Thanks for the replies - per my other post I am conintuing to have problems wiht the idle and the lurching on acceleration. I don't know if it's a carb problem or not - I have checked and re-checked the carbs for vacuum leaks (none found) and have balanced them (using a meter) and reset the idle.

Mike, I really don't know what you mean by getting the "correct setting of the zero's" and reworking the "cam slot"? Can you explain further?

I am thinking I more likely have an ignition problem and to that end I have ordered a Crane XR700 eletronic ignition (somethig that I have wanted to do for quite a while, but just haven't gotten around to it). I have a few questions about installation:

1) Do I have to replace the coil? I have ordered a new coil from Crane as well, but I get confusing answers as to the need to replace the stock blue Bosch coil.

2) Do I use the existing ballast resistors in my car, or will I bypass them?

3) Currently, I am running Bosch W7DC - should I switch to a hotter plug with the new ignition system (Bosch W8DC, or the NGK equivalent)?

4) If you read my other post (linked above), I installed a K&N air filter. Is it possible that it has screwed up my air/fuel mixture and thrown my car off? It really seems to have run worse coinciding with the installation of the K&N and I plan to buy a regular OEM air filter and see if it makes a difference.

I have taken the car on several hundred mile highway trips over the past month and at highway speeds the car runs great and I probably get 15-16 mpg - my problems still have to do with idle and initial acceleration.

Thanks in advance for any advice.

Ryan

__________________
RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

Hello Ryan,

I'm still interested in the car that all this pertains to, however the info I will provide ought to really help out regardless.

A bit of history - When I first got my 220Sb it ran just as you have described in most all of your experiences for 2 years now. Of course I did all the cleaning and vacuum checking stuff as we all do. I did find some literature along the way and I'm certain that somewere in this infinitesimal web there's more. However I did get some clues from the MB service manual of that era, very brief inasmuch as those Big Z's were "new" on the scene. In addition, I got a first blush attempt at a manual by a " college" person I believe, from the East coast from the web, and I picked up a copy of an MB manual section reprint from a Director of our MBUSA Club in Oak Ridge Tn. I also got a carb " parts " list set of sheets from a rebuilder on the east coast. The 3 latter items were for Z's of about 1967 or shortly thereafter. Being in the educational arena I was firmly convinced that I should make a manual for at least my 220SbZ. However I don't know of any others still running around this metro area, S/E Michigan, so I let the idea drop.

As I described about the cam plate, I was pleasantly surprised when 2 years after I had done the mod that I found that someone else had discovered the same problem too. He had purchased all the plates from a 1500 MB car yard in Ky, machined them as I did, and sold them.

As it applies to the throttle, the plate I describe mounts on the rear side of the Z's and converts the for/aft linkage rod motion to 90 degrees off and rotary motion. This converts the fore/aft rod motion to rotate the fore/aft Z throttle valve shafts. This plate has a slot in it for another piece of linkage that as I recall is the actuator for the Z secondary throttle valve plate sytem.

The prime factor as I said is to get each carb to start at the correct idle point. To do this you must get the plate to fully close and then just crack it open about 3/4 of a turn on the idle speed adjust screw. With the plate in place you cannot do this because the secondary barrel tang hits the botom/side of it's associated slot and holds the main throttle plate open. To do this adjustment on the car you must open the slot about 1/8" and then the main throttle valve can bottom out/fully close. When you do this and then adjust the throttle plate 3/4 turn open, the plate is in correct position for the vacuum bores on the main throat to correctly operate the vacuum systems as well as prime and start the accelerator pump discharge. This obviously relates to idle and throttle apply acceleration.

Of course all this and the rest depends upon the linkages being off the carbs for settings.

In addition, one must ensure the accel pump linkages are correctly gapped and that the plunger is in good working order as well as the two accel pump ball check valves.

An original problem that you described about the spray out of the accel pump jets can be directly caused, (as in mine originally ), by the throttle plate being open too wide at idle. Lotsa suction in those two coffee can sized carbs!! That's why for one reason you have to get the valves closed down to the proper position. It's like math and measurements, if your zeroe is wrong, every value after that is wrong too.

