Well fancy meeting you here.
Motor stopped running bout a half mile from the house but started right back up, drove home, put her in the driveway, no start this morning.
NO blown fuse this time, but the revolution counter isn't bouncing, when the key is turned.
Last time we went through this i had a bare wire going to the f/p that was blowing the #1 fuse, ergo no fuel no start.
What kind of horror is it to change the hall sender?
I have a a pick-a-part up the street with a couple of 740's about my year (87).
so I can p/u trial parts for a reasonable price.
Thoughts on this are sorely needed and greatly appreciated.
Paul

well i replaced the banged up wiring harness, i have appropriate voltages @ the harness, but no tach motion and no start.
Replaced the blue wire on the coil case it was nearly naked.
I'm done for the day, might look for another distributor, junk yard local.
I don't know hat else to do

Have you tested the hall sensor? You can do this test with the distributor out of the car.

http://www.brickboard.com/FAQ/700-900/ElectricalIgnition.htm#Testing_Hall_Sensor
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http://www.brickboard.com/RWD/volvo/1547450/740/760/780/stopped_started_start.html
per the FAQ

So your replacement distributor was bad?
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I have an 82 240 in the garage with the same symptoms, i went as far as replacing the hall sensor ( held on with two clips) after having replaced the distributor.
So I don't know if it's bad or not, except for the external symptoms. No tach bounce, no spark, and a known good power stage

It ran beautifully till,I attempted adjusting the timing, when it stopped dead.
I replaced the icu/ distributor harness (spliced in wire in much better condition). Readings at the harness are in spec.
I have a source for a used distributor, and will avail my self of it.
if this doesn't work I'm going to take the radio and tires and call a scrap yard.

I looked in my repair archives (yes I do save them), and I was able to get spark from the coli, and hear the fuel line charge, from jumping the appropriate leads on the harness.
Besides the obvious, that there is power going in, and no spark is being generated via the distributor, is there any way to make sure it's gone over, before I jam this thing down the vendor's throat?
The used distributor, i thought i had was vandalized before I could get back to it.
input as always is greatly appreciated.
Paul

Gave you this link before on how to test:

Full Hall Sensor Test: Undo the distributor connector. When the ignition is ON the Voltage between positive terminal (red lead -Nr. 3) and ground should be approx. 11V. Voltage between (blue lead - Nr.2; middle one) and ground should be 5V although if you put it on a scope you would see the sharp rise and fall from 12v to ground as the distributor rotates. Pulse frequency varies as rpm is increased. . Resistance between (black lead - Nr. 1) and ground should be close to zero Ohms. Undo connector from the control unit (above the brake pedal) and remove the sealing washers (plastic inserts on the side of the connector). Replace connector without cover or sealing washers.

- Disconnect the/red and blue leads from ignition coil. - Measure voltage between terminal 24 at rear of control unit connector (blue lead) and ground. NOTE: Connector must be attached to control unit. Switch on ignition. Turn crankshaft by hand. Voltage should indicate OVER 1.8V each time a vane passes Hall generator. Instrument should read approx."0" (0 - 0.7V) each time an opening passes Hall generator. The correct voltage is less than 0.7V or more than 1.8V.
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I appreciate the thought but this isn't what I asked.
Ive already done this.
What i really wanted to know is,if this is the , all i can do, and these procedures are final. I will crawl down the guys throat Monday morning, and get a replacement Distributor.
All you needed to say is"Yeah that's all you can do" get a replacement.

it lives
details to follow

Bought another new distributor (117 plus 2nd day air from MA.). Lo and behold it fired right up, ran a little crappy, so I did a little exploratory, #1 plug was black and sooty, replaced it, better but still that regular irregular miss, runs pretty well for the obvious misfire.
Checked the plug wires and other obvious misc related wires, to no avail. But did find that the throttle valve is not fully functional, and I will probably need an IAC in the near future.
So some time next week I will have a new distributor for sale,( will be getting a return new for the dysfunctional one) look for it in a Brickboard ad near you
TTYL
and thanks for all the help

Congrads. Your IAC. Yours is "take apart" and clean. Some you can't disassemble. You can also "ohm" it out to see if it is bad. Probably some general cleaning, IAC, throttle body, adjust if necessary.
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cam goes round and round
no spark
How catastrophic is it changing the distributor?

Yep it's the same car
1987, 740 turbo
No spark, cam is rolling around,
fuses are all good
How do i test the hall sensor in this car.
How much of a demolition derby is it to get the distributor out of its nesting place?
Just for Murphy's sake I put the original power stage back in, as it appears to have already been replaced. No joy but it''s one less question.
Thanks as always for your continued support.
Paul

I would first check if you have spark out of the coil. Just stick a plug wire in the coil slot, put a plug in it, lay it close to a metal area and see if you got spark jump. If spark, then suspect distributor hall sensor. Kinda hard to see, but check the plastic connector towards the base of the distributor. The wires have been know to crumble and ground themselves out. As far as removing the distributor, you need a 10mm gear wrench to remove the cap. The bolts have clip on the distributor so they won't fall out when you have them out. If you decide to remove the distributor, make a mark on the valve cover and the base of the distributor for re-install. Easier to replace the entire distributor because the hall sensor is riveted in place. Pretty sure the FAQs has an entire description on testing the hall sensor. You really need to become familiar with the FAQs. An enormous amount of info that members over the years have contributed.
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I have voltage to the coil but no spark, from it.
I am going to Pick-a-part in the morning, to pull a distributor and associated wiring with it.
I also have an 82 240 in the garage, with an ignition problem not unlike this.
On that year Hall sensor,
Can I still disconnect the harness from the distributor, and jump the ECU side harness to check for wiring issues?
I am assuming if I mark the distributor from the junkyard the exact same way I do my existing dist it should go in w/o a major battle.
I'm thinking i should set the timing, and mark the rotor, before i go swapping stuff around.

