Introduction:
I changed gearbox (transmission) oil then i rebuilt master and slave cylinder clutch pumps!
Then i turned on the car inside the garage (with the door opened) for almost 45 minutes. Then i turned off the car and played with the clutch pedal rod (to the clutch master cylinder) for adjusting the clutch engaging level after bleeding the clutch circuit

Few days passed from these operations........saturday i tried to start the car......it doesn't start anymore!

First thing i supposed: no fuel to the engine from the fuel pump!!!

Indeed i don't hear anymore the clicking sound inside the hood when i turn the key to the "on" position before starting the engine!

Since i bought the car i've always heard a repeated "machine gun" sound inside the hood when i turned the key in the on position

A sound like "tatatatatatata" or faster clickclickclickclickclick

Now i don't hear this sound anymore when i turn the key in the on position. Is it supposed to be the "main relay" click?

Things that i checked:
EGI 30 amps fuse inside the hood -> OK
15 amps ENGINE FUSE inside the box near driver foots ->ok

Then i removed the "main relay" and linked the 2 pins inside the white connector of the main relay to a spare 12v battery! I hear the click (one single click) so the main relay is good!

What it's messed up?

The thing the worries me first is that i don't hear anymore this "tatatatatata" or clickclickclickclick sound when i turn the key on the on position!

Can you help me please?

Thank you so much!

 

Clicking i heard was exactly this:

In this video it seems that disconnetting boost control unit it stopped

It wasn't the master relay!
I don't hear this sound anymore now that the car doesn't start!

However the think i didn't said is that the engine cranks but it does not start!

 

Sorry to read about your troubles. I really don't know much about the starting system on these cars. What I do know is the s4 and 5's are different under the dash. Perhaps you can mention what year you have and it will make it easier for someone to help.

Take this with a grain of salt, if i had a gun to my head and needed an answer quickly. I would say that your keyed ignition switch is bad. If you know how to hot wire this car, you will know for sure.

This might take a wiring schematic to figure out. Best wishes.

 

It's a 1990 Turbo 2 convertibile (S5)

 

Today update

i checked everything........everything........all fuses, tested all relays (main relay and circuit opening relay).......both relays work!

Jumped the fuel pump test connector near the engine......fuel pump don't work but is not burned!
There is no voltage to the fuel pump!

because coincidences dont exist in this world...........the only explanation is that when i adjusted the clutch rod on the back of the pedal i touched something near the steering wheel.....and.....

I am bloody sure that the previous owner installed a fuel pump kill switch.......as an anti theft measure (very common here in europe in 1980/1990 for expensive sport cars!

i had to find this switch but it won't be and easy job i think it's deeply hidden!

 

I am sorry to say this now, I noticed you that you mentioned working near the clutch pedal. There is a switch or lock out that if the clutch pedal isn't depressed, it won't turn over. Make sure the switch is working and is engaging when the pedal is depressed. It's a shot in the dark, you never know though. That switch is the reason I bought mine for dirt cheap. The owner forgot about pushing in the clutch to start. Sorry that I am no other help.

 

Checked for that switch

It s called Clutch interlock switch

Europe models (same for Japan) don t have this switch

 

the Circuit Opening relay is near the pedals, and the circuit it opens is the fuel pump circuit, so if you haven't, you should look at that

 

Thank you for your support!

I have the circuit opening relay: it's the one with the yellow connector! What i don't have is the clutch interlock switch!!

I measured the voltage on every pin (5) of the circuit opening relay and i have 0 volts on every one of the 5 pin whatever is the position of the key on the ignition switch!

I have no power to the circuit opening relay!

Also i tried to jumper the fuel pump yellow test connector inside the hood and obviously the fuel pump doesn't start with the key in on position (it should start with the yellow connector jumpered) that's because........i have no voltage in the circuit opening relay connector!

I double checked all the fuses: the EGI fuse inside the hood and the engine fuse in the box near the clutch pedal: they are ok and there is 12v inside the fuse contacts!

All of this problem started since i calibrated the clutch pedal push rod to the clutch master cylinder pump! I should have touched something.......a cable or an hidden fuel pump cutoff switch!

 

After in deep analysys i found that i have no voltage to black with white stripe wire to circuit opening relay! That's because the whole is not working! I will deeply check the ignition switch!

 

Problem solved (photo attached). A wire on the back of the internal fuse box is disconnected. The idiot that messed up with electric system made a disaster: a junction with a bad electrical terminal.

 

Nice work finding the offending culprit. It was a kill switch of sorts a you suspected. Have fun with your car!

 

I was indeed worse than a "kill switch".........because it wasn't also hidden......it was undetectable!

Now i have the knowledge to put a "real" kill switch somewhere as an anti thief deterrent!