Mercedes-Benz Forum banner

1 - 20 of 27 Posts

·
Registered
1969 Swiss 404 - 1977 Porsche 911 S
Joined
·
148 Posts
Discussion Starter #1 (Edited)
(edit: this is a continuation of this thread: http://www.benzworld.org/forums/unimog/1377473-404-suddenly-starts-running-poorly-backfiring-through-carb.html)

Everything worked great for about a month and then suddenly a misfire developed at moderate rpm. It went right from working great to misfiring in 1 second.

The distributor weights are advancing the timing as rpm's increase.

I've tried connecting the + wire (red) from the ignitor to both the input for the noise suppressor and the coil itself.

I had a look at the trouble shooting tips on Expedition Imports site. I tried moving the ignitor closer to the magnetic ring.

The problem has not gone away. My thoughts that the condensor wire had something to do with it were wrong, although it did work fine for a short time after disconnecting it. The condensor shouldn't be doing anything at all now anyway, right?

So it would seem that I've either had the new coil or the new ignitor suddenly go bad on me. I'm leaning toward the ignitor.

Is there a way to test it? I guess I'll have to call Pertronix and see what's up.
I also just noticed that the box that the flamethrower coil from the kit (40611) says " High Performance 12VOLT Universal Ignition Coil". Is it ok for 24 volt use?

The ignitor is UM-161.

This conversion kit was supposed to make things more reliable...

Scott at Expedition Imports - any suggestions?
 

·
Registered
Unimogs
Joined
·
864 Posts
Howdy Howdy,

In general the following is true......the ignitor either works or it does not. There is usually no "in-between." Considering the conversion was working well, and you suddenly get a miss, it's not likely the ignitor.

#1 - After install when you did the voltage test what was your input voltage to the coil at moderate/high RPM?

#2 - Do you have both the black and red wire running completely out of the distributor, or have you spliced the black wire inside the distributor? The condensor has NO bearing whatsoever on the system.

#3 - What cylinder are you missing on? The same cylinder each time, or different cylinders. The same cylinder and I would be looking towards a cap/wire/plug issue. If it is missing on different cylinders I would be looking towards the coil, or magnetic ring not fully seated. Simple test....take your timing light inductive pickup and put it on each wire while the truck is missing and see which cylinder it is....

#4 - 6V, 12V, 24V, 36V - doesn't mean much on a coil. As long as you are running a 3 ohm coil that can handle the input voltage and has it's corresponding output voltage you are good to go. Your ignition system does not work on 24V, it runs between 17-21 volts.....hence the reason to check the ballast resistor output voltage on installation. Pertronix themselves spec'd the complete ignitor/coil combination after testing a complete stock ignition system. The 40611 is what they called for.....I could have them make up pretty 24V boxes and jack the price by 20-30%, but it's not our style.

#5 - What is your timing set at? Double check it.

#6 - With the minimal information provided, it is difficult to armchair diagnose your problem. Make sure it is an ignition problem, and not something such as a sticky valve, etc.

#7 - Does the problem happen everytime even when cold? IE.....does it take a while to start showing up, or immediately. On overvoltage problems we see the coil work fine when cold, but after running a while it may start missing...usually occurs right before complete failure. Rule out voltage issues immediately as if the coil fails, it WILL likely take out the Ignitor immediately.

Everyone has their opinion on the kit. Considering that the conversions have been on the markets for over 8 years, with a combined "test group" of well over 1500 installations...the kits are definitely a proven upgrade. However, it is not a silver bullet and is only going to work as well as the rest of the system.

You have some homework, report back and let us know the answers to the above.

Cheers,

Scott Ingham
Expedition Imports
 

·
Registered
Unimogs
Joined
·
864 Posts
I just found your other post...would have been appreciated had you simply dropped me a PM and asked me to comment their....know we have two threads on the same problem. Anyways.....

How much did you shorten the rotor for installation? When the rotor is installed what is the gap between it and the magnetic ring. My guess is the reason why your "condensor" fix seemed to work was because when you re-installed the rotor/cap it was seated down properly. I'll bet you have either not taken enough material off the rotor and therefore it is not fully seating, or you have taken too much off and it is know coming off easily....

Just another thing to check.

