The Stovebolt Site Forums The Shop Area The Electrical Bay HEI module or coil Problem?? not running

Hey Gents,

Well I have incountered my next problem. we drove the truck about 2 weeks ago, then last week caroline wanted to go somewhere. the truck would not start.
So here is what I know: ''lucinda'' http://s67.photobucket.com/albums/h298/1951otter/?action=view&current=4495365-R1-004-0A_1.jpg is our 51 w/ a 292, I did a ground up/ rebuilt several years ago, almost new everything. 12 volt system /alternator, HEI w/ coil in cap, three wires from control module to cap, key switch start, #10 gauge wire from starter to key switch, #10 from key to HEI, ALL wires crimped & solder connections w/ heat shrink.
Last Sept. we had no spark, so no start. I tested the coil then and it was duff, so I bought a new coil, replaced it & life was good. We didn't drive her much over the wet snowy winter.

so now I have no spark again.

Tested the coil yesterday and all is good on that side of this equation. So I bought a new control module at 'flaps' yesterday and installed it, including the heat transfer di-electric paste. my thinking is, that's the other side of this equation, it must be faulty. That part I have not replaced as new. She then started but ran for about 3-5 seconds and died.
Again I have no spark !

What could be the possible cause, [I believe inside the ignition system] that causes this puppy not to start ???

I'm back in autoshop 101 again.

jim

Have you checked the pickup coil, the one that surrounds the shaft? Its wires move with every motion of the vacuum advance, and they're subject to breakage from millions of cycles of movement. Disconnect the 2-wire connector from the pickup coil to the module, and check it with an ohmmeter while moving the wire harness around. It should not go open-circuit at any time. Then, connect a low-scale AC voltmeter to the connectors, and crank the engine. At cranking speed, you should see at least 1/2 volt AC. The faster the distributor spins, the higher the voltage will be. If it fails either test, replace it. You'll need to remove the distributor shaft to do that- - - -there's a roll pin through the gear at the bottom of the shaft. Be sure to memorize the assembly of the gear, the shaft, and the thrust washers- - - -it's possible to reassemble things wrong. Also, you'll probably need to use some carburetor cleaner on the shaft- - - -sludge builds up and makes it hard to pull through the bushings.
Jerry

HRL has a good point. Another thing to check for is the ground term. There should be 3 terms. in the cap/coil that the 3 wire connector plugs into. Sometimes when a guy changes the cap he doesn't transfer the connector under the coil to the new cap. It runs that way but eats up components.

My running buddy put HEI coil not in cap (MSD) in a 350ci. First pickup lasted a couple of months. Second one lasted a couple of days. At our FLAPS (hot rod/streetrod type store) we found out that MSD was specifying the wrong pick up. After all that was strightend out his coil went out, OEM replacement went out also. He now runs a GM race coil (blue one) I got at a swap meet for five bucks and has had no futher problems. We also put in a resistor to cut the current to the coil even through the instructions said it wasn't needed.

I just love learning all kinds of things.
when I posted this problem I only said what I did and nothing more without feeding into or guessing .... whata shoulda mighta done.

Big Thanks for the replies gentlemen, ALL ways a never ending learning process.

OK

I removed the distributor and checked the 3 wires from the plug to the control module and internal condenser plastic block. these three wires go to an internal ''plastic block'' that has a condenser on one end and two connectors on the other end.
> One wire goes to the condenser [or noise suppressor?] via a small tab that when screwed down, grounds the condenser to the distributor body.
> The other two wires go to the connection that goes to the control module.
> these are all FIXED connections with coded wire connectors ie G =green, W = white as written on the control module to correspond to the colored whres from the pick up. the other side of the control module is fixed connectors and can not be swapped.

I removed the plastic block and put my VOM to 'ohms sound' mode, always check the VOM for it's function first, I heard that i had continuity. When I checked all three wires I moves the 3 plug end and plastic block around thus moving all the wires around. The continuity check was good on all three wires. I separated the condenser from the tab and checked that NO connection was present when I touched each of the wires at the 3 plug end to the ground tab. I then checked that none of the three wires at the 3 plug end made connection to the condenser [or noise suppressor?] housing itself being separated from the tab. So that tells me that the condenser is NOT connected or shorted to any of the wires through some fault. Just for cause I removed each wire solderless connector [one at a time ] and scraped the metal to show a good clean metal making a solid connection when it was plugged back into the coil assy. double checked the solderless connector tab so it would not back out of the plastic plug holder when it was plugged back in. I did this for ALL solderless wire connectors. I also scrapped the area where the screw touches the condenser [or noise suppressor?] hold down and just under the condenser on the distributor body so when the screw is tight it makes a good solid contact. I took the distributor to my work place mechanic and we checked the VDC of the pickup. the faster we spun the distributor shaft the voltage increased. The shaft spins freely so no gum was detected on the shaft bushings. The two wires that are connected to the pickup that plug into the control module look good. No black arc marks, no power flash residue, no missing insulation on any of the 5 wires i inspected, all were flexible and showed no signs of cracked insulation w/ tight connectors. so far this distributer looks to be in good shape.

she would NOT start after I replaced the distributor back into the engine block and plugged all the wires back together.

