just spent $75 to replace the worn out fuel pressure regulator on Olga. don't know how long the old one was on her (maybe factory oem???), but the diaphragm was shot and needed to be replaced.


anyways, the issues seem to be the same as before replacement. acting as if she's getting too much fuel, like when the diaphragm was letting raw fuel dump into the manifold through the vacuum line. some backfiring and hesitation until the manifold caught up with the excess fuel being dumped in from a standing start.


should I reset the computer before a cold start and see if that will fix the issues? she already has new plugs, cap and rotor.

 

whenever i replace electrical stuff like you have, i re-set the computer.

 

How do you "reset the computer"? The FPR is not electrical, not that it matters...
Topcity, describe your symptoms better if you hope to get helpful advice.

 

I was wondering if there is a 'proper' way to reset the comp other than what I do, which is after the batt has been disconnected for a short while (>15 min) I do a cold start and don't touch the throttle until she's up to operating temp and idling smoothly. This way the comp can 'relearn' the sensor base positions. The first couple times I reset the comp, I did it the suggested way for modern Chryslers: fire it up after batt reconnect, wait until idle is smooth, kill engine and repeat two more times before touching the throttle or anything else. Found that when I do this with Olga, the SIL turns on with her sitting still until she's up to temp.


lev:


as far as the symptoms that I am experiencing are typically on cold start situations until up to temp: Lack of power and some backfiring under acceleration, rough low idle (round 650-750 but returns to 950ish once up to temp), exhaust smells as if she is running rich.


I am leaning towards the possibility of needing an O2 sensor replacement, but open to suggestions.

 

O2 sensor is not an issue here...
Computer "reset" on an '87 240 is not really a thing! May be disconnecting the battery to clear codes but besides that, not really.
Again, you are not elaborating on your symptoms but you can have MAFS issues, power stage problem, even a leaky injector or vacuum or intake leak which would cause rich running condition and associated problems.

 

by reset, i meant really just disconnecting the battery for awhile...
maybe i'm giving our old volvos' computers more credit that they are due!

 

May be too soon to say so, but believe I finally fixed Olga's issue of wanting to run rich, backfiring, acting like she's only running on two or three cylinders until she warmed up to operating temp.

The fix:

Went to the only salvage yard in Topeka that I have found a Volvo with a red block in it. Spent $44 after taxes for a new to Olga maf sensor. Results so far look promising. Patched a small hole in the hose that came with the maf with some super glue, slapped it all back together and fired the old gal up. Didn't 'reset' the comp either.

The old gal is even more spritely than when I first met her four years ago. The salvage yard even gave me a six month warranty for the maf.

Thanks to all that gave suggestions on getting Olga running more smoothly 🙌