I have just bought a 240, 1991 volvo and am just trying to get the bugs out of it. We have had it for 4 months and it has always been hard to start. It will often require two cranks and they are long 4 to 5 seconds. Yesterday the Check engine light came on and the codes were

231, 232, and 221 meaning engine is compensating for very lean or very rich condition. Any ideas were I should start in diagnosing this problem?

Well thanks for all your help everyone. Believe it or not it turned out to be the fuel filter I think. I had gone through all the connectors an cleaned and tested every device that I could. The fuel filter was not suspect because the car performed well at cruising speed. It did not buck at all. It wasn't until we disconnected the battery terminal, which appearantly puts the computer into a non compensating situation, that it really bucked and shuddered. It was almost impossible to keep it running. It sounded like no fuel. I changed the filter and it ran like a charm. The check engine codes have not reestablished themselves, so I think all is well.

Till next time,

Thankyou

What you need to know first is the fact that the car is running RICH or LEAN. Measure out the voltage (digital multimeter) from the O2 sensor while the engine is running. When its running lean, the voltage is between 0 and 200 mV. When its running rich, the voltage is 500 to 750 mV.

If the engine is not running and the O2 sensor is cold, the voltage is ca 550 mV (ignition on).

With a normal working injection system, the ECU regulates the mixture between lean and rich, with a frequency from about 1 sek. This gives the optimal working conditions for the cat.

If the O2 sensor is cold, it gives no signal. This is the reason that the O2 sensor is heated elektrically by a resistance. The green wire is the signal to the ECU, the connector with two black wires in it is the heating. To measure the signal, connect the + from the multimeter to the green wire, the - terminal to ground.

After the engine is running, the O2 sensor needs about 30 to 60 sekonds to heat. That means that the mixture from a cold engine is not regulated by the O2 sensor !

First things to suspect by this kind of failure :

- Fuel injectors clogged

- AMM out of spec

- Fuel pressure regulator

- Air intake leak

There is a cheap way to force the engine running richer, I did it two years ago, and still no check engine light !

I had the same codes show up on both my 90 and 91. I fixed them all by cleaning the connections at the air mass meter and especially at the oxygen sensor connection on the firewall, which had gotten corroded and was malfunctioning. Not that this is a guaranteed fix, but I just fixed a few codes on the 90 by re-cleaning the AMM connections. Little things that go a long way, I suppose.

This may be your lucky day. I just spent a lot of time and money diagnosing the same codes. Well, let's start with the basics; have you checked plugs, wires, car and rotor?

I have put new plugs in the car and they seem to have a nice blue spark. The rotor and cap look good. The wires look like wires! I have not looked at the engine running in the dark to watch for sparks. Perhaps I should do this?

My day did not go very well. A friend recommended that I check that the connections to the in tank fuel pump were good. So I did. I thought they would be like the contacts on a ford or any other in tank fuel pump. They are not. The pump has a pig tail that is disconnected about two feet from the pump. I thought that the connector at the fuel pump would come of. I gave it a yank and broke it right off. I spent two hours removing the pump and reconnecting the wires. Fun eh? It works fine now anyway.

Neil let me know the next step. I will also try the other advice of checking the oxygen sensor connection and the AMM connection.

Thanks folks

John Wilson

First, I made sure it was not ignition related. Pulled all of the plugs and checked the condition of each, all black. Car was running extremely rich. Check air box and hose for cracks or restrictions. Cleaned all connections on sensors, checked, cleaned and retightened all grounding points on the engine. After the basics were done it was going to be a hit or miss with sensor replacement or testing. First, O2 sensor, then TPS, fuel pressure regulator, Mass air, coolant temp sensor(make sure it's the one that's harder to reach, the easy one is for the gauge), if this still doesn't work, ohm out the wires from the coolant temp sensor to the computer.

After pulling my hair out nothing seemed to work I realised that this car might beat me. Then I decided to open up the computer. Turns out there was a burnt piece on the board, I'm not sure what it was. It wasn't a cap or resistor. It was a primer grey looking piece, almost appeared to be a volatage reducer? Small, about 3/4" long. I replaced it with one fron an old Renault computer. No luck!

Finally, we found a computer in a junkyard and replaced it, BINGO! BAD COMPUTER!

I had to go to the extreme end of the line. There was nothing left to change after this but the wiring harness.

Reset the computer after each attept to fix an item, run the car and pray each time that the light doesn't come back on.

neil

9 vovlos in the family over the years, still love 'em.