"I have voltage to the coil but no spark, from it."

Not sure why you are convinced it's a distributor problem. What you posted tells me your coil may be bad. Test it. The distri is murphy proof on install, it can not go in 180 out.
Tip: If you do pull your wires, mark them first. Lots of guys here have reinstalled them wrong relying on memory, me included.

http://www.brickboard.com/FAQ/700-900/ElectricalIgnition.htm#IgnitionCoilFailureandTesting
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previous replies to this question have indicated a questionable Hall sensor. Conventional wisdom implies, that the Hall Sensor assy replacement requires an immense amount of patience and eye hand coordination, neither of which I have in great abundance. So retrieving a used distributor, would seem the prudent approach @ this time.
My other concern at this time is the wiring , which was the problem with last weeks no start.
Does any one here have the Volvo wiring diagrams, for this car. I have questions, that could be easily answered if I knew where the various wires wires were (supposed to be)attached?
thanks for your help.
Paul

how/ where does the wiring harness for the 740 distributor/ hall sensor, connect /disconnect. The harness for the hall connector looks like it was JB welded into place.
I have found a distributor/rotor/cap on e-bay for $140, but currently have no earthly idea how to separate the Sensor from the associated wiring.
thanks as always
Paul

If someone glued it back in place it was because the original plastic connector was broken.

http://www.brickboard.com/FAQ/700-900/ElectricalIgnition.htm#DoesMyCarHaveaHallorRPMSensor

The plastic piece on the left side of the photo is the original connector. The wiring harness just plugs into it. That's what normally breaks. You use to be able to buy just the connector by itself, couple $. Pretty easy replacement with the distributor out.
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i've asked around at my local electronic stores and have gotten polite but WTF responses, concerning there being a mating connector available
So I have salvaged a harness,(ICU / Distributor) . In the process I followed the wires to the ICU under the dash over the brake pedal, and I can see no goo reason to go this far. The ground wire is wound around the power and neutral looks like it's also acting as a shield(not uncommon in microphones from the 60's). So the fix will be to splice the newer connector into the existing harness, The Ground I will just cut back far enough so I can twist enough together to tin, on both sides, leave room for some shrink tube, and solder it up. I'll add a little aluminum furnace tape to the RTV/shrink tube mix, to preserve signal integrity, and away we go.
I will get back to you as things progress

So apparently , I am going to need to replace the Sensor harness. To ease my angst about this Sisyphean torment, it would help greatly if I knew where the harness terminated,inside or outside of the engine compartment.
On my 82, it is part of an under the hood, harness, that terminates at the ECU.
So to save me the time of reinventing the wheel and the probability of doing something unintentionally ugly to the donor wiring, while extricating it.
Would some be so kind, as to share this with me?
I am changing to the name of the car to my first wife's (Vicki) as she had as many or more wiring and operational defects, that I didn't see till after I had the pink slip.
Paul

From the hall sensor, the wiring runs under the intake manifold(small shealth) to an area next to the idle control valve. It runs into a harness that also has the injector grounds going into it.(injector grounds bolted to the top of intake manifold(should be brown in color.)
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The previous owner super glued the icu harness and the hall sensor harness together.
I don't know if I can separate the two now conjoined wires w/o destroying the incoming harness connectors.
If the icu to to hall sensor terminates some where I can get to it and unplug it I won't need to pointlessly butcher another wiring harness.
I don't know if the wires on the ICU / hall sensor can be spliced and soldered.
I need to find a donor, where I can dissect a harness w/o having to worry about collateral damage.
When I find the terminus of the harness i can disconnect the old harness and run the new harness exterior to the existing wrapped harness w/o disturbing the questionable wiring in the harness bundle.
thoughts, guesses, and pictures are all welcome.
Thaks
Paul

Bought a distributor from E-Bay motors, for $138 shipping included, Ordered it Saturday, got it Tuesday(will buy extended warranty just because). Between the weather, my back and work schedule, I just installed it today.
First thing I was amazed that the Bad Bosch Boys actually made a Distributor that was easy to install, as in it only goes in one way, the dogs on the distributor are offset, so it only fits one way.
Put a timing light on it, and it was in range, like 12 degrees BTDC.
Boom fires right up, but it won't run over 40mph and if it wasn't a turbo, i doubt I'd get that out of it.
So the main problem was, the demise of the wiring in the dist.
I'll check the in tank pump tomorrow a.m. and just for grins i'll check the rotor while i'm at it.
So any ideas, what the current problem is ( i'm getting holy water tomorrow)
Thanks as always
Paul

Check all your turbo air hoses. Main one could be collapsing when getting into boost. Even with a failed intank pump, it still should run. Just the main pump will labor some.
Edit: Check the wiring to your knock sensor.
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is the 1988 (n/a) harness compatible with a 1987 turbo 740?

New spark plug wires, and it ran like a champ...........Wait for it......Till I was adjusting the timing, and it stopped dead, no bounce on the tach.
Removed the dist, and the connector (engine harness to dist) just sort of fell out of the distributor. That would be it I am supposing.
So tomorrow it is of to the pick-a-part in search of that harness. I will take various extraction tools with me, to see how close I can get to the origin of the wire.
It would be nice if I could splice and solder the replacement in. I am too big to cavorting around under the dash of a 740.
Ideas and comments welcome

My $.75 Haynes manual was waiting for me when I got home this evening.
I will delve into the FAQ in the a.m
If you say it's in there I'll look, then ask for what ever clarification needed.
It's easier if i get a consensus on the , like look here, do that, and I can spike my learning curve and avoid reinventing the wheel.
Thanks