1.6 GLI stops after 10 minutes running

I've got a 1.6 GLI which has had the extended cable connection from the fuseboard (dealer recall mod?) and is fitted with a suspect relay from an Opel (the relay water ingress and rust indside). The car starts and runs but cuts out after 10 minutes or so as if something is getting hot and failing. We know it's ignition as we drove it with a strobe fitted to the ignition and an LED strip connected across the fuel pump connections.
The fuel pump ran all the time but the strobe light stopped when the engine died. Could a faulty fuel pump relay be the cause? Which relay do I need to fit to this model and is that straight into the fusebox or still into the extended wiring? Attached is a photo of the diagnostic setup and also the relay that's currently fitted 

Does it instantly die or slowly run rougher and then conk out?

It cuts out and cuts back in perfectly in time with the strobe flashes before eventually dying so seems to be 100% ignition related.

It's possible that we are dealing with two separate problems. The relay had water in it at some stage but also there were some previous owner wiring horrors and bodges.

At the moment the relay activates as soon as the key is in ignition on position. It doesn't come on to prime and then go off. We tried a relay from a Mk2 that did that but the car didn't want to start. I'd like to change the relay just because it is suspect but that may not be the cause of the cutting out.

So Q1: which relay should I fit and what will it do given the car already has the 'retrofit' wiring?

Q2 For the ignition to break down after 10 minutes seems like something overheating. We've tried another coil, another CDI and new plugs leads and distributor cap. Any other ideas? Could it be the ignition switch or another relay at fault?

All things relay.
http://www.cabby-info.com/Files/Relays.pdf

if that fuel relay is a correct kjet/rev counter triggered type, then you could either have a faulty relay killing fuel then engine, or a fault in the ignition system killing spark which will then kill the relay

does the fuel pump run constant with ignition or only when cranking/running

rubjonny said

if that fuel relay is a correct kjet/rev counter triggered type, then you could either have a faulty relay killing fuel then engine, or a fault in the ignition system killing spark which will then kill the relay does the fuel pump run constant with ignition or only when cranking/running

The pump runs constantly with the key in ignition on position. It doesn't prime and then stop. But it's an Opel relay when we check the number.

Which relay should we be looking to fit now and should it go into the dealer retro-fit extension ro should we remove that and fit the replacement relay straight to the fuse board?

I've read that the original relays with the fuse on top were unreliable; which is what the retrofit extension was supposed to cure. Are later versions still unreliable?
 

From my perspective I think we might have 2 faults overlapping so it makes logical sense to sort out the fuel relay first and then test again for an ignition fault.

ok, assuming the open relay is same layout as VW you can swap it for a vw '53' or any standard 4 terminal relay which will bring fuel pump on with ignition (for testing purposes) if the car still cuts out then its not your fuel relay.

though you'll still want the correct VW unit ASAP as currently your fuel circuit isnt even fused unless whoever fitted the wrong relay put one inline. the original VW relay has a fuse in the end of it… part number is 321906059C or KAE part number 3.300.100
https://www.ebay.co.uk/itm/325096611643

if it turns out not to be fuel relay look at ignition switch, wiring from it, possible alarm/immobiliser issue or possibly coil though those are pretty bomb proof if original bosch unit. If it has electronic ignition then you an also look at the distributor hall sensor or the ignition module. if it is factory electronic ignition then you can use a mk2 golf ignition module they plug right in

rubjonny said

ok, assuming the open relay is same layout as VW you can swap it for a vw '53' or any standard 4 terminal relay which will bring fuel pump on with ignition (for testing purposes) if the car still cuts out then its not your fuel relay.

though you'll still want the correct VW unit ASAP as currently your fuel circuit isnt even fused unless whoever fitted the wrong relay put one inline. the original VW relay has a fuse in the end of it… part number is 321906059C or KAE part number 3.300.100
https://www.ebay.co.uk/itm/325096611643

if it turns out not to be fuel relay look at ignition switch, wiring from it, possible alarm/immobiliser issue or possibly coil though those are pretty bomb proof if original bosch unit. If it has electronic ignition then you an also look at the distributor hall sensor or the ignition module. if it is factory electronic ignition then you can use a mk2 golf ignition module they plug right in

Thanks Jonny, we'll sort the relay first. We've substituted the ignition module and the coil from a MK2 and the fault is still present. Hall sensor is a good shout, as is ignition switch. It's really annoying as it starts fine from cold but we are reasonably sure that it is igntion and not fuel supply.

As for the remote relay, I think this was the dealer mod and one of the wires might be fused.

If we get the relay you suggest should it be plugged into the main fuse board or into the remote assembly or doesn't it matter?

From my experience the fewer connectors usually the better.

Yeah the remote relay kit was a dealer retrofit, if there's a proper plastic connector pushed into the origin nal fuel relay socket chances are it's a legit one. The dealer would have retained the factory relay though with built in fuse, but if you have a fuse inline that's fine also. You do not want to use the original relay slot as it has or will burnt out the power pin round the back, that's why they fitted it