I have a 1982 Volvo 240DL 4cyl. with 163,000 miles. A few days ago it started puffing black smoke out of the tailpipe. My check engine light isn't on. It doesn't idle as well as it should, exhaust smells like fuel when stopped at a red light with the windows down and if I floor it alot of black smoke comes out and it doesn't accelerate correctly (i.e. it cuts out a bit) If I drive it normally it runs perfect with the exception of the sub-par idle. Obviously it is running rich but where should I start? I can't get it to the shop until Monday so maybe someone on here can help me figure this out before then! Here is a list of new parts within the last few thousand miles...

New Spark Plugs
New Wires
Oil Change and Filter 1000 miles ago
Flame trap cleaned out (Although the U shaped house is now gone and a much, much longer hose replaced it... Should I worry about that?)
Air Filter isn't dirty or clogged so it's not the cause of airflow restriction BUT there is a black plug that is plugged into the top ofthe metal housing that is connected to the plasticair filter housing, and I unplugged it with the car running and it didnt make a difference! Is that my MAF Sensor??

Sorry about my lack of knowledge of what everything is specifically called. My mechanical knowledge of cars in limited! Any help you guys could give me would be great!

 

bad fuel pressure regulator (on end of fuel rail) or bad disconnected temperature sender (You have 2, one for gage one for fuel injection) You can take off the hose off regulator and see if it has any effect this is your most likely candidate. If temperature sender is disconnected or open computer thinks it is -40 degrees and richens mixture.

 

Agree with wojeepster. Likely the fuel pressure regulator. It's a $75 item from FCP.

http://tinyurl.com/65save

But before you buy one, check yours first. Pull the vacuum hose off. If gas leaks out or if you smell gas in the line it means the diaphragm inside the FPR has failed.

 

Okay, I've got an update. I pulled the vacuum hose off the fuel pressure regulator this morning while the car was running. When I pull the hose off the idle perks up a bit and then it idles better without the hose attached to the regulator. Even with the hose removed im still getting black smoke. There isn't fuel leaking or a gas smell in the line. Does it still sound like the regulator is bad? I have yet to check the temperature sensor.

 

Preliminary check of the fuel pressure regulator is good. A fuel pressure test gauge would confirm this, but I wouldn't worry about it for now.

Next I suspect the O2 sensor. If the output voltage is too low the computer thinks the mixture is lean and makes it richer. If you have a digital voltmeter, you can check it. I think the '82 has an unheated O2 sensor (one wire instead of three). Unplug the O2 sensor at the firewall and measure the DC voltage with the engine running. It should be about 0.5 volts DC. But an unheated O2 sensor requires it to be warmed up by exhaust gases. What I would do is make the voltmeter connection with alligator clips, long test leads, set the voltmeter on my lap, and go for a test drive.

 

I got black smoke (and sluggish performance) out of my 740 going up hills. Couldn't figure it out at first. Then I changed the air filter and it was like night and day. Even though the air filter looks "clean," it could still be dirty. Try this simple fix first.

Volvo DIYers should visit www.stepbystepvolvo.com.