Would a bad fuel pump cause a voltage drain in the electrical system? I'm testing 12V at the battery and 12V at the alternator with the car running...it should be about 14V while in park. The alternator is a year old or less and just to rule out the battery, I swapped in a known good battery from the Sunfire, and the battery seems to be fine. I'm at a loss here right now. The car is hard to start after sitting for a while so this is why I'm wondering about the FP.

 

Usually when the pump is going it tends to draw more current...

It sounds like its on its last legs.. you ever bottom feed the pump???

It only takes a few times of bottom feeding but when it goes you'll know...

I noticed that too before my pump died, the voltage reading normally on the high side of 13 was suddenly below normal. Didn't think too much of it. Later when talking to a GM tech about it he told me that as the pump dies it has to work harder to pump the same amount of fuel, it thus draws more current...

You've been worried about this pump for awhile now.. just hope it doesn't die on you on the road...

 

Seriously...you noticed a change in voltage?!? The extra draw to make it work does make sense and this was my theory too. I just didn't know if it was realistic.

As far as bottom feeding...never. Expect for long trips where it gets down to the tip of the red but never empty...During normal driving around I never let it get below a half.

I'm calling my old mechanic today to see if he can advise me on this. I'm really getting fed up of not being able to drive my car and I don't want to miss this next drag event.

 

Then again age also takes its toll on a pump.

Mine died at 260000 kms and 14 years.

Looks are deceiving though.

Some questions though,

Do you have hard starting sometimes?
Do you notice a lack of power in the early gears, bottom end torque not like it was before?
Does it ever stumble or stall?

Even when a pump is going, pressure may remain high enough to maintain idle. This is usually as low as 30 psi. The volume of fuel on the other hand may not be enough though.

I believe you've already changed the fuel pump relay as I recall.

A pump should have a constant power draw, on a diagnostic device, a smooth waveform really. A multimeter checking amperage won't tell you that, but if you have one with a record function to check high and low current draw point, you'll notice intermittent spiking between high and low.

If the pump has burned out in a sense due to bottom feeding the current draw goes up as it struggles to move the gerotor in the pump. If the pump is just breaking due to age, current draw goes low and volume of fuel drops considerably.

Hope this helps a bit on figuring out the problem.

 

Your voltage should read more than 13 volts if the car is running be it the battery or alternator..It should be 13.7-14.2v at idle..Do a load test..see how much the voltage is when all the accesories are on..It shouldnt go below 12V(unless you have a pulley)..Is your battery seems swollen?(doubt it)but if it is its the regulator..Also check the terminals..

To test for a drain get a test light and take the negative terminal of the battery off..Clip the one side of the test light to the negative cable and touch the battery terminal with the lead(pointy thingy)If if lights up you have a draw(alarm maybe?)..Unplug one fuse and test again.If the light is still on when the said use is unplugged that means the draw is not coming from that set of electrical "components"move on to the next fuse..

Daz

 

doh didnt answer you question..

Any electrical component can cause a drain to your system..I doubt its the pump though cause it has to be turned on by the relay first..Dows your uel pressure go down when its sitting?
FYI ...A starter draws a lot of current when going bad and/or hot..

Daz

 

Slade: To answer your questions...It's hard to start cold and warm. Hot starts (sitting for like 5 minutes) is no problem. As far as power loss, nothing substantial. And stall or stumble, not really...only on cold starts when it's been sitting for a week. And yes the FP relay has been done in the past.

Daz: I don't really have any accessories other than a crappy stereo and I guess I could use the headlights. There doesn't appear to be any excessive drain while the car is off for extended periods...if the cars been sitting for a week, the starter will still crank hard with no obvious struggle. As far as the leak down, I'm gonna measure how long it holds take for the pressure to drop. I'm also gonna check the scanner to see if my BLMs are out of whack.

I just got off the phone with the dealership and my battery is indeed toast so it will be replaced under warranty. Thank *** for that part. The alternator is getting tested tommorrow to confirm whether it is ill as well. Then I'll continue from there with the other thousand tests I have to do.