cps coolant spill=no start? - PeachParts Mercedes-Benz Forum

artony12 · #1 11-27-2009, 10:14 PM

I have searched this forum and read about testing the CPS which may be causing my no-start. I have replaced the oil as there was a strong smell of fuel in my old oil. The car almost fires now and does momentarily at times. At one point, a few day ago, it did fire and run well but it wanted to stall at low RPM. At this point, i am starting my car with a can of ether and my fuel relay unplugged to simplify this matter as much possible-spark, fuel(ether) no electronic inputs ie coolant sensor, OVP, EHA out of the equation-purely mechanical.

I did spill some coolant just before my no-start issue arose although it did fire the first time. I have been told by obvious experts that unless the CPS is cracked, there should be no effect from spilled coolant. However, if googling causes of a bad CPS, it does state that spilling of fluids can "corrupt" a CPS-this also comes from reputable sellers of these sensors I believe one is redline.com I did not want to post this thread unless necessary but i cannot get my car to start and to say its frustrating is an understatement!! Any input much appreciated.

quaid · #2 11-28-2009, 06:04 AM

Do you have compression?

What about spark?

If you have no spark, then the things to check are:

Coil - basic checks can be done with an ohm meter. See the spec in the workshop manual.

Rotor arm and cap - both in good condition, clean, dry etc?

Plug leads - all in good condition? Good connection to cap/spark plugs?

Crank sensor - basic functionality can be tested with an ohm meter i.e. it shouldnt be open circuit. If you hook it up to an oscilloscope, and crank the engine you can determine if its actually picking up.

Ignition module - found on the inner fender on the left side. You can see if you have 12v feeding the unit, and a good ground. The wiring diagram is in the manual to see the pin designations.

Hopefully this will give you something to work at.

Cal Learner · #3 11-28-2009, 09:05 AM

What model and year are we talking about here? Not sure what your coolant leak is all about, but if you have reason to suspect the CPS, the test is very easy and quick to perform. Even better, if the CPS (L5 sensor) proves to be bad, the repair is easy and inexpensive.

For my W124 with M103 motor, this is the main diagnostic test for that L5 sensor (see FSM section 15-1250 for complete description). Engine cold. Ignition off. Multimeter set to Ohms. Unplug the L5 sensor at the EZL. Positive probe on inside of pin. Negative probe on outer part of pin. Spec is 680 -1200 Ohms. If no, rplc L5 sensor. Your test may be different depending on year/model.

artony12 · #4 11-28-2009, 01:58 PM

Guys(car learner and quaid) I can get the car to fire momentarily(sometimes) after spraying ether with the fuel relay disconnected and once last week the car easily fired with ether and immediately with the fuel relay re-installed. At the moment, its not giving me enough confidence that if i reinstalled the fuel relay, it will start. Does this point to anything?

I should add when it did fire the once with the fuel relay reinstalled, it drove well, just wanted to stall at low RPM.

Car learner-will look more at the CPS- I assume having spark at coil is not a significant indicator if this part fails?

Thanks guys!

artony12 · #5 11-28-2009, 08:29 PM

anybody have an opinion as to the fuel distributor causing a vacuum leak. My fuel distributor has a major leak-im just wondering if that could be the culprit. I have no understanding of the design of the distributor. I am spraying ether into the air sensor with very little success of a start although last week I had a start.

Cal Learner · #6 11-29-2009, 08:52 AM

Quote:

Originally Posted by artony12

anybody have an opinion as to the fuel distributor causing a vacuum leak. My fuel distributor has a major leak-im just wondering if that could be the culprit. I have no understanding of the design of the distributor. I am spraying ether into the air sensor with very little success of a start although last week I had a start.

The factory service manual is a great source not only for test procedures and correct operating specs, but for aiding in understanding how major mechanical systems work. If you can get hold of the FSM for your car, it'll be a good investment. As an alternative, since you have the M103 motor also used in W124 chassis, you can use the Polish website at the URL below. Simply select your model year, then go on to Engine Mechanical, then to CIS to find everything relevant to the injection system, including the fuel distributor and all the diagnostic test procedures for CPS and other components. Just a thought. (P.S. It's true I'm still learning about my car after 21+ years, but my I-net alias is actually a reference to my alma mater, now quite a bit more than 21 years ago.

)

http://mb.auto.pl/index.php/Dok.-serwisowa-CD1.html

artony12 · #7 11-29-2009, 10:38 AM

Am i right to assume you went to Cal as in the Bears as opposed to studying in California? I am in California at the moment-Big Bear.

