I have a 2008 ST hatch that I’ve owned for about 6 weeks now. The engine runs well with no problems when running however starting sometimes causes an issue. The car is driven daily and about once a week it won’t start. The engine turns over but does not fire no matter how much I turn it over. If I walk away and leave it to sulk for an hour or so it fires back up first time. This problem seems to occur after I have driven the car for half an hour or so so the engine bay is nicely heat soaked. Then if I stop at the shops for 10 mins and try and restart it that’s when the problem occurs. I have put several code readers on and the ecu is not throwing up any codes. All fuses are good. Alternator and battery are brand new as I replaced those and tested them to confirm they work with multi meter. I also replaced the crank sensor but now I’m left scratching my head as to what it could be. AI is suggesting I change the camshaft sensors but changing all 4 with oem would be pricey, also to change ignition and fuel pump relays. Before i go changing any other parts does anyone have any ideas where to look next?

 

Was it a genuine crank sensor you replaced it with? mine had a similar issue few years back and was the crank sensor also, a new genuine one sorted it

 

Yes it was a genuine Subaru crank sensor and brand new bought from RCM

 

Used a snap on code reader last night to see if I could delve a little deeper. Found several historical codes C0047 in-proper Can communication, C0071 steering angle sensor power malfunction, B1107 Rear foglamp circuit failure, U1201 high seed Can counter abnormal, U1221 high speed Can ECM no data received, B1101 battery power supply malfunction, B1102 battery supply backup malfunction, B1103 ignition power failure. I’m going to check/replace the ignition starter and main ignition relay. Dies anyone have any thoughts on this?

 

Your historical codes seem to suggest a previous battery power supply failure

DTC list for MY08 WRXSTI LAN System



Attached is the complete list for the VDC system in pdf

LAN SYSTEM (DIAGNOSTICS) > Diagnostic Procedure with Diagnostic Trouble Code (DTC)

DTC B1101 BATT P/SUPPLY MALFUNCTION CONT

DTC DETECTING CONDITION:

• Battery power supply backup circuit is open or shorted.

• Battery voltage is too high or too low.

TROUBLE SYMPTOM:

Each function stops operation.

NOTE:

• When B1102 BATT p/supply (backup) malfunction is output at the same time, all the function of body integrated unit may not operate.

• B1101 may input when the battery runout occurs.

 

Thanks for that. I’ve replaced the ignition switch on the ignition barrel and tested the main IG relays which seem to be working fine. However the problem still persists, when I’ve had a good half an hour run and stop at the shops car won’t start unless I leave it to cooldown fir about an hr then it starts first time. It’s so strange.

 

Just throwing this out there, fuel pump?

 

Fuel pump is new (RCM) and was fitted about 8K ago. It’s definitely priming as I can h at the pump go when I turn the ignition on and pressure is registering in the fuel one. However the hat doesn’t necessarily mean the injectors are firing. What’s the best was to test that?