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ON the main relay I get 12V to the #30 pole. When I turn the ignition on, the main relay does not close to complete the circuit. I now that if the main relay does not get power the ecu doesnt get power and the amm does not get power either. There for the car will not start. If I make the circuit close with a piece of paper it blows the 25a fuse. What would cause the fuse to blow. Also when I pull the relay out and stick in another relay it also blows the fuse. Even if I stick the same relay in also blows the relay. Is there a short somewhere. I pulled the harness and made sure that there was not a wire touching or crossed. I dont know what to do or check next. Please help. Thanks
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Did you replace any AMM wires when you did recent harness work? The Orange wire from the FI relay (Main) terminal 87 to the AMM pin 5 is the one that may be blowing the 25A fuse.
The other wire from 87 is Brown and goes to ECU 17, but since it is all inside the car, it was probably not part of your harness work.
If your meter measures resistance (ohms), measure from relay 87 to ground — with the AMM unplugged. I think it should show no continuity at all, meaning no connection to ground (which would blow the fuse).
Let us know what find, and please give some details about what wires you worked on.
--
Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.
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I tried disconnecting the amm and checking ground on the orange wire and yes it was grounded out. Somehow I switched both of the orange wires. So instead of going to the amm it was going to the microswitch from #3 from the ecu harness. The fuse does not blow anymore. Thanks for the help. Now why do you think I am not getting the main relay to turn on when I turn the ignition key on. Thanks again.
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" Now why do you think I am not getting the main relay to turn on when I turn the ignition key on."
I think we could make quicker progress if you would tell me what other wires (besides the orange ones) you replaced in your harness repair, and what you are using for a wiring diagram.
You seem to know "what goes where", but I feel I could give more specific tips if I knew more about what you've done, and what you have to work with.
As for the Main Relay—the +12V you see at terminal 30 goes 3 places inside the relay:
1) the + side of the Main relay coil
2) the Main relay armature—and then to output terminal 87/1 when the armature closes (what is failing now)
3) also to the Fuel relay armature, to power pumps, injectors, etc. from terminal 87/2 when the relay closes during cranking & running.
Assuming the +12V you see at 30 is also at the Main relay + side, you should also see it with your meter at the coil ground terminal 86/1, if the relay is failing to energize.
The ECU is supposed to energize the Main relay by grounding the Y/BLK wire at terminal 86/1 when the Key is turned ON. But if the ECU is failing to ground that wire (or you have another wiring error), the voltage at the coil + side should also be detectable at the ground terminal.
Let us know what you see at terminal 86/1—and any background information that may relate to the current problem(s).
--
Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.
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The wires I fixed were wires that whent to the starter and alternator. The insulation was falling apart and I replaced about 5 inches of the wires. The wires were still attached so I couldnt of crossed them. I did one at a time.
About 7 years ago I replaced other wires that were falling apart and cut the harness by the firewall before it whent inside the car. I didnt know that I could disconnect it at the ecu and relay. Now I know better.... I think. So I went ahead and unattched the harness the same way as I did 7 years ago and crossed the 2 orange wires. I had the #3 pin on ecu to the AMM instaed of the micoswitch. That was causing to blow the fuse.
with the ignition off I get power to the relay 86/1 & 30.
with the ignition on I get power to the relay 86/1 & 30 & 85 & 86/2.
with the engine cranking I get power to the relay 86/1 & 30 & 85 & 86/2.
I guess the 86/1 is not being grounded by the ecu?
On the relay I am getting with ignition: off on cranking
for your #
1) 12v 12v 12v on the side of relay.
2) 0v 0v .16v main relay armature.
3) 0v 0v 0v fuel relay armature.
On the coil with ignition off on cranking
on the negative side of the coil 0 12v 12v
on the positive side of the coil 0 12v 12v
I hope this helps you help me. Thanks again. I am using the Haynes manual to see where all the wires go. I think I am going blind looking at all the small diagrams. Thanks again.
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So I went ahead and unattched the harness the same way as I did 7 years ago and crossed the 2 orange wires
Are you saying that you cut it like you did 7 years ago?
Did you cut any other wires besides the 2 Orange ones?
When did the car stop running?
How did it fail?? Quit when running? Fail to start? What?
I had the #3 pin on ecu to the AMM instaed of the micoswitch. That was causing to blow the fuse.
No, it was the other orange wire that was blowing the fuse—the one from the relay going by mistake to the Throttle Position Switch.
I guess the 86/1 is not being grounded by the ecu?
Yes, that's what your meter tests say. But I haven't seen this happen before, so I don't have much advice to offer you. Seems like now it's an ECU problem, where I have little experience, and have never heard of this specific ECU trouble. The ECU itself may be bad or damaged in some way.
Maybe someone else reading this will have some ideas???