Thanks for the great link!!

If I may, on my no-start, can I totally rule out the ignition system as a factor if I have strong spark on the plugs-I was going to test the plugs installed with a tester that flashes an LED when the plugs sparks. I have been told that i can rule out the CPS for example by the mere presence of spark at the coil and that tests on the CPS are performed only if there is no presence of spark at the coil. I found that questionable.

Anyone else welcome to weigh in.

Thanks again Cal learner!!

slk230red · #8 11-29-2009, 11:18 AM

Have you verified that the Idle Control Valve hose is connected securely on both ends going over to the Air Intake Boot?

Here's why I always recommend checking this hose before replacing parts.
Other than a defective battery, the only time my '93 has failed to start since I bought it new is when I stopped at a Target store one day. When I returned to my car, it wouldn't start. I could have replaced the spark plugs, wires, fuel pump relay, ovp relay, fuel pumps, distributor cap, distributor, fuel pressure relay, etc.

Instead, I reached under the Air Intake Boot and I could feel that the hose was split.
I pulled the hose off, saw a technician pull into a parking space nearby and asked him if he had any electrical tape. Sure enough, he did so I taped up the hose and connector, re-intalled it and drove home. I purchased a new hose the next day.

artony12 · #9 11-29-2009, 11:59 AM

I have read many posts from you and always thought your input was accurate and based on sound judgement even to a total novice such as myself. I will check the 2 boots as you suggest-they are quite difficult to follow and access as well as being rock- hard. I have changed the ICV recently so it would make sense I have perhaps damaged the hoses/boots. I did seem to have a very lean mix before my no-start. Thanks for the advice!!

slk230red · #10 11-29-2009, 12:27 PM

Quote:

Originally Posted by artony12

I have read many posts from you and always thought your input was accurate and based on sound judgement even to a total novice such as myself. I will check the 2 boots as you suggest-they are quite difficult to follow and access as well as being rock- hard. I have changed the ICV recently so it would make sense I have perhaps damaged the hoses/boots. I did seem to have a very lean mix before my no-start. Thanks for the advice!!

Those hoses do become rock hard/brittle over time. I would suggest replacing them on both ends of the ICV. The hose connection on the bottom of the Air Intake Boot connects via a plastic male/male connector. It pulls straight out.

dhjenkins · #11 11-29-2009, 01:07 PM

You still haven't gotten this thing started yet?

Seriously, what's this, your 4th no-start thread on the same car?

Bottom line, without a scope, you can't reliably test the sensor.

You can get a Beru "reference sensor" for less than $60. I'd go with that and eliminate it as a suspect. They do wear out.

artony12 · #12 11-29-2009, 01:52 PM

Think its my third and no I have not got the car started but I have got it to fire somewhat whereas before it would not start at all most likely due to a compression loss with fuel in the oil. Even to some guys with obviously much more experience than me, the answers are not always that obvious.

Thanks for the info on CPS-that fits with someone who had his CPS pass all of the tests, then when he replaced it with a new one, it immediately fired. What I have been told is that with a strong spark at the coil, the CPS is fine. Now, if that is bad info, one can appreciate why I am having some difficulties.

quaid · #13 11-29-2009, 03:46 PM

If you have a strong spark at the coil, then your CPS is OK.

Look at the plug leads, rotor arm, cap, and plugs themselves.

dhjenkins · #14 11-29-2009, 04:08 PM

Quote:

Originally Posted by quaid

If you have a strong spark at the coil, then your CPS is OK.

Look at the plug leads, rotor arm, cap, and plugs themselves.

That's not true, and he's already done all that (or has claimed to).

A bad CPS can send a weak/false trigger signal, and/or a bad EZL can fire the coil at the wrong time.

The only thing a strong spark at the coil proves beyond a shadow of a doubt is that there is a strong spark at the coil.

artony12 · #15 11-29-2009, 05:26 PM

The only thing I can offer to the debate of the CPS and strong spark is that it would seem one of the tests for the CPS would involve checking the spark at the coil in the manual which I dont believe it does or perhaps its considered slightly dangerous. Perhaps more often than not, a strong spark is indicative of good CPS. Thats all i can add which obviously is not much. I do appreciate the comments here; hopefully this thread will be of some value to others if we can come to a definitive answer. Thanks guys for trying help!!