Fuel Pump Whine

[SuspiciousPizza]

I currently have my GL all torn apart to address some well entrenched gremlins.

The main issue I have a question regarding is why does my fuel pump bog and whine when I use my turn signals?

Fuel pump operates as it should (although I don't have a fuel pressure gauge hooked up at the moment, I will be adding several gauge pods, including a fuel pressure gauge, once I get the engine back in my car.)

However, whenever I used my turn signals my fuel pump would whine a different tone only when the turn signals blinked. Between blinks it would have a normal tone.

The negative terminal arcs when I plug in the battery, indicating a short (?)

Obviously I'd assume it's a wiring or ground issue (almost all the grounds in the engine bay were caked in oil, grease, and dirt but I've been thoroughly cleaning the engine bay with Simple Green and a multi-pack of tooth brushes while I have the space to do so.)

Would anyone have any pointers? Would I be able to use the fuse box to check which circuit is shorting? I can read a multimeter, have a very basic understanding of circuitry and have a full set of service manuals at my disposal.

 

Thanks!

:]

[el_freddo]

An aftermarket head unit will always create a tiny spark when connecting the battery. 

Other than that the fuel pump issue is either a poorly operating alternator, old wiring with resistance points or a battery that isn’t coping as well as it used to. Lastly could be some sketchy wiring done by a pervious owner. 

You’d really need to check out if anything was modified before your ownership. Eg: I have a Gen1 RS turbo Liberty (Legacy over your way) that someone used the door switch circuit as the earth for the aftermarket head unit. Whenever someone opens a door the headunit turns off as the circuit becomes active. Classic (*facepalm*). 

Cheers 

Bennie

[SuspiciousPizza]

I do have an aftermarket radio, and it's an absolute rat nest underneath the steering column and behind the glovebox. I figured this was a good candidate to begin diagnostics. There is plenty of wire nuts, misc wire gauges, and "good enough" wiring *facepalm* indeed.

Would anyone have a wiring diagram for an '89 radio? I don't even know which model of radio came with the car from factory, let alone the wiring. 

Alternator does seem to be pushed pretty close to its capacity, but I'm not convinced it's the alternator. Voltage drop during turn signal flashes is 2-4 volts according to the volt meter in the gauge cluster, a big drop. Alternator is a Nissan Maxima VG30E alternator mod. Pretty commonplace.

:]

[azdave]

I've had several pumps in my 87 DL wagon in the last two years and they all begin to whine and moan after a few months but only when they get warm. The whine pulses up and down when the turn signals are on or when any change is made to the loading on the battery. The pumps all work great at first and are pretty quiet but eventually I begin to hear them after a long drive home from work. I just figure it is cheap pumps that quickly lose the gearing tolerance after a few thousand miles.

[bushytails]

Battery voltage fluctuating with the turn signals is normal.  The two 1156 bulbs draw about 5A when hot (~27W each), and at least double that cold, i.e. every time they blink on.  The stock alternator is 55 or 60A iirc.  You're pulling surges of a quarter of its high-rpm rating, and you're at idle (since you can hear the fuel pump) where it can barely keep up with the loads anyway.  And when the voltage dips, the fuel pump slows down.

A spark when connecting the battery is also 100% normal, and does not imply anything wrong, modified or otherwise.  You're charging the capacitors in every electronic module, including the radio, ECU, fuel pump controller (I can't remember if that year has one or not), cruise control module, etc etc.

 

Edited yesterday at 02:42 AM by bushytails