I am in the process of trying to implement a full computer readout for Fieros. I do this stuff for a living and would really like to know what is going on with the ECM while driving. So, I would also like to implement an accurate fuel consumption measurement. There are 3 tubes going into the fuel tank. One is fuel pump out and one is fuel return from the pressure regulator. What is the third hose? I looked in my shop manual and did not see any description of these 3 lines. I am guessing it goes to the fuel canister, but could be way off base.
The hard part at this point is getting fuel metering devices to put in line with the fuel pump and fuel return.
Thanks Y'all. I missed the trip odometer thread when I posted the original question.
I see that the person doing that product is using the "guess" method of estimating consumption based on injector timing. I am looking at ways of implementing real flow sensors that will measure both inlet flow and fuel tank return. The hard part is getting a good enough seal while still allowing the "gears" to turn.
Also looking at tapping off the fuel gauge line to get an accurate measure of fuel in the tank. I put in a new sending unit and it reads about 2 gallons low. At least I know that when it hits the end, I don't have much range left.
A task for another day when I don't have to fix exhaust bolts and a leaking EGR pipe and a broken windshield washer paddle :-(
Correct. On '87/'88 cars the third hose goes to the expansion tank in the right rear wheel well, which is then vented to the fuel evap canister.
So that is what that is , I noticed it in the wheelwell last summer when I had the car tore apart. I had no idea what is was or what it was for. learn something new every day ( I wonder what I forgot to make room )
Is the expansion tank, the one that sits on the rear passenger side between the engine firewall and the rear quarter panel? If I remember correctly, there's a panel that goes from the tank to that "expansion" tank, and then to the fuel evap canister. But I'm curious exactly how or why this is an expansion tank. Is it for when the fuel expands it'll fill up that tank, or... what exactly does it do?
The expansion tank was added so there was no possibility of fuel getting sucked into the vacuum canister and messing up the charcoal filter. It's an emissions thing, so depending on how green you are, you can live without it. There may be an increased fuel odor if the evap system is not working.