MSD making car run bad? random spark?
Thread Starter
Race Director
Joined: May 2003
Posts: 10,956
Likes: 409
From: California
MSD making car run bad? random spark?
ok... Just a question, ..... i talked to MSD and they say that ether the unit works or its totally out. Now, i have not yet done a re-conversion back to standard ignition....O, question...
Has anyone ever has a MSD unit go bad but still make the car run, but as if it was missing random different cylinders, or feels like a bad valve...????
Has anyone ever has a MSD unit go bad but still make the car run, but as if it was missing random different cylinders, or feels like a bad valve...????
Melting Slicks
Joined: Sep 2007
Posts: 2,429
Likes: 0
From: Tucson AZ
Try putting a timing light on each plug wire to see if you have continuous or sparatic spark.
I put a MSD in my 69 big block 3 years ago, and I really like it, it works well. I set the timing and haven't touched it since.
BBTank
I put a MSD in my 69 big block 3 years ago, and I really like it, it works well. I set the timing and haven't touched it since.
BBTank
Tech Contributor
Joined: Jun 2004
Posts: 20,910
Likes: 962
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
ok... Just a question, ..... i talked to MSD and they say that ether the unit works or its totally out. Now, i have not yet done a re-conversion back to standard ignition....O, question...
Has anyone ever has a MSD unit go bad but still make the car run, but as if it was missing random different cylinders, or feels like a bad valve...????
Has anyone ever has a MSD unit go bad but still make the car run, but as if it was missing random different cylinders, or feels like a bad valve...????
(Disclaimer: I've never used an MSD unit, so I claim no expertise with them.)
Melting Slicks
Joined: Sep 2007
Posts: 2,429
Likes: 0
From: Tucson AZ
I used to design ignition modules and ECMs/PCMs for a living, and I'd never give an answer like that. Unless the module was comprised of only one internal part, there's going to be several potential failure or misfiring modes. Are you absolutely sure they said that simple of an answer?
(Disclaimer: I've never used an MSD unit, so I claim no expertise with them.)
(Disclaimer: I've never used an MSD unit, so I claim no expertise with them.)
It can be that simple, I wasn't suggesting that the module wasn't the problem. The OP needs to do a bit more diagnosis, or trust someone to do it.
This is my 4th MSD ignition system.
(Disclaimer: They've all been on different vehicles)
Thread Starter
Race Director
Joined: May 2003
Posts: 10,956
Likes: 409
From: California
i have done most everything now... including a new engine rebuild... (I had other reasons as well for the rebuild) and this is just weird...No back fires anytime anywhere. new engine, old one was doing the same....new demon carb...
Melting Slicks
Joined: Sep 2007
Posts: 2,429
Likes: 0
From: Tucson AZ
I've never owned a Demon carb, but have worked on them a few times at the drag strip, for friends. I really don't care too much for them. That's just my opinion.
Are you saying that you have the same problem on the "new" motor that you had on the "old" one?
Are you saying that you have the same problem on the "new" motor that you had on the "old" one?
Pro
Joined: Sep 2008
Posts: 508
Likes: 1
From: Olive Branch MS
Something I've seen before that is common is having the ouput wires (the ones that go to the coil) running beside the input wires (wires from the distributor). The huge spike (300 - 500 volts) going to fire the coil can create enough noise on the input wires to make the ignition box to fire spiratically.
Le Mans Master
Joined: Nov 2008
Posts: 5,691
Likes: 12
From: columbus oh
i am not saying this is your problem however when using the msd box it is imperitave you hook the ground directly to the battery and you may want to use their shielded cable also...good luck
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another common mistake.
Instructor
Joined: Jun 2009
Posts: 157
Likes: 1
From: Sebring florida
I ran into a simmalur problum with my pertronix ignitor.
I had done a lot of distributer work, limiting mech adavance, limiting vac adavance and had the distributer out and in many times. I was getting mis firing under load and thought that the pertronix was bad.
What I was getting was spark jumping between wires with my 45,000 volt coil.
What I had was, the dist was in backwards putting the #1 plug wire to the rear of the eng causing most of the wires crossing from left to right. By rotating the dist 180 and putting the #1 wire in the front it kept 3 of the left bank wires coming from the left of the dist and 3 of the right bank wires coming from the right of the dist. In addition to that I placed spiral wrap on all wires from the dist wire boots to where they exit my Ing crome shielding.
This seams to have corrected my problum, i'll find out if it 100% as soon as I reinstall the shielding.
I had done a lot of distributer work, limiting mech adavance, limiting vac adavance and had the distributer out and in many times. I was getting mis firing under load and thought that the pertronix was bad.
What I was getting was spark jumping between wires with my 45,000 volt coil.
