I have an '89 dodge van with a 318.
The Hall effect sensor in the distributor is a good guess. It is easy to replace, on my van, since I can sit in the driver's seat and do so.
You do not need to remove distributor, but perhaps it might be easier where it is located in your truck.
If the fuel pump is turning on, the ASD relay is fine.
Before I would attempt to get to the distributor on your truck, I would suspect the connector at the engine computer, specifically the 14 way connector.
Technicians prior to, or perhaps early in my ownership, pierced the insulation of the wires close to the base of this connector. Eventually many wires corroded out and broke.
One of the wires that is on the end of the connector feeds 9 volts to the other circuit board within the computer casing. If this wire is compromised, the engine will crank all day long, and never start, because of no spark.
Try wiggling this 14 way connector with the engine ignition to run, not start, then grab this 14 way connector, and wiggle it and the wires leading to it. If you hear the relays click on and off, BINGO.
Other things which might be helpful if this has no effect, is that mine has a bunch of fusible links stuffed behind the brake booster. One of these is for the engine computer.
Does the check engine light on the dash illuminate when key is turned to run, not start?
If so then you can pull computer codes by turning key on and off 3 times, leaving it to on the third time. The light will go out and start flashing.
2 flashes a pause and 4 more flashes is a code 24.
Expect to see a code 12
Expect to see a code 55
Any other codes can be found online under mopar OBD1 codes.
If the CEL does not illuminate when key is first turned on, check the bulb, it is a 194.
If a good bulb is known to be installed and still does not illuminate then the ECM is either bad or not getting power.
Not getting power is a blown fusible link, or a bad ground. Mine is grounded at the base of the coil. I have no idea about a truck.
I would suspect if relays are clicking and the asd and fuel pump work, the ECM is getting power.
On My engine computer, the 14 way connector was my nemesis for years. A couple of get me home fixes consisted of drilling through the back of the connector through the socket, stripping the broken wire, and inserting it through the connector so bare wire got compressed inbetween pins and socket. Over the years I did this to 4 separate wires. Each wire I did this to, later caused the solder joint on the circuit board where the Pin is fastened, to break and would cause stalling, or 1 fuel injector to not fire, or my alternator to not charge, or any combination of those. changing pressure on this connector would allow restarting and driving for a little while longer
I got a 14 way connector from a Dodge caravan in a junkyard and cleaned it up, and spliced it in, but my issues returned shortly, stalling and a no start, or no charge, or just one injector.
Later I acquired a 140 watt solder gun, removed the ECM from firewall, pulled the circuit board from the ECM casing, pulled the secondary casing off of circuitboard. Removed silicone potting from back of 14 way connector, cleaned it well, flux'ed it, and reflowed and added some solder to all 14 Pins and covered it with liquid electrical tape.
I was reluctant to try this myself, and now chide myself for this reluctance.
That was 3 weeks ago. No stalls since. it would have stalled by now. I consider it fixed.
One other thing I've got to Stress is the connector condition. I had used various tools to clean my 'new' junkyard connector along with 3/4 a can of CRC qed cleaner, and assumed they were pristine No more Dielectric grease, no particulates just Clean looking. I was wrong. Later I acquired some Caig Deoxit d5 spray and got this onto pins and sockets. The cotton q tips I used to buff the brass pins turned black. The precision q tips I used to clean inside the sockets, turned black, and both sockets and pin mating surfaces started gleaming like oiled gold or oiled chrome. where they were like white or clear 220 grit sandpaper covered beforehand.
They were this oxidized despite a liberal application of Dielectric grease since 1989!
There are also little tangs inside the sockets one can bend inward to further ensure good tight connection between pin and socket.
Anyway after I did this, as well as applying DeOxit D5 and then DeOxit Gold or DeOxit Shield to every sensor connector, in my 14 years of ownership of this van, it has never run better. the throttle pedal is more responsive and it feels like I took 500 LBS out from the Van as there is more power as well.
My theory is that substandard connections caused not quite 5 volts to reach the sensors from the ECM, and poor contacts at the sensors did not allow a true representation of the sensor's output back to the ECM so it could determine the best air fuel ratio and spark timing. My 02 sensor, Map, and Throttle position sensor connectors were horribly dirty, despite being encased in dielectric grease the entire time.
I now Consider Caig D5 to be magical electrical juice, and no electrical connection I ever remove ever again will not receive a blast of this product, followed by Deoxit Gold or Deoxit Shield to protect the longevity of those cleaned contacts. I'll use dielectric grease to prevent moisture intrusion, applied to the exterior of a closed connector, but never again will there be dielectric grease stuffed into the connector then the connector reseated.
I think ALL computer controlled vehicle would benefit from a cleaning with DeOxit D5 on the computer and sensor connectors. I went a bit nutty scrubbing the pins and sockets with mini bottle brushes q tips and precision q tips, but the product is designed to just be applied, excess wiped off and then have he connectors reseated.
Lemme know how these ideas work out for you, and best of luck.
