82 W150 no spark

Well, it's been a loooong time since I've been at this group! Of course, I need some help.

82 W150, 318 2bbl, no lean burn. No spark. I have voltage at both +/- at the coil, pull the coil wire of the distrib and hold near ground and still no spark. Replaced coil (2 different ones!) and coil wire...still no spark. Also replaced ballast resister and ECU (I always carry spares). I even ran a jumper straight from the ballast resister to the coil + (thnking a bad wire) and still nothing.

I am going nuts! How can I have no spark when there is voltage at both terminals of the coil? PLEASE...any ideas??

Reply to
CordobaMan
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If this is the standard Mopar electronic IGN system, check three things.

Ballast resister: You should have .5 ohm resistance on one side, 5.0 on the other, wires disconnected.

Harness to the ECU (five pin connector with phillips screw) must be disconnected while ign is OFF.

Pickup coil: resistance across this should be 150-900 ohm, measured at cavity 4 and 5 in the harness connecting to the ECU, 1 being in the pointed end. If it fails, repeat test at distributor connection, if its good, suspect wiring, if bad, replace. Air gap is set using a brass or plastic feeler (NO steel) to .008".

2 3 1 4 5

ECU Harness: IGN ON....Cavity 1, 2, and 3 should show battery voltage +/- 1 volt.

Check ECU ground by finding no resistance to ground on number five pin, 1 is in the pointed end. A no ground condition when ground is known to be good indicates ECU failure.

3 2 1 5 4

Tips:

A bad ballast resister can cause a crank but no start conditon, and cost very little. ALWAYS carry a spare in the glove box as insurance.

A pickup coil can do this, and it may also cause a hard start when engine is warm. NEVER use a steel feeler to set airgap, as it magnetizes the reluctor, causing a no start condition. Brass feelers are available from KD tools, among others, sold in bubble packs at auto parts stores.

The ECU is usually not the cause, unless it fails to ground. Check ground by making sure bare metal is on both the case and the mounting point on the truck. An ECU cost around $25 IIRC, and is also cheap insurance.

Biggest tip: If you don't already, get a cheap but decent multimeter, they are indespensible.

Reply to
Max Dodge

Hey Max--Nice to see you're still around... Appreciate the response, results of your tests below.

Max Dodge wrote:

One sided version, OK, just replaced anyway.

259 ohms

12.6V at 1 & 2, I have no pin 3 (mine's the 4 pin ECU)

No continuity between pin 5 and ground. This is with my "spare" ECU.

I have voltage at both +/- of the ignition coil. How can I get no spark? Even taking the distrib out of the pic and holding the coil wire near ground, I still get bo spark.

The truck ran fine last weekend. Parked it, and it sat untouched for a week. Now I have this. Strange...

Keep the ideas comin'!

Reply to
CordobaMan

Hey Max--Nice to see you're still around... Appreciate the response, results of your tests below.

Max Dodge wrote:

One sided version, OK, just replaced anyway.

259 ohms

12.6V at 1 & 2, I have no pin 3 (mine's the 4 pin ECU)

No continuity between pin 5 and ground. This is with my "spare" ECU.

I have voltage at both +/- of the ignition coil. How can I get no spark? Even taking the distrib out of the pic and holding the coil wire near ground, I still get bo spark.

The truck ran fine last weekend. Parked it, and it sat untouched for a week. Now I have this. Strange...

Keep the ideas comin'!

Reply to
CordobaMan

Ok, I see you have:

You MUST have continuity here. No ground here and the system does not work. One of two things cause this, bad ECU, or bad ground. On an 1982 truck that sat a week, its possible rust has broken the ground connection. Not sure what you mean by "spare", but the one on the truck running the system must be grounded.

The only other possibility is wiring being broken somewhere. I have a 1975 FSM, which shows the typical Chrysler electronic ignition system, but if you find a 1982 FSM, that would be better. Then you can check all circuits for continuity using the factory wiring diagram.

However, if I had to guess, I bet the ground is not working due to rust.

Reply to
Max Dodge

Easy enuf to run a jumper from the ECU body to the -bat terminal...will try that in the AM. THANKS.

Reply to
CordobaMan

Even easier to pop it off the firewall (or where ever) and clean the rust from both surfaces.

Reply to
Max Dodge

You have +12V on both sides of the coil because there is no ground available. The ignition works by switching the ground on and off on the coil primary and yours is in a switched off mode. I don't remember what type of transistor it is using so this may be normal when the engine is not cranking and if so would indicate either a bad pickup coil or reluctor (star shaped wheel in the distributor) otherwise it could be a bad connection between the coil negative and the ECU. It could also be that the pickup coil is loose and has moved to far away from the reluctor to send a strong enough trigger signal to the ECU.

Reply to
TBone

He'll have 12v on both sides because the switch isn't inside the coil. Since he has voltage on both sides of the coil, its an indication that the primary side is good, since it should have complete circuit through it. Resistance according to spec should be about 1.6 to 1.8 ohms for Prestolite and 1.4 to

1.55 for Essex on the primary side.

