Mike M Posted January 10, 2008 Share Posted January 10, 2008 how come when sitting at idle with the lights on my walbro fuel pump gets slightly noisier when i press the brake pedal then more noisier if I turn on the rear screen demister? Obviously a big load on the alternator at 600revs but seems to effect the pump. The brake lights arent that power hungry surely? Quote Link to comment Share on other sites More sharing options...
Daston Posted January 10, 2008 Share Posted January 10, 2008 Well when you dab the breaks look at your odo display that dims slighty as does the headlights. My guess is more load on the alternator means a drop in revs so the engine puts more fuel in to keep the revs the same, and more fuel means more pump, and more pump means more pump noise, and more pump noise means Mike posts a question, and mike posting a question means daston answers................oh no I'm stuck in a rut!!!! Quote Link to comment Share on other sites More sharing options...
Mike M Posted January 10, 2008 Author Share Posted January 10, 2008 Well when you dab the breaks look at your odo display that dims slighty as does the headlights. My guess is more load on the alternator means a drop in revs so the engine puts more fuel in to keep the revs the same, and more fuel means more pump, and more pump means more pump noise, and more pump noise means Mike posts a question, and mike posting a question means daston answers................oh no I'm stuck in a rut!!!! Hehe. I see where your going with this:d I was thinking more load = more strain on alt = dimmed headlights and less voltage to pump to make it sound strained or noisier. Its ok when you blip the throttle you hear it picking up again I guess in time with the headlights brightening up. kindoff answered my own question here LOL Quote Link to comment Share on other sites More sharing options...
TurboBrett Posted January 10, 2008 Share Posted January 10, 2008 Hehe. I see where your going with this:d I was thinking more load = more strain on alt = dimmed headlights and less voltage to pump to make it sound strained or noisier. Its ok when you blip the throttle you hear it picking up again I guess in time with the headlights brightening up. kindoff answered my own question here LOL i had a similar thing on the mini when all the lights and spots was on to the point where the engine could empty the float bowl faster than the pump could fill it:d made for some dodgy getaways at the lights:innocent: i found as the pump slowed it got louder but tbh i wouldnt worry about it, if you wanna test it, let it idle for 10 minutes with every thing that drains power running if it doesnt cut out or blow up were all safe Quote Link to comment Share on other sites More sharing options...
Mike M Posted January 11, 2008 Author Share Posted January 11, 2008 i had a similar thing on the mini when all the lights and spots was on to the point where the engine could empty the float bowl faster than the pump could fill it:d made for some dodgy getaways at the lights:innocent: i found as the pump slowed it got louder but tbh i wouldnt worry about it, if you wanna test it, let it idle for 10 minutes with every thing that drains power running if it doesnt cut out or blow up were all safe Yeah sounds like it's the same louder as it gets slower. I know sometimes the car wont start 1st time after sitting a couple of weeks and the pump gets more noisy as the engines about to stall. Cheers Mike Quote Link to comment Share on other sites More sharing options...
Kranz Posted January 11, 2008 Share Posted January 11, 2008 If you're really worried about it then replace the power wire to the pump with a heavier guage cable all the way to the battery. Otherwise don't worry, its normal Quote Link to comment Share on other sites More sharing options...
Mike M Posted January 11, 2008 Author Share Posted January 11, 2008 If you're really worried about it then replace the power wire to the pump with a heavier guage cable all the way to the battery. Otherwise don't worry, its normal LOL,no i'm not that worried and I hate running wire through the car at the best of times. Quote Link to comment Share on other sites More sharing options...
Ian C Posted January 11, 2008 Share Posted January 11, 2008 Hehe. I see where your going with this:d I was thinking more load = more strain on alt = dimmed headlights and less voltage to pump to make it sound strained or noisier. Its ok when you blip the throttle you hear it picking up again I guess in time with the headlights brightening up. kindoff answered my own question here LOL The fuel pump ECU ensures that the voltage to the pump remains constant. Putting extra load on the engine with the demister and the brake pedal sends signals to the ECU, and it compensates by cracking open the idle control a bit more and ups the engine idle revs. This increases fuel pressure slightly by changing the vacuum signal in the plenum (which the FPR takes a reference off) and the pump whines a bit harder. It's perfectly normal -Ian Quote Link to comment Share on other sites More sharing options...
Mike M Posted January 11, 2008 Author Share Posted January 11, 2008 The fuel pump ECU ensures that the voltage to the pump remains constant. Putting extra load on the engine with the demister and the brake pedal sends signals to the ECU, and it compensates by cracking open the idle control a bit more and ups the engine idle revs. This increases fuel pressure slightly by changing the vacuum signal in the plenum (which the FPR takes a reference off) and the pump whines a bit harder. It's perfectly normal -Ian Very informative, thanks for that Ian. Cheers Mike Quote Link to comment Share on other sites More sharing options...
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