Idle mixture?? Yeah lots writen about setting those, I won't elaborate. You'll know when you get it right, by sight and by ear and feel. & a Tach.

Oh, the accel pump discharge volume. There was a nice MB tool for that. It was shaped like a kidney bean withe little verticle stick handle, graduations for the volume spec on the side. Shaped like one of those little hospital trays that you "spit" into. It has a number, but unavailable from MB. Plan B. Get a piece of small diameter flexible tubing and a nice hypodermic needle. Plug the tube onto the accel nozzle, pump, suck it up, measure, worked great. Just remember that the diaphragms are leather, if they get the slightest hint of being dry/derprived of fully wet with gasoline, they WILL warp, beyond repair. That's one big reason that those old cars have such a hell of a time after they sit for a long time and the bowl fuels dry up. Makes for a nice gummy bear in there too.

Synching the carbs, good luck. Go for the best you can get. Are you married, do you always get her to agree with you?? Same ratio as carbs 100% synching!!

Also, don't use anything other than a bristle to clean any orifice. One scratch will raise unbelievable hell with flow patterns that you won't believe it. Speaking of "orify", you may wish to clean those two on top of the carb, high speed jets and emulsion tubes. Carefully, and don't criss-cross the parts. Plus when you remove the two brass orify, use a "minus" that is snug. This so as you don't distort even the slot on top.

Let know how all this sounds to you, good luck, willing to help, regards,

Mike

Ryan,
I put a XR700 in my 280C and a XR3000 in my 250C. The XR3000 uses no ballast resistor and I used a new coil. The XR700 needs a ballast resistor or a internal resistor coil. I replaced the coil with a non-resistor type and used a Chrysler ballast resistor as recommened in the instructions. They gave the part number which I don't remember right now. Be ready for an alarming amount of smoke from the resistor on startup. It has oil on it that will burn off in a few minutes.
Find the wire that is hot with key on, it goes through the resistor. There is another wire that comes from the starter, it bypasses the resistor to provide full voltage on startup.

I wonder if you timing chain is a bit stretched. Do your timing marks jump around at idle?
As for the 42 degrees timing, thats at something like 3500-3800 RPM. The vacuum advance is about 4 degrees and the retard is 8 or so. I pulled both lines from the can, plugged them and set the timing to 40 degrees and ignored the idle timing. I only run the advance side of the can and have no idea if it even works. The car pulls strongly from a stop and will go sideways on the 1-2 shift in the rain. But then I only get 13MPG.

Michael

__________________
Usta haves '69 250/8, '76 280C, 1971 250C 114.023, 1976 450SEL 116.033
Current have, 1983 300SD 126.120

Regarding MikesRadioShop thoughtful observations -

On th 114 cars, the linkage is in-line, meaning that there is no mechanism to turn the motion of the throttle "sideways." The absolute idle is controlled by a stop on the front carb, linked to the rear by an adjustable rod. TTBOMK, there is no way to adjust the relative "start" positions of the throttles except by setting the front carb against the stop and then balancing the carbs.

I don't have a live car with Zenith's any more, but I will pull out the parts carbs and have a look.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

Chuck,

So that's why I was so confused about Mike's suggestions ( I don't think he was aware that the car in question was a '72 250).

My Crane unit and coil is being delivered today - do I use the exsiting blue coil and ballast resistors or should I use the new coil (Fireball PS40, I believe)? I believe that the new coil comes with it's own resistor???

And what about changing the plugs to a hotter plug?

Any thoughts on the idle/lurching problem possibly being related to the K&N air filter?

Thanks, as always.

Ryan

__________________
RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

The whole point of the Crane breakerless ignition is to take the points out of the picture so as to be able to run more voltage to the coil. So if you have the model with internal resistance, I think you bypass the resistors and run 12V to it. But the instructions should clarify this.