Cheers,

Scott
Expedition Improts
 

·
Registered
1969 Swiss 404 - 1977 Porsche 911 S
Joined
·
148 Posts
Discussion Starter #4
.
.
Hi Scott, I really appreciate your getting right back to me. You're right, I should have PM'd you rather than start a second thread. I didn't think of it at the time. I've never done one. I couldn't edit the title of the other thread and I wanted to get your attention. Selfish of me.
Anyway, maybe this thread will help someone else with what to check if they have a problem:

Howdy Howdy,

In general the following is true......the ignitor either works or it does not. There is usually no "in-between." Considering the conversion was working well, and you suddenly get a miss, it's not likely the ignitor.
OK, thats good to know.

#1 - After install when you did the voltage test what was your input voltage to the coil at moderate/high RPM?
I remember seeing 18.9 ish, but I don't recall that I revved it up. I'll check it today.

#2 - Do you have both the black and red wire running completely out of the distributor, or have you spliced the black wire inside the distributor? The condensor has NO bearing whatsoever on the system.
Both wires out through, no splices. Originally I had just put the condenser wire back on its screw to keep it out of the way. I thought the same thing.

#3 - What cylinder are you missing on? The same cylinder each time, or different cylinders. The same cylinder and I would be looking towards a cap/wire/plug issue. If it is missing on different cylinders I would be looking towards the coil, or magnetic ring not fully seated. Simple test....take your timing light inductive pickup and put it on each wire while the truck is missing and see which cylinder it is....
That is something I didn't think of. I know it misses on #1 from using the timing light. I'll check other cyls with the light and see what I get. That should help narrow it down a lot. The mag ring is flush with the top of the ignitor and seems secure.

#4 - 6V, 12V, 24V, 36V - doesn't mean much on a coil. As long as you are running a 3 ohm coil that can handle the input voltage and has it's corresponding output voltage you are good to go. Your ignition system does not work on 24V, it runs between 17-21 volts.....hence the reason to check the ballast resistor output voltage on installation. Pertronix themselves spec'd the complete ignitor/coil combination after testing a complete stock ignition system. The 40611 is what they called for.....I could have them make up pretty 24V boxes and jack the price by 20-30%, but it's not our style.
Understood. Scott, is there a test I can do to check if the coil itself has gone bad?

#5 - What is your timing set at? Double check it.
14 deg BTDC at 850 rpm. I tried varying it yesterday between 10 and 18 for short runs with no change in the miss. The advance is working but I didn't do an exact test as to what maximum advance is.

#6 - With the minimal information provided, it is difficult to armchair diagnose your problem. Make sure it is an ignition problem, and not something such as a sticky valve, etc.
I hear you there. I have to do quite a bit of that in my business. I'm pretty sure its ignition related due to the fact that the timing light strobe falters in sync with the miss.

#7 - Does the problem happen everytime even when cold? IE.....does it take a while to start showing up, or immediately. On overvoltage problems we see the coil work fine when cold, but after running a while it may start missing...usually occurs right before complete failure. Rule out voltage issues immediately as if the coil fails, it WILL likely take out the Ignitor immediately.
It does it right from cold. I'll check the voltage first when I start on it today

Everyone has their opinion on the kit. Considering that the conversions have been on the markets for over 8 years, with a combined "test group" of well over 1500 installations...the kits are definitely a proven upgrade. However, it is not a silver bullet and is only going to work as well as the rest of the system.

You have some homework, report back and let us know the answers to the above.
I really like the concept of the kit. I wanted one the second I read about it and based on what others have said, it obviously works well and I will continue on with it. It's frustrating when you make an improvement to something that is already working adequately and the improvement fails, but then again, we still don't know for sure what the problem is either.

How much did you shorten the rotor for installation? When the rotor is installed what is the gap between it and the magnetic ring. My guess is the reason why your "condensor" fix seemed to work was because when you re-installed the rotor/cap it was seated down properly. I'll bet you have either not taken enough material off the rotor and therefore it is not fully seating, or you have taken too much off and it is know coming off easily....
I took off 1/8". There is a visible gap between the rotor base and the mag ring. The rotor snaps on very securely and is still securely fastened when I remove the cap, ie you have to pull on it a bit to pop it off. I don't think the problem lies here.

Scott, thanks for the checklist. I'll report back with voltage and a check on the other cylinders.

Again, I appreciate the help.
 