What I had was, the dist was in backwards putting the #1 plug wire to the rear of the eng causing most of the wires crossing from left to right. By rotating the dist 180 and putting the #1 wire in the front it kept 3 of the left bank wires coming from the left of the dist and 3 of the right bank wires coming from the right of the dist. In addition to that I placed spiral wrap on all wires from the dist wire boots to where they exit my Ing crome shielding.
This seams to have corrected my problum, i'll find out if it 100% as soon as I reinstall the shielding.
Tech Contributor
Joined: Jun 2004
Posts: 20,910
Likes: 962
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
I had Harley-Davidson tell me the basic same thing. It can be that simple, I wasn't suggesting that the module wasn't the problem. The OP needs to do a bit more diagnosis, or trust someone to do it.
This is my 4th MSD ignition system.
(Disclaimer: They've all been on different vehicles)
This is my 4th MSD ignition system.
(Disclaimer: They've all been on different vehicles)
Melting Slicks
Joined: Sep 2007
Posts: 2,429
Likes: 0
From: Tucson AZ
I'm assuming that was an old carbureted ignition module part versus the later bikes with EFI. (I designed the ECMs used in most Harleys for the last decade, and it's not a simple "it works or it doesn't work" issue. If the part is miswired or physically damaged, a bunch of odd drivability issues will result.)
BTW, EFI still, doesn't belong on real bikes. I don't care what anybody says, I'm not going to change on some things. I still like a carburetor on my motorcycle.
Hey, it "works" for me!!
Tech Contributor
Joined: Jun 2004
Posts: 20,910
Likes: 962
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
That would be correct sir. I am lucky enough to own a 1988 FXST which I installed the Screaming Eagle ignition module with the wiring harness that had to be added. As you know, the stock unit had to be unwired from each individual end point. H-D told me that that module worked or it didn't work, so I must have wired it wrong. I proved them wrong, and got a refund of my money, never doubt a strong willed country boy, with an education.
BTW, EFI still, doesn't belong on real bikes. I don't care what anybody says, I'm not going to change on some things. I still like a carburetor on my motorcycle.
Hey, it "works" for me!!:cheers:
BTW, EFI still, doesn't belong on real bikes. I don't care what anybody says, I'm not going to change on some things. I still like a carburetor on my motorcycle.
Hey, it "works" for me!!:cheers:
Melting Slicks
Joined: Sep 2007
Posts: 2,429
Likes: 0
From: Tucson AZ
Tank
Burning Brakes
Joined: Dec 2007
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Thread Starter
Race Director
Joined: May 2003
Posts: 10,956
Likes: 409
From: California
Something I've seen before that is common is having the ouput wires (the ones that go to the coil) running beside the input wires (wires from the distributor). The huge spike (300 - 500 volts) going to fire the coil can create enough noise on the input wires to make the ignition box to fire spiratically.
I ran into a simmalur problum with my pertronix ignitor.
I had done a lot of distributer work, limiting mech adavance, limiting vac adavance and had the distributer out and in many times. I was getting mis firing under load and thought that the pertronix was bad.
What I was getting was spark jumping between wires with my 45,000 volt coil.
What I had was, the dist was in backwards putting the #1 plug wire to the rear of the eng causing most of the wires crossing from left to right. By rotating the dist 180 and putting the #1 wire in the front it kept 3 of the left bank wires coming from the left of the dist and 3 of the right bank wires coming from the right of the dist. In addition to that I placed spiral wrap on all wires from the dist wire boots to where they exit my Ing crome shielding.
This seams to have corrected my problum, i'll find out if it 100% as soon as I reinstall the shielding.
I had done a lot of distributer work, limiting mech adavance, limiting vac adavance and had the distributer out and in many times. I was getting mis firing under load and thought that the pertronix was bad.
What I was getting was spark jumping between wires with my 45,000 volt coil.
What I had was, the dist was in backwards putting the #1 plug wire to the rear of the eng causing most of the wires crossing from left to right. By rotating the dist 180 and putting the #1 wire in the front it kept 3 of the left bank wires coming from the left of the dist and 3 of the right bank wires coming from the right of the dist. In addition to that I placed spiral wrap on all wires from the dist wire boots to where they exit my Ing crome shielding.
This seams to have corrected my problum, i'll find out if it 100% as soon as I reinstall the shielding.
yes... ???... what happened? what did you do? more please...
Pro
Joined: Nov 2007
Posts: 721
Likes: 105
From: hernando fl
when i bought the car , it had the msd installed. the person who installed it had the positive lead connected to the starter and the negative lead connected to the engine block. the result was timing was never consistent , it would jump around 4 or 5 degrees when trying to set timing and would have an intermitent miss. after a lot of messing around. wired it up directly to the battery and it was like waving a magic wand , stable timing and the miss was gone.