What is a "fuel cooler"... regarding A/C and FPR

[bwanac]

Ok so I was taking out my a/c. i got the compressor out and disconnected the line that leads up to the strut tower. but when the line goes behind the strut tower, it goes into a metal piece wrapped in foam. two fuel lines lead off of that piece. one is the return fuel line from the FPR. the other i dont know. does anyone have this setup?

why would the return line be connected to this a/c line? where should i be routing the return line, now that it had nowhere to go?

please help, i cant figure this out!

[Spaz]

i don't see how the fuel lines and the ac lines are on the smae side. the fuel lines are on the left side and then a/c lines are on the right.

if you can post a pic i maybe able to help you.

-cam

[bwanac]

i dont have a camera. I have tried to find pics but I cant seem to find any. Pete(OreoGaborio) and I have been trying to figure this out, but we can't. If anyone has a similar set-up please help, or who knows what is going on.

Car is an 87 325(e) if that helps. My parts car, also an 87, has the a/c setup that most people have. On my car though the fuel lines seem to be connected to the a/c.

[bwanac]

i sorta figured it out, but it makes no sense.

ok, so line from the compressor leads to the metal/foam piece. off of that piece there are 4 things. two from the a/c that lead into the firewall, as they normally do.

then there are the two fuel lines that run through the foam piece for some reason. one of them leads to the return fuel line of the FPR. the other leads down under the car, on the drivers side. that line, is where the fuel return line normally runs.

so what i think is happening is a big loop. the fuel return line from the FPR leads back to that foam piece. from there the fuel is lead through the second fuel line coming out of the piece and down to where the return fuel line normally goes.

now i dont understand why they would run the return fuel line in this big loop in my car, while in your car it just goes straight down. and more confusing is why the a/c lines and the fuel lines go through the same little piece of metal.

anyone, does anyone know?

[bwanac]

http://bimmer.roadfly.org/e30/messages/archive/msgsy2000w09/14815.html

http://bimmer.roadfly.org/bmw/forums/e30/forum.php?postid=4266429&page=1

a couple of links from roadfly, calling this thing a "fuel cooler." does anyone know what this does, or why my car has it but most dont?

[rs4pro3]

Must of been something BMW tried in 87. I gues it could cool down the fuel as it inters the engine and make it burn more efficient.

[bwanac]

but it was on the return fuel line that leads back to the tank. so i dont get how that helps.

i read some stuff online talking about vaporlock and the gas actually boiling, but i dont know how that matters on the fuel return line.

but my fuel will never be that hot up here in the northeast. this car is from FL so maybe it was specifaclly for down there in the heat

[rs4pro3]

That could be I know here In Tn if I drive the car in the hear and stop somewhere for around 4-5 mins and go back out the car gives me a hard time starting in the heat.

[Inspar8r]

i dont have a camera. I have tried to find pics but I cant seem to find any. Pete(OreoGaborio) and I have been trying to figure this out, but we can't. If anyone has a similar set-up please help, or who knows what is going on.

Car is an 87 325(e) if that helps. My parts car, also an 87, has the a/c setup that most people have. On my car though the fuel lines seem to be connected to the a/c. wtf?!

Mine too!!! You just asked before i did.... i figured i just had a fuel cooling system or something... but i doubt it..

[DaN]

The fuel is probably cooled to prevent vapor lock, or air in the fuel lines caused by hot fuel. Heat makes the fuel vaporize more easily, if it vaporizes then air bubbles are created, and you get a driveability problem.

The fact that it is used on the return line doesn't really matter. The fuel is constantly circulating, so as long as there is something in the loop to absorb heat, then the fuel will run cooler.

[bwanac]

So even though my A/C did not work, it was doing something? I doubt it in that case, but I guess it makes sense for when the A/C was charged with R12 or whatever.

[De //m3]

This was also done on the E28 five series. The fuel return line runs behind the firewall over to the A/C side where it runs through the "Fuel Cooler" then back behind the firewall to the original side where it goes back to the tank. I would that this is possibly to combat hot starting problems in the summer, but I am really not sure. When we removed my buddies A/C in his 87' 535is we just plugged the line back into itself where it came out on the A/C side and experienced no difference in starting. Maybe it would make a difference on some cars though.

[DaN]

So even though my A/C did not work, it was doing something? I doubt it in that case, but I guess it makes sense for when the A/C was charged with R12 or whatever.

Well it was designed with a functioning A/C system in mind. If your A/C doesnt work, then the cooler is pointless.

I'm just guessing, but I think it was made for cars in very hot climates, or maybe it was just over-engineering on BMWs part.

I didn't think vapor lock was an issue on fuel injected cars, since fuel pressure is so high. Its a problem usually associated with carburetors.