·
Registered
1969 Swiss 404 - 1977 Porsche 911 S
Joined
·
148 Posts
Discussion Starter #5
Output Voltage from ballast is high

I checked the other cylinders, the miss corresponds to a faltering timing light for all of them.

I checked the input voltage to the ballast resistor. 28.4V which I think is normal.

The output voltage from the ballast resistor however seems to be high.

25.2 Volts. I think this should be between 17 - 21 volts. I remember 18.9 at installation of the kit. All of these checks were done at 2800 rpm.

I assume this means I need a new ballast? It still gets hot but it's obviously not reducing the voltage enough. Does this also mean that the coil is wrecked?

I won't run it any further until I get this resolved to avoid possible damage to the ignitor.

So to summarize:

-Input voltage of 28.4 seems normal.
-Output voltage from the ballast is 25.2 which is way too high.

-Do I need a new ballast or is there a way to fix or substitute it?
-Is the coil ruined and is there a way to determine this?

Scott, let me know what you think. I'll order the appropriate parts from you as soon as I get your input.

Thanks.
 

·
Registered
'88 U-1300L, '70 406, '78 406, '78 416 project, '82 406, '57 404, '65 404, '70 404, '68 Haflinger.
Joined
·
1,849 Posts
This sure sounds like a voltage breakdown in some of the secondary wiring (spark wires) of the system from the higher voltage achieved by the Pertronix ignition upgrade. If you are getting spark at all, the Pertronix is good.

Scott has been a real sport to jump in to help with this problem. IMHO, when the first part of the thread says "Everything worked great for about a month", that lets Scott completely off the hook for being responsible for this problem. Just the heading of this thread points fingers at Scott and that's not fair. If you took an electronic part back to Pep Boys, told them it worked for a month, and wanted them to fix some new problem, they'd snicker and show you the door, or sell you another part.

Sometimes a rethink of the problem will help, and an understanding of the system would really help you. To jump the Pertronix power source around to different places in 'hope' of fixing the problem is scary. The installation says to use a solid 28 vdc source, and that means to avoid the ballast entirely.

Think about the voltage at the output of the ballast. The reason the voltage varies from 28 vdc (or whatever generator output voltage is) is because the Pertronix switches in the coil's primary winding in series with the ballast, drawing current, and current flowing through a resistor (the ballast) causes a voltage drop across it. Every time a spark is generated, the voltage at the ballast drops. The reason the voltage "looks" like 17-18 volts is because it's a series of spikes and the voltmeter does it's best to average those spikes. The 'apparent' average voltage will vary with the meter used.

Hooking the Pertronix to either end of the ballast is asking for trouble. Think about it, when the Pertronix fires (conducts) the voltage at the ballast drops considerably. If the Pertronix is getting power there, then it's source voltage drops. Not exactly easy for the Pertronix to operate under those spiky voltage source conditions.

You should pick up 24vdc from the main source, like the B+ terminal on the voltage regulator. Install a relay to provide key-switching of that voltage source. (The relay should turn on when the key is activated.) FYI, there are key switched wires to several of the fuses along the front of the firewall.

If you think your ballast is bad, you can check your ballast with an Ohmmeter. It's just a resistor.

Sorry this got long.

Bob
 

·
BenzWorld UNIMOG statesman
Unimog 404.1 Diesel (sold :( )1995 LMTV 1078
Joined
·
5,856 Posts
...Scott has been a real sport to jump in to help with this problem. IMHO, when the first part of the thread says "Everything worked great for about a month", that lets Scott completely off the hook for being responsible for this problem. Just the heading of this thread points fingers at Scott and that's not fair. If you took an electronic part back to Pep Boys, told them it worked for a month, and wanted them to fix some new problem, they'd snicker and show you the door, or sell you another part....
It's a rather interesting dynamic on what people percieve when they read stuff. Why I hated some of my Lit. classes in college. Some professor telling me "what the author meant". Like how the heck do you know what the author meant, the dudes been dead for 100 years so I know you didnt ask him.

Anyyyyway... I didnt read the Scott call out the same way you did at all. Just sounded to me like.... "HELLLLPPPPP Scott your the man and I'm so frustrated.... what do you think is wrong?"
 

