1980 Mk1 GTI

[Vinda76]

I agree with Grant. My first thoughts were that the system isn't holding pressure once the engine is switched off, fuel under pressure has a higher boiling/vapourisation point. Originally there would have been two non-return (check) valves (one after the pump, one after the filter - I've read that the one on the filter was removed by vw in some cases during early services, no idea why). Leaky injectors will also cause pressure drop, which is probably more likely than faulty check valves and easier to check.

[Lima]

Liam, if your car has only run for a few minutes, switched of then attempted to be re started in 30 mins, I would think you dont have enough heat in the engine bay to cause the heat soak the hot start pulse fix is designed for

Sorry Grant, the video may be misleading. After the initial start I did go for a drive, maybe 15-20 minutes from memory. And the subsequent non-starts were after the car had returned from that drive. So there should have been sufficient heat soak to meet the symptoms being discussed.

If I move the car to wash it, or just a quick spin around the block, it will restart no problems.

The first post in the PeachParts Mercedes link above is pretty much a perfect description for my car. The only difference being it can take more starting attempts and/or a longer period of rest before it will eventually start. When it does finally start it runs really rough for 15-30 seconds, before settling to a more appropriate idle speed.

[mikinoz]

I will report back once I have had time to go for a drive, problem is having the time to do it when I might get stuck somewhere!

[Lima]

Don't forget you only have until Wednesday 9 May (technically) and I will send you the new rego sticker as soon as I have it, haha. Although, 12 months rego has been paid for so you'd probably be right anyway I guess.

[roccodingo]

hot start pulse relay wiring.



Unsure of the actual relay part number but try google .

[mikinoz]

Thanks for the diagram! It will help a lot.

I have looked and there is no relay on the fuse panel that relates to this that I can tell, but I will inspect under the dash in due course.

[mikinoz]

So Grant if I simply put a momentary switch in the circuit for the cold start then you could over ride it and prime when required?

I'm planning to investigate this afternoon.

[roccodingo]

Cold start valve has 2 wires going into it, one from the ignition switch cranking position ( circuit 50 ) via the relay plate and / or from terminal 15a on the starter cold start valve gets power when cranking. Mine is red/ black trace if from the relay plate, black if from the starter. the other wire is green/ white trace coming from the thermo time switch.

Check you get ~ 12 volts at the red/ black on cranking at the cold start valve, cut the green / white and earth it against one of the CSValve bolts. This will make the injector squirt whenever the engine is cranking,hot or cold. When starting hot crank with the accelerator down to allow more air for the now over rich starting mixture.

If you want to operate it through a switch, run the green / / white back to the switch, then other side of the switch to earth. flick the switch when you need it hot or cold start, coming off circuit 50 it will only power the injector while cranking.

I piddled about yesterday with the cabriolet here, checked 2 Cold S valves and 2 thermo time switches, think I will replace them both and re check the operation. Cabrio starts first kick however if its hot it will flood easy so hot start with the gas pedal on the floor.

hope that helps mate.

[mikinoz]

So I have been stranded now and understand the frustration. I disconnected the cold start valve plug and it disintegrated in my hands. So I placed the wires straight on to the pins and and nothing happens.

There is no relay for hot start pulse, so the next plan is to directly supply voltage to the cold start injector and see if that helps in starting it. But I had to leave the car at the shops as it would not start after half an hour so will go back later to collect it!

[roccodingo]

Umm, yeah, ok Mik.

have you checked to see if either of the 2 wires is recieving power when the starter is cranked. do that.

PM me an address and I will mail you a plug and some new terminals.

If one wire has 12 V ( or thereabouts ) when cranking you want that wire, then an earth wire from the other plug terminal via a switch to ground. LMK if you got that or I will send a wiring sketch with the plug.

To test the cold start valve, you will need the fuel pump running or the fuel system pressure charged ( run the ign and then turn off, should hear the pump run then stop ) power and earth to the cold start valve with it removed from the manifold so you can see it spray. WATCH out for fire risk !! If the valve is operating then its only a wiring issue to make it work using a bypass switch.

keep going, it'll work.

The car was not retrofitted with a hot pulse set up then. ( no relay ) but can be done so if required.

Grant

[Lima]

I think you two are doing a sterling job.

[Lima]

Just got an update from Mick and he's making good progress.

[mikinoz]

Umm, yeah, ok Mik.

have you checked to see if either of the 2 wires is recieving power when the starter is cranked. do that.

PM me an address and I will mail you a plug and some new terminals.

Grant I will PM you tonight. A plug and terminals would be ideal.

The situation is that I have tested the theory of the hot pulse and it manages to start the car when hot and won't start normally. I have also ordered a hot start pulse relay from the USA to wire in as per the diagram.

It is running awfully rich as well so I am going to start from scratch and tune the car and see if I can improve things from the bottom up.

Took it for a drive to Katoomba today, and loved driving a MK1 that has a reasonable ride (not kidney jarring) and not have to worry about scraping the sump on potholes!

[mikinoz]

Hot Start Pulse Relay has arrived during the week. Now to install it without botching anything!

[roccodingo]

Well done man. the diagram is pretty self explanitory.

Still waiting for a new Thermo time switch here