Astra H VXR Sprint

An intermittent fault is somewhat tricky to diagnose and identify the cause until it becomes a permanent fault! So an intermittent non start was going to be entertaining to find as it could be electrical or fuel related. Additionally until rectified it meant trackdays had to be put on hold for obvious reasons.

After three weeks or so of using the car daily and having the non-start occur a couple of times, it eventually became a permanent non-start. Finally that gave me something to look for. Eliminating the crank sensor (they are occasionally prone to failure), as a crank signal was still present during cranking, it turned out that there was no fuel at the rail, and the fuel pump was not working.

Checked and tried a second known working fuel pump relay, not that. Removed the housing to check the pump in the tank; with the pump out of the tank, 12v from a second battery and the pump ran fine. So the pump was ok, which was good news as I have never seen a failure of an aeromotive 340 fuel pump to date. Next check all the fuel pump wiring in the housing, all ok.

Initially bridging/bypassing the fuel pump relay in the UEC (Underhood Electrical Centre) and the pump would run, so next check through the car loom from the UEC to the pump and the wiring all checked out ok for continuity. Also checked the 4 pin plug under the car next to the tank, in case it had suffered from corrosion.

So could it be the UEC? Fit another ‘slave’ test UEC, programme to the car, and fit the fuel pump relay and turn the key. Fuel pump primes and the car fires into life.

So problem solved, a fault within the UEC. Originally fitted with a UEC with Ident GR, a secondhand UEC from a 2010 car within the same Ident range (Ident LP) was sourced from a mate who runs a breakers for £50 which has since be fitted and programmed to the car and all is well.

Uunderhood Electrical Centre:
Vauxhall/Opel: UEC Part Number: 93184656 Ident GS Production Number: 13206746
Also Services Idents: GR GT GU GX GY GZ HA HB HC LM LN LP LQ LR

When sourcing a second hand unit ensure it has been correctly reset on Tech2 (or similar) for reprogramming.

UEC Ident LP