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Kblack1101
Samba Member
Joined: August 05, 2020
Posts: 162
Location: Wisconsin
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 Posted: Tue Aug 03, 2021 10:40 am Post subject: Pertronix / Distributor anomoly |
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I have been doing some digging online and within the forum and I cannot seem to find a definitive answer, so I would like to describe my situation and ask if anyone can provide some insight.
- Recently acquired 77 bus with stock Fuel injected. 2.0l. PO mentioned that they installed pertronix and it seemed to run OK. Completed a compression / leak down test and had good results across all 4 cylinders. However, I noticed during driving it was underpowered - more than it should be LOL
- Investigated timing with digital timing light. Seems OK
- Investigated vacuum leaks, wiring issues, anything which was obvious - Nothing which stands out immediately.
- Decided to check plugs / wires ... This is where it gets interesting.
- Cyl 3 is not firing. NO SPARK. Plug has fuel on it, swapping wires results in the same dead spot in the distributor cap.
- As far as I can tell, The Pertronix unit has a "dead" spot. Not sure how this is possible. The magnetic collar on the distributor checks out. I obviously cant diagnose the sealed chip but something just doesn't add up.
- Distributor cap reflects the dead spot- the contact inside the distributor cap shows no sign of ever seeing spark - no marking / blemish / burn...it is clean!
- Visible spark can be seen from every other cylinder when the plug is removed
Has anyone encountered this? I can swap out for a new Pertronix, or go back to points / condenser... either route is going to cost me some money and time. I feel pretty confident in the diagnosis, but from a function of the design, why would Pertronix only fire 3 out of 4 cylinders?
According to Pertronix website - it is either a GO or NO GO system, which by my interpretation indicates that if one cant work they all cant work. Could it be low voltage? But again, if that were the case - why is only one cylinder not getting signal to fire?
Thanks in advance   |
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SGKent 
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Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Tue Aug 03, 2021 10:54 am Post subject: Re: Pertronix / Distributor anomoly |
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unusual situation. I guess technically it is possible. I would first try a new cap and rotor to be sure that there is no internal defect in either. If that fails, replace the pertronix ring first. All that said, there may be an airgap that has to be within tolerance between the ring and pickup. Make sure that is correct. Also I am hoping you tried a new spark plug although if you get no spark trying to ground the wire then you can almost rule that out because you know it won't matter.
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Kblack1101
Samba Member
Joined: August 05, 2020
Posts: 162
Location: Wisconsin
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| Posted: Tue Aug 03, 2021 10:57 am Post subject: Re: Pertronix / Distributor anomoly |
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| SGKent wrote: |
| unusual situation. I guess technically it is possible. I would first try a new cap and rotor to be sure that there is no internal defect in either. If that fails, replace the pertronix ring first. All that said, there may be an airgap that has to be within tolerance between the ring and pickup. Make sure that is correct. Also I am hoping you tried a new spark plug although if you get no spark trying to ground the wire then you can almost rule that out because you know it won't matter. |
Check, check and check. 
- Tried new cap same rotor
- Tried new rotor same cap
- Tried new rotor new cap
- Grounded all wires without plugs
- New plug
- New plug wire
- Swapped known bad location to a different cylinder - same scenario, different cylinder.
Thanks for the inputs - all valid and agreed upon ! |
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Glenn
Mr. 010
Joined: December 25, 2001
Posts: 76939
Location: Sneaking up behind you
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| Posted: Tue Aug 03, 2021 11:05 am Post subject: Re: Pertronix / Distributor anomoly |
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Are you sure there are 4 magnets in the plastic ring?
Remove the ring and rotate it 90* and see if the dead cylinder moves.
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21520
Location: Oklahoma City
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| Posted: Tue Aug 03, 2021 11:09 am Post subject: Re: Pertronix / Distributor anomoly |
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| Kblack1101 wrote: |
I have been doing some digging online and within the forum and I cannot seem to find a definitive answer, so I would like to describe my situation and ask if anyone can provide some insight.
