Fuel Filter Question

[998automan]

Hi all. I installed an inline fuel filter (just before the carb) about a year ago without any issues, however when at my local garage for an MOT the tester mentioned that SU carbed minis don`t like them and some performance can be lost, can anyone confirm if this is the case? - Filter still looks as clean as the day it went in so am wondering if I really need it anyway?  

[richard1]

You should always have a filter of some kind. Most cars have a "sock" type strainer in the tank that keeps the big crud out, but you never get to see it rot. sometimes it is very open.
Some carburetors have a "stone" type filter at their inlet. Those don't really need additional filtration, but can get stopped up more easily if no prefilter.

Carbureted engines only need gasoline filtered down to about 100 um, or a little wider than a human hair (80um). Injected gasoline engines need to filter down to about 20um. Common rail diesels need filtration down to 2um.

So, yes, I would keep a filter there, although I do not like plastic, as the last plastic one I put on my Corvair disintegrated and started leaking. Fortunately not in the engine compartment. I like to keep all rubber and plastic out of the engine compartment.


Then again, some cheap metal filters aren't worth their weight in steel.
Here is one I cut open


On my pickup I put an in-tank pump, with a filter between the wheels before it goes up to the SPI engine.

[998automan]

Thanks Richard. Interesting to hear what you say about keeping plastic & rubber out of the engine compartment. I have always wondered about the design that sited the fuel pump/carb with all its hose/pipe unions so close to the exhaust manifold, I know it is a matter of limited space but surprising it was never changed. How do you get around this on your car as the fuel pump to carb connection involves some short sections of hose to connect pipe to fuel pump and then to the carb? 

[mra-minis]

I can be contacted on [e-mail]

needs must....

unless the filter is restrictive in some way it is not an issue, don't forget the SU has a fuel chamber and as long as it is full always then no issues. If you do feel like you are losing power try to pull the choke out a little if nothing happens chances are your filter is cutting the flow.

[998automan]

Thanks Martin, will try that next time i`m out & about!

[richard1]

Mar 28, 2016 8:30:51 GMT 998automan said:

Thanks Richard. Interesting to hear what you say about keeping plastic & rubber out of the engine compartment. I have always wondered about the design that sited the fuel pump/carb with all its hose/pipe unions so close to the exhaust manifold, I know it is a matter of limited space but surprising it was never changed. How do you get around this on your car as the fuel pump to carb connection involves some short sections of hose to connect pipe to fuel pump and then to the carb? 

Metal filters with the special hoses that come with them. But when possible, get them away from the engine, especially things like exhaust manifolds and things that might spark.