Are you using the Haynes diagram on page 4A-28? One thing to check is the ground connection in the intake manifold from ECU pin 25 (item "T" on the schematic). See figure 13.1f on page 4A-3. Remove and clean both ground connections. Then see if you can get the ground at Relay 86/1 with Key ON.
Let us know if this changes anything—and please answer my questions above to help me better understand the overall situation.
--
Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.
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yes, I cut all the wires near the firewall. Thats were I had the two orange wires crossed. The rest of the wires all matched up. There was also the black wires but all went to ground.
The car ran fine and I let it sit for about a week. After several days of rain I tried starting the car and it would not start. I checked spark and that was good. The fuel was flowing but I was not getting fuel to the spark plugs. The spark plugs were dry. When I would let the car sit over night the first crank the car would want to start. But again, no go on starting the car. I than decided to take the harness out because I saw the starter wires without insulation. At that point b4 taking the harness out I dont remember if the main relay was making contact. I took the harness and cut each of the three wires out one at a time. Thats were I cut all the wires near the firewall confusing the orange and black wires. ((For about three years I had to jump the armature on the fuel relay to make the fuel pump work. The main relay always maded contact.))
On the y/blk wire with the grounds on the manifold disconnected I get flow from the y/blk wire to the ecu connection 1,2,5,10,13,16,18,21,23. with the grounds connected I get flow from the y/blk to ecu 1,2,3,5,10,11,13,16,18,19,20,21,23,25. I dont know what you can do with this information.
I dont think we have the same volvo manual
I think the ecu is bad for the fuel relay, because I have had to jump the armature. The ecu for the main relay. I dont know. Were can I get a used one and how much do they cost. I wonder if this will fix my main relay problem.
No I still dont get groubd with key on for 86/1.
Thanks
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Hi Rob, I'm still in the dark on many things. So this will be sort of long, but please bear with me.
• yes, I cut all the wires near the firewall. Thats were I had the two orange wires crossed. The rest of the wires all matched up. There was also the black wires but all went to ground.
<> I still don't know just which wires you mean, but "all" the wires sounds serious. Even if the colors matched, could you have a bad splice showing up now, where you reconnected?
• The car ran fine and I let it sit for about a week. After several days of rain I tried starting the car and it would not start. I checked spark and that was good.
<> Spark is good on all plugs? Just checking at the coil is sometimes misleading
• The fuel was flowing but I was not getting fuel to the spark plugs. The spark plugs were dry.
<> "fuel was flowing", then the Main relay worked at this point? And you jumpered the Fuel relay (as mentioned below)?
<> If fuel was really flowing (jumpered relay?), then the dry plugs might have been cause by a failure in the Injector control wiring. They all get +12V from Fuel Relay 87/2, but don't "fire" until the ECU grounds them from pin 13.
<> Again, that sort of points to the ECU, but doesn't seem related to the solid ECU - Main relay problem you are having now.
• I took the harness and cut each of the three wires out one at a time. Thats were I cut all the wires near the firewall confusing the orange and black wires.
<> I'm still confused here Which "three" wires? You can't mean the 2 orange and 1 black, because you mention them where you cut "all" the wires. I have no clue what "all" means or what might be affected.
• ((For about three years I had to jump the armature on the fuel relay to make the fuel pump work. The main relay always maded contact.))
<> That sounds like you are pretty handy with relays and electrics. Knowing that helps me on this end.
• On the y/blk wire with the grounds on the manifold disconnected I get flow from the y/blk wire to the ecu connection 1,2,5,10,13,16,18,21,23. with the grounds connected I get flow from the y/blk to ecu 1,2,3,5,10,11,13,16,18,19,20,21,23,25. I dont know what you can do with this information.
<> I don't either. But at least it shows that all the ECU ground pins (21 y/blk and 11, 19, 20, 25) are all grounding OK.
• I dont think we have the same volvo manual
<> Then please tell me what (Haynes) you have. I have 2 different ones and referred to my '76 thru '93 because I thought it would be like yours. Just telling me we don't have the same manuals doesn't help. I believe that we should be on the same page as much as possible. So please don't make me beg for this stuff.
• I think the ecu is bad for the fuel relay, because I have had to jump the armature. The ecu for the main relay. I dont know.
<> I don't know much about ECUs, but from reading on the Brickboard, I think that the failing ECU ground for Fuel relay is more common on later ones.
• Were can I get a used one and how much do they cost. I wonder if this will fix my main relay problem.
<> Yours is the same as all 240 and 740 non-turbos '85 thru '87 and the '87 740 turbo, so maybe you can get one frome a junkyard and try it. The Bosch number should be 0-280-000-554. Most U-pull-it yards will let you return something that doesn't fix your problem. Last I knew they get about $25 plus $10 that you get back if you return it or bring your old one in.
• No I still dont get ground with key on for 86/1.
<>I was afraid of that.
--
Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.
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I forgot it is a 1985 240.
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