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Volvo 240 1984 LH jetronic 2.0:
So we had to smog this month, and the tech said that the timing was off. I though the timing was 100% computer controlled, but he convinced me to try to rotate the distributor (it was 16BTDC instead of 12BTDC +-2 degrees). Well, I get the timing dialed in and then the car stops starting up. I figured I fried something while messing with the distributor.
After some troubleshooting I find that the system relay is not activating. When I jumper the relay plug (30 & 87 or Red to BN), the car starts up fine. It just appears that there is no ground signal from ECU terminal 21 to the relay terminal 85. I checked everything out that I could think of. With key on, power is present at ECU terminal 18 and System Relay plug at 30 and 86,(power from ignition switch), there is power on ECU terminal 1 (from coil). But no matter what I do the relay plug @85 has no continuity to ground from ECU terminal 21. ECU ground checks out OK *(ECU 25 I believe), but no continuity between ground and ECU terminal 21 with ECU plug disconnected.
Again, when I jumper the system relay the car runs fine, but for some reason the ECU is not activating the system relay when the ignition is turned on. Is there something else that has to happen before the ECU ground the system relay?
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Hello
I was chasing down a similar no start no ground at ecu
on a lark I changed the relay same one you speak of
Presto
Started right up
Can not explain it , didn't expect it to fix it but there you go.
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If you've been accurate in your measurements at 5,18, and 21, the transistor T-305 inside your ECU has opened. It is a very simple circuit (comparatively) in there which logically ORs the presence of ignition switched battery at 18 and a delay timer used to keep the AMM powered after shutdown for the burnoff duty. The only way this would die is if you accidentally shorted battery (like at terminal 30) to terminal 85 on the relay while the ignition was on. I can't yet imagine how this would have resulted from work at the dizzy.
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Art Benstein near Baltimore
Since it's the early worm that gets eaten by the bird, sleep late.
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Art,
I think you nailed it. Since I only had one working relay during trouble shooting I was using a jumper in place of the other relay for testing. I think I must have jumpered the System Relay plug incorrectly, basically making a short where the relay coil was supposed to be or just like you said connecting terminal 30 to terminal 85.
I have the computer out of the car, and two used ECUs coming from ebay. I can see the transistor you are talking about (can type). Looks like a BNSS50 NPN darlington type. Any way of testing it on the board? I just looked through my electronics stash and I have some MPSA14s darlington type (and some 2N3904s NPN bipolar). Would the MSPA14 work? Do you have an ECU circuit diagram (0 280 000 510)?
Run down of what happened:
- Adjusted timing.
- Car stops starting up.
- Identified non clicking fuel pump relay.
- While swapping fuel pump and system relay and using a jumper I fried T-305 in the ECU.
It was just dumb luck that the fuel pump relay went out at the same time as I was messing with the distributor. Then me being dumb that fried the ECU.
Thanks again, this forum is amazing!!
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Oh man!
I am sorry to hear that you may have done something like that!
From what I just read, Art and you know a how lot more about the insides of those boxes.
Wouldn't have known you guys knew each other with electronic part numbers!
That's enough to reassure me to keep my 10 little "do-dads" on my palms out of there!
I can spot items and solder things but explaining, what does what, is way far over my head!
How much are those ECU's costing nowadays?
Sounds like you got a Rexall, two for one sale or was it one more for a penny? (:-)
Phil
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It is amazing what just happened on this board, but it makes sense.
I think anybody who has tried trouble shooting tricky EFI issues with these LH 2.0 systems has read a lot of the same forum posts here and on other boards which all seem to reference the haynes figure 13.1b or something similar. I read all these posts yesterday and reached the end of the posted internet knowledge. I had already taken apart the ECU to see if there was any obviously burned items (looked AOK). As for the transistors, I have taken a circuit class, have some experience (built a megasquirt which is where some of my spares come from), and you learn to look up the part numbers and find the data sheets by reading the little numbers on the components.
What is really amazing is that Art read right through my story, and knew the part. On the circuit board it is labeled T-305 which was hard to read since the text was almost under the component. And more amazingly he correctly guessed the action that messed it up! I looked up the number on the top of the metal can read the datasheet which said NPN darlington type. Looked through my spares for something similar, then I punted back to Art about which part to try since he seemed more experienced than I.