If you are getting the right burn on the current plugs, I would stick with them, but maybe open the gap. Again, the instructions should advise. Drive the car for a while and see what the plugs look like.

I don't see how the new air filter could have caused the lurching problem.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

The low end Crane device replaces points and still requires resistance regardless of what coil you use. The instructions will tell you that very clearly.
The Crane (or MSD or other mfg) high end device is a capacitive discharge ignition box that derives several hundred volts from a switching power supply, charges up a capacitor and dumps that energy into the primary of the spark coil when it is triggered. It applies more volts but less amperage to the coil, so the stock resistor can be removed (and should be removed) if using a CD, otherwise voltage dropped across that resistor will be wasted.

You will find that the plug gap can be increased substantially when using a CD. I use .042 in gap. I use the low end (Crane XR-700-0231) to trigger the high end Crane HI-6 CD.
see my setup pictured in this thread:
Distributor Rebuild Kit?
The XR700 is the small black module in front of the blue HI-6.
I have since replaced the coil shown (MSD oil filled) with a Crane LX-91 coil. The resistor, although shown in the picture, is not there anymore (it was not connected anyway, I left it installed in case I ever had to revert to the stock coil and points setup)
I am using NGK BP-6ES and used BPR-6ES (resistor plugs) they all worked the same I can't tell any difference except my radio goes swish-swish much worse with the resistorless pugs
oh yes, this is on my 1971 220.
1971 220 (gas) 4-spd manual 106441
1979 300TD w/ ’85 turbo engine 296650
1983 300D 243280
1985 300TD 223470
1987 300D 262300

__________________
'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

Ryan:

When I put the Crane XR700 on my 250C I also used the Crane ps40 coil and mine came with a ballast resistor and I used that. I ran NGK BP5ES plugs gapped .045. The BP5ES plugs are one step hotter than the W7DC Bosch units. (The comprable NGK plug to the W7DC is the BP6ES). In my case the NGK plugs always performed better than the Bosch and I ran both brands to get a comparison. I had better idle, less fouling and smoother transition with the NGK. That was just my experience. The local "Weber Guru" who jetted my Webers just happened to be Japanese (concidence huh?) but he knows his stuff and he also had two (2) 250's "back when". Said he always used NGK plugs - that is how I got to try them and I was most satisfied.

When I installed my XR700 I already had the Webers on the car and I still had an off-idle stumble and a slight hesitation at part-throttle acceleration between 25 and about 50 MPH. The Crane unit totally eliminated that.

You might have to play around with the trigger point on the unit - I did on mine at first. Since you have the Zeinth carbs and your static timing is different from what I ran (I ran 10 Degrees Before TDC with ported vacuum advance from the front Weber) I an not sure where to exactly set your initial trigger point (I no longer have the car or the instructions). I do remember, the last time I set the trigger point it was around the 10 degree mark and that is where I left it for over 3 years. I never had to reset the trigger point or retime the iginition.

Hope this helps. good luck (again).

Dan

Oh, one more thing. since the ignition is fired by an optical trigger make very sure that you clean any and all oil residue from the base plate and inside of the dizzy above the plate. If you are not replacing the distributor cap, make very sure that you clean the inside of the old cap very well. Same with the rotor. It doesn't take much "residue" to have an adverse affect on the optical trigger. Needless to say, don't ask how I know this!!!

__________________
Dan Taylor/ Tulsa, OK MBCA
'84 300D/'90 Jaguar XJ6/XJ40

Afternoon Gents!!

Nope I didn't know "till now what the car is that I was speaking to. Although I may have seen this set-up before.

In this case then, I can't imagine an air filter causing the accel problem. Plus if the zero TV opening is fixed to a hard stop I would bet the Accel pump circuit is highly suspect. The pump volume & timing is very important so as to avoid your described problem. You will need to measure the volume to confirm indications of both ball check valves and diaphragm capability. I'm sure that your Z's have some means of setting the Accel pump apply point. This point also closes, if I recall correctly, a spring loaded air bleed port to the bowl. On the side and under the bowl cover.

