Jetronic Swap?

gmasters · Post by **gmasters** » 03 May 2012, 13:49

I have a 1991 Volvo 240 wagon that has a bad Jetronic ignition control module, item number 028000572. I swapped it with a good working one off of a friends 240 that was 0280000933 and it started and ran beautifully. I asked my friend if he wanted to trade my bad one for his good one, he laughed and took his back. I went to a local pick and pull and I found a couple, however there numbers are significantly lower: 028000544, 028000556. Since these were from mid to late 80's cars I was wondering if they would work. Does any one have any experience in trying something like this. I am reluctant on purchasing one, just in case it wont work. Any help would be appreciated.

Thanks,
Garrett

Post by **billofdurham** » 04 May 2012, 13:39

Have you any easier questions, please?

The '91 240 is using the Bosch LH3.1 system. The 544 ECU is from the LH2.2 system and the 556 is from the LH2.4 system as is your friend's 933. The 933 was used in later models and eliminated the use of the cold start injector.

This is where things get complicated. My list shows the 933 was only used on the '91 - '92 740.

Bill.

gmasters · Post by **gmasters** » 04 May 2012, 21:14

I apologize, all my question seem to straddle on the edge of the unanswerable.

I thought the 933 was only on the 740's as well, however it was on my friends 240 and I am pretty sure it was factory. Since I was only borrowing it I was unable to test it thoroughly, I just tested starting, and idling. I believe it might of worked because it was a newer model vs being the older model late 80's 554 or 556.

Since my 91 240 is a 5 speed with the Bosch 3.1 system, I think it would be in my best interest to replace it with the ECU that was originally intended for the 3.1 system. That model of course being the 572. This of course will be difficult, considering they were only produced from 90-92 and only put on the 240 models with the M47 transmission.

I appreciate your generous help, now begins the search for a Bosch 572. If anyone happens to have one laying around or one that they want to get rid of please let me know.

Thanks
Garrett

Post by **jimmy57** » 04 May 2012, 21:25

Is your ECU not running fuel pump or what is it failing to do?
You are right. LH 3.1 cars are rare. They didn't sell that many in those three years.
BTW, if you ever get the notion to change your trans fluid DO NOT PUT AUTO TRANS FLUID IN IT!
Lots of M47's have galled a thrust washer and melted the plastic needle bearing cage on 1st gear after they were drained and refilled with ATF. You can get by once as some of the factory fill synthetic oil is still there. WHen you do it the 2nd time the failure risk goes WAY up.
Use synthetic oil, 5w20 or 5w30 works well.

gmasters · Post by **gmasters** » 05 May 2012, 10:34

My fuel pump is running because it runs fine on idle. As soon as I press the gas pedal in gear it dies. Considering this sounds like the symptoms of the Air Mass Meter, I opted to replace that. It did not fix anything because I received a faulty after market one. However when I replaced the ECU with my friends everything seemed to work fine, with my original Air Mass Meter. I am waiting on my replacement Air Mass Meter to arrive in the mail to make sure I cover all the bases.

I want to get everything running in top shape, due to the fact that I have a big trip coming up really soon. I would like to try to avoid any problems on the road because I have been there and done that many times before.

Post by **billofdurham** » 05 May 2012, 12:26

What led you to think the ECU was bad? Did you get a fault code or did you run a test on the ECU to come to that conclusion?

Bill.

gmasters · Post by **gmasters** » 05 May 2012, 15:11

I figured that since I replaced almost every part of the ignition system, except the fuel injection ECU that it was the only thing left. So when I swapped it out with my friends fuel injection ECU it ran fine with no hesitation at idle or while driving. It also did not die when I pressed on the accelerator while in gear which is what it did every time when the original ECU was in place. I figure the only two things that could be a result of dying while the accelerator was engaged was the Air Mass Meter and the ECU, so if I replace both it should run solid. Granted I have already cleaned and replaced all the fuses, cleaned the ground contacts, cleaned the throttle body, replaced the fuel pump relay, main fuel pump, in tank fuel pump, fuel filter, throttle body switch, air box thermostat, power stage, ignition coil, rotor, distributor cap, distributor cables, plugs, and Air Mass Meter (turned out to be faulty) I should receive another in the next couple of days. I am also working on replacing the PCV components, the exhaust, and the oxygen sensor.

Post by **billofdurham** » 05 May 2012, 16:26

Have you checked for fault codes?

Bill.

gmasters · Post by **gmasters** » 05 May 2012, 21:06

Yeah I am getting 121 (AMM faulty). I thought I should be getting a fault code for the oxygen sensor, due to the fact that I bought the car with one not installed. Weird!

Post by **jimmy57** » 05 May 2012, 21:57

Some faults when detected will stop the car from entering closed loop. If in open loop the oxygen sensors are not used and are ignored effectively.