks his personal vehicle over to the official gas pump and tops it off. However, a warm temperature front moved through so it was warmer in the morning when he went to his car to leave. Tank had overflowed, making a pool of gas under the boss's car. Magic.
I daily drive, but never on the freeway (I don't commute that far.) I get about 16 MPG, so I go about a max of 110 miles between fill ups. Based on what I'm reading with the pick ups and design, maybe I don't have a real issue, although I would guess that the vent isn't venting as well as it should based on how it acts during fueling. I've done a ton of work on the vacuum issues, checked compression, new coil setup, new plugs, and I went from 14 to 16 mpg. Where else should I focus if I wanted to improve gas mileage?
I'm running new tires, suspension is good, and I always keep an eye on pressure to make sure I'm not running on floppy tires.
Didn't mean to turn this into a thread about OE fuel pump life, it was just a figure of speech to draw attention to the possibility that as a result of a pump replacement, the pump maybe riding a little high in the tank. As for the EVAP line, I've had mine plugged before as a result of a piece of charcoal from the canister getting lodged in it, possibly from me turning it upside down while performing maintenance. The symptoms were pretty obvious as that's the only vent from the tank. When ever the temperature of the fuel increased from extended driving or a sunny day, there would be a considerable woosh from release of pressure from the tank when the cap was removed for a fill up. I disconnected the metal line at the bottom of the car and blew it out instantly correcting the problem.
Fuel economy can be a mix of things, high mileage (after a good hot drive remove the oil filler cap with the engine running and observe the level of smoke blowing from the port and hold your hand just above to gauge the strength of the puff from blow by gasses), alcohol content in the fuel, slipping automatic transmission, failed TCC circuit where the converter is not locking up, etc...
I don't know about other states but here in Houston we have these vapor recovery fuel pump hoses that are ridiculously sensitive. They will shut off far from full on a tank. Sometimes they shut off a half dozen times on my truck when I know the truck needs 20 gallons to fill. They do this on my brand new car as well as the Fiero, so you never really know when the tank is full or not.