Tomorrow I'll have Caroline crank the engine over again and i'll double check for spark to ground.
With the key turned to ''on position'' I have 12.0vdc at the battery and a slight voltage drop at the HEI red coil wire. I'll scrap the battery and starter terminals /lugs tomorrow after she gets a good trickle charge tonight cause she's been sitting so long.

Then I'll retest the coil ........................ again.

Did i miss anything ??

Jim

Do you know what the control module looks like electrictally inside? In other words, diodes, transistors and such? You know to reverse the ohmmeter leads for checking diodes, and transistors (that foward and reverse bias thing) right?
A log of guys buy a spare module for both testing and keep it in the truck toolbag for roadside repair.

i have NO idea how to check a control module.

Some auto parts stores have a module tester, but it sounds like you've got a bad module. Here's one thing that can happen- - - -an open-circuited spark plug wire can cause the coil high voltage (over 50,000 volts) to fire through the insulation in the coil windings and hit the 12 volt primary winding with a shot of very high voltage. This can cause repeated module failures, often after a very short period of running the engine. Modules just aren't made to handle spark plug voltage. There's no test for an internal arc-through- - - - -all the ohmmeter checks will be normal. If in doubt at all, change the module, coil, and plug wires at the same time. The normal resistance for a plug wire is up to 1,000 ohms per inch, so an 18" wire can have up to 18K ohms of resistance and still be good. Plug wires that measure up into the meg-ohm scale, or show a complete open circuit need to be replaced.
Jerry

Both of my modules check out OK. I forgot to do the tug test on the pickup wires, they appear to be OK, the cap does not look like it has been compromised with a crack allowing the HV arc to pass through to the metal on the rotor.

i will replace plug wires today w/ my extra set.
i guess i will start replacing one item at a time???
pretty lane way to shoot trouble

success

would you believe
i don't but wow what a wild answer & how it was found

ok
here is what i found:
stick w/ me on this..........

the coil ground wire [all three] is/are about 1.5'' long. i had it placed under the cap [remember it's a coil in cap setup], with this cap the coil is held up inside the cap by 4 brass furrels. these furrels push into the 4 holes that the screws also go thru and are a pressure fit into the plastic hole. when you remove the 4 screws and lift off the cap the coil is still attached to the plastic cap. the thought was when this was altogether the coil was hanging down and the weight of the coil left a gap and for ?+*#@?? reason & the brass didn't make contact!! :mad:!!! i had the solderless ring terminal end touching the brass furrells as it was pushed into the cap, LAST, between the plastic and coil frame BUT still ''touching the brass ???? HUMMMM NOT !!

what i should have done is have the ground ring terminal end first, like this photo shows, where the larger part of the brass makes better contact w/ the ground ring terminal.

http://s67.photobucket.com/albums/h298/1951otter/?action=view&current=IMG_1198.jpg

all HEI's have a bent piece of metal that this brass furrell and coil frame comes to contact & grounds to when everything is screwed down snug. appearantly there must be some sort of a gap in my cap where the plastic and coil frame touch and for some strange reason the brass furrell did not complete a circuit!!!!! WOW it did not allow a solid ground to the center spade when it was plugged into the three wire HEI coil/ control module plug.

http://s67.photobucket.com/albums/h298/1951otter/?action=view&current=IMG_1195.jpg

i discovered this when we had it all apart and made up a series of wire clips so we knew just what was touching what.

http://s67.photobucket.com/albums/h298/1951otter/?action=view&current=IMG_1193.jpg
http://s67.photobucket.com/albums/h298/1951otter/?action=view&current=IMG_1191.jpg
http://s67.photobucket.com/albums/h298/1951otter/?action=view&current=IMG_1190.jpg

this photo shows a couple clips to ground and a 12vdc hot wire

ADDED INFO: as far as the bent piece that actually grounds the screw, the coil frame to the bent metal piece that is the center spade of the three spade wire connector to the distributor plug, i filed the end to get to bare unplated metal and added a dab of soft solder to build it up and create a good contact to the screw and brass furrel when the cap was all put back together. this we cannot see when put together. the soldered ring end is where the brass furrell is next to in photo.

http://s67.photobucket.com/albums/h298/1951otter/?action=view&current=IMG_1197.jpg

the coil was not grounded in the right/best possible location .... go figure
thanks guys
WOW

"The devil is in the details"! The reward for fixing it ourselves is that great feeling of satisfaction and the cold can of brew for a job well done. You are to be commended for "staying the path", something that is all too lacking in this throw-away world in which we now live.