hall sensor replacement Topic is solved

85 760 Turbo · Post by **85 760 Turbo** » 17 Jan 2006, 11:27

i have a 1985 760 Turbo(b230t 2.3L)165,000 i've had stalling problems for 4 months. all parts replaced on car are: intank fuel pump, external fuel pump, fuel filters and screens, air intake hose, pressure regulator, air mass meter, air filter, new battery and connections.while the car runs great when driving everyday; lots of power, no excessive engine noise, no leaks or smoking, everyday/every other day it stalls while driving, with no warning and no real clues as to what's doing it. the fuel relay is not original, it was replaced before i bought it and it has been tested numerous times and seems to be work fine. the tach. immediatly drops to zero with no hesitation or 'spurting' when it stalls. while trying to restart the tach stays on zero. engine turns but doesn't start, as if its out of gas. always restarts without fail, and is back to normal immediatly after restarting. i never have to wait more than five minutes, but i always have to wait at least 3-5 minutes, it will never restart right after stalling, and occasionally it won't restart immediatly after i shut the engine off, if only a few seconds have passed.please tell me this means something specific to someone. the hall sensor is what everyone keeps telling to replace. i've looked at it, the connection does seem to be loose where the plug goes into the distibutor. other than that the only other thing i can think of is the electronic control unit. i can't test it personally to see if it working(the ecu) so it's rplace it or trust it. should i just replace the hall sensor? if someone feels sure of what i should do, good advice would be much appreciated.

LaRy · Post by **LaRy** » 17 Jan 2006, 13:54

It sounds like the Hall-sensor! It is typical that the tach drops to zero while running. I have had a Hall sensor problem in my 740 from 1986. Your discription of the problem is exactly the same as I had. My car was sometimes stopping almoste every day and then it was sometimes working for several months without problem.
Try this as an experiment: When the engine is dead, shut off the ignition and loosen the wire harness from the ignition amplifier. Put the wire harness back and check if the engine will start right away. My did, but don't ask me why it helped. This is just a test, it will not "repair" the Hall-sensor. What I mean is that if it works, you will be absolutely shure that it is the Hall sensor.

Hall sensor problem is typical for Volvo's manufactured in 1985 and 1986. The ignition amplifier is also a weak component, but if I remember right, that one was more causing problems when trying to start the engine again after switching the engine off. The ignition amplifier never stopped my car while running but the Hall sensor did!

I am a lucky guy now, and the engine has now been running reliable for the last eight years since I changed the Hall sensor.

Guest · Post by **Guest** » 17 Jan 2006, 18:50

i had the same problem 1988 740 gl I got my hall pickup from fpcgroton.com as I remember it was $90 i also got the seal and oring for the distributor. mine just crumbled when i took it apart and i had evidence of oil in dist.

Harlangesq · Post by **Harlangesq** » 18 Jan 2006, 20:14

I also have a 1993 940 wagon. the tack drops - If
I pump the gas nothing happens and car stalls.
It wont start up . Then it takes a few minutes and starts
up with no problem. I have gone weeks without it
happening then it happens all the time

Does this car have a Hall sensor?

Guest · Post by **Guest** » 19 Jan 2006, 15:22

i think the 93 940 has a 'speed sensor' behind the cyl head in the bellhousing. it does the same thing (it is also a hall pickup) and has the same symptoms when it fails. it is easier to change. look and see if the insulation is failing on the wires back there.....you can check for pulse with a logic probe on the signal wire (probes cost 10-30$) if you dont have a distributor you have a speed sensor.

turbo no/go · Post by **turbo no/go** » 27 Jan 2006, 19:23

the hall sensor turned out to be the problem. the wires had gotten worn over the years and the housing had broken and was just hanging from the bottom of my distributor, exposing the wiring. i found a distributor for not much more than a new hall sensor, and my points and rotor were pretty worn anyway.problem solved.