Not starting - '90 8v GTI

Discussion in '8-valve' started by R1ch, Feb 2, 2020.

  1. R1ch New Member

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    I can't get my 8v PB engine to start and its getting really frustrating - any help diagnosing this problem would be great. A bit of history and description of the problem below:
    • Rebuilt the cylinder head in the autumn (new valve guides, seals, etc)
    • Had it running at idle earlier this year, but after about 15mins when it was up to temperature it just cut out
    • Added fuel to make sure tank not empty
    • Cranks but won't start
    • Both pumps sound like they are priming. 12v across the terminals on the main pump when priming. (0v once primed and not cranking)
    • I've not been able to swap the fuel pump relay for a 17, 18 or 100 as 18 & 100 have different size spades and i don't have a 17. I did try a spare 72 i had - no change.
    • I've changed the distributor as i thought the hall sender might be the problem - no change. I had spark between the coil HT cable and the cylinder head when spinning the distributor (out of the engine)
    • Spark at each plug when out of the head and earthed.
    • Checked the airflow meter with a multi-meter and getting all the right resistance readings
    • I get 9.5v between the injector live and battery earth when cranking, but 0v when just ignition live
    • Checked the engine wiring inc. temp sender and all seems good
    • Tried a spare ECU I've got (untested though) and no difference
    • Good gearbox earth and earths to the head
    • Triple checked the static timing and I'm happy is aligned (crank mark, cam marks and distributors marks all good)
    I thinking that i need to check that I'm getting a good fuel supply to the injectors - what is the best way to do this safely? (don't fancy getting petrol everywhere). Could the pressure regulator be the problem, or maybe one of the rubber lines be pinched? (I changed the return rubber line from the regulator as the old one had perished - i couldn't get a shaped line so just generic hose curved; its not folded anywhere)

    Thanks
    GTI 8v PB.jpg
     
  2. Tristan Forum Junkie

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    An ordinary 4 relay will do for the fuel pump to test, it'll just run continuously. Check the ecu plug for corrosion too.
     
  3. Tristan Forum Junkie

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    Also, a quick squirt of easy start of similar into the intake. If it fires, you've a fuel issue. Almost unheard of for the fuel reg to give trouble. You hardly took off both pipes and mixed them up?
     
  4. rubjonny

    rubjonny Administrator Admin

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    fuel relay is in slot 12, which has same size terminals as 17, 18 & 100 which is why I recommend those. If the fuel pumps are priming with ignition (not sticking on) then this suggests fuel relay is ok anyway. do the pumps run while cranking? if not you may have an issue with hall sensor signal from distributor. You should see rev counter jiggle while cranking also.

    unplug the ecu, tcvi and 5 pin plugs in scuttle, check all the pins are straight, tight, clean and any terminals are fully inserted. peel back rubber boots on the TCI make sure wires underneath are good. do the same for all the plugs in the engine bay, pay close attention to the dizzy plug.

    pull the spark plugs to check the condition, also if you've been cranking it you should smell fuel. to check power on the fuel rail fit 17/18/100 relay in slot 12 unplug the fuel rail and switch on the ignition. you should see 12v between the red wire on the plug and the battery negative. if nothing you've lost injector power, this one is fed by Z1 on fusebox via the 5 pin plug in the scuttle mentioned above. if you check across the pins while cranking you should see a pulsed earth, can be tricky to measure but can use a test lamp

    if you want to check injector spray pattern and flow rate disconnect the black wires from the coil as well as the king lead to prevent any chance of a spark. find 4 equally sized containers that are fuel safe. remove rail and drop the injectors in and crank it over on the starter. check spray pattern and volume delivered, helps to have a friend when checking spray pattern but you can switch the ignition on then jump the starter with a live from battery.
     
  5. Simon Peter Dodgson Forum Member

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    Yes please disconnect the coil. I didn't and had a fireball. Not something I ever want to repeat
     
  6. R1ch New Member

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    Thanks for all the replies. I've only just got round to sorting this...

    I'd done a few of the tests you suggested John and so investigated the fuel supply a bit further including disconnecting the line and pressure regulator at the rail. There was definitely fuel at the rail from previous cranking so I replaced the return rubber hose as it looked a bit short/over curved and put all that back together. The supply and return lines were the correct way round.
    I then started to concentrate on the under-car pump. I replaced a few of the aging rubber hoses and the fuel filter. I tested the pump with a 100 relay in slot 12 and it was running continuously and pumped fine into a container under the car.
    I then made sure i had plenty of fuel in the tank (20+ litres) and it fired up fine.

    My best guest is the pump was struggling and the old filter potentially blocked as the tank had got very low previously (possibly even empty :o[:$]) and there just wasn't enough fuel in the tank to get it up and running again. It may be that the return line at the engine was a little tight as well.

    Thanks you all your help and advice - this forum is such a fantastic wealth of knowledge and experience!
     
  7. rubjonny

    rubjonny Administrator Admin

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    lovely stuff :thumbup:
     
  8. Tristan Forum Junkie

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    Great that you got sorted, and that you told us so. So many people never come back to report that the advice freely given, but hard learnt, was useful.
     

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