After repairing vacuum tube to Fuel pressure Controller warn start is difficult

June 13, 2024, 02:55:48 PM

1989 Mk2 Golf GTI 8V (Digifant)
Car has previously not had starting problems hot or cold, passed its last MoT fine (garage had to adjust mixture screw to get it through emissions) since when it has hardly been out of the garage.
The other day while I had the bonnet open to fix a rear washer tube problem I noticed that the short piece of vacuum tube from the fuel pressure control valve to the green tee piece (connected also to the manifold and to the air box actuator) had split and come off the fuel pressure control valve.
I removed the split tube,cut it in half to check it's internal diameter (3.5mm) and purchased a length of 3.5 mm vacuum tube from Heritage who confirmed that it should be 3.5mm.
I fitted a length of the new tube (it was hard to get on the pipe on the Fuel pressure Regulator but I eventually managed to).
Since then I've noticed that although the engine starts fine (first crank with no throttle) from cold, when hot or even warm (after an hour or so standing) I can only get it to start by depressing the throttle after if fails to start without throttle and cranking for several seconds.
I rang the mechanic who did the MoT (who is "old school" but not a GTI Digifant specialist) and he wasn't able to suggest what might be wrong and said I should bring the car back for him to look at.
I've checked that the blue temperature sender has suitable resistance cold and correct operation of the idle and full throttle switches.
I haven't checked any other wiring but intend do so - including temperature sender resistance at Digifant connector and continuity in wiring between sender, switches and Digifant connector.
Can't get my head round why it would start fine with the leaky vacuum pipe (which presumably means air box actuator may not have been operating correctly and manifold would have had a vacuum leak).
Any help and suggestions for further testing appreciated.

Re: After repairing vacuum tube to Fuel pressure Controller warn start is difficult

Reply #1 – June 13, 2024, 11:35:27 PM

if you remove your fix, does it resort back to normal