phychotron

Thanks. I've got a 78 distributor and coil on the way. Was looking for a cheaper alternative from a junk yard but its probably better to just throw a rebuilt one on and spare any hassles from a worn one.

Finally posted it for sale if anyone was interested if checking out the listing... http://lazydayheadsupply.com/Chinook4Sale.php

13Swords

Smart thinking, given the age of these parts & the somewhat unknown condition of junkyard parts. Plus the A1 Cardone rebuilt part has a lifetime warranty to go with it. Excellent write-up of your for sale posting sir, best of luck!

phychotron

Got the distributor installed and everything wired up but its not turrning over. I pulled plug number 1 but its not getting any spark. I bought the igniter on ebay and was wondering if it might be the problem. Is there any way to test the igniter? I might just order one from another place and see if that fixes it. Any ideas why it might be this way?

13Swords

Without having more detailed info it's hard to say, but here's some diagnostic questions for you.

1. Is it "not turning over" or "not starting"? There is a difference between the two.

2. Does the battery have a full charge? Check with a voltmeter, it should be at least 13.7 volts. If it's below that charge the battery up.

3. Battery ground strap/wire firmly connected to battery & frame? It should be running from the battery to the motor mount on the passenger side. There is also another ground wire from engine block to the firewall for the body ground. Make sure connections are tight & clean.

4. Did you remember to ground the ignition module? It won't work at all if it doesn't have a good ground connection & this is usually the number 1 cause of it not working. The module switches your ignition coil on & off through the ground side. The module grounds through the round mounting hole on the W/G terminal side of it. You should see a round "tab" at the top of the hole. The most common way to do this is a piece of 18 gauge wire (or thicker) with a round eye lug attached to that point by using the mounting screw, with the other end of the wire attached to a good, clean ground point. I used one of the bolts that holds the voltage regulator to the inside driver's side fender well.

5. All wires to module on the correct terminals & firmly secured? Are you getting 12 volt power with the ignition switch on? Use a volt meter at the module end to verify. Check for loose connections, poor crimps or solder joints on wires to lugs etc. B terminal - 12 volt switched power from ignition switch; C terminal to ignition coil - (negative) post; W terminal to white wire from distributor pickup coil; G terminal to red (sometimes pink) wire from distributor pickup coil. + (Positive) terminal on ignition coil should have 12 volt switched power from ignition switch. Again, make sure the module is grounded well, as described above.

6. Plug wires in good condition & properly seated in the sockets on the distributor cap? Cap & rotor in good condition? Plugs properly gapped? Gap Spec is 0.032".

7. What ignition coil did you get, model & part #? Are you using the LX301 ignition module? If not what brand/part #?

8. Are you sure the distributor is installed correctly?
It can sometimes be easy to mess this up, even for those of us that have done several distributor installs. You may have to remove the distributor, rotate the engine to the compression stroke on #1 cylinder & re-install the distributor. Check out the video link above, it explains it better than I can here. Don't worry about timing on this; even with the timing set to 0 (Top Dead Center) the truck should still start & run if all else is correct. I personally set the engine to compression stroke on #1 cylinder & set the timing mark on the crankshaft pulley to 8 (8 degrees before top dead center) before installing the distributor. This is the stock timing for the '78 20R so once you get the distributor installed, it should be dead on.

9. A long shot - Maybe the distributor rebuilder didn't set the air gap on the pickup coil properly? Use feeler gauges to check the gap, with one of the blades of the ring directly facing the pickup coil (least space possible). The spec is 0.008" to 0.016", or 0.2mm to 0.4 mm. I have mine set at 0.012". If you don't have a feeler gauge for this you can use a dollar bill. The paper of a dollar bill is 0.004" so if you fold it into three layers (0.012") & it fits in the space with a little drag you're good. If not there is a hold-down screw on the pickup col you can loosen, set the gap & retighten the screw.

If all of the above is in order it should work. It usually something basic & simple. If you still suspect that the module was bad out of the box, you can have it tested for free at some parts stores (O'Reilleys, AutoZone, Advance, etc.)

phychotron

I"m pretty sure I installed the distributor properly, it went right in exactly how its explained. Its not starting, its cranking though.

