Bosch 044 fuel pump testing

[tomwood_uk]

Morning gents,

Trying to get to the bottom of the lean running I've been experiencing on my aby recently and I'm suspecting a fuel delivery issue. With the fuel return line draining into a container I'm getting around 1.3 litres after running the engine for 15 seconds. That's with my 3 bar fpr, with the standard 4 bar fpr it's around 750ml. I've temporarily relayed the power supply which has made no difference (13V at pump).

I've been informed that I should be looking for around 2 litres of return flow after 15s but some of the info I've read on the forum contradicts this. Can anyone shed some light on this ?

Cheers

[andyg plym]

2 litres in 15 seconds? That doesn't sound right surely ? A gallon is roughly a Jerry can which is somewhere between 4.5-5 litres so surely you can't use half a gallon after just 15 seconds?

[AndyP]

According to this:-

http://www.boschfuelpumps.com/

They do 300lph, which works out to 1.25ltrs in 15seconds.

[tomwood_uk]

2 litres in 15 seconds? That doesn't sound right surely ? A gallon is roughly a Jerry can which is somewhere between 4.5-5 litres so surely you can't use half a gallon after just 15 seconds?

This is measuring the return flow back to tank, not what is used by engine.

[tomwood_uk]

According to this:-

http://www.boschfuelpumps.com/

They do 300lph, which works out to 1.25ltrs in 15seconds.

Hmm maybe I'm on the wrong track then. I presume that 1.25l in 15 seconds is unrestricted flow.

[AndyP]

Yes, I'd say that was straight out the top of the pump, not going through the fuel system and out the return. You'd have to take it out the tank to test properly

[tomwood_uk]

Yes, I'd say that was straight out the top of the pump, not going through the fuel system and out the return. You'd have to take it out the tank to test properly

Yea. I suppose I could just disconnect the fuel line from the filter and measure it from there.

[prj]

If it's 1.25 at 3 bar, but 750ml at 4 bar, then 100% the pump is bad!

On boost it has to deliver up to 6 bar (2 bar boost).

[tomwood_uk]

I'm about to refit the std pump to test that

[tomwood_uk]

Std pump returned less than 250ml in the same test (3bar fpr). It's pretty old and has been sitting in a box for a while but still a huge difference.

[prj]

Then the std pump is dead or you are doing something wrong.

Standard injectors at 100% opening flow 323cc/min.
With five of them it makes 1615cc/min. or 1.615l/min.

That means 97l/h fully maxed out. The pump should be able to provide at least that at 5.5 bar if the car runs 1.5 bar boost.

if it provides 250cc per 15 sec, that means 60l/min, which is more than 30% short.

[UrS4boy]

20VT Fuel Pump Testing

Audi suggests that 20VT fuel pump flow should be tested at the point where the fuel rail inlet line connects to the hard fuel line.

Here is a C4 UrS fuel pump testing procedure that you could adapt to the B3/B4 fuse box, etc. You would use Fuse 13, the fuel pump fuse, which is the 15A fuse just above the "r" in the French "Moteur" in the diagram below:

Fuel pump testing: http://forums.quattroworld.com/s4s6/msgs/260108.phtml

[tomwood_uk]

Then the std pump is dead or you are doing something wrong.

Standard injectors at 100% opening flow 323cc/min.
With five of them it makes 1615cc/min. or 1.615l/min.

That means 97l/h fully maxed out. The pump should be able to provide at least that at 5.5 bar if the car runs 1.5 bar boost.

if it provides 250cc per 15 sec, that means 60l/min, which is more than 30% short.

I'm measuring return flow, so not absolute flow as the engine is obviously consuming some fuel

[UrS4boy]

I'm measuring return flow, so not absolute flow as the engine is obviously consuming some fuel

See my post above. You are testing incorrectly.

[tomwood_uk]

See my post above. You are testing incorrectly.

Thanks I had seen it just advised to perform a different method.