Problem:
My 1998 S70 Turbo flat-out refused to start whenever temps dipped below 0 °C. Crank, crank, crank… nothing. It would eventually catch if I played games with the key and gas petal, but as winter got serious, even that stopped working.
Bought the car last summer as my first ride for a steal, but it needed a laundry list of mechanical parts to pass inspection. Summer? Drove like a dream.
Then winter hit.
When it got around to below freezing (-5°C - +1°C) when starting it would repeatedly crank, it maybe started after 10–15 seconds of cranking, but only if was slightly warmer the day before or if there was some fuel pressure still in the lines. I figured out that if I left the key in position II for about 5-10 minutes first, then when I would go to start it I would have to give the throttle a quick flick. With those steps, it would start 70% of the time, although if it didn't start in that moment I would have to wait and try again. The colder it got, the longer I had to wait with the key in position II. Once below -15 °C (5 °F), forget it... Even an hour with the key in pos II did nothing. Engine would just crank without firing. (I would try cycling the key on and off to continually to start the fuel pump, but I don't think that made a difference).
But once I got it running in the cold it was perfect. No stalling on idle or when driving, not much of a rough idle, no weirdness at all. Drove great.
What I tried:
- Tested fuel pressure with pressure gauge: 39 - 41 psi at cold start idle (at exterior air temp around 5°C to 10°C). A touch low, but in spec-ish. (Regret not checking the fuel pressure fall off after turning off the car to see if there was a leak).
- Replaced the ECT (Engine Coolant Temperature) sensor. No dice.
- New battery. Still nothing.
- New Wix fuel filter (replacing the original 28-year-old one
). No resolve.- Inspected the fuel pump itself. Ran fine, no issues.
- Reviewed wiring, spark plugs, grounds, everything, nothing seemed off.
I took a look at the fuel pump relay 103. It looked brand new, no cracks, no burnt pins, nothing visually obvious. But I've heard that this could cause issues, but I figured since my fuel pump ran fine, then there shouldn't be a need to replace.
But I ordered a new relay from Professional Parts Sweden off of RockAuto for CAD$28.37 (USD$20.54) anyway since it was a good price. I popped it in…
Instant fix. One turn of the key and she fired right up, in -10 °C weather. No pre-heating the key, no throttle dance. Just started like a normal car again. Mind blown.
I still can’t fully wrap my head around why this relay would only fail in cold weather. Maybe temperature-sensitive contacts, a solder joint inside that only acts up when it gets cold, or something with the electronics inside getting finicky below freezing. I don't know...
The fuel pump always primed and ran once I turned the key over, so I never suspected it. But apparently these 103 relays do cause starting issues on the 850/S70/V70 platforms.
If anyone has a solid technical explanation for the cold-only behavior, that would be greatly appreciated!
)