Fuel pump.

[jmec]

Hi, 1990 325i. The fuel pump is pressure is 2.5 bar. I understand it should be 3 bar. On removal I can see very fine pieces of debris. Shiny, non ferrous. I'm guessing it's an aluminium impeller. Question is what is a reasonable replacement choice. The interweb comes up with all kinds of make at prices from £24 to £420! Thanks in advance.

[reggid]

depends how long you intend to keep the car, a genuine or VDO one will last a good while and therefore may make sense even if spendy while cheap ones wont and should be avoided. there are some good aftermrket brands but depends what brands you have access to.

make sure the tank is clean

also FPR could be a culprit if yu havent checked that

[jmec]

I replaced the FPR a short time ago because it failed on the pressure check carried out following the Bentley Manual. However the pressures remained low and that prompted a pressure check on the pump. I fitted a tee piece and gauge in line directly to pump outlet. There it indicated 2.5 bar. I've blown through the lines and checked the gauge for accuracy against a known source. As I mentioned there's small traces of non ferrous shiny metal in the tank directly below the pump and tapping the pump when removed revealed more traces. It's a VDO unit. There's no shortage of pumps available and an array of good makes. There is a selection of Bosch replacements for instance. Ranging from mid £70s to £150 ++. Just wondering if anyone has similar experience and have fitted a pump they're happy with.

[Brianmoooore]

You are making a fundamental mistake with your understanding of fuel pressure. The FP, as written on the regulator, is the pressure difference between the fuel in the injector rail and the inside of the inlet plenum. A gauge measures the difference between the rail fuel pressure and atmosphere, which will be around 0.4 bar or so lower when the engine is idling.
It's very rare for a E30 fuel pump to fail just giving insufficient pressure. It's usually either wear in the gears, causing them to jam, or the motor commutator completely wearing away.

[jmec]

Now that's interesting Brian. I get what you're saying. Was my understanding of the Bentley FPR flawed because it mentions fitting the pressure gauge to the shraider valve at the end of the injection rail. My car hasn't got that facility so I fitted the gauge in line to the rail feed?

[BenHar]

I think the point Brian is making is that 2.5 bar is fine.

Ben

[Brianmoooore]

Never seen a shraeder valve on a E30 fuel rail yet, unless it has a M5x engine. The Bentley manual seems to be considered the gold standard, but I've never been particularly impressed with it.
Disconnect the small reference hose to the FPR and you should see nearer 3.0 bar on your gauge.

[jmec]

Thanks again Brian. I'll view the Bentley Manual with less reverence in future!

[Blanca]

If you have to referee to a Haynes manual you really are in trouble. Bentleys we don't have here. Datacar, yes.