Ignition/ pickup coil issues

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BigBlockMopar28

BigBlockMopar28

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Lean burn to electronic swap, coil wire spark when key is first turned to on is perfect, but coil wire spark when cranking was blue but weak and slow, maybe once every reluctor rotation. Distributor was questionable anyways so i got a new parts house one and put the old one back to rebuild later, dropped the new one in, crank tested coil wire, flawless at key on and cranking, adjusted for tdc, lined up dist cap, never even hit. Crank tested again, same deal, good when key is turned, weak/ slow when cranking. Box and dist runs from keyed hotwire thru the ballast before hand except for the coil +, there was already a connection there for the previous system. Keyed hot on drivers fender i tapped into for the box doesnt get power unless that keyed hot at the coil is connected. 87 w150 if it matters, is the truck burning through pickup coils? Really stumped here
 
Have you set the reluctor gap to .007 in the distributor???
 
I bet you are on the wrong track. Access the coil+ with a meter and see what you have with key in "run." Should be anywhere from 8--10V. Then crank it and WHILE cranking read the meter. Should have AT LEAST 10.5 or more. This voltage should be nearly same as battery voltage when cranking

The "run" (IGN1) CIRCUIT is ONLY HOT in "run." It goes dead in "crank."

The "bypass" circuit (IGN2) is usually brown, comes direct from the ignition switch, and connects to the coil+ side of the coil

Check/ clean/ replace the distributor connector, they are troublesome. Make CERTAIN the ECU has a good ground. Scrape the bolt holes and firewall, and use star lock washers.

Do the "in/out" on all the connectors several times to "feel" for tight and to scrub them clean.

Another test is to turn the key to "run" and disconnect the distributor. Take hold of the engine side of the connector (not the distributor) and tap the exposed terminal on ground. Each time it should make one hot "snap" spark. Test this with a WIRE coil wire, NOT a resistive one. Even low voltage wire will work, "rigged" to some sort of test gap. Spark should jump at least 3/8 or more usual, 1/2" nice and hot and blue
 
They run from zero to .030 without prejudice. They're not fussy like points. The ECU is just looking for a spike. The spec,IMO, must be for wear compensation in the bushing, and top driveshaft. I run mine at .011, and it happily revs to 7200.

OK, what I mean is; Mine runs from zero to .030,lol, during testing.
 
Here is a test;
Pull the D out, but leave the pick-up coil attached.
Near-ground the coil wire,and
Turn the key to run.
Spin the distributor driveshaft, and
A stream of sparks should issue from the coil wire.
Try not to set the car on fire.

If the pick-up is out of the D,you can test it by leaving it in circuit, with the coil near-grounded,and with the key in run, just pass any thing with iron in it, over the pole piece. Every time that item passes over the pole, it will generate one spark. Either direction, touching or not, within about .030.
For some real excitement drag it over a coarse file.

Next to the coil, that little magnetic pick-up is probably the most robust item in that system. The most usual pick-up failure in my travels, has been the wire where it passes out of the housing.
The lean burn pick-up is different from the non, and you will see it in the wire colors. For a SBM,you want the one with the Orange wire. I think the difference is strictly in the polarity. You can convert an LB to to a non-lb, by cutting and splicing it reversed.
The ECU must be properly grounded back to the battery.Clean case, clean body, special washers under the special mounting screws; whatever gets the job done
 
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Just to clarify, the old dist and new one are both for old style electronic, vacuum advanced, old one had the orange wire on the dist plug, new has blue on positive part of plug and red on negative on dist end of plug
 
If you have not, I would cut the system loose from the vehicle wiring and hot wire it direct to battery "to try."

It is rare, but not unheard of for this to be a "bad ECU" problem
 
BigBlockMopar28 said:
Just to clarify, the old dist and new one are both for old style electronic, vacuum advanced, old one had the orange wire on the dist plug, new has blue on positive part of plug and red on negative on dist end of plug
Click to expand...
I haven't seen the oddball colors.
The engine can be timed and will idle on either pick-up. But with the reverse-polarity one, as soon as you try to bring up the rpms, the system will randomly missfire and drop sparks. If you are watching this on the balancer with a timing lite, it's freaky the first time you see it,lol.
 
67Dart273 said:
If you have not, I would cut the system loose from the vehicle wiring and hot wire it direct to battery "to try."

It is rare, but not unheard of for this to be a "bad ECU" problem
Click to expand...
Ill try that, ecu and ballast is brand new but ya never know nowadays lol
 
I 2nd the suggestion to go basic and spin the distributor by hand with a spark plug tester on the HV coil wire. If your coil is from the "lean burn" setup, it might be a "ballasted coil", in which case I don't think you want the additional ballast in series. That shouldn't matter when cranking since the firewall ballast is bypassed. Kind of hard to follow what did and found since your post doesn't use normal sentence structure and uses inexact terms like "hit", "good", ...
 
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