Ok, now this has happened twice. I drive my car somewhere, turn it off for a few minutes, and it will not restart. The engine turns over and over and over. Then, miraculously, just before I give up and call a tow truck, it will start up just fine (usually 15-30 minutes later).

Is this the fuel pump or what? I decided the first time was a fluke, but now its happened again. The car is starmarked with 80k miles but a trip to the dealer is a hassle-any ideas on diagnosis?

Thanks!

 

That may rule out the fuel pump. It may also be the fuel pump relay going bad.

 

I was going through this problem not long ago.

It was intermittent and started happening EVERY stop for less than 10 minutes.

This is what I did: Took out the OVP relay, shook it around, removed the fuse put a new one in.

Then put fuel line cleaner in the gas line.

Haven't had a problem since. I used like DRY GAS and HEET, they both did the trick. I suspect my OVP is not operating completely up to par as well, as I have a minorly rough idle when sitting in D or 3 or 2. Either way, these two things were somewhat resolved.

I have a better suspicion that one of my fuel pumps is causing the problem though. But instead of fixing the pump, i just use gas line cleaner. My guess is that fuel vapor is cloggin the fuel lines. The vapor subsides after 10 minutes of leaving the car, allowing fuel into the engine and then starting up.

If you ever have a problem of nonstarting, just wait ten minutes and the car will start. ALso, try opening your hood. Let the car get a little cooler if you can.

SO, like I said, I dont know whether its the OVP or fuel vapor in the lines, but I resolved both possibilities, so I am in good shape.

Good luck, this is an extremely annoying problem (trust me, I feel your pain)

 

I would change your OVP.

It is the cause of 90% of these kind of starting problems. The original part was updated with a new one.

 

what the heck is the ovp? i have called mercedes roadside who guessed it could be the fuel pump relay, but it would need to be doing it "non-intermittently" for a positive diagnosis. So, I wait to be stranded?

Thanks for your posts!

 

OVP stands for Over Voltage Protection Relay. It is behind the black plastic panel behind the battery. Remove the plastic cover. It is a tall aluminum can with a fuse on top.

The OVP relay is really just a fuse. It powers the systems involved. It is the ultimate in simplicity.

Older fuel injection systems, like those on 1992 and earlier 300E's, have a KE CIS fuel injection system, which allows the car to start just fine when warm with a defective OVP or even with the OVP removed.

An HFM fuel injection system, as on 1993 and newer 300E / E320's, are fully electronic and a faulty OVP is usually the cause of poor warm start problems.

The early OVP's were bad and the failure rate is very high. The old part number is 201 540 38 45, made by Siemens, in Austria . It as replaced by part number new part # 000-540-67-45.

Now, regarding the recommendations on the fuel pump or fuel pump relay. This would be the diagnosis if you had a KE controlled 1992 and earlier 300E. The NUMBER ONE, all time answer, for hard hot starting on any K, K-Jet w/Lambda, or KE system is fuel pressure leak down caused vapor locking. This leakdown doesn't matter to cold starting as pressure builds almost instantly. On a hot motor if you release the pressure the fuel boils in the injectors and lines. This messes with fuel delivery.

It is because you have a hot starting problem only that your problem is surely the OVP.

 

It is also possible its the check valve in the fuel line.

The valve keeps the fuel in the line and stops it from draining back into the tank. if this valve is malfunctioning, the fuel will leak out of the fuel line back into the tank and you will have hard starting, because the fuel needs to make its way through the line again.

Definately have it checked, I'm going to have my mechanic check mine soon, as we have checked most everything else. OVP, fuel pumps, fuel filter, etc etc. the only we havent checked is the check valve in the fuel line. Luckily my mechanic is not the kind to throw parts at it, he finds the actual problem and fixes it, he doesn't guess.

Alon

 

Hmmmmmm........95 E320...........104 engine!? You may want to check the wiring harness. Sounds like just the sort of weird problems a bad harness will present.....for no reason!!!!
MB has extended a warranty (hidden) to 125K miles.

 

JUST GOT A 1994 320E. WHILE DRIVING IT HOME CHECK ENGINE LIGHT CAME ON.
DISCONNECTED BATTERY AND IT WENT OFF. CAR BATTLES TO START NOW WHEN COLD. WILL EVENTUALLY RUN AND THEN HAS NO PROBLEMS. THE CAR HAD A NEW THROTTLE ASSEMBLY DONE 2 WEEKS AGO($1600)!!! WOW!!!

CALLED THE MECHANIC AND HE SAID IT WAS THE OVER LOAD CIRCUIT FUSE BEHIND THE BATTERY. TRIED THAT AND OTHER FUSES BUT WERE ALL O.K

ANY ADVISE????

 

Well, you replaced your throttle actuator and OVP (over voltage protection relay).

If your CE light came on, then you have a fault code stored. There are something like 26 separate faults that will cause a check engine light to come on. And the only fault codes that will cause a CE light to come on are only related to emissions / smog issues.

My best guess is that you have an EGR valve stuck in the open position. The original EGR valves were replaced with an updated part becaue the old ones had a tendency to stick.

Do a simple EGR test or ask your mechanic do one.

The egr gets no vacum from the ecu until closed loop [ warm 02 sensor]. So, once it opens, it may leak/stick open. This will show as a large vac leak at idle. The ecu also calls for no egr at idle, but if it has opened and sticks open, rough idle will result.

The test is to pull a vac on the egr valve line with a hand vac pump at idle . [ or steal vac somewhere off engine for test.]
At idle , when you pull the valve open, the engine should run pretty rough. When you release it, you should hear it pop closed and eng idle smooth. If it sticks open, you have found the problem. If, when you give it vac., it does not hold the vac., it is leaking by internaly , also causing same .. If so, replace it.

