gti 8v not starting

[Tinkley]

1 bar is 14.7psi - atmospheric pressure at 1000 millibars. So 2.5 X 14.7 = 36.75psi so your not far out.
A quick rule of thumb is to use 1 atmosphere (bar) = 15psi for quick mental calcs.

Have you taken the fuel pump out and cleaned any filters? Obviously its in the tank, empirical testing - it should spurt like letting the air out your tyres at 32psi approx. Don't have a flow meter to hand....
It should depending on the orifice size produce a small continous squirt. There will also be a return for unused fuel in the system. If you can pull water up a tube by vacuum you know you have more than 1 bar, you are defeating gravity!

Good luck withthe testing, its frustrating but I wish you well with getting her to start. On the carb fuel pumps the diaghram inside fails - rubber and old age. Maybe Malcolm or someone with more experience of the tank fuel pumps knows their weakness?

[mat_fenwick]

As mentioned previously, you can check the injectors are firing cheaply and easily.
http://www.ebay.co.uk/itm/Noid-light-Bo ... 0809117048" onclick="window.open(this.href);return false;?

Again, it's not that expensive to buy a fuel pressure gauge (£10-£15 from the same source) and plumb that into the fuel line to check the pressure. So for £20 you would be able to diagnose where the fault lies, rather than having to stab in the dark and swap the ECU. Plus you would have tools that you can use again and again.

Other ECUs will probably work to prove or disprove a fault but may well have a different fuel map. I really doubt the ECU has failed though.

[rutter123]

have checked injectors with said light and all good there after fitting new relay, spark is good, fuel pump good, filters cleaned, the fuel pump pumping approx a gallon of fuel in under 2 mins, power to ecu ok relays ok, tps ok, water temp sensor ok, but no signs of any fuel getting in, dry plugs. as if there is not enough pressure in the rail to open the injectors.

[sdelasal]

Is there any sign of petrol actually reaching the fuel rail? Have a root around - key off, then disconnect the return line to see if there is any sign of fuel - be careful of any residual fuel at high pressure. Another test you can do is see if you can pull a vacuum on the pipe into the pressure regulator that connects 'intake manifold pressure' into the pressure regulator. If no, that tells you the internal diaphragm is damaged. If fuel leaks out of the regulator from that pressure connection, that's another sign it's broken.
If those simple tests are okay, you need that pressure guage & follow the test procedure. steve

[Jaba]

From memory: with 3.1 ignition when the ignition is turned on then the pump runs for a second or so to get the fuel pressurised in the feed rail. The pressure is governed by the regulator at the fuel return end. The pump also runs while cranking until the engine fires when it runs permanently.
This might help you to establish if everything is normal.
A simple fuel pressure test would be to to gently remove the supply hose immediately after a quick crank. Fuel should spurt out under pressure.

Have you checked cam belt timing ?

[rutter123]

yes that is how it is, ign on pump runs for a few secs then shuts off, when cranking the pump cuts back in, same set up on the injectors, yes there is plenty of pressure in the fuel rail, enough to pop the hose off, tho not fully tightened, should i get fuel freeflowing out of the return side of the pres/reg when the pump is running? or does the pressure reg "hold" the fuel in the rail until sufficient pressure is reached to feed the injectors, then the vacuum controls that pressure according to load, or am i barking up the wrong tree? this is my main suspect as its the original 23yr old unit, and prob a contributer to the lumpy running, i need to find out if this is the fault as a new one is £70 and could be an expensive error.

i have not touched the cambelt or any associated parts as this was only done 100 miles back by darren at citroen classics when the new head was fitted, so i wouldnt suspect anything wrong there.

i still suspect the fpr or at worst ecu which some have said prob not causing the prob.

[sdelasal]

The pressure regulator maintains the rail pressure at a fixed offset relative to the pressure in the intake manifold - hence the pipe connecting the two. That way, the injector sees a near constant differential pressure between the fuel pressure and the intake manifold pressure - hence better fuel flow control. There has to be some continual bleed back to the tank otherwise the fuel rail pressure would rise to that generated by the fuel pump 'dead ending' into the rail. See if you can hire, or borrow, the pressure tester locally ? If you are keeping the car, it's a good tool to have.