·
Registered
1969 Swiss 404 - 1977 Porsche 911 S
Joined
·
148 Posts
Discussion Starter #8
This sure sounds like a voltage breakdown in some of the secondary wiring (spark wires) of the system from the higher voltage achieved by the Pertronix ignition upgrade. If you are getting spark at all, the Pertronix is good.
Well they're all new too. I got the whole kit.

Scott has been a real sport to jump in to help with this problem. IMHO, when the first part of the thread says "Everything worked great for about a month", that lets Scott completely off the hook for being responsible for this problem. Just the heading of this thread points fingers at Scott and that's not fair. If you took an electronic part back to Pep Boys, told them it worked for a month, and wanted them to fix some new problem, they'd snicker and show you the door, or sell you another part.
You misunderstand, I'm certainly not blaming Scott or expecting him to give me free stuff. I simply know that he knows the products he sells and as a customer I'm asking him for help. I've seen him give good advice on this forum before and he's already given me some too. I thought it might serve to help others as well since a lot of the stuff on here about the pertronix upgrade is sketchy and conflicting. Again, I'm not trying to point a finger at Scott at all.

Sometimes a rethink of the problem will help, and an understanding of the system would really help you. To jump the Pertronix power source around to different places in 'hope' of fixing the problem is scary. The installation says to use a solid 28 vdc source, and that means to avoid the ballast entirely.
Scott's instructions say to connect power source to the input at the noise suppressor which reads the same voltage as the output of the ballast. The pertronix instructions say it may also be connected at the coil. Some others, like yourself say to connect it 28V. The ignitor box says it has an operating voltage of 8v to 16v. See what I mean about conflicting information here? I'm pretty sure that Scott does not recommend running the ignitor at 28v but I may be wrong. There's nothing scary about connecting the damn thing in two of the three places that many different people have used it successfully is there? I haven't tried a solid 28v source yet.

Think about the voltage at the output of the ballast. The reason the voltage varies from 28 vdc (or whatever generator output voltage is) is because the Pertronix switches in the coil's primary winding in series with the ballast, drawing current, and current flowing through a resistor (the ballast) causes a voltage drop across it. Every time a spark is generated, the voltage at the ballast drops. The reason the voltage "looks" like 17-18 volts is because it's a series of spikes and the voltmeter does it's best to average those spikes. The 'apparent' average voltage will vary with the meter used.
Well, that does seem to make sense.

Hooking the Pertronix to either end of the ballast is asking for trouble. Think about it, when the Pertronix fires (conducts) the voltage at the ballast drops considerably. If the Pertronix is getting power there, then it's source voltage drops. Not exactly easy for the Pertronix to operate under those spiky voltage source conditions.
That make sense too but the instructions don't agree with you.

You should pick up 24vdc from the main source, like the B+ terminal on the voltage regulator. Install a relay to provide key-switching of that voltage source. (The relay should turn on when the key is activated.) FYI, there are key switched wires to several of the fuses along the front of the firewall.
None of this is recommended by Pertronix or Scott that I have seen. Mine has breakers.

If you think your ballast is bad, you can check your ballast with an Ohmmeter. It's just a resistor.
Yes, I will. Any idea what the resistance should be?

Sorry this got long.

Bob
You sound like my father, he's a ham too.
 

·
Registered
1969 Swiss 404 - 1977 Porsche 911 S
Joined
·
148 Posts
Discussion Starter #9
It's a rather interesting dynamic on what people percieve when they read stuff. Why I hated some of my Lit. classes in college. Some professor telling me "what the author meant". Like how the heck do you know what the author meant, the dudes been dead for 100 years so I know you didnt ask him.

Anyyyyway... I didnt read the Scott call out the same way you did at all. Just sounded to me like.... "HELLLLPPPPP Scott your the man and I'm so frustrated.... what do you think is wrong?"
Coachgeo, that is in fact exactly the way I meant it. I guess it does kind of look like I might be taking Scott and EE to task but that is certainly not what I intended. I was just trying to get answers as fast as possible to maybe solve this problem by the weekend.

As a customer I have a right to ask the seller questions, maybe not on a public forum in front of everyone though. I just thought the info would be useful.
 

·
Registered
1967 404 Unimog (Belgian), 2010 Ford Fusion Hybrid
Joined
·
253 Posts
This +24V +12V conflict regarding the Pertronix ignitor is something I'd like to understand. I've known for a while that there were two schools of thought on that, but didn't understand why.

