4 cylinder not turbo. What color is the wire supposed to be to the temperature sender under the intake manifold? My insulation is shredded. Where does this wire go? What is the second sensor (brown wire) below it in the block for? My fuel injectors aren't getting any signal and so never open. Car will run on ether, smoothly even with the right amount. Fuel pumps ok, if i take hose off at rail, can pump fuel out hose by normal starting with ig switch. Spark works but maybe weak. I've replaced some other shredded wires between ecm and distributor, rest look ok there. thanks for any help

The yellow wire to the coolant temp sender (talks to the temp gauge) is one of the group from the gray 8-place connector on the firewall.

Not all the 8 places are used, unless the car is both gas and diesel. However, all the wires are subject to the insulation deterioration. Yellow, as above. Red to back of alternator, black to oil pressure sensor, blue-yellow to starter #50, brown to starter #16 (next to block).

All wires can be replaced and re-routed. Must keep the terminal ends from that 8-place connector, use a butt crimp connector. Try to keep colors as stock.

Good Luck,

Bob

:>)

you've pointed out a new pandora's box, I had not looked at that plug. All 5 wires at back of that plug have shredded insulation, and corroded separated strands of copper and 1000 ohm resistance between wires. Will these problems keep the car from starting? I have no wire at all plugged into starter 16 and this area is unchanged since car last ran. But I do have the brown wire at the firewall 8 place plug. You said keep the terminal ends. The similar female plugs I have are slightly too big so it looks like it will take a miracle fluxing/soldering job to salvage the originals.
thanks for your help
Joe

The terminal ends in the gray connector need to be re-used, as they fit into the pigeon-holes. Attach them to the new wires with but type crimp connectors. Cover the connector with shrink tubing, it will be weather proof.

The brown wire in place #8 which shows in the wiring diagram to starter #16, is part of the coil primary voltage supply, which system also includes a ballast resistor.

The system operates thusly: While the engine is operating after the starter is shut off, voltage to the coil is reduced a bit by said resistor.

While the starter is engaged, the brown wire carries full 12 volts to the coil, by-passing the resistor. Thus the coil gets all the battery can provide during a time when that voltage is reduced due to the load drawn by the starter.

My diagram shows the resistor to be mounted on the right inner fender, I have seen it on pre-1984 models on the firewall right side. It is a cylindrical shape, one end with one brown wire, the other end with two.

All the wires in the gray connector can be replaced, with the originals left isolated in place. They came to the factory as a single harness and were "woven" into the main harness. Other wires in the main harness can suffer deterioration due to time, heat, oily residue, etc., but not to the extent that those five do.

Replacing the five wires might, or might not, solve your starting problems. Try it first, however.

Good Luck,

Bob

:>)

thanks, you guys are keeping me from giving up in frustration. I've replaced the 5 shredded wires all the way from the 8 wire plug. Engine still cranks but doesn't start. My other wiring looks ok. I've cut off pieces of the shroud in several places.

However, my brown wire went straight to coil (according to ohmeter) not via the starter motor. I can't even find the resister you mention.

My yellow blue wire went to the spade on the starter solenoid farthest from block. There a second wire also with shredded insulation connects in the same connector as did the yellow blue wire which is still identifiable. What color is this second wire likely to be and where does it go? My manual's circuit diagram says this second wire should go to a cold start injector but I can't find any such thing that would allow any gas to get into engine other than the regular injectors. The spade nearest the block has and had no wire connecting to it.

I am not original owner but we drove it for 4 years. Then mostly parked last year. The wiring has a little evidence of previous work.

Understand your frustration! Been there, done that! Volvo did a horrible job of documenting the electricals in the green books for '83-84 models when they changed to the LH2.0 system used in US models. First, there is no ballast resistor, e.g., the brown wire does indeed go straight to the coil. Also there is no cold start injector as shown in the diagrams.

The Coolant Temperature Sensor wire is blue. The Temperature Sensor wire is yellow. The Knock Sensor wire is brown.

How do you know the fuel injectors aren't getting any signal?
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john

I disconnected the plug and stuck a xenon light probe in each of the two wires and get no flicker as someone cranks car. Where is the blue wired coolant temp sensor you referred to? I'm assuming the yellow wired one is in the head above the knock sensor that is in the block. Will the bad wiring to these sensors keep the car from running?
thanks

"I disconnected the plug "

I don't understand which plug you disconnected.

The Coolant Temperature Sensor is under intake manifold runner 3. Yes, a bad engine wiring harness can keep the car from running. That is why Volvo owners buy new (or used) engine wiring harnesses.

I suggest you visit Dave Barton's site. He sells new and used engine wiring harnesses made with the improved insulation. Go to
http://www.linkline.com/personal/dbarton/WireHarnesses.html#Used%20Harnesses
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john

The electrical plug immediately on top of the fuel injectors above the fuel rail. Has a metal spring clip on 3 sides.
Yes, I've seen Barton's web site. It's very helpful. I've pulled the shroud off the ignition harness and it looks ok except the oil pressure and alternator wires which I have replace that end of it but now looks like I'll replace those two back to the 8 wire plug you pointed out to me. The rest of the wires in the ignition bundle under the crankshaft pulley look ok. I do stare at the aftermarket manuals and circuit diagrams. I'm not sure I'm up for a complete replacement just yet. Maybe after I have replacement wires dangling everywhere but have the engine working.

The fuel injectors have power 100% of the time when the key is on. The ECU simultaneously grounds all of the injectors in order to open them and provide the correct amount of fuel to the engine. If the injectors are not cycling, you also need to look at the ignition system. The Hall effect signal goes to the ECU. Without that signal, the injectors will not open.
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john