- Recently acquired 77 bus with stock Fuel injected. 2.0l. PO mentioned that they installed pertronix and it seemed to run OK. Completed a compression / leak down test and had good results across all 4 cylinders. However, I noticed during driving it was underpowered - more than it should be LOL
- Investigated timing with digital timing light. Seems OK
- Investigated vacuum leaks, wiring issues, anything which was obvious - Nothing which stands out immediately.
- Decided to check plugs / wires ... This is where it gets interesting.
- Cyl 3 is not firing. NO SPARK. Plug has fuel on it, swapping wires results in the same dead spot in the distributor cap.
- As far as I can tell, The Pertronix unit has a "dead" spot. Not sure how this is possible. The magnetic collar on the distributor checks out. I obviously cant diagnose the sealed chip but something just doesn't add up.
- Distributor cap reflects the dead spot- the contact inside the distributor cap shows no sign of ever seeing spark - no marking / blemish / burn...it is clean!
- Visible spark can be seen from every other cylinder when the plug is removed
Has anyone encountered this? I can swap out for a new Pertronix, or go back to points / condenser... either route is going to cost me some money and time. I feel pretty confident in the diagnosis, but from a function of the design, why would Pertronix only fire 3 out of 4 cylinders?
According to Pertronix website - it is either a GO or NO GO system, which by my interpretation indicates that if one cant work they all cant work. Could it be low voltage? But again, if that were the case - why is only one cylinder not getting signal to fire?
Thanks in advance |
Check the simple things first.
Take your volt meter...put one probe on the wire side of #3 on the distributor cap and one probe on the inside contact. Make sure you have continuity. I have only found one cap in my life that was damaged like this.....but its possible.
So is this pertronix complete distributor or the pertronix module system?
If its the module system.....While it is possible that there is something wrong with the magnet at #3 ...like it was installed too far back in its notch inside or one of the wrong polarity was installed...hard to say.
First...try repositioning the sleeve on the shaft to see if the problem moves around. If it does....there is a part of the problem....
BUT...one of the more common issues is that people assume that pertronix is just a drop in and go. There are a whole slew of small fit issues because of the wide variation in distributor machining over the eons.....and....due to distributor WEAR.
The actual gap between the module and the magnet ring is important. But...while it has a pretty wide effective range (compared to points) If its not paid attention to and you are at the outside edge of its range (too far away from teh magnet ring).....and you have any wear in the distributor shaft causing radial play by just a few thousandths ...you an be outside of the range of the module to magnet and get no triggering at one or more spark plug locations.
So if the magnet at #3...currently...is say...slightly farther away from the module because of how it mounted in the ring....with no other changes....moving the magnet ring around like I suggested above....will move the problem to another wire.
BUT...if its also "helicoptering" from shaft wear.....it may not move ....and continue to stay at #3.
Check the gap between module and magnet on all four locations. Typically the module kit is sent with a plastic feeler gauge to set the gap at 0.034"...which typically gives a dwell of 52 to 54 degrees.
But if something is off either in one of the magnets or in the shaft movement....this may be slightly too much. Decrease gap by about 0.005" and see what you get. Ray |
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Kblack1101
Samba Member
Joined: August 05, 2020
Posts: 162
Location: Wisconsin
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| Posted: Tue Aug 03, 2021 11:14 am Post subject: Re: Pertronix / Distributor anomoly |
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| Glenn wrote: |
Are you sure there are 4 magnets in the plastic ring?
Remove the ring and rotate it 90* and see if the dead cylinder moves. |
4 magnets present - confirmed |
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Kblack1101
Samba Member
Joined: August 05, 2020
Posts: 162
Location: Wisconsin
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| Posted: Tue Aug 03, 2021 11:21 am Post subject: Re: Pertronix / Distributor anomoly |
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| Quote: |
Check the simple things first.
