I've looked through multiple threads trying to solve my problems, but none that I've seen have been able to help very much.
My starting problem is such that after I turn the key to "on" and hear the audible tone, I turn the key over and all I get is cranking. I have to hold it over about 2-3 times for at least 10 seconds each for it to finally turn over.
I've ran a ton of cleaner through it, STP and Seafoam to be specific, thinking that it might be a clogged injector but it hasn't seemed to work. Fuel pressure is holding and apparently my ignition equipment is in good condition. The shop I've taken it to thinks that the cause may be a faulty crank sensor. I assumed that if it were faulty the car wouldn't start at all.
My second problem is rough idling.
Once the car has started and warmed up, it will idle between 1000 and 1300 and have a slight but sometimes hard shake. Occasionally it will surge. When the car is shifted into gear(drive or reverse) it will idle smoothly and drop to about 500.
Hi, not sure if this will be of much help to you, but I recently changed all of the crankcase ventilation hoses on my '92 500SL. I thought i'd start the car up to make sure everything was ok before putting the air filter box back on. The car wouldn't start. Cranking quite happily, but never looked like it wanted to fire. Had me stumped for a bit I can tell you. Out of disgust, I stuck the air box back on and was about to slam the garage door on the car when I decided to try starting it once more. Fired up straight away. I can only assume that it was getting too much air.
The circular rubber sealing ring on the underside of your air box might be getting hard, preventing correct sealing, and allowing in too much air. I recently tried to get a new one from MB, but they are discontinued unfortunately. I feel a DIY fix coming on!
With your high idle, you may need another Idle Control Valve. It's the cylindrical object with the white sticker in this photo.
Also definitely worth checking any vacuum lines that you can see. They should all fit onto whatever they are attached to quite firmly. Any looseness needs attending to, as does any cracked, split or perished lines or hoses.
Have you checked the state of the inside of your distributor caps by the way?
I started with vacuum lines, then Rotors and distributor caps. Next spark plugs and wires. Clean your ICV by soaking it in carb cleaner. If its still not helping test your fuel distributor. If that's not the problem hard starting may be caused by the fuel pressure regulator. Also check the EHA for leaks. I suggest you buy your rotors from the dealer.
Thanks for the feedback, guys. When I bought the car, my other shop recommended that I replace the EHA valve due it being faulty, but assumed they were trying to milk me for everything due to the 30-60% markup on all parts I noticed. I did replace the o-rings, but I'll have my mechanic check the EHA valve tonight. I read an article this morning that mentioned the air intake plate(not the right term) underneath the air cleaner might be getting stuck.
The odd thing about my starting problem is that it isn't uniform. Sometimes I'll be able to start it in 5-10 secs, other times it will take 30 seconds. It has trouble starting when cold and when it's been sitting hot for more than 5-10 minutes.
Hopefully this is something simple and doesn't require anything too expensive.
It's very rare that replacing O rings will cure a bad EHA valve. Idle in the high ranges you speak of need to be sorted asap. The ICV is usually the first port of call with this issue. Unfortunately there are no cheap repairs on the R129 it was the MB flagship car of it's era. My 1992 cost AUD $256,000.00 when new and as such cost me $30k in repairs and updates to get it back in show room condition, doing 90% myself. Love em or Lose em :smile
I had the same symptoms on my 1997 and they replaced the crank sensor. The sensor had a hairline crack which accounted for the hot/cold start problems and bad idle.
I also can verify that a bad CPS is not necessarily a ~start/no-start only~ result...
I had a recurring misfire on my '01 SL500, setting OBD engine misfire codes at anywhere from 20-50 miles driven.. No specific CPS - Crank Position Sensor - codes were noted, just various cylinder misfire codes.
It ran great for 20-50 miles, and never stopped running, but the CEL would come on and then just run very rough, like cylinders were dropping out from firing... Anyway, finally changed out the CPS, and it's been smooth and no CEL codes since...
I know it's terrible to just throw parts at a problem, but just don't discount the CPS as an issue...
And again, I had no OBD codes specific to the CPS, and yet......
There's really nothing to re-set or anything on the crankshaft position sensor...
Are you getting any sort of codes set, and did you clear them after the new CPS?
Without knowing more, I really don't really have any other suggestions.. Sorry...
I'll have to clear anything that came up tomorrow as I didn't have time to do anything before I left for work today. When I left work this evening the car seemed to start up a bit better than normal, but maybe I'm just being wrongly optimistic.
There's really nothing to re-set or anything on the crankshaft position sensor...
Are you getting any sort of codes set, and did you clear them after the new CPS?
Without knowing more, I really don't really have any other suggestions.. Sorry...
For the benefit of others who may hope to learn from this thread I note that replacing the cam sensor was a waste of time and money. The cam sensor has no discernible effect on the running of an engine with continuous fuel injection -- its only purpose is to identify cylinders in which a knock is detected, and when this occurs spark to the affected cylinders is retarded and then gradually advanced. This is probably documented in Mercedes' WIS.
It's in the front of the engine, obviously down low to be sensing the crankshaft. It's known as the TDC sender (versus EZL sender in the rear), MB part number 003 153 0528. It's seems not to be very critical because it was simply eliminated on later V8s. There's been a lot of confusion about the two over the years.
So I installed a new starter motor because my car wouldn't crank the other day. Once the shop installed it the car was starting perfectly. Since driving it, I've noticed that it is back to its extended cranking routine, although it starts up quicker now, it still cranks for a bit.
Is it possible that prior to this new motor, the pinion teeth were damaged and in turn damaged the flywheel teeth? This would explain the slow startup as the teeth had to catch on something or gain enough momentum to start.
Seeing as I can't hear any grinding I should assume that my crankshaft is turning then? It's odd that it would start immediately when I tried it at the shop but since then is back to normal. Could the EHA valve be at fault? The crank might be turning and moving the pistons but a limited amount of fuel would be getting through.
Alright, I finally made some progress. Since my last post I installed a used EHA valve and it has made a considerable improvement towards my starting. It still has cranking but it has shortened up to about a maximum of 5 seconds before the engine will turn over. It isn't perfect yet, but at least I have somewhere to start from.
My friend is recommending I replace my injectors, but I'm not sure this will help my problem.
I recently read a thread recommending the replacement of the coolant temperature sender and thought I'd ask around to see if I could get any input from anyone regarding it. I measured the resistance of the unit last night(plug with 4 prongs inside) and came out with around 1800-1900 ohms. I don't know if this is the correct number and was hoping someone could advise and provide the other numbers for running temp., etc.
I also saw a thread stating that a faulty injection computer was to blame for two members starting problems.
I just took the resistance of the coolant temp sensor. Engine off and cold: 1700. Engine on and warmed: 430. Not sure what this means as I have yet to find any articles about the resistances.
I also unplugged the CSI before my first start this morning and it seemed to start much easier. Could have just been luck though so I will have to try a few more times today.
I just took the resistance of the coolant temp sensor. Engine off and cold: 1700. Engine on and warmed: 430. Not sure what this means as I have yet to find any articles about the resistances.
The correlation between sensor resistance and coolant temperature is shown in the attached chart. You can start a cold engine, and as the coolant warms you can compare sensor resistance against the chart. Coolant temperature can be read from the instrument cluster or from the in-dash climate control unit's diagnostic mode (menu item #12). A second temperature sensor is the source for the cluster and climate controller, so the sensor being evaluated can remain disconnected.
First check all the fuses ,and earth points .Then i would purchase a good engine cleaner .Like Forte or REDX put it in the tank .Do this useing information thats on the container Next give it a good hi speed run .As it sits over night it will work on the carbon in the injection system . Good luck .
Trevor, I've done all this more than enough times to make any difference.
My extended cranking problems are back. I guess the luck I had yesterday was purely luck. I thought this morning that the reason I was able to leave it for so long and still be able to fire again when I came back is because the temperature was so low, not completely cold but slightly above 40. This led me to believe that vapour lock could be a serious possibility. The low temperatures would allow fuel to remain in the lines without evaporating. This would also explain my ability to start the car immediately after turning it off(when hot), before the heat soak could affect the fuel.
I spoke with a Mercedes specialist in Victoria who specializes in W198s but is regarded to be one of the best, who recommended that I replace the thermostat. I assumed he didn't know what he was talking about until I realized what I stated above. My car does run hot, close to 110 C, so if the thermostat isn't opening fully and allowing the coolant to work properly then then that extra 30 degrees of heat could be the cause of the vapour lock. I also spoke with a MB parts guy in Surrey who is very knowledgeable regarding all things R129, that said it could also be a clogged radiator creating the vapour lock.
To support the vapour lock theory even further, I removed my injectors 2 days ago and noticed that there wasn't a drop of fuel that came out of the lines between the distributor and the injectors. My only concern with this is I don't know if fuel should remain in those lines or not when the engine is off.
I feel like I'm actually onto something here and I hope that one these things will cure my problem!
I went to down to my car to get some more information.
The noted coolant temperature was between 40 and 50 C
-I removed the #5 injector fuel line and found there was no fuel inside, and I can only assume the same for the other 7 lines.
-I turned the key to prime the fuel line and ensure there was sufficient pressure and then loosened one of the injector retaining bolts to ensure fuel was present, which there was.
-I turned the key to start the car and got excessive cranking. I turned the key multiple times without cranking to build pressure.
-The engine eventually started and ran normally after a few tries.
-Once running, I turned it off and then on again and repeated this 3 or 4 times where it continued to start properly.
I don't know what to do with this information. It seems to me that nothing has changed and that the only variable is the time between turning the engine off and back on again.
I thought it might be the accumulator, Trevor. I just went out to the garage to start it and it turned over immediately. This is somewhat confusing so I'll try my best to explain it.
I'll park the car after driving(operating temperature) and when I go to start it again, it will crank forever and eventually turn over. If I've driven the car and leave it to cool overnight and go to start it in the morning, it will be easier to start but will still crank for quite a while.
I finished driving by 12pm yesterday and left my car to sit and attempted starting at 3pm. It had the extended cranking and eventually fired up. I turned it off and came back in an hour to start it and it started fine. I tried again at 9pm and it started perfectly again. It also started perfectly for me about 10 minutes ago.
Am I safe to assume pressure is holding? My two concerns are that this problem is going to be pressure drop or vapour lock.
I warmed the engine up to 80 C this morning, which I think is the normal operating temperature(mine runs between 100 and 110), turned it off and let it sit for 30 minutes. After the wait I started it and it turned over without any problems. I've ordered a replacement thermostat and it will be installed early next week and hopefully I'll see an improvement with that. If the thermostat alleviates the problem somewhat, my next guess would be replacing the accumulator.
Just sent the car back in for some more work and had a brand new EHA valve installed. Will see how it starts tomorrow but I am not optimistic. One thing I've noticed is that it's been starting much better due to the cold weather(probably due to the cold start injector). This problem is a make or break for me, if I can't figure it out soon then I can't imagine I'll keep it around much longer. Shame because it has a gorgeous 2nd gen AMG kit on it.
Yes mine does better in the cold also. But I'm in Florida so it doesn't stay cold for long. I've learned to live with the hard start. Yes, it's very embarrassing if someone notices.
I have to take the door panel off to adjust a limit switch that is keeping my top from closing. I've let this go for probably 6 months. So will only drive with the top down.
Hey Norm! How's life in the UK with the grandkids?
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