I put a new fuel filter on my car (2002 Citroen Saxo, 1.1 petrol engine) yesterday - pretty simple, just unclipping the lines from the old one and putting the new one in the same place. It's located at the rear, right beside the tank under the car. I should have blocked off the lines before unplugging the filter, but I didn't have anything to hand so I just did the swap as quick as I could and lost some fuel in the process.

After doing it, the car took about 5 seconds of cranking to start up - and ran fine for the rest of the day. I started it twice more after sitting a few hours each time, and it fired right up. When I started it again this morning though, it took another 5 seconds or so to get running - almost like there wasn't fuel at the injectors right away. This makes me think - do I need to bleed the system somehow given that I let fuel leak out? I would have thought any air would escape through the injectors but I might be wrong! There's no leaking from the new filter by the way.

Attached is a photo of the old one, showing you how it's set up. This is the 'out' end, which has two lines (I'm guessing one is a return line from the fuel rail).

Fuel filter

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    When you turn the ignition on, but without trying to start the engine, you should hear the fuel pump run. Leave it run for a few seconds before trying to start the engine to see if that makes a difference.
    – HandyHowie
    Jun 18, 2022 at 20:16

1 Answer 1


No, you shouldn't need to bleed a petrol system. If it was diesel, some require bleeding, because air pockets can act like cavitation points and it won't pump the fuel. Petrol systems should be self bleeding.

Considering you're able to get it started, it seems like this is a little bit more of an annoyance than a real issue. You may or may not find this goes away after a little bit of time. Overall, unless you are unable to get it started at any time, I'd suggest there isn't any issue here. If it becomes a little bit more of a problem (the interval becomes longer before it will start, or it becomes harder to start), you may have either a leaky injector or the anti-drain back mechanism in the fuel pump may be wearing out.

  • Ok, thanks! Yeah it doesn't seem like a big problem or anything, I just wondered if I'd missed a step.
    – el_zilcho
    Jun 18, 2022 at 19:08

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