As for the ECUs some guy on ebay had two for sale of the exact part number I needed for 25 plus shipping ending at the same exact time last night so I couldn't wait for a response on the board and just bought them. Who the hck posts two of the some part on ebay to end at the same time?? So for 75 bucks I am getting two ECUs in the mail by Wednesday. And for $0 I already fixed my broken one.
Art is my hero.
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Great piece of work you two. I think I'd swap the two eBay ones to see if they work and then perhaps run each of them for a week or two. Perhaps keep one and resell one?
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Hi there
So you fixed it already wow!
That's about all I can do too! Look for solder cracks or smoke.
Read numbers and those data sheets. After that, I stand there pretty much mystified!
Art is my hero too!
Your right it's amazing what is on this board but unlike my guessing or trying to remember, he whips out facts!
Pages of Illustrations and how to pictures!
Happy for you, thanks for the ECU prices. Sounds like you didn't get hurt jumping in there!
Phil
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If mine, I would try the 2N3904. I know that would handle the relay coil and what I see on the base only needs to get a couple milliamps from the ignition signal at pin 18 to turn on the relay. That would get you by until your replacement ECU, but I see why they might have used a Darlington for the output of the delay timer, which is sourced by the A-to-D converter. So you'd be without AMM burn-off if it didn't saturate the 3904. For a lasting repair you might want to look up a Darlington with some heft for holding in that relay coil all the live-long day.
No, I don't have a map of the ECU, just notes from tracing inward from the pins.
Regarding the fuel pump relay, you are aware the fuel ECU must see a succession of ignition pulses on its pin 1 to pull in that relay, right? That might lay the original blame at the very fragile Hall-effect wiring at the dizzy.
Edit: I just looked up the MPS-A14. Pretty sure I had some of these and recall they were little TO-92's, but I didn't realize they were rated 500mA. Should work fine with that relay. Good call.
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Art Benstein near Baltimore
I have several of each awaiting time and inclination, as the Tower of Pisa said to Big Ben, "If you've got the time, I've got the inclination." - GD III
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Once again you are amazing!!
I put the MPS-A14 in, put the box back together and the thing starts right up!! Is there a final test I should do to make sure the AMM burn-off is working right?
Once again thank you for giving me the info so I could feel like some sort of Volvo ECU god!! Amazing that you figured this out from tracing the pins, and my description.
I might be putting some ECUs up on ebay.. . .
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Thanks, but you'd do the same if you happened to have been down this road before.
I traced these ins and outs 15 years ago when I had an 84. Some, like this circuit, had no trouble in my car, but I wanted to know what it was doing.
That was my favorite Volvo until it succumbed to the tinworm. I don't envy you your smog testing system, but there's no place like your place to keep an old car going.
Testing the AMM cleaning... I think you have to drive the car over some number of RPM for some time period before the burn-off cycle will be allowed, but if you do take a ride, you could come back, leave the motor running, lift the hood, and connect a test light to the orange wire on your AMM -- then have someone turn the car off and see if power remains on for a few seconds. That's the whole reason for that "system" relay.
This picture is of a later type car, but same wire, same function.
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Art Benstein near Baltimore
A truly happy person is one who can enjoy the scenery on a detour.
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Great work Art!
I found a Saab site that says you have to get it over 3000rpms and 150F before it will initiate a burn off. I'll check it out.
But the bad luck continues, I started up the car, and it ran better than it has for a while now that it was properly timed. Went to the smog place who said they would retest for free, and their smog machine was broken. It just keeps going. . .
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As I remember there are two relays under the glove box.
They look and are identical but work separately. One for ignition and the other for fuel pumps!
Turn the key on and do a short bump crank of the engine to see if both click.
You should feel and hear both click but only one runs the pumps or not!
You cannot tell if the ignition turned on but you can do this!
Reverse the relays once until you hear the pumps turn on briefly.
If you then hear the pumps run, the other relay is not making up inside.
Open it up, tie a string around the contacts and the car should start.
You can not leave it that way or you run down the battery, plus it's not safe.
I was in town when this happened to me and that's how I got it home to plug in another relay.
I now carry one of those varmints with me!
Phil
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