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I just got two ECU's online for my 740, tried them both, but my 740 still doesn't work. I have a 1987 740 sedan (no turbo) B230F. I replaced the wiring harness, checked the fuel rail leading to the injectors after checking pumps and pump relay and the lines are pressurized with gas. I put some fuel in the intake and she fired right up then died. So my ignition is working and there's fuel heading to the injectors. However, I pulled the plugs and they were dry after cranking the engine, so I am thinking that I'm having an injector problem. I connected the two large wires in the radio control relay and still no go. I tried installing a Jetronic 511 and 544 ECU, still no go. Could the ignition control in the driver side fender by the headlights have something to do with it? Any ideas? I am stumped and need help.
Thanks a ton.
John
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I haven't read all the posts but would encourage you to check and double check that your ECU is properly plugged in. After about a month of the same sort of misery you describe I did this on my 87 740 and it started and has kept on starting.
Ron
87 745 320,000 km
93 245 305,000 km
near Brantford, ON
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Thanks for the info. I replaced my ECU with two used ones, each in turn, but to no avail. There's just the main harness plug leading into it right? No extra grounds or anything?
Thanks, John
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posted by
someone claiming to be fixit2003
on
Wed Nov 28 01:48 CST 2007 [ RELATED]
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Unplug all the injector plugs and turn the ignition on. You should have 12 volts to ground on one pin of each plug and zero on the other. No voltage means nothing is getting through or being supplied to the injector relay.
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the ground return for the injectors is switched by the computer?
You'll have to see 12VDC between two of the pins at the injectors and NOT
between the +12v pin and the chassis ground. Thus the presence of +12V
isn't enough to drive the injectors, gotta have the ground too.
In the 89 740 you can measure at the "Right Wheelhouse 8 pin connector
pins 7 Gnd (Green wire) and pin 6 (Green/Red wire) +12V
If you get in there with a meter, you can save a lot of expensive
guesswork.
This connector is inside the engine compartment near the firewall on the passenger side.
You can avoid painfull troubleshooting migraines by getting the Volvo
wiring greenbook for your carl.
Post back with your results.
Bill
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So unplug the engine wiring harness and test the plug leading into the firewall? Green and G/Red. Got it. I'll go try that now. And I should have 12v DC power? Ok.
Thanks a ton. John
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Ok, that sounds like a start. I have a volt/OHM meter, but where exactly do I place each contact?
Thanks a million, John
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posted by
someone claiming to be fixit2003
on
Fri Nov 30 04:01 CST 2007 [ RELATED]
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Put the meter ground wire (black) on the block/manifold somewhere or the battery negative post and touch the red probe to the plug pins. With the ignition key on one of the plug pins should have 12 volts.
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That's perfect. Thanks a ton. I'll try that. Should there be twelve volts if the Radio supression Control Relay is dead? What about if I link the two big wires leading into it?
John
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posted by
someone claiming to be fixit2003
on
Sat Dec 1 01:48 CST 2007 [ RELATED]
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If the relay is dead you won't get anything at the injector plugs. You can pry the relay cover off and check if it energizes. The relay plug pins are known to loosen up and get pushed back into plug so they don't make contact. With the ignition on one of the relay plug pins should have 12 volts.
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You're talking about the Radion Control Relay or the Fuel Pump relay?
Thanks a ton, John
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Had I seen this, I would have made a strong case for the fact that the LH 2.2 ECU does not fail, or does so very rarely. My usual guess is the injector relay or its wire plug. It is the only way to have air, fuel pressure, correct timing, and spark and still have no start. Two black relays, engine bay, one is AC fan, the other "radio suppression" or injector relay. Swap them, but be aware the connector for the relay degrades at teh plugs into a waxy mush, so you can have a good relay and still no start.
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I looked for the AC relay and don't think I have one. I did find the Radio Supression Relay though, pulled out the wires, cleaned out the waxy goo, re-soldered the contacts inside and no go. I used the two big wires leading into the relay and linked them (I heard that's supposed to bypass the relay and force the injectors to work) still no go. It is a possibility I don't have the wires arranged right going to the relay ad I pulled them all and didn't label them (I know, I know). But going through a schematic I replaced them how they should be. The two big wires I linked were the yellow-blue and the red if I remember right.
