Is 106 Gti ECU immobilising my fuel pump

[karl_mh]

Stupid question coming up!! my 106 Gtl has been in bits for so long Ive now arrived at the stage where I'm doing some testing of the electrics, everything works as it should so I connected the engine loom and ECU for a fuel pump test.

Unfortunately not a peep from the fuel pump, the ECU is currently standard and is still programmed with all the immobiliser etc blah blah bla, I assumed that the pump would prime but the engine would not start.

could anyone confirm if the ECU would have to be unlocked (free of immobiliser) for the pump the prime.

[MartinObviously]

Originally Posted by karl_mh

Stupid question coming up!! my 106 Gtl has been in bits for so long Ive now arrived at the stage where I'm doing some testing of the electrics, everything works as it should so I connected the engine loom and ECU for a fuel pump test.

Unfortunately not a peep from the fuel pump, the ECU is currently standard and is still programmed with all the immobiliser etc blah blah bla, I assumed that the pump would prime but the engine would not start.

could anyone confirm if the ECU would have to be unlocked (free of immobiliser) for the pump the prime.

The fuel pump always primes regardless of the immobiliser.

Check the relay under the ECU (well wherever you located it lol) and check the wiring on the starter - as that's where the ECU gets its power from.

I assume you've checked the crash button and reset it (or even bypassed it to rule it out)

[karl_mh]

Oh dear!! That's not good, the ECU is now stashed under the dash but the fuel pump relay is still in the same place (i think it's the large black relay exactly where you said) although I didn't mention, the engine isn't in yet so am I correct in assuming that it won't have a power supply unless the loom is connected to the starter, if this is the case would I be able to connect a 12v supply to the correct terminal thus powering the ECU and enabling the pump to prime?

[karl_mh]

Forgot to mention, the crash button has been reset and appears to work as it should, I’ve tested it but flipping it upside down and depressing the button to reset.


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[MartinObviously]

Originally Posted by karl_mh

Oh dear!! That's not good, the ECU is now stashed under the dash but the fuel pump relay is still in the same place (i think it's the large black relay exactly where you said) although I didn't mention, the engine isn't in yet so am I correct in assuming that it won't have a power supply unless the loom is connected to the starter, if this is the case would I be able to connect a 12v supply to the correct terminal thus powering the ECU and enabling the pump to prime?

That's correct. Well at least need 12v to the O terminal on the loom that goes to the starter if you need to test it before fitting the engine.

[karl_mh]

Top Man!! you refer to the O terminal, just to confirm...would this be the live to the starter which is No 13 on the attached picture.

[MartinObviously]

Yes I think it's 13

15 will be the trigger wire for the starter. unless it's the other way around lol

[karl_mh]

I did check the voltage earlier when the ignition was on the second stage prior to the start position but no voltage detected at 13 or 15

Ill drag it out of the garage tomorrow and double check for 12v when the ignition is on and if I get my lovely wife () to turn the key to the engine crank position without moaning I can also check both for the trigger voltage.

Im sure I've mentioned it...... I hate electrics!! give me a Mk2 escort wiring loom any day

[karl_mh]

Right then!!!! had an hour trying to get the fuel pump to prime again......no luck I'm afraid. Martin..you were again correct regarding the identification of the wires, when I turn the ignition to the crank position No 15 (smaller blue) shows 12v however, there isn't any voltage to No 13 (larger red) with the ignition of or on. I can only assume but shouldn't there be 12v to this permanently ?

Not sure if the yellow wire without an eyelet could be the live feed from the starter to the ECU.

[karl_mh]

Also just double checked the standard loom configuration just to make sure the modified engine loom connectors ended up in the same place, all ok on that front!


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[MartinObviously]

it's a feed, it needs 12v to go to the terminal. it won't show 12v on it!

Normally, that terminal joins onto the post on the starter which goes straight to the live on the battery via the fuse box.

[karl_mh]

Just had 5 mins to do a quick test....back to basics so I checked continuity across the inertia switch when made and is ok, also checked when broken and this is also ok.

I have also tested from the outgoing side of the inertia switch to the fuel pump, this also has continuity. I have marked on the drawing in green as checked ok, however, Ive checked from the incoming side of the inertia switch to pin 13 (as per drawing) located on the main fuel relay plug of the engine loom but nothing!! I tested all the other pins and pin 5 buzzed the multimeter? I have highlighted pin 5 as a red square and pin 13 as green circle. After this disaster I've shoved it back into the garage in the hope the auto electrical fairies will have sorted it overnight

So unless I'm mistaken pin 13 should buzz with the incoming side of the inertia switch , the interior and engine looms are from 1998 (within 2 month of each other) models albeit different cars.

[MartinObviously]

Remember that's a Haynes. I know for a fact that there's wiring diagram mistakes at the dashboard end.

So, that relay may actually represent the other type (the one you don't have).

By that diagram you should be getting something on 13.

[karl_mh]

Typical Haynes.....just when I need it the most hopefully it shows the other relay, that would make more sense why mine doesn't correspond.

I managed to get some basic tests done earlier.

1) Removed the fuel pump relay and tested continuity from pin 5 on the socket all the way to the fuel pump - OK

2) Connected a live supply to pin 5 to the above and the pump ran without any issues.

3) connected the starter motor - large red to the large post and the small blue to the small post and turned the key to the crank position, the bendix shot out so the starter works.

The wire positions on the pre and post loom modifications are the same and as you mentioned in one of your replies the ECU needs a live feed from the starter but currently I only have the blue trigger and the red live connected to the starter and 3 other wires fitted with plugs plus the mysterious broken yellow wire that i'm unsure what it is all in the starter location, possibly the yellow could be the live ECU feed and I would assume it would be fed from the trigger wire post. I will connect the yellow up tomorrow and see if the pump prime kicks in.

Just an after thought......would ECU have to be earthed? its just floating about at the moment.

I hate wiring looms!!!

[MartinObviously]

Originally Posted by karl_mh

Typical Haynes.....just when I need it the most hopefully it shows the other relay, that would make more sense why mine doesn't correspond.

I managed to get some basic tests done earlier.

1) Removed the fuel pump relay and tested continuity from pin 5 on the socket all the way to the fuel pump - OK

2) Connected a live supply to pin 5 to the above and the pump ran without any issues.

3) connected the starter motor - large red to the large post and the small blue to the small post and turned the key to the crank position, the bendix shot out so the starter works.

The wire positions on the pre and post loom modifications are the same and as you mentioned in one of your replies the ECU needs a live feed from the starter but currently I only have the blue trigger and the red live connected to the starter and 3 other wires fitted with plugs plus the mysterious broken yellow wire that i'm unsure what it is all in the starter location, possibly the yellow could be the live ECU feed and I would assume it would be fed from the trigger wire post. I will connect the yellow up tomorrow and see if the pump prime kicks in.

Just an after thought......would ECU have to be earthed? its just floating about at the moment.

I hate wiring looms!!!

The ECU doesn't have to be earthed. So there's one bit of good news

I'm so confused now, I've not got a loom to hand else I'd go look. I've got a labelled S1 loom that might yield some clues. I'll look at it tomorrow.

[karl_mh]

Anyone have a 106 gti that they can photograph the starter motor wired up in situ, just need to confirm that there are three wires to it and not just two plus determine the colours.

[Furioman]

single plug vts cross over model sorry the pic is upside down as well, the wire that looks blue is more of a green colour

[karl_mh]

Great, thanks for the pic, I thought there were three wires. I've had a few days away from the dreaded wiring but I'll be back on it on Friday