I suspect the igniter because the coil was bunk too, ebay is an outlet for randomly acquired things. I got the coil you recommended as well as an SMP LX301.

The ICM is grounded,though I'll check to see if moving it helps. The sun went down while working on it and I'll be out on vacation for another 2 weeks before i can find the time to work on it again.

I didn't see any of the wire you specified. I just got 16g 2 strand insulated wire.

I have 3 wires on my + side of the coil. 1 switched wire from the ignition, 1 red wire randomly coming from my wiring harness and 1 wire going to igniter. - side of coil has 1 wire going to igniter, 1 ground cable to firewall. Had to build the wire. one wire was not hooked back up because it was connected to a bullet connector on the old ICM and connected to multiple wires at the - terminal of the coil.I'm going to work on getting that grounded again, but not sure if it needs to be on the - side of the terminal. The truck ran without it on the last distributor, it goes to the A/C somewhere.

13Swords

Thanks for the specific info, it helps. I want to jump on the 1 thing that sticks out to me.

You wrote "- side of coil has 1 wire going to igniter, 1 ground cable to firewall." I think this is your problem. There should NOT be a SEPARATE ground wire/cable going to the negative (-) terminal of the coil. Since you do have one there, you are essentially "bypassing" the module & it's intended function of switching the coil on & off. I will explain & I apologize in advance if you already know this information, but I want to be as complete as possible so things are clear.

Without getting too technical, the ignition coil is basically a transformer, turning 12 volt battery power into tens of thousands of volts (sometimes as much as 100,000 volts). It also has an iron core, which generates a magnetic field. The key to the coil working is what happens to this magnetic field when the voltage to the Primary side of the coil is turned off by ignition points or the igniter/ignition module, via the Negative (-) side of the circuit. When this happens, the magnetic field collapses & induces a current in the Secondary side of the coil, which then rushes out of the central terminal of the coil & goes to the distributor center post. Without being able to turn off the Primary side of the coil, no current will flow to the distributor, even with the coil "turned on" or still powered. It HAS to switch off to generate spark power.

The igniter/ignition module acts like a switch to do this, on the Negative (-) side of the circuit. It uses the Ground connection in the mounting hole (and usually the "base plate" part of it) as it's connection to Battery Ground. This then goes through a Power Transistor (switch), out the "C" Terminal & to the Negative (-) post on the Ignition Coil. It turns the Negative side on & off.
***By adding the Ground Wire/Cable from the firewall to the Negative (-) post on the coil, you are giving the coil direct connection to ground. No switching can possibly happen this way.

1st suggestion is to Disconnect (eliminate) the Ground Wire/Cable from the firewall to the Negative Post on the coil & see if she will start for you. If it works, that was your problem. If it will reach you may want to consider using that Ground Wire on that mounting hole, if you haven't already done so, & if it will reach.
If it still won't start you have another issue. I am not sure why you have three (3) wire connections on the Positive (+) side of the coil. Also, what's this "random wire from the harness" all about? The other two wires sound OK, but this one stumps me. I'd like to be sure it's also not causing a problem in the circuit. Also, what is the wire with the "bullet connector"? What does that go to? If it goes to the A/c somewhere as you say, it's likely a power tap for the A/C kickdown/kickup solenoid.

By the way, here is a basic, simplified diagram of the conversion (sorry, I just remembered I had it on flle):


As for the rest of it, in order:

Distributor - as long as you're sure. Don't know about you but I've learned to always back-check myself to make sure.

Ebay - Yeah, ya really gotta know what you are looking at there before you buy.

ICM Grounding - Not sure what you mean by "see if moving it helps". I just know that grounding it through that mounting hold with a wire to body or frame ground is the best way to go.

16 Gauge Wire - That's just fine. I specified the 18 Gauge because that's the thinnest wire to safely handle the Amperage loads & still have about a 20% safety margin. I did all the "electrical math" on this project when I first did it, because I didn't want a "melt down". Thicker wire is always OK for this as it will handle more current (Amps) than you will be running through it.

