Alfa Romeo Forums banner

1 - 7 of 7 Posts

·
Registered
Joined
·
434 Posts
Discussion Starter #1
OKAY, the fuel pump nightmare is nearly over. I have determined that the pink-white wire going from the ECU area behind the passenger seat, up to the firewall at the inertia switch, has a short somewhere. I've snipped the wire just behind the passenger seat, and when I apply voltage to it, the pumps run fine. My plan is to just cut the inertia switch circuit out completely, since it's redundant (the switch is missing on my car anyway, the two leads up front were just jumped together).

Looks like the simplest (and least damaging) way to do this would be to run a wire from the #87 lead at the fuel pump relay, to the pink-white fuel pump wire. However, I have a problem with the power going to the relay. Right now I have the relay out and am just checking at the connector itself; under no load, if I measure the voltage at pin #30 (which is supposed to be connected to the battery positive terminal, through a fuse), it's a little low, like 10.87 volts (other voltage leads show 12+ right now). If I put any load to it (connecting the pink-white wire to run the pumps) voltage drops to like less than 1. So it would seem I have a bad/high resistance connection somewhere.

Unfortunately the #30 lead which is supposedly straight to the battery, disappears within the massive bundle at the ECU connector. Ditto for both ends of the fused lead coming off the battery. Looks like voltage is supplied at the fuse section via a blue wire that goes to the harness. I have verified that the voltage loss occurs at or before the fuse, not in the circuit going from the harness to the relay. I would reeeaaally like to avoid tearing apart that harness....could anyone give me some info on how those blue wires are connected? The diagram makes it look simple, like it should go directly to the battery. But just looking at it, it obviously doesn't, plus it's switched power.

Confused and annoyed. :/
 

·
1966-2013
Joined
·
13,741 Posts
The fused lead back by the ECU should be 12V all the time as part of an un-switched circut. (it does go straight to the battery per the diagram)

The larger relay (which runs the pumps) won't show proper output voltage until the engine is cranked and the coil gives off a pulse signal back to that relay, which may be why you're getting funny readings when you test it. (just turning the key on won't do it, the engine has to be turning and the plugs firing)

Papajam may have some infobits on the method to the madness as he's been working with/around the S3 stuff for a bit of time now trying to decipher some of the nuances and changes throughout that particular series run. (no diagrams yet that I'm aware of, but a lot of information)
 

·
Registered
Joined
·
434 Posts
Discussion Starter #3
Ahhh that's what I thought. Just to clarify...there are 2 wires going to the fused area. Both have red on one end of the fuse, and blue-white on the other. On the lead I'm talking about right now, power comes from the blue side....it should be always on, correct? On the other lead, as I recall, power came from the red side and went to the blue side.

The ignition pulse just makes the relay close, right? Or is its voltage utilized somehow other than just switching the relay? I'm shorting terminals #30 and #87 together now to "simulate" the relay being closed during normal operation. Incidentally, I just hot-wired the red connector at the fuse to a known good voltage source, and plugged the relay back in....I have the car too torn apart right now to run it, but when I turn the key on the fuel pumps run briefly and shut off, as they are supposed to. That means if I can just get good voltage at the fuse, I should be good to go...I think. :p I suppose if I have to I can just run a jumper from that connector to the voltage source, but I'd rather avoid that if possible....I suppose it wouldn't make any difference operationally, I've been driving the car with that lead completely disconnected (hot-wired fuel pump) without issue, but I'd just like to get things back to the way they are supposed to be.

I know what happened.....whatever genius owned this car years ago when the pink wire shorted, noticed the fuel pump fuse kept blowing so he just removed the fuse entirely. That resulted in the pump wiring (or a connection) near the fuse to nuke itself, apparently. In fact, this might have even been what melted the insulation around the wire bundle up front (the pink wire goes through this bundle to connect to the inertia switch). Crazy PO's!!!!
 

·
1966-2013
Joined
·
13,741 Posts
Oooh, creative wiring modifications, they're always fun when you don't have that drawing on the back of a napkin or whatever to see what someone did.......


However, after getting power to the fuse as you did:

when I turn the key on the fuel pumps run briefly and shut off, as they are supposed to. That means if I can just get good voltage at the fuse, I should be good to go...I think.
That sounds correct.

The pumps run for around 1/2 a second or so then shut down again when the key is first turned on. (coil getting it's initial charge then discharge)

Theoretically (as you say you can't crank it) it should pick up and run as it should when cranked and running from there. (the relay acts as a safety switch: you get in an accident, the engine stalls, coil stops sending signal, pumps shut down, no all consuming fire being fed by fuel at 40psi)

The secondary purpose of the big relay is to send a trigger signal to the small relay which is what controls the injectors on the intake manifold. (cold start injector is controlled by a different source)
 

·
Registered
Joined
·
434 Posts
Discussion Starter #5
Thanks, ya that's pretty much how I thought it was supposed to be.

I was just poking around the harness again and I had a thought........could you tell me what the pump fuse looks like that's supposed to go there? Does it have provision to connect two different circuits, or is it just one huge fuse with a connection on each end (so all the wires going to the fuse end up connecting to each other)?
 

·
1966-2013
Joined
·
13,741 Posts
The ony fuse I can recall right off is the one that comes from the battery and that has a big red plastic cover on it.

Beyond that, I don't believe there are any other fuses in that area, nor elsewhere that deal with the pumps specifically. Strictly relay control, and the fuse works the big relay. (could be wrong on that though. I'm kinda brain tired right now)

EDIT:

There should be one large caliber wire in and one large caliber wire out of the fuse holder. Both ends then kinda find there way into the harness bundle and head off in whatever direction they go.
 

·
Registered
Joined
·
434 Posts
Discussion Starter #7
Hmmm, well that's the fuse I'm referring to (the fuel pump fuse pictured on your excellent website, Tifosi). But I have two large red wires going into the fuse on one end, a blue-black wire and two blue-white wires coming out of the other end.

One of the red wires going into the fuse is unswitched voltage. The other red wire (on the same side as the first) seems to be voltage to pin #30 of the fuel pump relay, that's where I have to apply voltage to allow the pump and relay to operate properly. The fuse is gone, all I have left is the big red connector with two pins in it.

IIRC, the car died when I unplugged the first red wire (the one that supplies voltage to the fuse connection) so I assume it's needed for the other relay or the ECU or something. The wire on the other end of the fuse that this red wire connects to is the blue-black one. The other pin in that red connector has two blue-white wires coming out of one end, which connect to the second red wire (the one that seems to be going to pin #30 of the fuel pump relay) through the red connector.

Well, a picture's worth a thousand words:

http://www.theplaceofcoolness.com/pics/alfa/alfa_fuelwire.jpg

I'm guessing the blue-black wire is for something with the ECU, which might explain why it shows a tiny bit of voltage with the key on.

If I were to just bridge the two pins inside the connector together (which I'm thinking may be what the fuse did), I'm pretty sure the car would run fine. The only thing that bothers me is that those two blue-white wires, whatever they are, would be getting 12 volts to them. Of course this was already happening anyway when I had the fuel pumps hotwired, but I did notice some weeks ago when I had the engine running, that when I unplugged that second red wire (thus removing voltage from the two blue-white wires), engine RPM increased. But this could just be due to the short circuit in the fuel pump wire going to the inertia switch, which would have been getting power (a dead short....big alternator load).
 
1 - 7 of 7 Posts
Top