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Discussion Starter · #1 ·
I'm a little ashamed it's megasquirt, not 034. Someday i'll have that, i just don't have the funds for it now. College steals it all!

So the car is running quite well, but when it's really cold out, like now, -26 degrees F. Or during warm up when it's warmer out, there's a bit of a knock coming from the fuel accumulator/fuel pump. Is there a dampner of some kind that can be installed to quiet this? It exactly matches when the injectors fire, increases and decreases in the number of pulses accordingly. I'm wondering if this is a problem? Do i need to worry about fixing this?

Good stuff here, much more than repairs, THANK GOD!
Jeff Redig
Bozeman, MT
 

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First of all, welcome to the forum! No reason to be "ashamed" of using megasquirt, it has advantages and disadvantages just like every other aftermarket EFI computer out there.

Now onto your problem :D

A few thoughts/suggestions...

I've personally never had the problem you describe but one reason it may seem like this only occurs when the car is cold could be due to the fact that the engine is stumbling a bit/generally idling lower than normal. During this period your alternator might not be generating as much juice as normal and your fuel pump might make funny noises, especially when the added current draw from the fuel injectors kicks in.

Another possibility could be that your fuel pump is generally getting old and starting to make more noise under certain conditions. The pump on my 90q started doing this not too long ago (the pump was brand new as of ~2 years ago). I drove it buzzing like a can full of mad hornets for quite some time before the car started to hesitate. I swapped in a used fuel pump and all was well.

Just for laughs, try hooking up a battery charger to your car set to the "start" mode when it is cold out and the car would normally exhibit the symptoms you mention. If it doesn't make the noises with the charger connected you have your answer. If not, hopefully somebody else out there has better suggestions than me :slap:
 

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Discussion Starter · #3 ·
Thanks for the welcome!

ok, well i've looked at some of that already.....The fuel pump is new. less than 3K miles ago. Pierburg My old pump buzzed like a nest of hornets, it's not that sound.

I have enough voltage. According to my laptop the alternator is putting out 13.8 volts or better. Double checked with a voltmeter, all's well. the noise is unaffected by whether or not the car is idling. It doesn't dissipate with revs until about 2500 and then i think it's only because the engine becomes loud enough that you can't hear it.

I don't think it's the pump. I think it's more toward the accumulator. The sound is very audible in the passenger compartment. Outside of the car you can't find it. Too much other noise between exhaust etc... If you put your head in the front passenger footwell it's very loud, and louder in the rear foot well. Take off the seat and it sounds like someone is softly knocking on the frame/undercarriage beneath the seat exactly where the accumulator is.

When it's cold out it does it all the time, but when warmer temperatures arise it only does it during warmup, first 10 minutes of driving. If the car gets shut off and turned back on once warmed up it doesn't make the sound......WEIRD!

I can't remember who's site, but someone with an audi website had a similar issue and had some sort of pulse dampner/noise reducer that he put inline. I wish i could remember where i read that. It was a while ago.

Thanks for your thoughts marc
jeff
 
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