Fuel pump priming question

[Theo205 0]

I lately had issues cold and warm starting my 1.9 Gti. I noticed that pump is rarely priming when I switch on the ignition. if it primes beforehand it starts right away. I went through many many posts regarding the tacho relay and I still havent found a direct answer. Question is : Is the tacho relay responsible for priming? Under what conditions does it prime? Is it always as soon as ignition is turned on or it depends on other factors too?

Any help appreciated before ordering a new tacho relay. prices have gone crazy on them nowdays.

Thank you

Theo

[stewal 8]

As I remember it, it primes the pump for a couple of seconds when the ignition is put on, then it supplies the pump whilst cranking using the starter supply, then if the engine fires and runs above a certain rpm it maintains a supply to the pump cutting out again if engine speed drops below that rpm: hence its name.

 

If your ignition priming is intermittent it could be the relay, I think you can carefully open them up to inspect and I managed to revive mine with a good spray of proper electrical contact cleaner both inside and on the plug contacts. It limped on for best part of a year but ultimately I did have to bite the bullet and get a new one.