Take your volt meter...put one probe on the wire side of #3 on the distributor cap and one probe on the inside contact. Make sure you have continuity. I have only found one cap in my life that was damaged like this.....but its possible. |
Good idea - can try this, however I did try a different cap with the same results
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| So is this pertronix complete distributor or the pertronix module system? |
Complete distributor as far as I can tell
| Quote: |
If its the module system.....While it is possible that there is something wrong with the magnet at #3 ...like it was installed too far back in its notch inside or one of the wrong polarity was installed...hard to say.
First...try repositioning the sleeve on the shaft to see if the problem moves around. If it does....there is a part of the problem.... |
Had the same thought - rotated and same position does not fire
| Quote: |
| BUT...one of the more common issues is that people assume that pertronix is just a drop in and go. There are a whole slew of small fit issues because of the wide variation in distributor machining over the eons.....and....due to distributor WEAR. |
This is where my mind is starting to go - suspecting stack of wear / bad parts / tolerance issues
| Quote: |
The actual gap between the module and the magnet ring is important. But...while it has a pretty wide effective range (compared to points) If its not paid attention to and you are at the outside edge of its range (too far away from teh magnet ring).....and you have any wear in the distributor shaft causing radial play by just a few thousandths ...you an be outside of the range of the module to magnet and get no triggering at one or more spark plug locations.
So if the magnet at #3...currently...is say...slightly farther away from the module because of how it mounted in the ring....with no other changes....moving the magnet ring around like I suggested above....will move the problem to another wire.
BUT...if its also "helicoptering" from shaft wear.....it may not move ....and continue to stay at #3. |
This seams feasible - hard to test due to it being a complete Pertronix dizzy
| Quote: |
| Check the gap between module and magnet on all four locations. Typically the module kit is sent with a plastic feeler gauge to set the gap at 0.034"...which typically gives a dwell of 52 to 54 degrees. |
Will do and report back Thank you!
| Quote: |
| But if something is off either in one of the magnets or in the shaft movement....this may be slightly too much. Decrease gap by about 0.005" and see what you get. Ray |
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Starbucket
Samba Member
Joined: April 30, 2007
Posts: 4026
Location: WA
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| Posted: Tue Aug 03, 2021 2:59 pm Post subject: Re: Pertronix / Distributor anomoly |
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| Try having a helper crank the motor with the cap removed watch the rotor and see if it wobbles and dips down by #3, sounds like a defective dist. as the PO said it runs ok not great. |
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Jeff Geisen
Samba Chaplain
Joined: December 21, 2004
Posts: 1882
Location: N.W. Georgia
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| Posted: Tue Aug 03, 2021 3:48 pm Post subject: Re: Pertronix / Distributor anomoly |
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I’m with Glenn here. It’s in the magnet collar. They’re fragile. Had a client’s FI bus with your issue. Changed out collar and viola-no misfire.
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aeromech
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Joined: January 24, 2006
Posts: 16971
Location: San Diego, California
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| Posted: Tue Aug 03, 2021 6:38 pm Post subject: Re: Pertronix / Distributor anomoly |
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Fuck that pertronics. Swap in a complete known good German made distributor. Those distributors suck ass
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raygreenwood
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Joined: November 24, 2008
Posts: 21520
Location: Oklahoma City
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| Posted: Tue Aug 03, 2021 6:47 pm Post subject: Re: Pertronix / Distributor anomoly |
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| aeromech wrote: |
| Fuck that pertronics. Swap in a complete known good German made distributor. Those distributors suck ass |
Yep...I have not heard good things (or not many) about the complete distributor unit.
However...if its a stock distributor with a module kit....keep it...but make sure the distributor itself is in good shape (bearings, axial play, points plate etc.).
Ray |
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Kblack1101
Samba Member
Joined: August 05, 2020
Posts: 162
Location: Wisconsin
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| Posted: Tue Aug 03, 2021 7:17 pm Post subject: Re: Pertronix / Distributor anomoly |
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Update for everyone:
Swapped out the distributor for a rebuilt OEM. Previous owner said it never ran right when installed.
