GTi Cabriolet will not start

Hello, just joined looking for a little help with '86 Cab K-jet GTI.

Been a great runner since we got her, always started no matter what, until the other morning it just turned over but would not fire up.

We put some fuel in as it was low, and it was the same. then some time later it did start… went for a drive… got home and then nothing again.
Just turning over and no vroom vroom

Checks done so far…

battery shows 12.7V
Both fuel pumps working, in tank and under car.
There is a spark at plugs.
Control Pressure regulator - low voltage, 10.5v, and a raised resistance… 24ohms… our book say min 11.5v and max 22 ohms ??
Thermotime switch and cold start valve also showing 10.5-11v

I thought maybe this low voltage might be something to do with the old immobiliser on the car, so we dug that out and bypassed it, but no change.

Is that low voltage enough to stop the systems working?

Could there be a fuel blockage?

tomorrow going to test 5th injector…

Any other ideas? Does it sound electrical or fuel??


thanks in advance!









 

Ok, so this K-Jet stuff is like black magic.

I thought I would go through the relays etc. Just to see if there was anything amis.
All seemed fine, although I have no HOT PULSE RELAY, and there was an unidentified relay in there doing something… I dont know what… I am going to guess immobiliser? This needs more investigation with mirrors and some practice contortion.

Is it normal not to have a HOT PULSE RELAY?

Anyway… so I thought I would check the THERMO SWITCH and COLD START VALVE again, I had a feeling this was the issue.

Red/Black wire on the COLD START VALVE showed 10V when cranking.
Red/Black wire on the THERMO SWITCH showed 10V when cranking.

Then I checked Continuity… this is where things get weird. There is no continuity between Green/White at the THERMO SWITCH and Green/White at the COLD START VALVE. How is this possible? Every wiring diagram I have shows them to be the same wire, which gives the COLD START VALVE an earth via the THERMO SWITCH. Right?

But then, the Red/Black at the COLD START VALVE has continuity with the Green/White at the THERMO SWITCH. This has to be wrong right?

Please bear in mind that this car has worked perfectly for 2 years of ownership, and this wiring has never been touched in that time. It was sometimes difficult to start in the cold though…. but always got there.

So… kind of by accident… I had both the COLD START VALVE and the THERMO SWITCH disconnected, turned the key and she ran. Fired right up. Like old times.

So then tried different combos of connected/not connected…

COLD START VALVE > on
THERMO SWITCH > on

no dice.

COLD START VALVE > on
THERMO SWITCH > OFF

no dice.

COLD START VALVE > OFF
THERMO SWITCH > ON

starts and runs.

COLD START VALVE > OFF
THERMO SWITCH > OFF

starts and runs.

SO… There is something wrong with the COLD START VALVE and or its wiring. That continuity issue is melting my melon for sure.


My questions are now… I am running without a COLD START VALVE. Is this OK? Idle seems a little bit 'rangey'… like its a bit up and down.
Any ideas about the continuity???
Have I been running for 2 years WITHOUT a COLD START VALVE???
Why did this suddenly become an issue???

Is that mystery relay someone's attempt at rigging something up as a HOT PULSE RELAY replacement… its life has now ended… and whatever was going on within it is causing the continuity issues and weirdness?

And... none of these musings give me any clue why plugging the COLD START VALVE back in makes the car not start.

Please help / advise















 

Hi

Engine cold = continuity between the TTS & CSV via the green/white wire.
Engine hot, or the heater element inside the TTS hot = no continuity between the TTS & CSV via the green/white wire.

More info to explain that here:
https://vwts.ru/vw_doc/eva2/FU01/ch5.2.html#:~:text=5.2%20Cold%20Start,Fig.%205%2D6.

Plugging the CSV back in will mean, when the TTS completes the circuit, than an earth connection is provided and power will open the CSV  that petrol will be delivered via the intake manifold, too much of that will flood the engine and it won't start.

Disconnecting it will make the car harder to start, as it's relying on fuel at the injectors via the metering head lift plate rising and letting the plunger inside move to deliver petrol.

I would disconnect the CSV via the 2 allen bolts holding it to the inlet.
put that in a jar to catch the fuel.
then, with CSV, TTS, WUR, AAV wiring connected, crank the engine to see how much fuel is sprayed and also to check it's not leaking or remaining open.

More on that here:
https://vwts.ru/vw_doc/eva2/FU01/ch5.2.html#:~:text=To%20test%20cold,Fig.%205%2D7.

A tell tail sign of leaky injectors or leaky CSV will be fuel in the oil, so dip that and check to see the level is raised or there is petrol in there.


Re Hot start relay, can't help there, I have an 83 model, it doesn't have a hot start relay, but there's posts here on that topic:

https://vwgolfmk1.org.uk/forum/index.php?page=topicview&id=helllllpppp%2Fauto-wont-start

 

lancsgti said

Engine cold = continuity between the TTS & CSV via the green/white wire.<br />
Engine hot, or the heater element inside the TTS hot = no continuity between the TTS & CSV via the green/white wire.<br />

understood completely… however I have continuity between red/black and green/white which is what is confusing me….

But then, the Red/Black at the COLD START VALVE has continuity with the Green/White at the THERMO SWITCH. This has to be wrong right?

When the TTS is active the circuit is complete between the G/W on the CSV & R/B on the TTS.

Hello, many thanks for you help.
I think maybe I wasnt totally clear or I am not understanding….

When I did the continuity test it was on the wire, from connector to connector… with both unplugged… so no valve or sensor was playing any part.

the red/black pin in the VALVE connector showed continuity to the green/white pin on the THERMO SWITCH connector….

green/white to green/white showed nothing…