Tuning and bad fuel pump

[acarmody]

Just wondering something weird going on with car.

I got my car dyno tuned about a month ago, and it wasn't till after the tune that I noticed that there was some sort or air suction/escaping noise coming from the rear-right tyre area (no not tyre), also about the same time my car was harder to start after I have released the fuel cap to fill up.I was guessing that the pump was on its last legs and that revving the tits off on the dyno mave have started to make it fail.

Anyway on Tuesday I got my mechanic to install a new genuine pump, and when starting it, it was running pretty rich. I have currently stalled it 4 times when idleing (auto btw), when you accelerate normally from stop it seems to lose all power before catching with revs dropping very low, and it also idles pretty rough.

The mechanic and me where thinking that the car might have been dynoed with the bad pump and tuned to suit the bad pump. Does anyone know if that is plausible?

I'm trying to get some dyno time soonest but i'll see how I go.

[ari666]

well, i dunno about efi, but i had my 308 dyno'd with a dud pump and when i installed a decent one after the tune the secondary throttle flaps were way too loose and my floats were way too high which meant the car was constantly stalling.

even having a source of air coming into your fuel system, i.e. a fuel filter or hose that isnt sealed 100% can cause all sorts of tuning problems, due to it sending little bubbles into the fuel bowls (which you dont have) and "carbonating" the fuel. (i say carbonating very loosely cos' i dunno what else to call it... you know, like lemonaid or beer with the bubbles)

so yeah. my opinion is yes, tuning it on a dud pump can throw the tune out.

[acarmody]

I just got it tuned the other day, managed to snag a early morning time slot. Yep as guessed it was rich as hell at idle, so they tuned it up properly. All good now.

Fuel pump replacement costs:
Genuine Holden pump $210
Installation $60
Tune $200
Total $470 for a friggin pump

[ari666]

yeah but itll be worth it though. the money you save on fuel running with a decent tune will be enough. especially at 1.45 per litre

the reason i answered this thread is funny, cos i had just changed-out my holley pressure regulator cos it had little drips of fuel around it all the time. wasnt expecting any change in performance, was just wanting to stop wasting fuel. anyways, got it back on, started it, drove it and instantly noticed the smell. was running way too rich. drove round the block, parked back at work, gave it a really quick tweak on the mixtures, then launched off, twin spins which left black lines on my driveway

so yeah. bubbles in fuel=bad - no bubbles=wheels spin and launches and smiley faces and giggling like little kids