240 Wont Start! ECU?

[240man91]

I have a 1991 Volvo 240 wagon that does not want to start. It would normally start and run really rough and eventually die. Now it wont start at all. I replaced the air mass meter and the rpm sensor but with no luck. I have been testing the ignition coil and the powerstage and this is what I have found.

Testing in situ gives the following recommended readings. (a) Terminal 4
to ground and/or ignition coil terminal 15 should read 12Volts.
(b) Terminal 5 to ground with starter motor operating should show a pulsating
reading between 0 and 2 Volts. (c) Terminal 1 to coil terminal 15 should read 0.6
to 1.2 Ohms resistance. (d) Terminal 1 to king lead connector on coil (HT
terminal) should read 6.5 - 9.0 Ohms resistance. (e) Terminal 2 to ground
should read 0 Ohms resistance. (f) Ensure that screen (shield) of screened
cable is connected to Terminal 3. If (c) reading is too low replace coil. If
(c) is too high, check wire between Terminal 1 and coil terminal 15, replace
or repair if necessary. If (d) is too low or too high replace coil. If (b)
is OK but unit is not working try replacement unit. The above information
comes from the EZ 116 K Ignition system Green Book.

My Tests:

A) 12V Pass
B) 0V (No Pulse) Fail
C) 1.1 Ohms Pass
D) 0 Ohms Fail
E) 0 Ohms Pass
F) UNSURE

Luckily I had access to another Volvo 240 Sedan that I was able to compare a couple of issues on. Test (B) on the Sedan came back normal = 0 to 1.8V. However I was not getting any Pulse on the stalled wagon. As far as test (D) goes I was unable to get any reading from it. I thought this was strange and tested the good sedan and got the same no reading, however the sedan runs fine so I might be doing something wrong. What I did was connected the positive lead of the tester to terminal 1 and the negative to the top of the coil (King Lead?). I also swapped the tester lead to see if there was any difference but it showed none. I thought the problem would be regarding test (B) as that was the only real difference I could find between the cars. I tried swapping out the ignition coil of the good sedan to the stalled wagon but same results. In the test procedure it says if (B) is OK but unit is not working then replace. However it does not state what to do if test (B) fails. As far as test (F) goes I am not sure what it is asking for. If it is saying make sure that terminal 3 is plugged into the wire harness then I have done that. Any suggestions would be greatly appreciate, as I am wondering what to try next. I want to get my wagon up an running as soon as possible.

Thanks,
GARRETT

[electech]

I am not sure what the troubleshooting refers to...What does pin 5 do on the ECU? If it is crank position sensor, that is your problem.

I would back off the troubleshooting chart for a bit and rethink. Won't start, needs spark fuel and air. To get spark it needs ECU, which means PNP switch, main relay, and whatever else the EPU requires on that model.

Do you have spark when cranking? If so, the EPU is probably happy. Is your fuel pressure within spec? Check fuel pressure and fuses. If you don't have spark, then the troubleshooting the EPU is more important. Again, what is the test "B" for? Is it crank position sensor? (That's what it sounds like). Is your multimeter of the quality to read rapid pulsing? Analog meters can't respond fast enough, neither can time delay readouts. Use the AC volts setting and see if you get around 1 volt AC, if so you have 0-2V pulsing.

Test F refers to the sheilding on the wire connected to terminal 3. The wire is sheilded, it usually looks like either tin foil or copper weaving. The sheilding itself needs to be connected to the terminal. (think of it like attaching a ground wire to a radio.)

[240man91]

Thanks for the response, and unfortunately troubleshooting is the only thing I have left.

The problem I believe why it wont start is because there is no spark to the coil. So I have been troubleshooting because I have replace every component with a know working one from the coil back. Correct me if I am wrong but I believe that the ignition sends current to the ICU then onto the crank position sensor, to the powerstage, then to the coil. With this in mind I have replace the ICU, powerstage, and the ignition coil with working parts. I have also replaced the crank position sensor with a new one however there is a possibility that it I received a non working part.

Is there some way to test the CPS to ensure it is working properly?

As far as pin 5 on the powerstage wire harness, to be honest I am not sure what it is referring to. I believe it is the wire giving the signal from the crank position sensor to the powerstage. However I was able to do the same test on a working 240 and my meter showed it at 0V and when cranking went to about 1.8V. This is why I suspected my problem might have to due with this particular reading.

Also I have replace the Fuel pump relay and the pumps engage when I turn on the ignition, this is why I suspect it is some type of an electrical issue.

Thanks for you help!

[electech]

I strongly suspect the crank position sensor, if that is in fact what pin 5 goes to. I am not in front of VADIS or I would post a test procedure. Look at the wire color on pin 5 and see if that wire is also at the sensor. If it is, test for current at the sensor itself when cranking (just like testing at pin 5). Also check for power and ground at the sensor connector. if the sensor gives voltage but it doesn't appear at pin 5, you have an open circuit between the sensor and powerstage. If the sensor is getting current and ground but does not produce voltage when cranking, it's a bad part. If the sensor is not getting current....back to the drawing board. Have you checked all the fuses? And the ground screw near the ECU?

[240man91]

Alright sorry I haven't gotten back to you sooner, but on the contrary she is running! I cleans the ground contacts really well, then I checked to make sure the Crank Sensor was getting power and had ground. Since that checked out I make sure I was getting battery voltage at the powerstage as well as ground. From there I went to the ignition coil and was getting power off of that as well.

I went ahead and tried to start her and she wanted to but would not catch. I heard a clicking noise when I tried to start it and traced it back to the ignition coil. It was arching between terminal 2 and the top terminal. So I switch it out the the working sedan volvo and tried the arching ignition coil on the working sedan and it ran fine with no arching. So I took the other ignition coil that was from the working sedan and put it on the wagon and she started with no arching on the coil (weird).

However the problem is not yet solved, She runs but whenever I give it gas it just revs up and then dies. I am thinking it might have to do with the Mass Airflow Sensor. Since this was not working before I replaced it but there is a possibility that it is also DOA (like the Crank Sensor). Is there any test that can be performed on it to insure it works. I checked the voltage and ground at the wire harness and that checks out. I thought I read somewhere that you can do an ohms test on terminal 2 and 4 and should get a reading at about 4 ohms. I tried but was only getting around 1.8. However on the old Airflow Sensor I got 0 ohms. I would greatly appreciate any help you could offer.

Thanks,
Garrett

[billofdurham]

Garrett, welcome to Matthew's Volvo Site.

I have been away for a few days and have just come in on this one. Have you checked for fault codes using the On-Board Diagnostic (OBD) unit in the engine compartment?

How to test the MAF is in the attached:

240 MAF testing.pdf

(562.88 KiB) Downloaded 2874 times

I have included the procedure for the LH 2.4 and LH 3.1.

Bill.