Fuel pump prime - sounds slow when cold?

[Jeffs Black 97 Formula A4]

Never really paid attention before, but does anyone else's fuel pump prime sound slow on a cold engine (turn the key without starting engine), compared to a warm engine (where the prime sounds faster)? Thanks!

[FTA1995]

The key here would be fuel temperature, which gets pretty warm after running through a good amount of return cycles through the fuel rails. It may also be from a weakening battery, whereas there would be a considerable drop in voltage difference between when the car is cold overnight and when it was running warm, and charging the battery. If your worried about a problem, it could be time to change the pump, but check your fuel pressure first. If your pressure is at spec, 44 ish psi, and your fuel pressure does not bleed off rapidly after stoping the pump, it's probably fine.

How full do you keep your fuel tank? Anything below 1/4 in any car puts excessive wear on in tank pumps; they are dependent on the fuel itself for cooling and lubrication.
Hope this helps a bit,

[FTA1995]

To answer your original question, my old oem pump did, got a 255 LPh Wally and haven't met with a single inconsistency yet

[Jeffs Black 97 Formula A4]

I usually fill up when the fuel gauge reads 1/4 or a little less (never ran it dry). I also installed a new battery 3 months ago.

I have almost 30000 miles and it still runs strong. Starts right up too (cranking for less than a second every time).

[FTA1995]

It's probably from some tolerance differences on some moving components inside the pump, I'd say that could vary unit to unit. What brand is your pump?

[Jeffs Black 97 Formula A4]

It's probably from some tolerance differences on some moving components inside the pump, I'd say that could vary unit to unit. What brand is your pump?

Stock, and original.

[FTA1995]

Probably low cold cranking amps (?) from your battery, do your headlights dim hard on a start? This is assuming all other tests have passed and your only symptom is the noise change.

[Jeffs Black 97 Formula A4]

Well, I still seem to have a slow fuel pump prime on a cold engine.

Today, I noticed if I turn the key once to "prime" the engine, and it is slow, I turn the key off and don't hear the "whistle" sound I normally hear when I turn the ignition off (while the engine is NOT running). I then proceed to turn the key to the ON position and heard a strange "mechanical sound" under the hood! (sounded like it came from the passenger side under the hood). Any ideas what that could've been? Thanks!

BTW, car started right up after that...and continues to run like a champ...

[FTA1995]

The only kind of non engine related mechanical noises I've ever heard under the hood of a 4th gen is either a cooling fan, hiss of fuel past the regulator, and (this sounds like what you're talking about) a high frequency beep click click which I believe is the abs unit(?). The only "whistle" sound I've observed is my iac valve parking on a warm engine when I shut it down, since I don't have much overlap on my cam I still draw good vacuum at idle.

I think you might need to give a little more detail as to what's going on with your fuel pressure throughout a start process on a cold motor...
If it runs well and doesn't start to lean out on you, it might not be the pumps fault.
Do you have any extra accessories that are on and drawing power when you turn the key?

[Jeffs Black 97 Formula A4]

Well, I finally decided to have the dealer look at it and they told me the fuel pump is starting to go (fuel pressure was 45PSI with engine off, 35PSI with engine running).

What's crazy is on some boards, people say those are acceptable numbers but after the fuel pump swap (PSI is back to GM specs, at 58PSI acording to the dealer), the engine definitely feels a bit stronger and more willing when I floor it now! They also performed the fuel injection service (which I thought was just another "quick lube scam", but I guess it isn't).

Only issue I have now is the fuel gauge is inaccurate from the swap (gassed it up after picking up the car, and the gauge is between 3/4 and F, where it used to be about 2-3mm beyond the "F").

Any idead what I should tell the dealer (I actually left it with them and told them I wanted it fixed). Thanks!

BTW, what I really find strange is at just 31000 miles the fuel pump started to give out??? Another thing I found strange is I never had a SES light or even a trouble code while all of this was happening with the original fuel pump. Car wasn't running rough but I definitely feel a bit more power (so I must've been losing power along the way).

[Trash man]

fuel pumps is a electric motor basically, it doesnt go by miles, it goes by hours of service. as for the fuel gauge issue, did they reuse the orginal float assembly? maybe they bent the float arm by accident. if you know its full for sure, you can take the gaugle cluster cover off and readjust the needle to F

[Jeffs Black 97 Formula A4]

fuel pumps is a electric motor basically, it doesnt go by miles, it goes by hours of service. as for the fuel gauge issue, did they reuse the orginal float assembly? maybe they bent the float arm by accident. if you know its full for sure, you can take the gaugle cluster cover off and readjust the needle to F

I know the sender is new (not sure on the float arm). Anyway, they tried another "new" fuel pump w/sendor (they said the pump and sending unit is one piece). Same result, they then compared the new sending unit to the old one (the new one registered at 90 ohms, the old one was 103 ohms). They then told me they "tweaked" the float (did not bend it), but I am not sure how effective that is until I fill up again. I might have to take your advice and open up the gauge cluster. and move the needle next time it is full.

What will really confuse me is what will it read when empty?

[Trash man]

make sure you top it off as much as you car too, so that you know its truely full. i never run any of my cars below 1/4 tanks, esp if it was a GM product, GMs are knowing to eat fuel pumps.

[sneitzel]

What will really confuse me is what will it read when empty?

Do a little math. You should have a pretty good idea of the MPG you normally get and how many gallons it normally takes when you fill your tank from 1/4 full. Using that info, fill her up and drive approx. that number of miles then see what the gauge reads.

[Trash man]

i beleive the tanks are 16 gallons, so when the current gauge reads 1/4, fill it up and see what it clicks off at, if it says 8 then you know you had 1/2 a tank still