Fuel pump duty cycle

[matts]

When I start the car up the fuel pump runs at 100% dc for like the first minute. The ecu is trying like hell to correct AFR (-20% to -25%)at this totally unnecessary flow rate. When it goes back to 33% dc all is well. Does this huge negative compensation mean my fpr is bad or going bad? I guess I don't see the point of running the pump so high during idle. Is this maxed out condition at startup normal? Should I be concerned?

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[Cobb Tuning]

Originally Posted by matts

When I start the car up the fuel pump runs at 100% dc for like the first minute. The ecu is trying like hell to correct AFR (-20% to -25%)at this totally unnecessary flow rate. When it goes back to 33% dc all is well. Does this huge negative compensation mean my fpr is bad or going bad? I guess I don't see the point of running the pump so high during idle. Is this maxed out condition at startup normal? Should I be concerned?

Fuel pump duty at 100% after engine start for a short period of time is the expected behavior and part of the ECU code. As far as why you are seeing large corrections, we would need to know what car this is, your mods, what map you are running. That said, you can see some unusual corrections briefly after cold start or during warm-up enrichment even on a stock car. I would try to get a data log and post it up so we can take a look at it.

Bill

[matts]

The corrections taper off to +/- 1% to 3% after the duty cycle switches to 33%.

10' WRX. I have a walbro 255 and use the stock regulator setup. My map is the one editted from your ots stg2. I didn't edit anything in regard to the fuel pump.

I was just concerned about the stock regulator. If this behavior is the norm, then I will not worry about it.