[alfa] Re: fuel pump electrical help

["Dan Lewis" <lewisdk6@xxxxxxx>]

  Latest scoop on the sometimes-dead Quad... I traced the fuel pump wires
all around the car and they're OK.  Another "however" here: the other two
wires (ORG/BLK & BLK/ORG) off the combi relay pin that supplies power to the
pumps (through the wht/red wire), I traced to the O2 sensor and the aux air
device, respectively.  So, I disconnected both of those, the inline
connector to the fuel pumps (passenger side engine bay, pnk/wht to wht/red),
and ran a temporary line from the FP pin-out on the combi relay to the FP
connector in the engine bay.  I then re-installed the 10-Amp in-line fuse
and hit the ignition.  The fuse did not blow, so I must assume the fault
lies in the lines to either the O2 sensor, the aux air device, or the
wht/red wire to the FP circuit.
  The car starts and runs now, without blowing the fuse.  Hooray!!  I drove
it around a bit and noted a remarkable drop in power from before the engine
rebuild episode.  Throttle response is slow, too.  Along with that is a
noteable increase in the exhaust system temperature (the engine temp is
normal, though).    I ohmed out the O2 sensor wiring and found this - on the
sensor end of the engine bay connector: across the two wire connector about
1 M-ohm; from each to ground about 2 M-ohm; from the single black wire to
ground about 1 K-ohm. - - on the other side: across the two wire connector I
got 0 ohms; from each to ground I got about 98 K-ohm, same with the single
black wire.
  Here's my question: the exaust overheating and loss of power, I'm
guessing, is due to the O2 sensor either getting shorted out and/or it needs
replacement.  Sound about right?  Or, could the power/heat problems be
caused by the aux air device?  I'm at a bit of a loss on this one.
  I've gotten tons of information from here, both in response to my
questions and from just reading the archives.  I want to thank all of you
who post on here for all the info and help.  It's helped make this migraine
a mere headache.

Dan Lewis
Bellevue, NE
'88 Spider Quad


----- Original Message ----- 
From: "John Y. Hung" <jdaezhung@domain.elided>
To: <lewisdk6@domain.elided>
Cc: <alfa-digest@domain.elided>
Sent: Saturday, November 06, 2004 8:09 PM
Subject: fuel pump electrical help


> Dear Dan,
>
> I just traced the fuel pump electrical lines on my '88 Spider Veloce.
> Your car may be similar. I hope this description helps. Sorry for the
> length, but the electrical line is long also!
>
> Starting behind the passenger seat, the main fuel pump line comes into
> the car interior through the floor pan, behind the  computers. The line
> runs next to the computer, under the carpet, along the floor pan behind
> the seats, over the driveshaft tunnel, and then to the driver side. In
> the corner below the trunk and fuel door release handles, the in-tank
> fuel pump line joins the harness, but the two lines are still separate.
> Together, the lines run in the harness alongside the driver side floor
> channel, and then turn up at the firewall. There is a big connector up
> there, deep in the front left corner. At this connector, the two lines
> are crimped together into a male pin inside the connector. Both lines
> are pink with a white stripe.  (My fuel pump woes were at this
> connector - I had an intermittent open circuit, which prevented the
> pumps from getting voltage at inconvenient times. I squeezed down the
> female socket and spread the male pin, and things are now perfect for
> me.)  Anyway, from the other side of the connector is a line (same
> color) that runs up and then forward through the firewall. Once inside
> the engine compartment, the line runs in a harness across the firewall,
> past the hood release mechanism, and then comes out next to the
> windshield washer bottle. At this point, there is a spade connector,
> and the color of the line changes to white with red stripe. I suspect
> there used to be some kind of safety device that has been taken out.
> The new white/red line runs back into a harness that passes back
> through the firewall on the passenger side. Inside the interior again,
> the harness turns down to the floor, and runs along the passenger side
> floor channel. The white/red line comes out of the harness and goes to
> ... THE FUEL PUMP RELAY! The fuel pump relay is the taller of the two
> relays back there; the main relay is cube-shaped.  On my car, the
> white/red line is crimped to two orange/black lines at the relay socket.
>
> In summary, current for the main pump runs from the relay, and makes
> about a 15-18 foot trip around the car before coming back within 6
> inches of where the line passes through the floor pan! Current for the
> in-tank pump makes just as long a trip, but passes through the back
> wall on the driver side before going to the fuel sender/pump assembly.
> The lines are not particularly heavy, and I suspect the voltage drop
> along the line is not negligible.  If the voltage drop is significant,
> the motor will run slow, and the time period of heavy startup current
> draw will increase.
>
> In the future, I may bypass the long line, and splice a jumper between
> the white/red line (at the pump relay) and main pump line (in the area
> behind the computers).  I have read that some cars have had this
> modification done at dealers - anybody else seen this?
>
> My recommendation is to find the connector in the vicinity of the
> windshield washer bottle. Open up that connector and the connector on
> the driver side firewall (disconnects the fuel pumps). Now check for
> shorts to chassis: a) between driver side connector and spade
> connector, and b) between spade connector and fuel pump relay.
>
> Best wishes,
>
> John Hung
> Auburn, AL
> '88 Spider Veloce
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