I am about done chasing this problem. No start; no spark; no fuel pressure; fuse # 11 not engergizing (even though the fuse is good) ( # 11 controls the in-the-tank-fuel pump AND the Oxy sensor according to my wiring diagram). And the engine cranks over strongly, but to no avail.

I have not seen a problem quite like this described here.
To date I have:
Checked battery, and cleaned terminals, and ground connections-did not fix;
Changed out the ECU (the Fuel injection computer in the passenger footwell)-did not fix;
Changed out the Fuel pump relay -did not fix;
Changed out the Igniton module-did not fix;
There is Voltage at the coil and the Halls Effect terminals are 12 volts; 5 volts with a good ground;
I hear and feel the FPR click;
I have no indication of spark using a timing light.

I have NOT replaced the engine control unit, and I never see much discussed about this computer on this site, but the wiring diagram clues me in that it might be involved.


This had been an ongong problem, intermitent, and now finally, seemingly fatal!

Can anyone provide a clue as to what is going on, or if the Engine computer is worth a shot, or how fuse # 11 is controlled?
IF you made it through this long post, thanks for listening,
Linc

It was 1/2 off day at my local Pick-N-Pull--so I pulled a clean-looking distributor (took the coil, fpr, ign module, fuel injection relay, ign wire set and ecu just in case or for the future). I found my Halls Effect molded plug was broken inside the dist after taking it off, with wires apparently shorting out. THe replacement part had this kitty purring right after the install. I'm making myself a note about this episode!

Thanks everyone for narrowing this down for me.

Go to www.stepbystepvolvo.com for a free diagnostic guide to 740 no-starts.

Hi Linc,

You say:

1) "no spark; no fuel pressure" and "I have no indication of spark using a timing light".
• With one exception, no spark always means no fuel, because the FI system is dead without timing pulses from the Ignition CU.

2) "I hear and feel the FPR click"
• Your diagram should show two coils in that relay. What you hear is the "System" relay that (usually) always clicks on when the Key is turned. The "Fuel" relay depends on the ECU, which in turn depends on the ICU pulses mentioned above.
.
3) "Can anyone provide a clue as to what is going on, or if the Engine computer is worth a shot, or how fuse # 11 is controlled?"
• Fuse 11 gets +12V when the Fuel relay is energized (pink wire from relay 87/2).
• I don't know what you mean by the "Engine computer".

I think a failing Hall Sender (aka switch or sensor) is the most likely suspect. I'll see if I can find any diagnostic info on that in the 700/900 FAQ. If I find anything and come back with an edit/update to its FAQ location.

EDIT: Lots on the Hall switch here:
http://www.brickboard.com/FAQ/700-900/ElectricalIgnition.htm#Testing_Hall_Sensor
But with the cam-driven distributor, it seems like swapping in a used unit is the way to go.

Bruce


--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

I am not sure if this is logical based on your observations, but is the fuel injector relay and its harness plug up to snuff? In the event that fails, I think one has spark, fuel, air and a no start.

Does the twelve volts going to the coil fluctuate when you crank the engine? Check the coil HV wire for continuity. If OK try checking if there's a spark generated by the coil HV wire.

I got home early enough to check the continuity of the HT coil-distributor wire and there wasn't any. Not sure if this is conclusive, however, as it is one of those "carbon" filled coil wires. But I'll change it out with a new one tomorrow. I didn't have time to check the other things that you both posted, but I will tomorrow or over the weekend and will post back.

Thanks...