Fuel pump runs with engine off AND relay disconnected

[Skip1]

Well, now I move onto my next project. Although the car runs fine, it is obvious that my current situation is not normal. The issue is that my fuel pump will run (beyond the average 30 second pressurization estimates many have commented on), even with the engine off. The added interesting thing, is that I have removed the harness off the fuel pump relay (which I've replaced, thinking that was the culprit), and low and behold, the pump continues. Looking at the wiring diagram, that is definitely NOT correct. Based on the enclosed diagram, I have tested a couple of things on the harness:

(1) Pin 30 - power direct from battery has 12.42 V with ignition off - correct!
(2) Pin 86 - power with key in ON position - has 12.42 V - correct!
(3) Pin 85 - ground - correct!
(4) Pin 87 - appears to go to DME Unit pin 18 and 35 as well as feed fuel injectors (using Bentley wiring diagram for this one
(5) Pin 85b - DME unit Pin 20 - appears correct as well
(6) 87b - PROBLEM - I have no oxygen sensor link (RoW vehicle), so no 0.75 gel wire (no issue there), link to fuse #3 appears correct, however power should come through the relay from what I can see in the attached diagram. That said, if I pull the relay off the harness and turn the key to ON, the fuel pump starts right away and is constant.

I also tested jumping Pin 30 to Pin 87b in the harness to actuate the fuel pump directly, but no joy - nothing happened.

My question is, could someone have wired the fuel pump directly to the ignition switch, thereby bypassing the relay altogether? Previous owner obviously if so. Just curious, before I start disassembly of the wiring under the car.

Cheers

Skip

[HawgRyder]

My first idea would be that inside the fuse box...there is a short between the wire either to or from the fuse #3 and another (probably feed wire) connection.
The pump is obviously getting power from somewhere other than the DME controller/fuel pump relay.
Check the back of the fuse panel to see if a piece of wire or other metallic thing has fallen down to create a short.
Bob

[boyt911sc]

Skip,

You have 3.2 Carrera engine with DME and no OXS? Keep us posted. Thanks.

Tony

[E Sully]

Interesting situation. I am confused by your statement that you removed the harness from the fuel pump relay. The dme relay is also the fuel pump relay. It contains 2 sets of contacts internally. There is no 30 second pressurization. Initialy, the relay is closed when the key is in the start position, yellow wire to pin 4. When the dme gets a signal from the sensor that the engine is spinning it keeps the relay closed when the key is released to the run position, 85b. When the key is in the run position, if the sensor does not give the signal to dme, the relay will open and stop the fuel pump. There should be no power to fuse 3 when the key is off, or in the run position with the engine not running.

[Skip1]

Bob, I will check the issue of a possible short in the fuse box tomorrow - thanks.

Tony, As for the DME with no oxygen sensor connection - that is correct. The car is a GE / RoW car, and I read on numerous sites / forums that it might not have an O2 sensor connection - I'd be very interested to know if I'm wrong. If so, there is no harness in the engine compartment to connect the O2 sensor anyway - I have an '86 engine / transmission vice the original one, as it was imported to CA in '89. There is an O2 sensor and a CAT, but no plug anywhere that I can find (even looked when I had the engine out last winter). I had checked the connection in the large DME plug last year as well and don't recall seeing the green wire at pin 24 as per the wiring diagram I have. I'd love to actually connect the O2 sensor where it should be, as the engine does run a little rich I think - I'm not trying to increase HP or anything, just putting it back to a stock 3.2.

Ed, When I said I removed the harness (6 pin) from the relay, it was simply to test the wiring harness itself to ensure that the power / grd aspects where correct as they where supposed to be. in my Bentley manual it recommends testing jumping the pin 30 power (always on) to pin 87b to actuate the pump directly (without key action). That's where nothing happened, which leads me to believe there's a problem in the wiring (at least one of the problems would be in the wiring, as the power to the pump through the relay appears to be bypassed somehow. Understand on the "no 30 second pressurization - my bad". I do need to clarify one piece. You said "When the key is in the run position, if the sensor does not give the signal to dme, the relay will open and stop the fuel pump. There should be no power to fuse 3 when the key is off, or in the run position with the engine not running." The fuel pump DOES NOT run, with the key in the OFF position, but DOES run with the key in RUN when the engine is NOT running - that's the problem from my perspective. Does that make more sense?

Thanks

Skip

[r lane]

Either melted wires some where, or some one has decided to bypass the relay. If putting power to 87b doesn't run the pump, the wire is interupted somewhere. Bob

[E Sully]

The fact you get nothing when jumping 30 to 87b leads me to believe the relay was by-passed prior to your ownership. Someone must have found this as a fix to replacing a non functioning relay. It creates a safety issue as the fuel pump can continue to pump fuel after an accident.
You can confirm this by removing fuse #3 and doing a continuity test from the fuse holder to the fuel pump, and then from the other side of the fuse holder to pin #87b at the connector under the seat. Bob may be on the right track here as there may be a jumper installed at the fuse panel to give power whenever the key is in the run position.
I had an '86 3.2 engine and transmission in my 1973. Even though I had a US dme and chip, the Euro harness that came with the engine had no o2 sensor wiring, so I installed some wiring to to make it functional. I ran a one pair 14 awg shielded wire to the engine compartment. I was able to purchase the pin for the dme connector for the o2 sensor signal, and the other wire was soldered in with rd/grn for the missing yellow for the o2 sensor heating circuit. A third wire for the ground needed was connected to the ground point in the engine compartment. I used an o2 sensor recommended in another thread that used a universal connector.

[Skip1]

Fixed - you folks were correct about the bypass. When I originally bought the car, the DME relay was acting up, so I replaced it. The new relay allowed the fuel pump to run, so I thought nothing of it, until I read numerous other posts stating this wasn't normal. After crawling around under the hood and pulling off the fuse panel, I found.... a taped up red/green wire tucked away under numerous other wires. Tested continuity to the harness and confirmed that it didn't ground out somewhere in the line. GTG. Also found a jumper wire (as everyone indicated) across from pin #4 to pin #3 forcing power with ignition ON. Removed the jumper and reinstalled the correct relay wiring, and presto, the fuel pump now only runs while cranking or while the engine is running. Stalled the car to test, and the fuel pump stopped as well. Great news on that. Thanks to all for great info. Am including a couple of pictures.

Now, onto the O2 sensor issue. I opened up the DME connector under the driver's seat and confirmed there is no green wire connected at pin #24 (it's the gap between the black and small visible brown wire). Based on what you suggested Ed, I would be interested in creating this connection, expect I do not know whether it's a Euro DME with Euro chip (hence the EPROM piece may not have the correct software to deal with an O2 sensor), or perhaps a US / CA version which could accept it. Does anyone know whether this is somehow testable on a DME without possibly destroying it? Not so comfortable with that, but would be keen to try to figure it out and make use of the 3.2 Engine's truly capability instead of a loose O2 bung.

[luyckxglen]

hi i have the same situation , previous owner jumperd the fuel pump when u turn the key in acc STAND it wil go on and even after the engine is off it still runs untill you open the door..
But i have not found the origi wire to reconnect it..
Wat are the cons of running it like that?
greetz