Non-resistor Spark Plugs - Can they be found?

[bolomiester]

I recently bought an 89 300 SE. I was lusting after a diesel but stumbled accross it, and it was in such remakable condition and so cheap I couldn't pass it up.

The first couple of days it started, idled and ran perfectly. Then, on the third day, during a driving rain storm it started but then would immediately die. It did this about 5 times, then stated and ran perfectly as before. When I got it home I pulled one of the plugs and discovered it had Bosch Platinium Infusions installed. I figured this was the source of the starting/dieing problem and went looking for copper core non-resistor plugs.

No one local had them, of course, so I found a supplier who listed Bosch H9DC's and ordered a set. However, when they arrived they had subsituted HR9DC resistor plugs for the H9DC non-resistor. I called to complain but was told Bosch no longer made the non-resistor version. The sales desk guy was very helpful, but in tracking down every brand they carried (NGK, Champion, Denso, AC Delco) all companies were now suppling resistor plugs as replacements for non-resistor.

I called a few more suppliers and was told the same story. They did carry non-resistor plugs but now they could only get resistor type.

I finally went to my local Auto Zone where I had a choice of copper core, resistor Bosches made in India, or copper core resistor Champions made in USA. Based on advise from this forum, I choose the USA Champions over the Indian Bosches. I gapped them at .040, again, based on advise from the forum, and the car started, idled and ran perfectly; however, it only did the start/die thing one other time while I was tracking down spark plug, so the jury is still out on whether the spark plugs were the problem. The car does seem to idle smoother, though, and about 100 rpms faster than before. 600 rpms vrs. 500 before the plug change.

I said all that to ask if anyone knows of a "for sure" source for a brand still making non-resistor plugs. I can't swear it's true, but based on what the suppliers I spoke with are saying, every brand has stopped making non-resistor plugs so that even if there are a few on shelves here and there, the supply will, sooner or later, run out.

If that comes to pass what are we going to do to keep our older MBs on the road? Is there some way to change the combination of plug wire ends, distibutor cap etc. configuration so that the total resistance would be the same with resistor plugs as it was with non-resistor?

[mbdoc]

Your fear of resister plugs is un-founded, no problem using Bosch resistor plugs in that car! NOT platinums but normal plugs.

[Cal Learner]

MBUSA Classic Center in Irvine stocks the correct non-resistor NGK plugs.

[bolomiester]

Originally Posted by M.B.DOC

Your fear of resister plugs is un-founded, no problem using Bosch resistor plugs in that car! NOT platinums but normal plugs.

My fear of the resistor plugs comes from this forum, which has been a life saver. If not for its invaluable help my MB would probably have gone to the crusher not long after I bought it. However, with the help and advise of the members here, yours included, I've made my 380 sel a reliable and enjoyable car.

Of course, the problem is that I've come to rely on the forum's advise so much that whatever I read is practically gospil. Whenever I've asked for help, the responses I've received have been spot on. Therefor my fear of resistor plugs.

Maybe this will be a good test of resistor copper core vrs. platinum. The "new" car, an 89 300 se, is nearly perfect. The only fault, so far, being the 2 instances of start/die in a week of daily driving. It will be interesting to see if the problem reapears now that I replaced the platinums with copper cores. I'll report if it does.

[pawoSD]

Here is my interesting story:

I got my 300E last November....it was misfiring....so I replaced the distributor/rotor/cap and it got better, then I pulled the plugs....it had nasty old Champion Resistor plugs in it.....I went to the dealer and actually acquired a set of Real-deal Bosch non resistor H9DCO made in Germany plugs. Put them in, it ran amazing....for 60 miles....then it began misfiring bad and was way down in MPGs/power.....so I pull the plugs again, they were horribly coked and dirty. I went to autozone and got a set of super cheap "Splitfire" resistor China plugs.....put them in.....it ran great again for about 100 miles....then back to the same old....but even worse than before....so I put the formerly retired champions back in, but had cleaned them. It ran "ok" from here on....(several hundred miles)....but I still wanted to replace them with good plugs. This time I ordered NGK Resistor plugs online....put them in, and it ran beautifully.....it has been running those plugs for about 2 months....and close to 1500 miles....0 issues. Idles so smooth you can barely tell its running! Plenty of power.....good MPG's....I've been getting 20mpg even when I am a leadfoot.

Moral of the story, get good plugs, and the Resistor ones work fine. NGK are good, and the Bosch Resistor plugs are probably fine too.

The whole resistor/non-resistor thing is a myth.

The only important thing is to not use Platinum plugs as the electrode is too thin.

My 300E does the start/stall thing too....I am guessing it is the injectors or fuel accumulator....but it starts fine after 2-3 seconds of cranking on the second try....so I am not going to worry about it. Once it starts it runs perfectly.