In regard to the hard stop for the TV plate, then that still applies to what I was speaking of in getting to that point of the opening of the TV plate by approx. 3/4 turn on the idle set-screw, If it has one. I'm not sure of what you have from the added postings.

If there is no screw for idle speed setting, then the problem of Accel. nozzle spray at idle could well be caused by two simultaneous problems. This could be that the accel pump intake and exaust ball check valves are contaminated and held off their seats and maybe that the bowl float valve setting is worn/too high. This would cause the same probem as you have. I didn't mention this apect of things before because I presumed you had checked /cleaned that area.

Sounds like the other gents have a lot of experience in upgrading to modern ignition stuff. I will offer that NGK plugs are widely touted to be extermely good and better than Bosch in quite a wide area. Saabs use them and so does MB, even in their German museum/classic car restoration provider facility. Insofar as hotter plugs go, ain't too hard to burn a hole through aluminum pistons ya know.

This weekend I'll look for the Zenith manuals and see what I can find for you and get back with you Monday.

By the way are you a MBCA member?? I'll bet if you are/were, there would be a lot more literature available to you, especially from the National Technical Director. He's well seasoned and informed, plus a great guy to talk with.

Have a great weekend.

Mike

PS. Just had other thoughts for you. Sounds like your'e making your car into a runner. Have you shaved the heads? That will cause stumble if the plugs/proportional ingition voltage/timing isn't right. The higher the pressure, the harder to fire. If you have been in there or maybe not, consider too that carboned valves also cause stumble and idle problems too.
M

Appreciate the replies - Dan, let me ask you a few other questions about the Crane. I think am going to install the PS40 and the ballast resistor, but I'm trying to figure out how to hook up the wires that are currently connected to the 2 original resistors.

I have reviewed the ignition info you sent me last year - I have the first version of the transistorized igntion with the negative coil grounded (brown wire). The .06 resistor is connected to the coil+ and other side is connected to the ignition box. The other resistor has two wires connected to the left side and one wire connected to the right side. I believe one of these goes to the starter and one goes to box, but I don't know about the third (it appears to run over to the side panel under the fuse box - it might run directly to the fuse box). I know that I am replacing the two resistors with the one that came with the crane coil, but I'm not sure where all the wires are going to go. I'm pretty sure that I bypass the 'box' altogether and according to the coil instructions one side of the ballast resistor connects to the coil+ and the other side of the resistor is the other wire that connected to the coil+ (which if you are following above was connected to the .06 resistor ???). The coil- side connects to the points or ignition module. I'm confused - does the new coil still ground using the brown wire to coil-?

To recap - I've got two wires connected to the coil - coil- to ground and coil+ to the .06 resistor.

The resistors have 5 wires connected to them - 3 to the .04 resistor (in the ignition manual you sent me I see only two wires) and 2 to the .06 resistor (one running to the box and the other to the coil+). How do I wire in this new coil and ballast resistor?

I haven't even gotten to the trigger point yet, but do you just mean where I time my car? I still have the control valves connected so my car is timed at 4 degrees ATDC (per the manual). The Crane XR700 instructions say to the align the timing marks (on crankshaft damper, I assume) after marking distributor below the number one spark plug. Then I need to get the rotor pointing to the mark - with the timing marks still aligned - make sense?

Sorry this is so long...

Mike - I have checked and re-checked the accel pumps and I recently replaced the needle valves etc.. I don't have any way to mmeasure the exact amount of fuel pumped but I'm working on rigging up something.

I'm not a MBCA member - how do you join?

Ryan

__________________
RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

If you were to remove all resistors, the box and the coil, you should have three wires left.
The one from the distributor will be replaced by the three conductor wire that will connect the pickup to the XR700. Of the other two, one will be hot with the ignition on (run) and the other will be hot with the key turned to start (start).
The run wire will go to the resistor then to the + side of the coil.
The start wire will bypass the resistor and go to the + side of the coil and can be connected to the coil or the side of the resistor opposite the run wire.
The XR700 will draw it's power from the + side of the coil or the resistor opposite the run wire, with it's red wire.
The coil does not get grounded, the XR700 will do the "grounding" via its yellow wire which will be connected to the - side of the coil.