Thanks a ton, John
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I would tend to agree with Robert - If you're absolutely sure it's getting spark then wouldn't all the talk about ignition components and connections be somewhat mute? Maybe I'm wrong.....
If it were my 1990 740, this situation would really point to the Radio Suppression Relay. I don't know how the 87 works, but I would think there's some sort of relay feeding power to the injectors. If you could find that and temporarily jump it or feed power directly from the battery to the + sides of the injectors you may just uncover the problem. Just my 2 cents.....
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So the injectors need a constant 12v supply then. That makes sense. So somewhere the positive is not getting to my injectors. I tried linking the two big wires to Radio Supression Relay, and still no go. So is it possible that somewhere between the relay and the injectors there's a short? Or is there another relay or fuse or something that might be toast?
Thanks, John
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Sorry John if I was too vague. What I was telling you are the pinouts of the control unit (fuel computer) and the ignition unit (black box near the headlamp.)
I'm not sure John if you have the EZK setup, but if you do, those pins on the computers must be connected together with wires.
if you remove the connector of the control unit, you will see tiny numbers etched onto it. Those are the pin numbers.
Make sure that the connectors that interface between the units have been properly insralled.
I do not know where they are or how they look, you might seek a factory wiring diagram for your model, Volvo's webstie is : www.volvotechinfo.com
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I have a factory service manual here for Ignition System EZK 116 K, aka B230FS john. I am not sure if this is your setup.
I see that there are 6 connections involved between the Fuel Computer and the Ignition Computer. pins 1 2 3 28 13 25 are involved.
Pin three connects with a "B-LW" colored wire to pin 3 on the throttle switch
Pin two connects with a yellow-white wire to pin 7 on the Ignition Unit, as well as to pin 1 on the throttle switch.
Pins 1, 28, and 25 connect directly to the Ignition Unit 17, 4, and 8 respectively.
pin 13 on Electronic Fuel Computer connects with a Blue and Red wire to the tempurature sensor.
Post back if you want a scan e-mailed to you tommorrow.
Post back anyway, we all enjoy your correspondence!
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A lot of that was pretty foreign to me. Are you talking about the harness connection to the ECU near the right foot passenger cockpit? So there's six connectors leading to an injector control of some sort? I was told something about an ignition control near the headlamps in the driver side from fender. Does that have anything to do with the injectors?
Thanks a million! John
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Did it run before replacing the harness?
Power stage sends volts to the coil, you said you have spark.
4 things to run, fuel, spark, compression, and spark at the right time.
--
Post Back. That's whats makes this forum work.
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I have spark, there is fuel being delivered right up to the injectors, but not into the cylinders, hence the dry plugs. I am pretty sure I have spark at the right time because when I throw some gas into the intake right before the fire trap, the vapors give enough to the engine to make it bark to life then die immediately. Even if there was a horrible timing sequence, if there was fuel coming to the cylinders, I would have some dieseling going on. It's really puzzling because the hard metal rail leading from the fuel line to the injectors is pressurized with fuel, even when the ignition is off. So the lines are holsing pressure as they should. The pumps turn off when the ignition is off as they should as well. So it got to be something else. What do you think? I'm pretty new at this stuff. I bought my first 1986 245 DL in 2003 and have done nearly all of the work on it it has ever needed. I came out here to Hawaii for school at BYUH, and this 740 is just killing me. I've never been stumped for this long.
Thanks for the support.
John
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Actually, the fuel pump relay(behind the ashtray)is a 2 part relay, runs the fuel pumps and also provides 12v to the radio suppression relay for the injectors. The ECU provides the ground. Like someone else posted, check for 12v to the injectors 1st.
You didn't answer if it started before the harness change.
--
Post Back. That's whats makes this forum work.
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No, the car died before I replaced the harness. It would run fine, then not start again. Hot and cold starts were a gamble, and it got worse and worse until it wouldn't go anymore at all. So I replaced the badly deteriorated harness.
Where exactly do you check for voltage on the injector plugs? (Those are the rectangular ones (4) with the stainless steel retaining clip right?)
Thank a million, John
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