Electrical puzzle

RandyLok · 02-02-2005, 06:36 PM

Who's the 914 wiring expert? :-)

A couple of the white wires that run from the four-tab connector at the corner of the relay board to the fuel injection circuit(? I think) go to ground. Somehow I don't think that's right. My problem is, that's bringing ground to the ignition/solenoid wire.

I would really appreciate it if you would take a look at my problem, described on the following web page:
http://www.4nets.com/914

Are there complete wiring diagrams online somewhere? Or a better 914 electrical book than the Haynes manual?

RandyLok · 02-02-2005, 10:41 PM

914GT: Thanks for the reply.

I did check the wire with it disconnected from the solenoid. Definitely grounded. So I guess that confirms I have a short to ground somewhere. The seatbelt relay has been bypassed by the previous ownder. Actually, th the scary part is, the previous owner modified a lot of the wiring .

While it runs, the problem is... it only starts and runs if I disconnect the yellow (shorted) solenoid wire and use my jerry-rigged starter switch.

I need to find the short in the solenoid wire circuit. My best clue is that it's only shorted when the 4-tab connector at the lower corner of the relay board (with all-white wires) is connected. If I disconnect that connector and check those white wires, two of them are shorted to ground.

I guess that's the single most valuable piece of information I need to isolate this: Is it abnormal for any of those white wires to be grounded?

ruddyboys · 02-03-2005, 06:34 AM

Welcome Randy, Lets see The Yellow wire comes from the ignition in the column, and goes to pin 1 in the relay board, It comes out as yellow from pin 6 to the starter. It also gives power to some of the white wires comming out the relay board for fuel inj. Red wire to Alt and Black to battery +. Hope that helps you.

philinjax · 02-03-2005, 06:34 AM

The yellow wire is grounded all the time because it is a very low impedance circuit. Look at the wiring diagram, it shows the yellow wire grounded.
The problem is, you don't have continuity between the start position of the ignition switch (where the yellow wire begins, so to speak) and the starter solenoid. The most likely place to look for that disrupted continuity is under thke passenger seat where all the wires are jumbled up on most cars, or your ignition switch is defective. Start by finding the fat yellow wire in the jumble under the passenger seat. In many cases the connection made there by previous owner's, years ago, has deteriorated and become electrically disconnected. If that ain't it, it must be the ignition switch.

Phil

Dave at Pelican Parts · Dave at Pelican Parts's Garage

For a color diagram of the relay board's connections, check here:

http://www.pelicanparts.com/914/parts/Electrical/914_electric_73E.jpg

Both rear pins in that four-pin connector are tied into the starter circuit. Those go to the fuel injection system (only one is connected in a 1.8 car) and tell it when the starter is cranking. I don't believe that any of them should have a zero (-ish) resistance to ground. I would guess that something in the engine wiring harness (the one that plugs into the four-pin plug) is crossed-up.

Remove the ECU from the car, then pull the cover off the slot where the wiring goes. Unplug the wiring harness from the ECU, and then start checking for continuity with ground on each pin of the wiring harness. There should only be a couple that are grounded--see the "MPC current flow diagram" (either in Haynes, or in the 914 Electrical Diagrams section of this site) for which ones should be.

--DD

RandyLok · 02-03-2005, 10:55 AM

ruddyboys: Thanks - column to pin 1 of the relay board will isolate some of the stuff that's been confusing me...

Phil: Tracing to the ignition switch with a continuity beeper is the track I was originally on... but I got distracted from that when I found it went to ground, and that ground was coming from the white wires I referred to. That didn't seem right - wish I knew for sure. I'll get back to the ignition switch check. The seatbelt stuff has been bypassed, but I'll double check that connection too. Thanks.

RandyLok · 02-03-2005, 11:07 AM

Thanks Dave. The wires that connect to tabs III and IV on the lower left corner of this diagram are the ones that are grounded on my car.

http://www.pelicanparts.com/914/parts/Electrical/914_electric_73E.jpg

philinjax · 02-03-2005, 01:03 PM

Pins III and IV are supposed to be grounded.

Phil

RandyLok · 02-03-2005, 01:09 PM

Thanks Phil. I think it's the ignition switch.