Mercedes-Benz Forum banner

21 - 40 of 50 Posts

·
Registered
Joined
·
8,893 Posts
I just hope its none of the real pricey stuff, like the EHA($280), Idle control valve($150) or the Fuel regulator valve($250).
Have you checked the vacuum lines and connections, I have a MityVac for that IIRC was about 40 bucks or so. I ended up replacing several connctors (rubber vacuum line from OReilly's) and one of the hard plastic lines, again rubber line.

The EHA, regulator valve and others can be gotten at a you-pull-it yard, they are specific for the 6's but you'd have more to choose from as long as it's the M103 engine (300TE, 300E, as well as the 300SE/SEL). It's a crapshoot for the EHA but I found one that was still holding gas under pressure, no leaks. Also the timing controller on the left fender, can't remember it's name just now
 

·
Registered
Joined
·
26 Posts
Discussion Starter #22
Have you checked the vacuum lines and connections, I have a MityVac for that IIRC was about 40 bucks or so. I ended up replacing several connctors (rubber vacuum line from OReilly's) and one of the hard plastic lines, again rubber line.

The EHA, regulator valve and others can be gotten at a you-pull-it yard, they are specific for the 6's but you'd have more to choose from as long as it's the M103 engine (300TE, 300E, as well as the 300SE/SEL). It's a crapshoot for the EHA but I found one that was still holding gas under pressure, no leaks. Also the timing controller on the left fender, can't remember it's name just now
I replaced all vacuum lines(rubber and hard). As for the you-pull-it yards, I haven't seen any mercedes 300. Mostly newer 2000 on up.
 

·
Registered
Joined
·
8,893 Posts
Yea, Mercedes as a whole are getting hard to find, used to be a dime a dozen during cash for clunkers, especially 126's
 

·
Outstanding Contributor
Joined
·
1,363 Posts
... She has had it stall once while cruising ...
I just came over from the W124 group out of curiosity … and feel the urge to replay just because of this one quoted sentence (contains very helpful information).

I suggest, before you spend any money or time, keep a multimeter in the car and wait until the engine stalls and doesn’t restart again.
Then switch the key to “ON” (not crank) and check whether you can hear the fuel pumps run for a second or two. If they don’t briefly run: It’s the fuel pump relay!
If they do: Check voltage between terminal 1 and 2 of the diagnostic socket (mounted onto the left fender well) during cranking. If you don’t see voltage between 6 and 12 volts: It’s the crankshaft position sensor! (or - less likely - the EZL)
Otherwise it’s probably the distributor cap/rotor! (or - less likely - the ignition coil)
 

·
Registered
Joined
·
26 Posts
Discussion Starter #25
Update 2

All,
I have replaced the cap, rotor, wires, and plugs. Runs great, still having issue after car is at normal temperature. I will do the electrical test. I also plan on checking the spark. If I am getting spark during cranking, I am wondering if my fuel regulator may be bad and flooding it. Could it also be tank purge valve or EHA on the fuel distributor? If its that, doesn't this need to be tuned to the car or is it a simple swap?:confused:
 

·
Registered
Joined
·
26 Posts
Discussion Starter #26
Clarification

What has been replaced and tested:
1.)all rubber fuel lines, filter,accumulator, and pump(pump DOES come on when turning the ignition)
2.) Cap, rotor, plugs, wires are brand new and work great.
3.) Air filter, purge valve(from charcoal filter) are 6 months old and look good
4.) All vacuum lines (rubber and hard tubing) have been replaced
5.) oil and filter changed 3 months ago
6.) Using the proper gas octane level

Car DOES startup and idle fine. Runs great even warm(no rough idling or misfiring). It just doesn't want to restart after driving a while and warms up. Let it sit for approx. and hour and its starts up great. Working on electrical signal and/or fuel regulator. Does the sitting an hour allow the car to cool or gas to vaporize??? Will follow up
 

·
Outstanding Contributor
Joined
·
1,363 Posts
Okay Anthony, let’s see what we got:

1)
You say your “pump DOES come on when turning the ignition”
Does the fuel pump also come on when the car can not be restarted (with the engine still warm)
The tests I recommended in my last post refer to that situation only!
So, if not done so yet, first find out whether the fuel pump comes on when you or your daughter vainly try to restart the engine. Then we know whether there is a problem with the FPR (fuel pump relay) or not. Show your daughter what it should sound like when turning the key to ignition (not to crank), so that she knows how to check that next time!