Scott's instructions say to connect power source to the input at the noise suppressor which reads the same voltage as the output of the ballast. The Pertronix instructions say it may also be connected at the coil. Some others, like yourself say to connect it 28V. The ignitor box says it has an operating voltage of 8v to 16v. See what I mean about conflicting information here? I'm pretty sure that Scott does not recommend running the ignitor at 28v but I may be wrong.
I dug up my ignitor box and instructions and checked them. The instructions clearly say to connect the red lead to +24V and, if using a ballast resistor, to connect it before the resistor. The box didn't have any voltage values on it. Is it possible there are two variations of the Pertronix UM-161 out there? That would also explain why Scott recommends connecting it to +12V and Pertronix says use +24. I've bought a bit of stuff from EI over the years and gotten a fair amount of info from Scott. His advice has always proven to be correct (other than this ignitor thing).

Hammogger's explanation of voltage fluctuations between the coil and resistor fits with my understanding of how things work.
 

·
Registered
'88 U-1300L, '70 406, '78 406, '78 416 project, '82 406, '57 404, '65 404, '70 404, '68 Haflinger.
Joined
·
1,849 Posts
I did sound nasty in my defense of Scott, and didn't mean to be. The "scary" comment had to do with possibility of damage to the Pertronix. Any ignition coil, (transformer that it is) works by storage of energy in the field, and then kickback from the collapse of the field when disconnected from the power source. That's where the spark comes from as the secondary field collapses. But the primary has kickback too, and that voltage spike comes right out and hits the ballast. The scary part is hooking a solid state device to such a transient laden power source.

On the issue of 12v or 24v, I'd suggest the box your Pertronix came in might have been a 12v unit. Thus the understandable confusion. Way back when, in the '90's, when we were first seeing 404's come into the country, someone (John Wessels? or others in parallel efforts?) approached Pertronix to design a unit for our trucks in 24v. I really don't think Scott would have said the units need 12v. He's been around these special 24v Pertronix from the beginning.

As for the Pertronix box specifying connecting to the coil for power, coils have a "batt" terminal tied to vehicle power. That establishes the 'high' end for the coil's primary, and the Pertronix, or points, grounds the 'low' end then ungrounds it when a spark is needed. BTW, the period of time the points held the primary charging is the Dwell time, measured in portions of 360 degrees.

That coil 'batt' voltage suffers some spiky variation too, so why take a chance?

(once a ham, always a ham)

Bob
 

·
Registered
63 UNIMOG S404.115
Joined
·
116 Posts
This +24V +12V conflict regarding the Pertronix ignitor is something I'd like to understand... The instructions clearly say to connect the red lead to +24V and, if using a ballast resistor, to connect it before the resistor.... Hammogger's explanation of voltage fluctuations between the coil and resistor fits with my understanding of how things work.
Me too. My kit slipped straight in and I had no trouble setting the timing without major movement of the distributor. Used Scotts instructions for connecting and it runs fine. The only downside is that it is noticeably slower to start than it was when the points were fitted. One possible reason is low voltage to the ignitor, which is connected at the input to the radio suppressor. Despite a range of equipment I've never been able to successfully measure the voltage at various parts of the ignition system.

Like most I have accepted Scotts recommendations, but as I am a curious [email protected]#&* I'm always interested in why is it so.
 

·
Registered
Unimogs
Joined
·
864 Posts
Hi Guys,

The discussion here is great. Here is where we differ in our opinion from Pertronix. The ignitor is designed to run on a voltage range. Minimum 12.8-13.4 volts, and maximum 28 volts. If you do not have the minimum voltage the unit will not spark. If you overvoltage the unit it could fry.

It is quite common for a 404 spinning high RPM's to be close to 28V if not a little higher. Having a 1 Volt cushion does not make us very comfortable. However, when running the unit at post ballast resistor voltages 17/18 - 21/22 volts we still have a pretty good cushion both on the undervoltage side and the overvoltage side. We have been installing and reccomending this method in our literature for 8-9 years. (As a side, pertronix tech support reviewed our instructions years ago and did not have a problem with them.)

