Pertronix problems at 4500 RPM

[n/a]

I have read through the Pertronix topics through the search engine and have not found the answer to the following:

After installation by my mechanic:

At 4500 rpm's the car starts to run rough, does anyone have any experiences and maybe ideas what may be causing it.

I believe Naj brought this up in a previous discussion but got no responses.

Thanks

Can use the help so I can pass it on to the mechanic.

Howard Kramer
280SL71
387/255

[Cees Klumper]

I seem to recall from an earlier discussion that one of the electronic ignition types (could be Pertronix) can have this problem. Here's some comments I dug up from old Yahoo! posts:

"I have also tried the Pertronics hall effect unit, but found it weak at crank speed and idle."

"I too have tried the Pertronix and found it useless. It was for a 190 SL test engine I use to test carb rebuilds. Returned the Pertronix setup for a refund."

"The Pertronics Hall Effect pick-up is easier to install [than the Crane system, CK], but does not have as nice a spark [specially at starting]. The advantage is you can't see it has been modified as it is hidden in under the distributor cap."

"I have done/used/tested both and find the Hall Effect [Pertronix technology, CK] to lack performance at idle/low rpm (starting). Optical switching [Crane technology, CK] is just cleaner, faster switching and it shows up on a scope. The only advantage I have found in the Pertronix is it can be hidden as there is no switchgear."

and here is someone who is very positive about Pertronix, addressing specifically the higher-RPM range:

"I have been dealing with the points on my 66, they were burning out and causing the car to run poorly. I have been frustrated in dealing with the issue so I called and ordered the Pertronix electronic ignition and installed it last Saturday. WOW what a difference my car has NEVER run this well EVER in the 7 years I have owned it. The installation was all in all the easiest thing I have ever done regarding ignition systems. I removed the hood to make the install easier and pulled the points out and made a <very> minor alteration to the bracket that connects the vacuum advance arm. I replaced the cap rotor and ran the wires. The car fired right up with no problems and I believe I am driving a completely different car. It does not hesitate and pulls right off the line, revs cleaner at high RPM’s and shifts better it is amazing. If you have been bothered by your points I recommend making the swap, it looks stock and works great."

Could it be that the vacuum advance (or, on your car, more likely vacuum retard?) on your car or another part of the distributor is malfunctioning? How are the bearings inside the distributor etc? It may be worthwile to send the distributor to someone like Dan Caron (Dr Benz) to have it tested, if you can't pinpoint the problem.

Cees Klumper in Amsterdam
'69 white 280 SL automatic

[Naj ✝︎]

Hello, Howard,
Welcome to the site.
Sorry to say I'm still struggling with the Pertronix. I have tried various timing settings etc. and all it does is change the rev range at which the engine misfires/hesitates.
Upto now it thought it may be vacuum retard causing it, but I see yours is a '71 which takes out the vacuum at 2400 rpm - which takes that out of the equation!
I'm just about ready to give up on it and go back to points or Crane - which works great on my 230sl with vac advance.
Sorry, not much help in this instance  
naj

65 230SL
68 280SL

[hands_aus]

I installed the Pertronix on my 250SL and initially had lots of problems.

After adjusting the timing to factory specs, I adjusted the air/fuel mixture until I was happy with the performance and economy.

I have never had the engine at that high revs. The speed limit here in Australia is a maximum of 110 KmPH/65 MPH and that is achieved at 3500 RPM.

So I don't know if my car has the problem.

It starts and stops easily, goes like a rocket and the fuel economy has improved.

Have you had the timing checked and the air/fuel mixture checked?

Bob (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[Naj ✝︎]

Bob,
This was my guess - that most people have autos and probably do not use high revs and thus never experience the problem.
With the manual, I tend to excercise the engine - even upto 6000rpm for short bursts and the problem shows up here.
Could  I ask you to try higher revs in say second or third and see if it happens to your car?
Watch mirrors for blue flashing lights!!
naj

65 230SL
68 280SL

[Cees Klumper]

My car is an automatic but I frequently take it to 4,500 RPM's and beyond during acceleration and higher-speed cruising. I have an electronic ignition module (not Crane or Pertronix) and it uses an optical trigger. It's performed flawlessly and never misses, not even at the highest RPM's I've ever recorded (a bit over 6,000 I think).

Cees Klumper in Amsterdam
'69 white 280 SL automatic

[Douglas]

How old is your Pertronix system? My understanding is they recently made some necessary improvements on the model they're selling for the Pagoda. Perhaps you should take this up with the manufacturer. (Incidentally, the Pertronix unit I had installed back in March works flawlessly at all revs.)

Douglas Kim
New York, NY
280 SL #018260

[n/a]

First to answer Douglas question this is a brand new setup with the 40,000 ignition coil (Epoxy)

The unit that was recommended was the 1863 which my mechanic Wolfgang confirmed.

After talking to technical support at Pertronix they said that they never made a unit specifically for the newer distributor I believe the (062) and the recommended (1863) is actually from a porsche.
After telling him about the problems at 4500 RPM he said the good news is it proves there are no mechanical problems with the car and he believes the problem based on previous experience is in the dwell.
Apparently when the car achieves RPM's above the 4500 the dwell tends to fall.

The solution he said is to change the magnet to a different one that they will send out free of charge. He asked though which way the distributor turns in order to send out the correct magnet. After talking to Wolfgang today when I went to pick up my car for this weekends WestPoint outing he said the distributor turns clockwise.

So I will now pass this on to Pertronix and have them send out hopefully the correct magnet.

In the meantime new oem points were put in and the car seems to run well.

When I get the new magnet and my mechanic gets an opportunity to install the Pertonix I will give a update.

Hopefully this is the answer to alot of others who have similar problems without solutions.

It makes you wonder why Pertronix does'nt package this unit properly for the 70-71 280SL.

I hope this is helpful and at the end it works.


Howard Kramer
71280SL
387/255

[hands_aus]

Hey Naj,

Sounds promising for your problem.

Hey Howard did your mechanic check the Dwell angle of the existing Pertronix unit?

It will be interesting to compare the Dwell angle of the new magnet with the old magent.

Bob (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[Naj ✝︎]

Yes, Bob,
I've been promised a new magnet by mail as well, so waiting with abated breath :twisted:
naj

65 230SL
68 280SL

[Naj ✝︎]

Howard,
Thanks for bringing up this topic.
I got a new magnet from our UK supplier and I swapped it today.
Car runs much better now   .
Thanks again
naj

65 230SL
68 280SL

[hands_aus]

Naj,

I hope your Pertronix problems have now been sorted. It will be interesting to know what it is like after some use.
The Pertronix unit I installed was a 1864LA for the 051 distributor so maybe that magnet ring doesn't have problems at higher speed.
I will try the engine at lower gears and higher speeds just to see how it goes.
cheers

Bob (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[erickmarciano]

bob if you magnet has a white dot you have the new one

1971 280sl
1962 VW
1954 Allstate vespa
1958 gs150 vespa
1962 gs160 vespa

[hands_aus]

Hey Erick,

Thanks, I will have a look tomorrow.


Bob (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[hands_aus]

Hey Erick,

I checked the magnet. It has the white dot. I figure that will be why I have not had any "missing" problems.

Bob (Brisbane,Australia)
RHD,1967 early 250 SL, auto