2)
Your plan to do a spark test has the same meaning as what I suggested, when I said: check voltage between terminal 1 and 2 of the diagnostic socket during cranking. If you don’t see voltage between 6 and 12 volts, respectively if you don’t see sparks at your spark plug: It’s the CPS (crankshaft position sensor)! (or - less likely - the EZL)
Checking the voltage at the diagnostic socket is just a lot easier to do than a spark test.
And again: It only makes sence to do that, when the car can not be restarted.

3)
You wonder: "Could it also be tank purge valve or EHA on the fuel distributor? If its that, doesn't this need to be tuned to the car or is it a simple swap?"
Forget the fuel pressure regulator and the tank purge valve and at the moment also the EHA!
Generally, after replacing the EHA only the basic setting of the KE-Jetronic (or as many misleadingly call it “the air/fuel mixture”) needs to be checked and possibly readjusted.

4)
You ask: “Does the sitting an hour allow the car to cool or gas to vaporize?”
That’s indeed a justified question. Because there is another suspect, the fuel pump’s check valve.
If that is leaky, then you have reduced or even no more holding pressure in the system after the engine is switched off or stalls. That plus the heat of the engine (under the closed hood), which when no more cold fuel is pumped through the system heats up the fuel lines between the injectors and the fuel distributor causes “vapor locks”.
And as well as a faulty FPR or a faulty CPS, that, caused by a faulty fuel pump check valve (or any other leak, like for instance in the accumulator) can result in exactly the same problem that your daughter’s car shows. But checking the FPR and the CPS is a lot easier then checking the check valve.

So, if the FPR and the CPS should prove to be okay, then it’s very probably the check valve!

H.D.
 

·
Registered
Joined
·
26 Posts
Discussion Starter #28
Update3

I just finished testing a few items.
I allowed the engine to reach normal operating temperature. It ran for a while before it shut off. I tried to restart and it would crank but no startup.The pump DOES come on.
I tested leads 1 and 2. I am getting 8 to 9V BUT I am NOT getting a spark. (removed spark plug and cranked)
Does this mean I have another sensor(engine temp sensor) telling the car to shut down. See pic.
 

Attachments

·
Outstanding Contributor
Joined
·
1,363 Posts
Now we know:
- the FPR is okay!
- the CPS is okay!
- the EZL is also okay, as far as it generates the TD-signal (square wave voltage, which you measured)

But you have no spark … although you renewed the sparks, the spark plug wires and the distributor cap and rotor.

Provided that you have no doubts about the quality of the distributor cap and rotor, that means that there is either a problem with:
- the cable between the distributor and the coil
- the coil
- the wires connected to terminals 1 & 15 of the coil
- the coil’s connection to ground
- the EZL

Both the coil and the EZL can cause problems when hot. Check whether the EZL is solitely fixed to it’s monuting surface. There should also be functional heat conductive paste on the EZL’s mounting surface.

Forget the CTS (coolant temperature sensor). That one only has an influence on the ignition timing, but not on “spark” or “no spark”.
 

·
Registered
Joined
·
26 Posts
Discussion Starter #30
Update3a

I allowed the engine to cool and tried the spark test again. I am getting spark to the spark plug. BUT while it is running, my voltage test from leads 1 and 2 reads 4 to 6V.
Does this go back to be a crank pos. sensor? If so, where is it located? Any visual aids will help.
 

·
Outstanding Contributor
Joined
·
1,363 Posts
Hmmh! … that leads to assume, that:
  • when the engine is hot, the EZL generates a good TD-signal while it may not be giving correct input to the coil
  • after the engine cooled down again, the EZL generates a bad TD-signal while it seems to give correct input to the coil again
Before I jump to a conclusion about the EZL or the CPS, I would be interested to see whether that test result is reproducable.

Btw. … I think you know this already, but I want to mention it anyway:
The spark test should always be done with only one spark plug wire! ... while all other wires stay connected! ... It should never be done with all spark plug wires pulled off! ... or even with the distributor’s supply wire! … That could fry the EZL!
 

