Join Date: May 2015
Location: Loveland, Colorado USA
SPICA - Adjust mixture after new Bosch fuel pump?
The fuel pump on my '74 Spider finally gave up the ghost this past week. I can't verify it's age but it was a SPICA/Bosch two port version, so might have given 44 years of loyal service. Unreliable Italian cars indeed!!
The reason I replaced it was that the fuel pressure light was coming on and staying on for 30 seconds or so before going out prior to start. Otherwise the car was running fine. I replaced it with a new Bosch pump from Centerline. The install went fine and now the fuel pressure light blinks momentarily on start-up like normal. However, the car seems to be running rich after the swap. The idle is sort of 'loping' and it seems to stumble a bit at lower RPM's.
Based on my (admittedly less than expert) understanding of the SPICA system, even if the new pump is supplying a higher pressure of fuel to the SPICA pump than the loyal but tired original pump, the injection pump doesn't really care, right? It's going to ramp up the pressure going to the injectors independent of how much the supply side is providing...I think.
That said, I am definitely a believer in the "Strongly consider the last thing that changed prior to the problem" school of troubleshooting and the fuel pump is it.
Do I need to adjust the mixture or should I be looking elsewhere?
Loveland, CO USA
'74 Alfa Romeo Spider
'87 Porsche 944 turbo
'93 BMW 740i