I have had my 1983 1.8 DX GTi for 25 years and it has never let me down. Out of the blue, it has developed a cold start issue. When stone cold, the car turns over for about 20 seconds before spluttering into life. You then need a bit of throttle to keep it from stalling. About 5-10 seconds of rough running later, it idles and drives perfectly. If you start it from cold as above, run if for about 30 seconds until it is idling nicely, then turn it off (with the engine still cold) on a subsequent restart 10 minutes later it will start fine (even though the engine is still cold).
Wonder if your cold start injector is working, try disconnecting it to see if it makes any difference, there is also the warm up regulator, and after this age it may need a recondition. Is the fuel system staying pressurised, will it start better if you prime the fuel pump a couple of times. There may still be a small filter in the fuel feed line at the metering head, inside the banjo bolt, could be choked.
does it help if you spray some starter fluid/brake cleaner/whatever in the throttle before trying to crank it? try unplugging the 5th injector also, if it makes no difference it could be faulty. another potential issue is leaky injectors dripping excess fuel into the inlet after being sat have a read of my 16v troubleshooting thread, all the basic kjet tests still apply: https://clubgti.com/forums/index.ph...air-and-tune-your-mk2-corrado-1-8-16v.195423/
Thanks for the help here. Much appreciated! I did pull the 5th injector out and crank it when cold (about 22 degrees ambient, engine left overnight) and there was no fuel. Is it likely to be the injector or the thermo time switch. I only measured 5 volts at the connector and I understand it should be 12 ish? Also, I replaced the injectors and now it won’t run well at all. Very spluttery when hot, won’t idle well (sometimes stalls, sometimes the revs drop to almost zero before it saves itself). Would the new injectors increase fuel flow so that it is now running too rich? I don’t have a CO meter, and I’m waiting on a long 3mm Allen key to be able to adjust it. The old injectors had done 144k miles. I thought that putting in new injectors wouldn’t affect the fuel rate as this is determined by the fuel measuring head not the injectors
Did you replace the injector seals also, spraying some WD/brake cleaner around the area when running will let you see if they are not sealing and drawing air, you will hear a difference in the way it runs as it uses the other fluid. You can do this around the inlet manifold area, check all your vacuum hoses etc also. Swap the old injectors back and see how it runs before messing with the CO screw You could try running a switched power directly from the battery to the cold start injector to see if it will fire
I did put new seals on, but left the old inserts in. I’ll try the carb cleaner and see if that makes a difference. The old seals were quite compressed (taller but less wide) than the new ones. thanks again for all the input.
with the 5th injector pull the plug off the thermoswitch and earth the green/white, then redo that test you did earlier. if it does sparay and you get full 12v when cranking either the thermoswitch is bad or the engine was too warm when you performed the check earlier. the thermoswitch earths through the coolant flange to the block though so make sure all that is clean. you can run an earthed wire to the body of the thermoswitch to rule out a poor earth if you popped new injectors in it will probably need setting up again, if they were really bad you could have had an air leak past the injector seals which was compensated for by upping the CO
I've been tinkering with the car. It started fine from cold (about 12 ambient), so am thinking it might have been the old dripping injectors causing the start problem? However, it was still not running well. It was idling at around 500 rpm, and almost stalling. If you revved it, when you came off the throttle it would stall. I checked all the vacuum hoses, pulled the injectors out again and cleaned the injector inserts (which all seemed ok). Put everything back together, but still the same. I then played with the CO and found that about a quarter turn anticlockwise helped a little, but not much). I then adjusted the idle screw on the back of the inlet housing. This did the job. I had to go a whole half turn out (opening up the bypass) and that got it idling ok. I took it for a drive and it was a lot more responsive and seemed to have more power than before. The only slight snag is that I don't have a CO meter to check how rich it is now running. I have played a bit to get it running as smoothly as possible. The only thing it is still doing slightly, is that when you blip the throttle at idle, as the revs drop back down, it drops to about 600 rpm before stabilising back to 800.