Meanwhile have a good vacation & drop another reply on the board when you have an update.

phychotron

Disconnected the ground multiple times when I was first diagnosing it, it didn't solve anything. I think I actually added it after it wouldn't start. Have it hooked up accordingly and I was testing the igniter voltage. The B and ground light up a test ight but the B and C do not when cranking the engine. So I picked up another LX301 from the local store, same thing.

I also put a spark tester inline with one of the cylinders and its not getting anything. Could the pickup in the distributor be bad? in theory I should be able to get spark if I turn the ignition on and manually turn the engine (or distributor outside of the engine) but its getting nothing at all. Checked resistance of the coil and its within specs. Wires all seem to be tightly in place.

13Swords

It sounds like a circuit problem but let's narrow a few things down first.

There should NOT be a ground wire from the Negative Terminal of the coil to the body or frame. There should ONLY be a wire from the Coil's Negative Terminal to the "C" Terminal on the ignition module (see diagram).

You haven't mentioned anything about the required ground wire on the ignition module itself. This is a crucial item & the setup won't work without it, and 8 times out of 10 this is the main reason for the setup to not work. This wire should go from the ignition module's "left side" mounting hole (the hole closest to the "W" & "G" terminals, see diagram above) to a clean & solid body or frame grounding point. It does NOT have to be tied into the ground from the Distributor as shown in the diagram; it can be it's own separate ground wire. The Distributor ground itself through it's mount on the head. I used one of the bolts that holds the voltage regulator to the inside of the driver's side fender as my grounding point for this. I also removed the voltage regulator completely first and cleaned off a bit of paint from around the hole in the fender to make sure the voltage regulator body made a good connection to body ground. After getting all this done I used my Ohm Meter to check for continuity. One probe/lead on Negative battery terminal, other probe/lead to mounting bolt on voltage regulator then end of ground wire on ignition module mounting hole. This way I could be sure the ground side was properly connected all the way to the ignition module.

Have you checked your other grounds on the truck? Given the age of the vehicle these may or may not be in very good condition, or you could have dirty/corroded/loose connections on them .On my '78 I ended up replacing the ground cables because due to age & fatigue to the copper, the wires themselves were offering too much resistance. You can check them end to end with an Ohm meter to be sure. They should read close to or at zero resistance. Anything 0.01 Ohms or higher & they should be replaced. There are usually 2 grounds on the "77. Ground Cable or strap from negative battery terminal to passenger side motor mount (frame ground), and engine block to firewall (body ground), nearest to driver's side rear of engine.

I would also use a Volt Meter to verify/make sure I am getting voltage at the ignition module & the coil, in both the "start" and "run" positions of the ignition switch (key). Your test light session sort of indicates there may be a problem there.

Related - That "1 red wire randomly coming off the wiring harness" thing still bothers me. What is it & what is it for? I also have 2 "red wires" from the wiring harness going to my ignition setup; one is switched power from the ignition switch RUN & one is switched power from the ignition switch START. If everything else is OK, your test light session might be pointing to the setup not getting battery power while cranking, which would mean you do not have the START side hooked up to it. Again, I'd use the Volt Meter to find the correct wire to know what I'm dealing with. That would also explain your not getting anything on your spark tester. Either the ignition module or the coil or both are not being powered during starting.

I very much doubt the pickup coil would be bad in a newly remanufactured distributor but if you want to check it, probe the 2 leads coming from it with an Ohm Meter. It should read 130-190 Ohms cold. You can also check the Air Gap between the reluctor ring & coil. With one of the projections on the ring lined up with the center of the coil, the gap should be 0.008" to 0.016" (0.2mm to 0.4mm).

phychotron

I had it wired like shown but it still wasn't doing it. Someone is coming to look at it today so i put the old components on and it fired right up. Gonna work on bench testing the system before I attempt another install.

The alternator actually went out before I attempted it. I also want to fix that before I try again.

the gap on the pickup was fine. random red wire from harness had no effect. There is another red wire with a similar clip near the coil that was never used for anything so I left it alone.

The tab on the side of the igniter was grounded, but when I try again maybe I'll make a dedicated ground to the distributor instead of the panel.

phychotron

Could the wire between the distributor and igniter be too high of resistance for the signal to properly trigger the coil?