Comprehensive how-to repair the troublesome fuel pump relay
So when my cousin’s S70 started stalling, we looked at several possibilities we first thought fuel pump. Its been 130K, so its probably toast by now. But I decided to take the relay out of my 850, which in fact was different (one extra pin and yellow colored relay box, plus different part number) and put it in his car. His S70 no longer stalled and the problem went away. So I took his relay, opened it up and proceeded to remove the capacitors.
I ordered high grade capacitors to be installed in its place. I especially had trouble finding the right one for the silver one that is shown, because its size was unique and not easy to find. Which lead me to think, why was this capacitor so unique? It doesn’t look like any normal capacitors like the one next to it… something’s up.
I suspected that this was some sort of high density capacitor (perhaps a standard capacitor of the same value didn’t fit), but this is no longer a problem since time has past since this was constructed and capacitor technology had advanced (smaller and even better values). Once I removed them and put the new parts in, I decided to crack open the capacitor.
Turned out the silver one was the culprit all along. The internals of the capacitor was dried up, when it should be soaking wet with electrolytic chemicals, the paper inside it was all dry and falling apart. This capacitor basically crapped out over time. The other one I don’t even need to look at, since this was clearly why it failed. I did test the brown one and it did work…
My cousin’s S70 now runs fine and he can be rest assured that the repaired and beefed up relay won’t fail for a long long time to come.
MVS Forum Member billofdurham replied:
Thank you kelvin6. This is now in the Repair Database.