·
Registered
Joined
·
26 Posts
Discussion Starter #33
I only disconnected one. Plug #1 and left the rest connected. I am ordering crank sensor and coil. Besides possible coil or EZL, could there be ANYTHING else that would cause this.
 

·
Outstanding Contributor
Joined
·
1,363 Posts
In post 28 you said: “I allowed the engine to reach normal operating temperature. It ran for a while before it shut off.”
Just to avoid misunderstanding: You didn’t not switch off the engine … it stalled, right?

You did measure a correct TD-signal when the engine was hot and could not be restarted. The EZL can only generate a TD-signal if the CPS delivers correct input to it. And obiously it did that when the engine was hot (heat is a typical reason for CPS failure). But at that moment there was no spark (although the coil was not hot). After the engine had cooled down you had sparks, but an incorrect TD-signal.
The reason why I was thinking about repeating the test of the TD-signal between terminal 1 & 2 at the diagnostic socket and the spark test is that the EZL is coming a little more into the focus than I like.

Were the sparks you saw while the TD-signal was incorrect strong blue sparks?

... Besides possible coil or EZL, could there be ANYTHING else that would cause this.
If the spark & TD-signal test would be verified if done again and the answer to my first above-mentioned question would be “no” and the answer to my second question would be “yes”, then I would strongly suspect your fuel pump’s check valve (current price at MB about € 15 plus tax).
 

·
Registered
Joined
·
26 Posts
Discussion Starter #35
Yes, the car itself stopped. When testing and the spark was there, it was blue. I will perform the test again to verify my findings. (Once it stops raining :frown).
I don't think its the fuel pump check valve. After seeing the spark not appear after testing.
I will give an update when the parts come in and it stops raining
 

·
Premium Member
Joined
·
2,642 Posts
I am not familiar with your car, but I will throw in something that does not cost anything to check.... On the V8 engines, we have a ground cable that gets connected to the engine, right behind the power steering pump, with a M6 bolts and nut. Its connection gets dirty because of oil+dust in that area, especially if the pump leaks. To make things worse, the bolt can get a bit loose in time, so the ground connection is easily compromised. That ground cable feeds the coil (and I think the EZL too). You see where I am going with this ...

Check the integrity of the ground in that area, if you have such a cable, make sure that is clean and offers a good ground. The pictures below are for reference only, they are not from your engine.
 

Attachments

·
Registered
Joined
·
26 Posts
Discussion Starter #38
liviu165, I definitely see where you're going with this. The car DID have a steering pump leak (The hose to be exact), when she bought it. The leak was fixed and cleaned. I will add this to my list of things to check. I have seen this issue before with other car problems, but mostly lights, windshield wiper controls, etc...
Although most of the parts I have replaced may not have been necessary at this time, I see it as more of a PM and have found potential(s) future issues. Especially, considering all the items mentioned (replaced and not replaced) are (or were) original 1989 parts.
 

·
Registered
Joined
·
26 Posts
Discussion Starter #39
troubleshooting video for starting issues

I found this video on you tube. It goes through step by step troubleshooting the ignition system. He had the same exact problems I have. I will do the test and give feedback later

 

·
Premium Member
Joined
·
2,642 Posts
Thank you for sharing this video with us, it was fun to watch, and definitely something to learn. Yes, that could be your problem too. It's easy to check it using his methodology. That sensor is not cheap, and for the V8s is not easy to get too. If it turns out that you found the effective part, hopefully it will be easier to replace it in your case. For the V8s (420and 560) its cost was $177, from FCPeuro.com. You may actually have the exact same sensor. When I got it I noticed it was made by Bosch, and also had the MB part on it too (just like the one in the video).

Keep us posted please what you find. This is a very interesting thread.

EDIT: For 420SEL owners - I checked PCPEuro and noticed that they don't have the CPS Bosch I purchased some time ago (A0021533428) for $177. They have only the MB one ($269.99), which in this case is more expensive even than the dealer (example: Mercedes Alpharetta, GA= $219.60)
 
21 - 40 of 50 Posts
About this Discussion
49 Replies
13 Participants
Bruinou
Mercedes-Benz Forum
BenzWorld.org forum is one of the largest Mercedes-Benz owner websites offering the most comprehensive collection of Mercedes-Benz information anywhere in the world. The site includes MB Forums, News, Galleries, Publications, Classifieds, Events and much more!
Full Forum Listing
Top