Stupid question
Discussion
This will most likely seem like a stupid question for those that know the answer. Today I removed the fuel pump and filter and I noticed that behind the filter is another black cylinder - what is this? Second stupid question - could someone explain the fuel circuit - lots of hoses that would appear to have little purpose!!
The cylinder behind the filter is the carbon canister. It is supposed to stop petrol fumes from the tank being vented to atmosphere. It is connected back to one of the airboxes via a solenoid valve to allow the canister to purge when the engine is running.
I have never got my head around the actual fuel pipe routing and discussions on previous threads seem to indicate that the routing and direction in the pipes varies from car to car.
I have never got my head around the actual fuel pipe routing and discussions on previous threads seem to indicate that the routing and direction in the pipes varies from car to car.
Based only on a sample of one I would say change it. When i did the fuel pipes a couple of years ago the pump seized solid within 50 miles. I can only assume that I disturbed something in it, and that was without taking it off.
I didn't mean to be obtuse about the fuel pipe layout. At the back it is simple once you realise that some bits (two pipes and one electrical connection) are only connected to the carbon canister and not in the fuel flow system. The fuel then is simply the big pipe to the back of the pump, the link from the pump to the filter and the pipe from the filter into the tub/chassis towards the engine. On mine the fuel return lines are on the other side of the car I think.
There was a thread a couple of weeks ago about the fuel pressure regulator and fuel cooler arrangement, on my car the fuel cooler is connected to the pipe from the fuel pump and the pressure regulator is the outflow from the fuel rail back to the tank. But in other cars it is apparently the reverse of this.
I didn't mean to be obtuse about the fuel pipe layout. At the back it is simple once you realise that some bits (two pipes and one electrical connection) are only connected to the carbon canister and not in the fuel flow system. The fuel then is simply the big pipe to the back of the pump, the link from the pump to the filter and the pipe from the filter into the tub/chassis towards the engine. On mine the fuel return lines are on the other side of the car I think.
There was a thread a couple of weeks ago about the fuel pressure regulator and fuel cooler arrangement, on my car the fuel cooler is connected to the pipe from the fuel pump and the pressure regulator is the outflow from the fuel rail back to the tank. But in other cars it is apparently the reverse of this.
Your description is the reason that I'm asking the question - I do not appear to have a fuel return line from the engine bay. I suspect that the system is designed so that excess fuel is immediately returned to the tank after the "carbon canister. My main fuel line from the back of the car to the front comes off of the carbon canister and there is another line from the carbon canister back to the tank, however there are a couple of other spare lines - hence my confusion!!
mikeufo said:
Your description is the reason that I'm asking the question - I do not appear to have a fuel return line from the engine bay. I suspect that the system is designed so that excess fuel is immediately returned to the tank after the "carbon canister. My main fuel line from the back of the car to the front comes off of the carbon canister and there is another line from the carbon canister back to the tank, however there are a couple of other spare lines - hence my confusion!!
Liquid fuel never goes into the carbon canister - the lines to and from it are for vapour only.Fuel is returned to the tank from the engine bay, to the hard line underneath the water header tank or in very early cars possibly a flexible line running down the transmission tunnel, to the drivers side rear wheel arch and into the tank on the drivers side. Look underneath your water header tank. If there are 2 hardlines there then one is fuel supply and the other is fuel return.
Normally the only flexible hose to run down the transmission tunnel is the purge line that connects the carbon canister to manifold vacuum via a solenoid valve mounted on top of the carbon canister. Fuel feed is from the tank to the passenger wheel arch to the pump then up to the hard line entry at the back of the wheel arch, along the top of the centre console inside the cabin and out under the water header tank. It then goes to the fuel rail, out via the pressure regulator and to the fuel cooler then back to the other hard line back through the cabin to return to the tank via the drivers rear wheel arch.
There was some variation as to exactly where in the circuit the fuel cooler was originaly placed - pre or post fuel rail - and some early cars had hose through the underside of the tunnel instead of hardlines in the cabin.
Edited by Tanguero on Sunday 29th March 11:05
My car's system is exactly as described by Tanguero. There are two hard lines under the water header tank with one being the supply from the fuel filter in the passenger side rear wheel arch and the other being the fuel return which emerges in the drivers side rear wheel arch and into the tank.
With the early cars, you have a rubber line going from the fuel filter deep in the pass. rear wheel arch, connecting quickly to a hard line that runs down the pass. side transmission tunnel. This then connects to a rubber line again to appear by the rear of the pass. side airbox and travels on top of the middle of the engine down to the fuel cooler. Rubber line up from the drivers side of the fuel cooler up to the fuel rail.
Return comes off the fuel rail, again over to the pass. side airbox and down towards the gearbox, it then follows a chassis rail over the top of the clutch/gearbox right above the starter motor. At this point it will be wrapped in thermal foil protection. This solid line then goes down the length of the transmission on the drivers side, before connecting to a rubber line just before the diff, which goes back to the fuel tank in the boot on the.... drivers side still I think.
Return comes off the fuel rail, again over to the pass. side airbox and down towards the gearbox, it then follows a chassis rail over the top of the clutch/gearbox right above the starter motor. At this point it will be wrapped in thermal foil protection. This solid line then goes down the length of the transmission on the drivers side, before connecting to a rubber line just before the diff, which goes back to the fuel tank in the boot on the.... drivers side still I think.
Got it sorted I think, many thanks to those who responded. Quite correct - the fuel goes from tank to pump, through the metal filter then enters the hard pipe through the centre tunnel (this is the bit I was not getting) - somebody has conveniently marked the pipes as they come out from under the water header tank - see picture. The lines then return through the centre tunnel and emerge at the passengers side and return to the fuel tank. To be honest I'm very surprised that they got away with having a fuel line going through the centre tunnel carrying high pressure fuel (100 psi). Attaching photos so that it might help others that don't quite understand in the future ![](http://thumbsnap.com/t/ff2IuyH0.jpg[/img]</a> <a href="http://thumbsnap.com/3E7JaqX1" Target="_blank">[img]http://thumbsnap.com/t/3E7JaqX1.jpg)
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