- set static timing 7.5 deg BTDC and went for a short test drive
- all 4 cylinders firing! Test drive feels great
- engine starts to stumble so I turn around to get home and set dynamic timing
- shut engine off, gather tools, timing light etc…
- start engine, sounds pretty good again no stumbling
- start to walk to rear of bus and engine dies, now it won’t start
- sounds like it wants to start and then it doesn’t again
- static timing still good
- coil is hot
Cannot get it started  |
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aeromech
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Joined: January 24, 2006
Posts: 16971
Location: San Diego, California
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| Posted: Tue Aug 03, 2021 8:02 pm Post subject: Re: Pertronix / Distributor anomoly |
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Are you sure it’s not a fuel issue?
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
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DC9/MD80
BAe146
Fokker F28/F100
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Kblack1101
Samba Member
Joined: August 05, 2020
Posts: 162
Location: Wisconsin
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| Posted: Tue Aug 03, 2021 8:19 pm Post subject: Re: Pertronix / Distributor anomoly |
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| aeromech wrote: |
| Are you sure it’s not a fuel issue? |
Can’t be sure now. Seems oddly coincidental that I was having issues with timing / distributor but I certainly can’t rule it out.
Finally got the thing firing on all four and had about 1/8th mile of excitement and relief. Now I feel worse than before. It was seriously running great - started to buck / stumble… now I’m scratching my head  |
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aeromech
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Joined: January 24, 2006
Posts: 16971
Location: San Diego, California
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| Posted: Tue Aug 03, 2021 8:26 pm Post subject: Re: Pertronix / Distributor anomoly |
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Try this. Run a wire straight from your battery + to the coil +. This will bypass the ignition switch which could be your problem.
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21520
Location: Oklahoma City
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| Posted: Tue Aug 03, 2021 8:36 pm Post subject: Re: Pertronix / Distributor anomoly |
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| aeromech wrote: |
| Try this. Run a wire straight from your battery + to the coil +. This will bypass the ignition switch which could be your problem. |
^^^^
Coil is hot.... check your voltage. Low voltage could be the symptom...or as noted it could be the ignition switch being the root cause...or a poor ground network.
BUT....that does not cause ONE cylinder only to not fire. Ray |
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SGKent
Samba Member
Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Tue Aug 03, 2021 8:55 pm Post subject: Re: Pertronix / Distributor anomoly |
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piut a noid light on it and verify that the injector is getting a pulse. As to it dying, you may have a bad condenser. Also check the grounds for the FI system. You will solve the issue. Just be patient. That is why the last owner bailed.
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wihr
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Joined: August 15, 2010
Posts: 344
Location: PORTLAND, OR
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| Posted: Tue Aug 03, 2021 10:09 pm Post subject: Re: Pertronix / Distributor anomoly |
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I have over 300,000 on a Crane/Allison unit. Never a problem! No magnets!
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MuzzcoVW
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Joined: February 21, 2018
Posts: 1475
Location: Westfield, MA.
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| Posted: Wed Aug 04, 2021 4:16 am Post subject: Re: Pertronix / Distributor anomoly |
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| SGKent wrote: |
| piut a noid light on it and verify that the injector is getting a pulse. As to it dying, you may have a bad condenser. Also check the grounds for the FI system. You will solve the issue. Just be patient. That is why the last owner bailed. |
Was thinking the same thing. Between myself and a couple buddies we've had 5 Bosch condensers go bad in the last couple years. Running a Pertronix in my F.I. Bug in a rebuilt German dizzy and absolutely love it! New Bosch is mostly junk! |
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Kblack1101
Samba Member
Joined: August 05, 2020
Posts: 162
Location: Wisconsin
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| Posted: Wed Aug 04, 2021 4:31 am Post subject: Re: Pertronix / Distributor anomoly |
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| Hey everyone. Thanks for the great suggestions and the support. I will report back later with results. I haven’t thrown in the towel but I agree and also suspect this is why the PO gave up … thanks again |
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