See
http://www.cranecams.com/pdf/90000700.pdf
Check out page 10, figure 19.

The ignition fires when the slot in the shutter passes the optical trigger. Aligning the distributor at number one ensures that it will fire when the rotor is pointed to the number one tower. Your TDC marks will come up twice for each rotation of the distributor, make sure that the rotor is pointing to the number one tower and not 180 degrees out or it won't run when you are done.

My multiple wire connections (start and red wires) are done at the resistor so that there are only two wires to the coil. I thought it looked cleaner that way altho it makes no difference electrically.

By far the hardest part for me on both of my Crane conversions has been fitting the optical module in the distributor.

Michael

__________________
Usta haves '69 250/8, '76 280C, 1971 250C 114.023, 1976 450SEL 116.033
Current have, 1983 300SD 126.120

Ryan:

Sorry I didn't respond earlier - was "out of pocket" this weekend.

What Michael said is correct - including fitting the optical module inside the dizzy. Since I build and fly RC Model Airplanes I have a good collection of smaller screw and nut drivers. A small "holding" type screwdriver was a very big help during my installation as was a small hemostat.

One more thing I forgot to add was that I also replaced the dizzy cap, rotor and ignition wires. I figured that since I was replacing the ignition system might as well do it all.

You might want to try a set of NGK plugs sometime. If you do, I would keep the Bosch's until after you do the upgrade so you can have a better comparison - before and after. You also might want to play with the plug gap - I finally settled on .045 as that seemed to work well for me.

Good luck.

Dan

__________________
Dan Taylor/ Tulsa, OK MBCA
'84 300D/'90 Jaguar XJ6/XJ40

Ryan,
I'll see if I can remember to get some pictures of the installation on my 250C. It's a XR3000 so ballast resistors but the pickup is the same.

Michael

__________________
Usta haves '69 250/8, '76 280C, 1971 250C 114.023, 1976 450SEL 116.033
Current have, 1983 300SD 126.120

Mornin' all,

I perceive from your posting that you have checked both accel pump balls & seats plus addressed the float bowl inlet needle valve/seat/replacement soft washer. Of course along with that goes the specified height adjustment to the bottom of the bowl cover and bearing pin rattle.

You haven't said if you have looked at the external accel pump apply lever and it's specified gap. IE: I believe mine was 2.2mm. Thinking back now, I recall that on that lever there is a little roller that goes dry, binds up and wears a groove in the roller. In this instance, when the lever applies the pump it slips of the track into the groove and decreases apply stroke which backs off on the pump volume. This then causes a "hiccup" upon acceleration.

For volume determination, think about what I had mentioned earlier, re: syringe & tube.

Sounds like you & others conversing on this site would be excellent MBCA candidates! Amongst many attributes of membership you may well find lots of local folks who have the wherewithall & desire to "tinker" right there with you. As I would if you were here. Lots of technical events here as well at other places I'm sure, for you to enjoy. Blah-Blah-Blah.

MBCA = 1800-637-2360, www.mbca.org

Ask 'em for sample/s of past issue Star magazines, they are a "Wow".

If anyone is local to S/E Michigan & wants more info to join our Section, michael.mountain@us.marposs

Regards,

Mike

Thank you guys for the replies,

I have only one concern about the resistors and the existing wires - I found the wire that's hot when the key is on (11.5 volts at the right side of the 0.4 resistor), but I don't know where the other wire is? I have two wires hooked to the other side of the 0.4 resistor that I assumed both went to the control box. How do I track the hot wire in run and do you mean hot while I am cranking the starter?

I have the above diagram in my instructions but I was just confused about the 'run' and 'start' wires. I know I need more juice to start and that the run circuit will have the ballast resistor wired in - I just am not sure which wires are which on my current factory setup.

Thanks, Ryan

__________________
RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE