1989 190e no-start after spark plug change
 

Any help greatly appreciated-no start after changing spark plugs and coolant sensor-read on other posts but just feel a bit lost here. The fuel distributor is leaking somewhat as well- so i bought starter spray to eliminate the FDand sprayed into meter plate but nothing. I checked spark by pulling a spark plug and grounding on the exhaust manifold and it was present but I read(this forum) that is not a full-proof test of spark. The rotor and cap, coil, spark plug wires have probably never been changed in at least 10 years but this occurs just after i relaced the plugs?? I put the old plugs back in (platinum) still no start. Thanks guys.

update-I changed the coolant sensor one minute before spark plugs and it appears some coolant spilled on to the crankshaft position sensor that now appears quite wet in that area/connection. Could I have done something by getting the Crankshaft position sensor wet that effect ignition,coil etc?

What kind of plugs did you use?

The M103 engine requires H9DC0 Bosch NON-RESISTOR plugs....generally only obtainable at a MB dealer or from this site. If the distributor rotor/cap/wires/coil are all original, you can start there. ;) These are picky engines, and need to have the right stuff on them to run properly....but when they have the right stuff, they run smoooooth.

Platinum plugs should NEVER be used in an older MB engine.

thank you very much for your reply
 

I edited my post to say that i also changed the coolant sensor and some coolant seems to have leaked on the crank shaft position sensor as it is quite wet in that area. Could that effect my ignition?

the plugs I put in where Bosch super plus-HR9 DC+ It had platnums but it ran. Would it at least not fire? Thanks

The plugs you used are Resistor plugs.... HR9DC+.....you'll have to go to the dealer or this website to get the right ones.

It should have fired and possibly run, but not if the coil/wires/rotor/cap are not perfect. It is harder for the ignition system to get a decent spark with resistor plugs....so if it is weak in any way, it won't work. As you have mentioned all those parts are real old, you should probably replace all of it. I did on my 300E and it runs perfect now.

thanks
 

Ok will do that and replace all. Is there a way to check the coil spark quality other than disconnecting and looking for a fat blue spark? Do you see any connection to coolant going on to the crankshaft position sensor and having an ignition effect somehow? I m accepting your advice just a bit perplexed it will not pretend to fire up for a moment but I took in your advice regarding the resistor plugs especially. Thanks again!

PS would you recommend an in-line test of the spark plugs to confirm your feelings. I read i can buy a tester and check spark quality with plugs actually screwed in to the motor-would be nice to have confirmation.

Coolant on the crank sensor shouldn't affect it, unless it was cracked or something.

You can test spark with either an O-scope or an in-line tester. There are open, adjustable spark testers you can use, or sealed units. I don't work on small engines, so I have the sealed one from matco.

I tried to link, but it didn't work.

Just go to matcotools.com, search for "spark tester" and click on the first link. It'll show you both types.

thanks-you guys are really great for helping!
 

Ok on web site and perform the test of the spark. Could my timing be off-read about the rotor actually breaking but would seem very odd it ran then not just after replacing plugs. perhaps the new resistor plugs put a strain on the old coil, wires, rotor etc which have most likely have never been changed. Thanks again for your input and advice!

Calm down
 

If your engine was running before the plug change, it should run after the plug change regardless of platinum/non-platinum or resistor/non-resistor. May not run optimum, but should run.

If the only abberation in the job was wetting down your CPS, and it will not start, that is your problem. UNLESS of course you did something else like bollix your plug wires. Did you cross them? Did you pull on the wire to remove the connector rather than pull on the connector?

Anything you aren't telling us?

thank you for your reply rocky racoon-great questions
 

excellent questions even though i am no expert. The other issue was the fuel distributor which was leaking as the plug on the pententiometer had slid off somewhat but this happened before and it ran. I figured I should take the FD out of the equation so I used starter spray to eliminate the Fuel distributor issue entirely if i have a possible ignition issue-maybe I have not eliminated the FD?

To be honest, i was a bit awkward with the plug wires turning the socket wrench catching/pulling/knocking the wires at times as instead of disconnecting all of the wires at once I replaced one plug then replaced the wire then on to the next plug. I checked the wires for possible mix up but it seems quite difficult with the wire lengths to cross over but I may have done that in one cyclinder perhaps closer to the front of the engine. If it is the wet crank shaft postion sensor-would it be a case of simply disconnecting and cleaning it off? Thank you very much!!

update-wire connectors were very difficult to unplug now a few seem sloppy-moving back and forth-dont think that was the case b4 plug change.

confession
 

I must admit ,especially to rocky raccoon, that i pulled very hard to get the plug wires off-Now the wires are sloppy in comparison. Perhaps many years since plugs had been changed.

plug wires
 

O.K. Now, one more thing and please don't take offense. I have the impression you may be inexperienced on MBs.

Admittedly, I do not have the same model as you but almost all of the gas Benz do NOT use the threaded-on cap at the top of the spark plug. The plug connector is made to grip directly onto the threads. If you have the caps on the plugs, unscrew and discard them and you will find the connectors will fit easily and securely with a little push.

It is possible you have damaged the plug connectors by pulling on the wires instead of directly on the connectors. A simple pliers-like tool made for pulling spark plug connectors is available a very low cost at any chain auto parts store.

Let us know how you make out since it adds to the data base.

no offense taken
 

No experience with MBs at all-replaced the OVP relay to get the car to start cold but thats it apart from leak on the washer fluid pump. I checked the old spark plugs and they still had the caps on but what you say makes sense. I did pull at the wire connector housing ,not on the wire, but I did have to pull very hard. Thanks again!

Will of course try plug without cap and post result.

If it has spark, gas is making it to the cylinders, and the cylinders have compression, and it's in good timing it should make at least some indication that it wants to start. I might be wrong, but I think the CPS just let's the computer know what the RPMs are (I think I'll start my car and unplug it to see if it stalls, obviously I couldn't drive it, but it might start or run?). Anyway, I would be surprised if the CPS had anything to do with it.
But a weak spark might be a problem.

The plug wires on these engines should really only be removed with plug wire pliers. Obviously it can be done without them, but they are on pretty tight and deeply seated, with time and heat they can be clamped in there real tight. If you grab them at the wrong place and pull them it's very easy to pull the wire out of its metal connector as it comes off. In many cases the wire will still work by arcing to its connector inside the boot, [perhaps] creating a very weak spark.
Likewise, even if you don't yank any wires out of place, the boots need to be pushed ALL the way in until they are tightly gripped on the plug and all the way forward. It should feel pretty firm laterally as well, that is, they should feel relatively stiff when wiggled side to side. Once again, failure to do this could mean that the wire connector may not be in contact (or tight contact) with the plug terminal and [perhaps] causing a weak spark as above.
A combination of the two is certainly worse yet.
I say "perhaps" in brackets because an arcing spark can sometimes (if it's not arcing too far) actually intensify the juice to the plug. In the 50-60s they used to sell "spark intensifiers" that went on the ends of the plugs ahead of the wires and were basically just a measured gap for the spark to arc across. Some kits had transparent tubes so you could watch your poppin' engine give a light show. I once had a mopar with a fouling plug and temporarily pulled the boot away from the plug so the arcing spark would make the plug fire hot enough to keep it from fouling until I had the time to fix it.
Actually, with that in mind, it might help to have someone crank it at night and see (and listen) if there are any wires arcing.
Make sure the coil wire is secure on the coil, look for grey/black chalky marks on the coil wire where it comes close to/touches metal engine parts. Also, if you did the job on a rainy, damp day maybe the dist. cap got damp or is arcing out along a trace or a crack. Lastly, if the dist. cap is 20 years old the carbon center contact might be fouled or just about worn out.

All weak suggestions I know but might possibly help.

terrific
 

Thanks long gone. Will have to check that tomorrow night. My connectors do move from side to side and have been advised to unscrew the caps of the plugs. Do you think it would be wise to pull the spark plugs with the connectors and check for spark on every cylinder? I assume this would tell if the wires are damaged but perhap not totally. So far i have only checked one spark plug and grounded it to the manifold and saw spark. Thanks for all the great info and taking the time ouf of your evening to reply-I will reread to take it in better.

Long-gone-Ok on arcing-so will perform test as you suggest-seems my test will not be that useful if a weak spark.

Actually it's kind of hard to imagine that the car wouldn't at least try to start even if you messed up half of the wire connectors. I'm inclined that there's something else up with it.
But, maybe you ruined 4 or 5 of them, I don't know, sounds like you weren't exactly gentle with them. One other thing came to mind, when you put in the plugs the seats in the heads should be as clean as possible so they seal well and don't leak compression (and hopefully you remembered to tighten them) :), but again you'd have to mess up more than half of them to be where you're at.
Just make sure the boots are pushed in tightly, you can kind of feel them lock onto the plugs. As far as the plug tips, I don't recall whether mine are on or not, I'd have to pull a wire and see, though I have no reason to doubt that they might need to be removed. Look at your old plugs, it ran okay before I presume, are the tips still on them?
It might be hard to tell if you pulled a wire out of it's connector. Maybe take a good look at the wires where they enter the boot, if it's real clean for a quarter inch or so that might mean you pulled it out. Maybe the spark tester would be a good idea, I've never used one.
There are 190's and 300Es showing up in the junk yards pretty regular now, especially after the cash-for-clunkers program. I got a set of Beru wires in their plastic cover with a cap and rotor for $10. They were virtually brand new. Maybe you could find a decent set that way (grab the coil too) and swap them out at a tenth of the regular price and see if that's the trouble.

update on no start
 

long-gone-think you were right being something else because I had mentioned that there was a leak on to the crank shaft postion sensor-dh jenkins had mentioned that unless there was a crack there should no effect. There is in fact a crack so much so that I feel I could easily snap the line/wire-feels very, very brittle. It lies directly below were a bit of coolant spilled when I changed the coolant sensor just before the spark plugs then no start. What do you guys think?

If it's cracked, it's probably bad. The CPS is a hall-effect sensor, and reacts to tabs on the crank to get the timing signal. The slightest change in the distance between the sensor and the tab can screw up the signal, and any liquid inside the sensor will more than likely corrode the windings.

Congrats - I believe you just solved your no-start issue.

dhjenkins esp
 

I may have spoke too soon. that wire does not appear to be the connection of the CPS. I did spill some coolant but another tech said the same as you with regard to spillage-very difficult to upset that connection although I read that is a possibility of a no-start if is disconnected/damaged. Thanks.

I thought you said there was a crack in the sensor itself, not the wiring...

update on no start
 

to be honest, at this point i dont know where the connection for the CPS is-there was a cracked wire right behind the oil filter and down a bit but thats does not look like the plug of the CPS I saw on the net. I am about to pull my coil to make sure there is spark there. Do you or anyone here know if I buy an in line tester for the spark plugs how useful that test is. Will it only tell me i have spark? Or will it give me an idea of the strength?

I read where someone had a 190e-same year-had spark, timing was right, had fuel, etc and it turned out to be a bad ignition module or whatever the coil plugs into is named. Perhaps that is very rare.

Read my post on the 1st page about spark testers. They are useful in determining spark, but it takes a timing light to determine if it's sparking at the right time.

Ignition module is the correct part, and they do go bad; like any part. Of course, a bad ground could cause all your problems as well. People always forget about grounds... Voltage to the part is useless if it can't get to ground and complete the circuit.

At this point, I'd take it to an indy - they'll have the necessary tools to verify everything at once in less than an hour so you can replace the correct part and be done with it.

To be honest, unless you have the correct tools to check & verify things, all the FSM's, guides & advice in world can only lead you to an educated guess. As I've stated before, I've seen countless people spend many hours and hundreds of dollars replacing parts on the advice of others before coming to me (or my shop), only to find that the correct repair cost less than 1/4 of what they spent on their goose chase. An hour of 'real' diagnostic time performed by a 'real' tech with 'real' tools is worth more than you know.

very difficult to argue with that
 

Dh Jenkins-I will reread what you say about plug testers. Its very hard to argue with your advice and experience about going to an indy for the repair.

I tested for spark which I have from the coil. I was going to pull the fuel relay and then spray ether and then i think thats it for me. May also pull the rotor cap to see if the rotor spins and somone said something about it possibly breaking from the bracket but still spinning.

The only other things is I had to hammer (a bit) this metal tab thing to unscew the coolant sensor-silver with a round hole. It started right away though. It was only after changing the spark plugs it would not start.

Ok, it took me long enough to locate this thread again, but read it and see if it helps your situation.
http://www.peachparts.com/shopforum/tech-help/264898-1990-190e-no-start.html

thanks ismalley
 

Ok will read that-thanks for helping!

ok, no problem
cheers!

I read the thread that ismalley just suggested to read. This is all quite interesting. If it has spark, at the right time, and compression (even low) and you shoot ether in the intake it should at least try to start.

I don't know where he hooked the timing light on the wires. Presumably it was an induction type light and he had it looped over wire #1 just before it went to the plug.
On the M103, the wires run together through the plastic housing that snaps into the valve cover. Except #1, which only briefly passes through the corner of it. What if the wires are worn out and the remaining 5 wires that are all in contact with one another were arcing across to each other and wreaking havoc with the firing order.
Individually they may seem to be intermittently sparking but perhaps somewhat randomly, except #1 which could be unaffected. Although in that thread I think he mentioned he had all the wires out and saw them sparking in sequence. Just grasping here!

One time on my M103 I gave it a tune up and it wouldn't start afterwards. I finally figured out the when I replaced the cap I unknowingly knocked the carbon tip off the spring on the center electrode. I had to put the one off the old cap in it and it started right up. Another time (an American car) I had a new cap & rotor but of different manufacture. The car started but had a wandering miss. I got a matching rotor and it went away.

thanks long-gone
 

I have now disconnected the fuel pump relay to keep this bare bones and the can of ether! Some of the spark plugs I actually broke not using a spark plug wrench so that was pretty stupid however the car did not start with old plugs re-installed that did not appear damaged. I follow your point on the timing of spark with fuel(this case my can of ether) Will let you know the results. I have been advised against the platinums(plugs) but the local shop here only sells those and that was what was in the car for years so it should fire at the very least IMHO. Thanks for all the input.

Possible other issues-clogged exhaust, crankshaft position sensor, vaccum leak, and a member mentioned bad ground as a possibility. After checking timing, thats it for me if it does not fire.

Try getting the H9DC0 spark plugs from the dealer or send me a pm with your personal email and I will send you the online company I use that has OEM parts for a fraction of the cost. It does not make any sense to do a tune up and continue using the old wires and spark plugs....but the spark plugs are not really that expensive...under $6 at the dealer. Keep us posted on this.

Actually, at least the Bosh wires are designed to clip on to the knobs and not the bare threads. I wasted some time when I first acquired my 300E because I thought it was like my old Audi [which did have wires that attached to the threads]. Perhaps the [more expensive] Beru wires still use the bare threads.

update on no start
 

Guys-i got the car to fire by disconnecting the fuel relay to only have a can of ether as my fuel-if there is any lesson here is reduce the car to the basics with no input from the computer sensors-probably very obvious to most here on this forum.

I had been trying to richen up my fuel air/mix with a new coolant sensor(car running) that was off and I believe it would not re-start due to too much fuel which I wrongly connected to the spark plug job that followed. When I put the computer back into the equation and reconnected the EHA it continued to run but when I went to put it in gear it stalled and would only start again if I disconnected the EHA.

Thanks to everyone who chimed in-I have certainly learned alot from everyone so I feel the problem was a blessing in disguise!!

Not so fast!!-the car ran but then it wanted to stall. I got it home but it does not want to start again!! My pententiometer is most likely a dud as the motor surges and sticks at 2500 and sometimes fall back to 7-800 rpm. I did lean the fuel/mix adjuster-perhaps too much as the one of the spark plugs I pulled was bone dry!! I should add the car wanted to stall even before I adjusted the fuel air mix but at least i got it to run for a while. The car ran fantastically with the new coolant sensor just a desire to stall at low speed.

The plugs should be "bone dry".

Have you tested the throttle position sensor yet? It's far more likely to be a dud than the air flow sensor. Just hook up an ohmeter and slowly press down on the gas pedal (with the car off). The resistance should increase/decrease smoothly as you move the pedal. If the resistance drops out or increases suddenly, you've got a bad TPS.

What are you doing when you say the motor surges & sticks "at 2500 and sometimes fall back to 7-800 rpm"? Are you driving it? Are you idling?

Do you have an FSM?

no start 190e
 

the plugs were bone-dry after cranking the motor with no start several times-that does not seem right to me. I failed to specify.

DhJenkins-I believe you mean the pententiometer resistance test-think thats different from the TPS which is supposed to click when closed. I did that test and the numbers jumped-I have had a surging engine for some time but thats another matter I believe. I have a new pentetiometer ready to install. Thanks for your input.

reread and see you mean TPS as another test-sorry about that-would this cause a no start even with the EHA disconnected?

Yes, having dry plugs after several no-starts probably means no fuel; depends on the chamber design.

So you did a test which showed you had a bad part and you're not replacing that first?!

And it's POTentiometer.

dhjenkins esp
 

I hear you dh!! I have been paying on-line with a tech guy and he assures me that with the EHA disconnected that pentetniometer is out of the equation with regard to a no-start, the reason being that although the fuel is not being fine tuned by sensors, it still will be getting some fuel mimicing what I had with a bad OVP which did start with some difficulty.

I disconnected the fuel relay and spayed ether but the spark plugs are totally dry. It appears to be drawing in fuel and or ether and at other times not-I say that with a fair amount of confidence having had wet spark plugs at times and other times dry plugs after cranking. Thanks.

What I believe contradicts the tech guy on-line is that if i recall, I had a misbehaving idle even withthe EHA disconnected but i could be mistaken.

On your system, the EHA direcly controls the air/fuel mixture. Depending upon the shape of the vane inside the fuel distributor, disconnecting it may completely shut off fuel, even though it's designed to allow a very small amount of fuel to keep a *warm* engine running. This is the "limp home" mode.

The tech is right, sort of. The fuel mix cannot be fine-tuned because it is the EHA alone that does the fine-tuning; the computer will still be getting all of the other signals and will attempt to correct things via the cold-start valve, warm-up regulator, idle control valve, etc... during start-up, though.

Have you tested your fuel pressure regulator? Your's isn't integrated into the fuel distributor like older models, so if it is sticking or has a torn diaphram, it will not deliver the correct volume or pressure of fuel to the fuel distributor. You might also check your fuel return line at the engine compartment. You should be able to blow into it (or use an air tool with the pressure set at 20psi) and hear bubbles in the gas tank (remove the fuel cap first!). If there is any obstruction, then you've probably got a stuck fuel return check valve. If no fuel can go back into the tank, very little fuel can leave the tank.

Oh, and a guy in another thread had a very long no-start problem with his 190E. The problem ended up being too much fuel in his oil, which caused cylinder wash and super low compression - no start.

He changed the oil and it started right up. Something to think about. If you have a compression tester, see what you're getting.