Bubbles in fuel pump?


Active Member
2000 SC glass bowl fuel pump.
is it normal to have bubbles forming in the glass dome on the petrol pump? (This is at very fast idol) I can’t say I’ve never really noticed it before on normal tickover but playing around with my car today on fast idle, I could see bubbles coming and going. Not really sure how the fuel pump works so not sure whether or not I need to be anxious about this or it’s just normal behaviour?
If it's happening when the engine is well warmed up, then maybe the fuel – more volatile nowadays than it used to be – is boiling. My car does that when idling after a good hot run. Nothing much to worry about. Alternatively there might be a slight leak on the pump's input side, enough to suck in air but perhaps not ooze fuel. Might be worth checking for wetness around the inflow pipe, and also around the petrol reserve valve especially if the O-ring in the latter hasn't been changed in living memory.
Thanks John...Good advice. O-ring replaced few years back now, however I will have a good look for any leaks. Pretty sure I'm okay as I never smell fuel in the garage, however worth checking. The bubbles don't "look" like boiling and they come and go so to speak.
When they started adding ethanol to fuel here in NJ I had a fuel pump failure that may have started this way. In my case I noticed a miss at high speed or load at first. But I’d bet you’d see bubbles if I had looked (scrub that, I have a IS spec pump with a steel top). The ethanol had damaged the rubber causing the valve flaps to cup and lose sealing.
So far, I have managed to run ethanol free, not sure how long that will last though, and then all the fun will begin