Car loses Fuel Over Time

Maintenance/Repairs
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1

My 91’ MR2 seems to lose fuel over time when parked for a while (3+ weeks). I have it parked indoors in an underground parking garage.
I don’t smell any gasoline around/in the car, but the leak is extremely slow.
Any ideas where I can be losing gas from?

2

Someone syphoning gas out of the tank?

Tester

4 Likes
3

How do you know if it is losing a small amount of fuel? Seriously…

Are you noticing it on the fuel gauge? Are you noticing fewer miles (or drive days) per fill-up? Are you calculating fuel mileage every time you fill-up… miles on the odometer divided by fuel input??

Which is it?

4 Likes
4

I wonder if the OP can mark the gas cap in some way that would indicate if it had been removed.

1 Like
5

Highly doubt someone is stealing the fuel. It is more likely that the fuel is evaporating, and if the rate of evaporation is slow enough, you won’t smell it, but over time fuel will be lost.

6

Agree between having to have the car doors to access the fuel door release and the fact most cars have a anti syphon tank.

7

could be a leak that evaporates

8

Thanks for all the replies. I marked the tank level when i filled up yesterday and ill update in two weeks.
I was hoping it was something simple like a gas cap leaking or something but it doesn’t seem like that is very common.

9

You may in fact not be losing any fuel, measurement of fuel level is the problem. That mechanism uses a float and variable resistor. The float can develop a leak and sink below the top of the fuel level, which would indicate by the dash gauge there’s less fuel in the tank than there actually is. The variable resistor (sender unit) can get gunked up and fail to report the correct fuel level as well. Either is a pretty likely culprit on a 30+ year old vehicle. You could try asking your shop to replace the sender unit, usually contains both the float and the variable resistor, see if that solves the problem.

1 Like
10

Any chance this 32 year old car has a corroded fuel tank, hole in the top? I’d get the car’s fuel system carefully inspected.

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11

+1
If Toyota was still using metal gas tanks at the time of that car’s manufacture, a corroded hole in the top of the tank is a real possibility. That actually happened to me with two cars over the years, a '66 Galaxie 500 and a '73 VW Karmann Ghia.