[bolomiester]

Originally Posted by pawoSD

Here is my interesting story:

I got my 300E last November....it was misfiring....so I replaced the distributor/rotor/cap and it got better, then I pulled the plugs....it had nasty old Champion Resistor plugs in it.....I went to the dealer and actually acquired a set of Real-deal Bosch non resistor H9DCO made in Germany plugs. Put them in, it ran amazing....for 60 miles....then it began misfiring bad and was way down in MPGs/power.....so I pull the plugs again, they were horribly coked and dirty. I went to autozone and got a set of super cheap "Splitfire" resistor China plugs.....put them in.....it ran great again for about 100 miles....then back to the same old....but even worse than before....so I put the formerly retired champions back in, but had cleaned them. It ran "ok" from here on....(several hundred miles)....but I still wanted to replace them with good plugs. This time I ordered NGK Resistor plugs online....put them in, and it ran beautifully.....it has been running those plugs for about 2 months....and close to 1500 miles....0 issues. Idles so smooth you can barely tell its running! Plenty of power.....good MPG's....I've been getting 20mpg even when I am a leadfoot.

Moral of the story, get good plugs, and the Resistor ones work fine. NGK are good, and the Bosch Resistor plugs are probably fine too.

The whole resistor/non-resistor thing is a myth.

The only important thing is to not use Platinum plugs as the electrode is too thin.

My 300E does the start/stall thing too....I am guessing it is the injectors or fuel accumulator....but it starts fine after 2-3 seconds of cranking on the second try....so I am not going to worry about it. Once it starts it runs perfectly.

That is a very interesting story, and valuble as well. I didn't want to buy the Champions because of poor reports from some of the forum members, but I was even less willing to buy the India made Bosches, again because of negative reports from forum members. However, I knew the platinums had to go so, your experience with the NGK's is much appreciated. I've used that brand on other cars (Volvo & Toyota)and had great luck with them. Looks like I'll be ordering a set today. However, I'll leave the Champions in for awhile to see what happens.

[teezer]

i'm sitting on 17 boxes (170 plugs) of nos H9DC0

6 for $25.00 shipped to U.S.

[RBYCC]

Originally Posted by bolomiester

That is a very interesting story, and valuble as well. I didn't want to buy the Champions because of poor reports from some of the forum members, but I was even less willing to buy the India made Bosches, again because of negative reports from forum members. However, I knew the platinums had to go so, your experience with the NGK's is much appreciated. I've used that brand on other cars (Volvo & Toyota)and had great luck with them. Looks like I'll be ordering a set today. However, I'll leave the Champions in for awhile to see what happens.

NGK's are great and still available !
I run BP6EFS in my M103-12V twin turbo.
They are one step colder then the BP5EFS which is the same range as the Bosch H9DCO.

[JonL]

Originally Posted by bolomiester

The first couple of days it started, idled and ran perfectly. Then, on the third day, during a driving rain storm it started but then would immediately die. It did this about 5 times, then stated and ran perfectly as before.

This could very well be caused by faulty ignition wires, distributor cap, and rotor. If your spark plugs are requiring more voltage to fire (because of their resistance, the eroded gap, the small electrode, perhaps a non-optimal mixture strength during starting) this, along with the dampness, may encourage arcing elsewhere in the secondary ignition circuit. If your cap/rotor/wires are in good shape, they should not arc even with very marginal spark plugs.

[lkchris]

Get the Beru plugs listed in your owners manual.

http://www.beruparts.com/main.sc

[pawoSD]

Originally Posted by teezer

i'm sitting on 17 boxes (170 plugs) of nos H9DC0

6 for $25.00 shipped to U.S.

That's more than I paid for them at the dealer...though with shipping I suppose its ok.

Paid about $11.50 for my 6 NGK's.

Why do you have so many??

[Cal Learner]

Originally Posted by RBYCC

NGK's are great and still available !
I run BP6EFS in my M103-12V twin turbo.
They are one step colder then the BP5EFS which is the same range as the Bosch H9DCO.

Right about NGKs, they are great. Out of curiosity, why did you step down to a colder plug? What difference have you noticed?

[OliverVB]

Nology silver electrode spark plugs are available for some Mercedes engines. These are non-resistor plugs and used by the racing folks, not generally available in regular auto parts stores. I have been running a set in my M103 '90 300E for a few years and just recently installed a set in my '77 M115 engined 230. These plugs have less resistance then even the copper electrode plugs and have a large diameter center electrode like we need. The theory behind not using the slim electrode plugs is that with the relatively low energy ignition system we have in older cars the weaker spark may be disrupted during the compression cycle. Bought my first set directly from Nology in CA and the most recent set from an ebay dealer. There is an application chart that may help finding out if a plug is available for your engine on Nology's website: www.nology.com

[teezer]

Originally Posted by pawoSD

That's more than I paid for them at the dealer...though with shipping I suppose its ok.

Paid about $11.50 for my 6 NGK's.

Why do you have so many??

bought out the inventory from a farm implement place in oklahoma, evidently these were used in generators and other equipment of some sort

having been in the parts game years ago, i learned to stock up when something has been discontinued, i should never run out

[Strife]

Originally Posted by RBYCC

NGK's are great and still available !
I run BP6EFS in my M103-12V twin turbo.
They are one step colder then the BP5EFS which is the same range as the Bosch H9DCO.

I am very happy with NGK and am not having a problem finding them, and they are cheap too!

The importance of using a non-resistor plug in a system (coil, cap, rotor, and wires) designed for them has been beaten to death in this forum. My opinion FWIW: different resistance from that originally specified will change the waveform, height, and duration of the spark. Not by much, but maybe by enough to cause a problem.