Fuel Filter

[tonyroc14]

Since search isnt working, (for me) i think ill ask a quick question. Will old, dirty, possibly clogged fuel filters cause hard starting? Sometimes my car takes a while to start, and when it does it feels like it has no fuel.

[Mr 535i]

Maybe, maybe not but the fuel filter is pretty cheap and easy to change. I changed mine a month ago and my obc MPG already improved, "mpg1" is higher than "mpg2" (I resetted the mpg1 after the fuel filter change). Autohaus has a great price on those, $10.17.

[zubbie]

Could also be leaky injectors, vacuum leaks, worn internals, nesting mice....

[ross1]

Fuel filter isn't the problem. The demand is least at idle and starting, a restricted filter will manifest itself first with high speed starvation.
Your problem, long cranking, if fuel related at all will be low pressure in the fuel rail at start up, either from injectors leaking down or a weak pump. EDIT Thecheck valve at the pump can also account for this.
BTW, a fresh filter cannot improve fuel economy, any difference noticed by the other poster is coincedental.

[m60b30530i]

Could also be leaky injectors, vacuum leaks, worn internals, nesting mice....

i found nesting mice on my intake manifold under the injector box :shifty

lets just say they didn't survive the high speed run :stickoutt

[tonyroc14]

Fuel filter isn't the problem. The demand is least at idle and starting, a restricted filter will manifest itself first with high speed starvation.
Your problem, long cranking, if fuel related at all will be low pressure in the fuel rail at start up, either from injectors leaking down or a weak pump.
BTW, a fresh filter cannot improve fuel economy, any difference noticed by the other poster is coincedental.
See, no pressure is exactly what i thought it was in the begining. How could i test this? Also, should i get a fuel pressure test done, or something like that to check my fuel pump.

[sfgearhead]

if you're not sure when the fuel filter was changed, do it just to be sure.

[mhax]

i do have the same kind of problem, the engine is hard to start after i drove it and parked it for about 20 minutes. I dont have much trouble starting the engine when the car is cold and when it has not been driven in the last hours.

[attack eagle]

BTW, a fresh filter cannot improve fuel economy, any difference noticed by the other poster is coincedental.

that's what I always thought, but the real workld data indicates it can.
I'm guessing trims are set longer due to slightly lower pressure and putting things back in range cleans the trims back up.

[funnyman06]

Replacing a fuel filter will increase fuel economy, and this is why. When your filter is dirty, fuel/ air whatever, your engine has to work harder to pull the fuel or air through the filter media. Any extra work the engine has to do effects the performance of the engine. I'm not sure if these cars run electric or mechanical fuel pumps, but it has to work harder on a dirty filter than it does on a clean one, and that means less MPG's.

[93FIM5]

Hum Im not so sure how much changing a fuel filter helps with MPG but it cant hurt. The pump is electric so surely replacing a dirty old filter will help the pump out if nothing else. I would check your fuel pressure at the rail and see what you get first. Also when was the last time you changed your plugs or did general maintenance?

[sfgearhead]

whether or not it will increase your fuel economy, when you're chasing a problem start with the simple stuff.

am i the only one here who follows the bmw recommended maintenance schedule? i know you're short on cash tony, but a $15 fuel filter is a good investment.

we lost a fuel pump (and 600 euros to fix) on an e36 due to a clogged filter which blew the pump.