It's worth another look. I will talk with product development at Pertronix and see what they have to say. I believe we are in the 3rd generation of the module and some things have changed. For example, pertronix use to warn against splicing the Pertronix wires, that warning has been dropped and replaced with (use quality splices...)

Two Tone, I would suggest you replace your coil and I'll bet that will solve the missing problem. Then you can deal with your overvoltage issue if it exists. Extended periods of overvoltage are one of the most common reasons for the 40611 coil to fail.

Cheers,

Scott Ingham
Expedition Imports
 

·
Registered
63 UNIMOG S404.115
Joined
·
116 Posts
It's worth another look. I will talk with product development at Pertronix and see what they have to say.
Hi Scott,

Sounds good. Can see the issue with a max 28v input as I'm on 28.8v at mid RPM. I can also see the rationale in Bobs comments about a clean steady input voltage so would an acceptable solution be to put in a quality voltage drop resistor to drop the input voltage by ~4v to provide a safety margin if it is still required.

You'll hate this :( but just done some numbers on my system (as I can't actually measure the voltages despite....) and I get 13.2v (calculated) at the input to the radio suppressor with the full pertronix kit. My actual resistances are Ballast 4.6, Suppressor .9, Pertronix coil 3, input voltage 28.8, cumulative ign cct resistance 8.5 Ohm, calc Ign load 3.39 Amp.

Using exactly the same process with my Mil components ie 6 Ohm for the coil gives a calculated 17.3v at the input to the suppressor, which is the voltage commonly referred to. Any chance that this is actually (physically) correct using the full kit????

Whilst you are on-line, did you manage to sort out the tyre inflation kit?

Tony
 

·
Registered
1969 Swiss 404 - 1977 Porsche 911 S
Joined
·
148 Posts
Discussion Starter #16
Two Tone, I would suggest you replace your coil and I'll bet that will solve the missing problem. Then you can deal with your overvoltage issue if it exists. Extended periods of overvoltage are one of the most common reasons for the 40611 coil to fail.
I've got no problem with replacing the coil but doesn't it make sense to first determine what caused it to fail?

When I installed the kit I had 18.9 volts at the ballast output, I now have over 25 using the same meter. This suggests to me that the ballast has 'changed' and may be faulty.

Should I not compare it to 63TLF8's resistance measurement of 4.9 ohms?

I assume that since the coil is a 3 ohm coil it should have a resistanc of 3 ohms across the primary winding. Can anybody tell me what the resistance across the secondary winding should be?

Shouldn't I be able to determine if the coil is faulty with an ohm meter?

If anybody knows please let me know, meanwhile I'll measure some resistances.

Thanks everbody.
 

·
Registered
1969 Swiss 404 - 1977 Porsche 911 S
Joined
·
148 Posts
Discussion Starter #18 (Edited)
Scott is right, it's the coil

Thanks graphic66.

I found some specs for the 40611 that state primary resistance should be 3.0 ohms and secondary resistance should be 8.5k ohms. Those are the exact values I get when I test the coil.

I checked the original Bosch coil: Primary 6.0 ohms, Secondary 11.5k ohms.

I replaced the Flamethrower with the Bosch and the truck runs perfectly again so it would seem that although the Flamethower is up to the resistance specs there's still something wrong with it.

The post ballast voltage is still 25+ so I'm guessing my ballast went bad and the over voltage ruined the Flamethrower coil. I got a resistance of 4.5 ohms across the ballast which is .4 lower than 63TLF8's measurement of 4.9 on his ballast. Not sure if that is a significant difference or not.

Scott, I'll be placing an order for another coil and a new ballast resistor right away. Thanks for the time and help.

If anybody has more input feel free.

I'll update when I install the new coil and ballast.
 

·
Registered
63 UNIMOG S404.115
Joined
·
116 Posts
I got a resistance of 4.5 ohms across the ballast which is .4 lower than 63TLF8's measurement of 4.9 on his ballast. .
Two Tone,

My Ballast resistance is / was 4.6 Ohm. You may have seen the .9 Ohm suppressor resistance following that and rounded up. If you are showing 4.5 ohm, allowing for instrument calibration etc, I would say its OK.

By changing your coil you are also changing the voltages where you measure them in the system so there is always the possibility that may be connected to your problem. Also, correct resistance cold for your flamethrower coil may not mean that it's OK hot.
 
1 - 20 of 27 Posts
Top