T4 Starting problem (Electrical ).

[ocdrbug]

The Van - 94 T4 Petrol 2.5L Manual LWB.
My ignition switch has a push button start set up as the starter part of my ignition switch is cactus and its been this way for the last 3 years that i have owned it without any problems.
The problem i'm having just of late is when i switch the ignition on i can hear the fuel pump priming and then when i hit the start button nothing is happening starter motor wise (i do hear the pump priming again as i push the button). Once or twice it has actually started but for the most nothing.
The battery is a 600 cranking amp battery and reasonably new, the starter was replaced with a new unit, the button was replaced with a better quaility unit, and i have checked every relay & fuse that i can find to no avail.
Now i simply roll start it(clutch start )and it fires every time and drives perfectly as it always has. Now after warming it up (average 3 to 5 minutes) i can turn it off on the ignition switch, then turn my ignition switch back on, hit the start button and no problem it starts straight away and i have done this repeatedly but if i leave it for 15 to 20 minutes or longer it reverts back to the same no start on the starter button problem again.
I now have a replacement Ignition switch, matching Immobiliser and ecu that i bought but am wondering is there any relays that are problematic that i should check first as i now realise that changing the ignition ( switch/lock assembly ) & immobiliser inside the dash instrument cluster area is a pain in the arse job so i'm just looking for any imput from others that have had similar issues with their T4's. Thanks Mike.

[Bryn23]

Haven't owned a T4, but the T4 model has have an issue with a relay when i was researching getting a T4...

this may be your issue, one of the guys on here will be able to confirm.

[Umai Naa!!]

Yes, there is an ECU relay that craps out on them.

[Sunny43.5]

As Umai says the relay in the fuse box was a known problem , mine used to cut out with no warning once in the middle of an intersection but I was still able to use the starter to move it forward in gear to get clear . Yours sounds different as you have no start signal , the relay problem was something to do with power to the ECU itself .

[jets]

Changing ignition switch is fairly easy from what I have read. [Mine is original] Here's a link.

How to fit a new ignition switch - VW T4 Forum - VW T5 Forum

[ocdrbug]

Does anyone know what the numbers for the relays are as the workshop manual i have is very vague in the electrical section and with regard to identifying specific relays by the numbers on them and their location ( in the fuse box area or else where ). Any help appreciated guys.

[AALocksmiths]

I have had one where the switch on the back of the barrel was completely melted. After talking to a guy at a VW workshop he said that he has seen a couple where the starter shorts out and that feeds back to the switch causing it to over heat., so it could be worth checking the switch out.