This would be found during testing by looking for battery voltage on the #2 cavity on the ECU connector. This comes from the ignition switch. Switching is inside the ECU.

All of which can be found with the tests I described. I'd bet on a rusted ground for the ECU, or a pickup coil failure, assuming all wires are still in good shape.

Reply to
Max Dodge

OK. My spare ECU must be dead. No continuity between pin 5 and it's body. The "old" ECU does have continuity between pin 5 and its body, do I wire-brushed the mount, bolts, and firewall. Good continuity between pin 5 and ground now. Still no start/spark.

NOW...I noticed that there was some ooze on the firewall starting directly under the bottom of the ECU. Also a rusty spot on the ECU at the same spot.

I'm on my way to the parts store for a new ECU unless someone has another test to run first?

THANKS ALL!

Reply to
CordobaMan

No Go with the new ECU..and it's cold and snowing like mad. Obviously, thowing parts at it isn't the answer, so I'll have to find my gremlin in the wiring somewhere...

Reply to
CordobaMan

According to the FSM, the only other thing that can be wrong is the coil. The FSM actually suggests swapping out the ECU and then the coil if the new ECU doesn't work. Beyond that, ring out the wiring and see if there are any shorts. Given that I'm looking at 1975 info, you should find a 1982 manual if at all possible.

Reply to
Max Dodge

Did you try replacing the pickup coil in the distributor or at least check for continuity between the two pins coming from the distributor?

Reply to
TBone

What in the hell are you talking about Max? The coil not being grounded is the ONLY reason that he is getting 12V on both sides. You really need to pick up a little electrical theory here dude.

If the internals of the coil are ok or completely shorted he will still get

12V on both sides if the negative terminal is not grounded so getting 12V on both sides of the coil only indicates that the coil is not open, not that it is good. It also indicates that the coil primary is not grounded at that point which may also be normal when the engine is not running. Your resistance measurement is the only way to tell if the primary side is good.

I think that I already said that but it is the ground that is switched, not the hot side.

I doubt that the ground on the ECU has anything to do with it as he has already replaced it and simply removing and retightening the ECU should have cleaned up that ground enough to work. It could be a pickup coil failure or a wiring problem but I doubt much else.

Reply to
TBone

Part of the test procedure that I listed for him does exactly that. It does not have perfect continuity, and I listed the resistance value as well.

You awake and ok?

Reply to
Max Dodge

And you need to look at hte wiring diagram. Coil on this set up is fed from the ignition switch, so its hot on both sides unless it has a break in the windings. It is switched at ground (you knew that!) and as such will be hot on both sides no matter what the switch position is.

Correct, but the voltage reading on both sides indicates that the circuit (not the coil) is functioning as it should.

Precisely why the coil will have 12v on both positive and negative terminals.

Personal experience tells me you could be wrong on the rust issue. Test results posted by the OP tell me you are wrong on the pickup coil.

That leaves coil and wiring issues, as I stated previously.

Interesting idea... test the coil while cranking, see if the ign switch feeds 12v during cranking as well as "run".

Reply to
Max Dodge

Just because you told him to do it doesn't mean that he did so I asked. Are you awake?

Reply to
TBone

I am aware of the wiring Max and if you understood it you would realise that it is impossible for 12V to be on both sides of the coil at all times. When the switch is "on" or conducting, the voltage on the negative side will be just about zero as the coil will drop the voltage and for that matter, even the positive side will not be at 12V due to a voltage drop from the ballast resistor.

How do you know? If the circuit is not conducting and never does, then something IS wrong and that 12V on both sides means little, only that it is not completely dead.

You need to do a little review of a simple circuit to see how wrong you are here. If one side is grounded, then there will be no measurable voltage on that side so during the non-conducting phase you would be correct but during the conducting phase (coil build up) the ground side has to be zero.

I could be but I doubt it. As for the pickup coil, since he replaced everything but the pickup and reluctor, it looks like the most likely cause. If it is a ground issue, just put a continuity tester on one of the bolts holding the ECU and the other side on the negative of the battery. If he has continuity, then he has a ground, simple as that.

You will never get 12V when cranking as the starter motor draws too much current. That is why the ballast resistor is bypassed during cranking to boost the voltage up as much as possible. What he really should do is put a dwell meter across the coil and crank it. If he gets a valid reading, then the primary side of the circuit is ok.

Reply to
TBone

I got about 6-1/2 volts at the prime coil + while cranking...measured before I replaced the coil (and not since). As far as it being the PU coil/reluctor, those are "after" the primary coil and I am not getting a spark out it when holding the coil wire near ground during crank.

Here's a scan from the FSM of the wiring diagram:

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Note that I have the SINGLE pickup system in my distrib (the diagram in the book is for the dual style, however everything else is the same).

As soon as the wind/snow dies down I'm going to start the FSM troubleshoot proceure all over again, fresh.

Reply to
CordobaMan

Yup, I read his reply where he listed what he did in reply to my post.

Just checking.

Reply to
Max Dodge

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