Series 3 fuel pump open circuit

I noticed some time ago that my Bosch Series 3 FI fuel pump wasn’t making any noise when I turned on the ignition. Thought it was not getting voltage but it was. Removed it and it is open circuit–infinite ohms between 12V terminal and ground. I assume I should throw it out? In lister’s experience, does this happen very often? I replaced the pump with a very old one and the car runs fine, but there’s some reason I replaced the old pump, which I can’t remember (haha, very typical these days). This is an Alfa BTW, whose OE pump is NLA and for which the Jag pump is supplied in the aftermarket.

If the pump is open-circuit then of course throw it out (or have a look inside).
The pump unit is a rotary vane type but with rollers and is directly driven by the electric motor. All is cooled by fuel.
The motor has probably lost it‘s winding (fatigue) where that attaches to the commutator or something like that. Don’t know how often this happens but I guess every so many thousand hours. It’s gone.

The FI pumps are probably all identical pretty much but there are differences in quality so don’t buy the cheapest.


If there is open circuit between the two connectors of the pump, Robert - it is defective for whatever reason. It is very seldom the pump fails this way - but not impossible…

You will only read continuity between the pump’s ‘12V’ and ground if the pump’s ground wire is connected to pump’s ground terminal…

The S3 fuel pump will work on any EFI system - it’s just a matter of relevant hose connections…

xj6 85 Sov Europe (UK/NZ)

Thanks David and Frank. It looked like it didn’t want to come apart easily, but I might do so destructively just out of curiosity.

They might all look the same, but they aren’t all the same. If you look at the Bosch pdf for fuel pumps and go to the graphs at the back, you’ll see that they pull different amounts of amps and have slightly different specs.

I’d chose the one which pulls least current given the flow rate you require at maximum revs.

kind regards