Timing light not working on GM HEI Dizzy
Thread Starter
Heel & Toe
Joined: Jan 2011
Posts: 16
Likes: 0
From: Niles Ohio
Timing light not working on GM HEI Dizzy
Having a problem with a new timing light I picked up.
Actron CP7529 http://www.summitracing.com/parts/ANM-CP7529/
Reads RPMs accurately of #1 plug wire but timing is waaaay off. Timing line on balancer doesn't show up until light is advanced 80-90 degrees. Car is a 1980 L48 with factory GM HEI dizzy. When I set initial timing I found TDC with valve cover off watching lifters. Timing line on balancer was accurate when TDC was found so I highly doubt it has spun. Plug wires used are Moroso blue max spiral core. Will be trying a generic wire on #1 to test, as well as a different light. Any ideas what the problem may be with this light? It functions but the timing readings are bogus.
Actron CP7529 http://www.summitracing.com/parts/ANM-CP7529/
Reads RPMs accurately of #1 plug wire but timing is waaaay off. Timing line on balancer doesn't show up until light is advanced 80-90 degrees. Car is a 1980 L48 with factory GM HEI dizzy. When I set initial timing I found TDC with valve cover off watching lifters. Timing line on balancer was accurate when TDC was found so I highly doubt it has spun. Plug wires used are Moroso blue max spiral core. Will be trying a generic wire on #1 to test, as well as a different light. Any ideas what the problem may be with this light? It functions but the timing readings are bogus.
Drifting
Joined: Dec 2009
Posts: 1,349
Likes: 34
From: Porterville Ca
I assume you're connected to the # 1 cyl, drivers side front? Timing lights are a pain in the A$$, I finally broke down and spent too much on an awesome Snap-on light, it's been repaired twice, and is almost a worthless dinosaur, good thing I drive old cars that still have Dizzys...
Thread Starter
Heel & Toe
Joined: Jan 2011
Posts: 16
Likes: 0
From: Niles Ohio
Yeah I've checked and rechecked the simple things like that. It's on #1. I've researched this model online and others have used it without issue, I just can't figure out why its so messed up with my setup. If the timing was actually 90 degrees bdtc the car wouldnt even run. I'm about to drop by sears to pick up a different light to test. The manufacturer claims it should work with HEI setups so this is confusing.
Thread Starter
Heel & Toe
Joined: Jan 2011
Posts: 16
Likes: 0
From: Niles Ohio
I have tried hooking up the inductive pickup both at the plug end, the distributor end, and in the middle of the wire with the same results. It is absolutely on #1 based off the labeling on the distributor wire retaining cap, and double checked online to make sure the layout was correct. If you were facing the distributor from the front of the car it's the post at roughly the 4-5 oclock position.
As previously mentioned above yes it is true sears is selling these same exact guns relabeled. The CP7529 was relabeled a "Craftsman Professional" timing light. Looked exactly the same minus the color difference. They also had a similar gun without the built in tach and only a dial back type setup. While still an Actron, I picked this dial back gun up for testing purposes. When hooked up I got a reading of approximately 39 degrees with the engine at idle, vacuum advance disconnected, with the mr gasket gold springs on the centrifugal advance.
As previously mentioned above yes it is true sears is selling these same exact guns relabeled. The CP7529 was relabeled a "Craftsman Professional" timing light. Looked exactly the same minus the color difference. They also had a similar gun without the built in tach and only a dial back type setup. While still an Actron, I picked this dial back gun up for testing purposes. When hooked up I got a reading of approximately 39 degrees with the engine at idle, vacuum advance disconnected, with the mr gasket gold springs on the centrifugal advance.
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Burning Brakes
Joined: Dec 2005
Posts: 992
Likes: 56
From: Baldwinsville, NY
I have a similar Equus 3568 digital dial back timing light. It works great on my 78 with HEI dizzy.
Are you using any kind of box like MSD multi spark units, I know it will not work well.
Here is a picture of the dizzy showing the plug numbers and the order of location on the engine, take a moment to study it.
Are you using any kind of box like MSD multi spark units, I know it will not work well.
Here is a picture of the dizzy showing the plug numbers and the order of location on the engine, take a moment to study it.
Thread Starter
Heel & Toe
Joined: Jan 2011
Posts: 16
Likes: 0
From: Niles Ohio
Yep thats exactly how my distributor and wires are setup. Just like the above picture. No MSD box, completely stock HEI distributor. Beginning to think it may be a flawed/broken gun despite being brand new.
Safety Car
Joined: Sep 2007
Posts: 4,458
Likes: 331
From: Indy Indiana
if you hooked it up to cylinder number 2 on the wrong bank, then according to the firing order it fires last, 90 degrees before cylinder number 1 on the other bank does..
that would explain why you are 90 degrees off.
also if you are definately connected properly to cylinder number 1, then you may be getting a false signal bleed off somehow from cylinder number 2 plug wire. The engine would run like crap though.
check for carbon tracks inside your distributor cap...
that would explain why you are 90 degrees off.
also if you are definately connected properly to cylinder number 1, then you may be getting a false signal bleed off somehow from cylinder number 2 plug wire. The engine would run like crap though.
check for carbon tracks inside your distributor cap...
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
The distributor wires could have been re-clocked by a PO or a mechanic (without changing the labels). That is the only possible answer. Track that "#1" wire down to which plug it is connected. If the wiring is hidden, pull the wire out of the dizzy and also off the #1 plug and use an ohmmeter to see if there is really continuity on that line. {I highly doubt it.}
Thread Starter
Heel & Toe
Joined: Jan 2011
Posts: 16
Likes: 0
From: Niles Ohio
The wires are run properly and verified in correct order. I replaced them myself about a month ago. Wires are run over top of valve covers with looms so very easy to see/select right wire. Engine rev's fine to 4500rpm without issue so nothing is crossed or out of whack with the setup. I will be doing more testing with the other light I picked up from sears shortly to see if I can some how figure out what is making the first Actron light be so ridiculously off its reading. Good point about the distributor cap. It is all original. I will look and give it a good cleaning just in case.
Burning Brakes
Joined: Jun 2008
Posts: 1,086
Likes: 1
From: Michigan
You may have the wires connected to the correct cylinders per the sketch and the timing light on the correct #1 spark plug. How about the rotor position inside the distributor when it is at #1 TDC? Is the rotor contact at the #1 position on the cap post you labeled #1? When the distributor was installed was it done with the #1 at TDC and the rotor pointing to #1 at the same time? Any cap wire post can be called #1 but the rotor must be timed to "that" post.
Intermediate
Joined: Oct 2010
Posts: 47
Likes: 0
Maybe a little late, but i agree, the rotor is probably out 180 degrees. lifting out the distributor and resetting it back in 180 degrees should line it up correctly. The engine would still run with it backwards but you will never see the timing marks. I may be wrong, but for some reason i think i had this problem before and that was the problem. Good luck!
Le Mans Master
Joined: Oct 2010
Posts: 6,938
Likes: 848
From: melbourne florida
2023 C3 of the Year Finalist - Modified
i have never trusted "dial back" lights. snap ons are usually better than the others. i use a timing tape or degreed balanced. yes its more work but I've never had an issue.