You can also tell your mechanic to check for a blocked EGR pipe. It's the one that runs from the EGR valve on the passenger side of the engine, around the back of the engine, to the intake manifold. This "hot inlet pipe" is notorious on M104 engines to get plugged up with cargon from EGR vapors. The fix is to either clean up the blocked pipe with a thin wire (like a speedometer cable) attached to a drill motor. Many mechanics are simply replacing the pipe with a new one as it takes time to clean out the pipe.

Another item to check is the fuel pressure regulator which can be the cause of a rough idle.

Both of these things are pretty easy to check and frequent failure items for the average Mercedes mechanic. If he doesn't know about the EGR pipe blockage issue, he is incompetent and you should find another mechanic.

There is a black box with a pulse indicator that will flash a red light for fault codes in your engine compartment near the battery. Do you know how to pull codes? If not, I will tell you how and we can check the code.

 

I would check for a vacuum leak or disconnected hose/sensor.

 

Actually, the first thing that came to my mind was a vacuum leak, but he would have the opposite problem.

It is common on vacum leaks to not be as pronounced with a cold engine. Cold engines are running rich until warm and that helps off-set the added intake of air caused by the leak. With a vacum leak, the engine will run rough after it has warmed up.

 

THANKS SUGINAMI
I DID NOT REPLACE THE OVERLOAD CIRCUIT. I ONLY CHECKED THE FUSE.
WHERE IS THE EGR VALVE?

AS SOON AS THE CAR HAS STARTED AND YOU REV IT "CLEAR" IT IS SMOOTH AND NO PROBLEMS. DEFINATELY ON THE ENRICHMENT COLD START CIRCUIT?

THANKS FOR YOUR REPLY.

 

First, check the part number of the OVP and if it says "made in Austria". If it does and it's the old part number. Change it. It is bad anyway and they are cheap.

The egr valve is on the passenger side of the engine, to the left of the valve cover near the back of the engine. There is a vacum line going to it, and the small diameter, shiny metal pipe going from the back of it around the back of the engine.

But, you are describing your car different now. Does it idle badly just for a moment when you start the car, and the problem goes away immediately after you "rev it clear" one time?

Even though you rev it once, the car is still cold and is not in closed loop, yet.

If after revving the car once and the problem clears up, it's sounding more like a fuel supply / pressure problem to me. Fuel pressure regulator? Fuel accumulator?

Still, you need to check part number on the egr valve. There was a TSB, too, that told technicians of the new part number. And, you need to check for blockage of that EGR tube. It should be checked and cleaned as part of your 60,000 maintenance interval.

 

Still, it would be nice to know what code is coming up.

It is not hard to check the pulse counter for the code.

You just press a button for 3-4 seconds and count the number of flashes.

Do you know how to do it?

The code will tell you a lot...

 

no it does not clear. it will stall/ restart a few times and after you nursed the throttle and get a "clean " rev it will then clear. only after some 10 starting attempts.

no i dont know how to get and interpret codes. although the check engine light is of......are the codes still in the memory?
does disconnecting the batt clear it? i know on the e36 bmw's it does.
i did find a vacuum line off at the bottom of thre throttle housing.
this made no difference at cold. i have not driven the cat since this problem started.

 

That's right. I forgot that you disconnected the battery. That cleared the codes.

You'll have to drive the car until the CE light comes back on.

But still, check the OVP. Could solve your problem.

I'd also check the EGR valve and the hot inlet pipe.

You have a black box with an LED display unit in your engine compartment, on the passenger side near the firewall. Press the button for 3 seconds (with the engine off and the ignition in the on position) and release. Count the number of flashes for the fault code. One blink indicates no codes present. Repeat the code retrieval by again depressing the button and count the blinks a second time. If you get the same number then there is only one code. If you get a different number of flashes, then you have more than one code. Keep repeating till all codes are read. This is indicated by the repeat of the first code received. After you've checked the codes, wait at least two seconds, then you hold the button down for six seconds. Each code must be erased individually. When you turn the key to the off position, and then restart the car, the light will be off.

Here is a site which shows the fault codes and what they mean:

http://www.batauto.com/MB/

 

thank you. i will try all this. will let you know what happened.

thnaks again.

 

Hi there, it seems that suginami knows a lot about problems that everyone is having with their cars. I am hopefull that you might be able to solve some of my problems. I have a '92 400E that has the classic idle problem and have heard from others that the wiring harness is to blame. Because I don't, or rather can't spend the money to fix it and don't think it is the problem I am now looking at the OVP. The thing is since my car is an 8-cylinder the battery is located in the trunk and I do not know where the OVP is. If you could let me know the location that would be great. Another thing as well is my check engine light is on and I don't know if the "black box" is in a different location or not, I have not been under the hood yet but assume that it has probally moved. And at last my brake pad wear indicator light comes on but I know that my pads still have at least 5cm left on them. It started to come on after a car wash. Any knowledge by you or any one would be greatly appreciated.

 

THIS IS WHAT I HAVE DONE:
THE OVP PART IS SIEMENS 000 540 52 45 WHICH IS NOT THE OLD 201....NUMBER BUT NOT THE SAME AS NEW 000 540 67 45 NUMBER YOU MENTIONED.

I HAVE NOT REPLACED IT YET AS THEY COST ABOUT $80.00 AND IT MIGHT BE THE NEWER ONE??????

CHECKED CODES ..... THERE WERE NONE.
STARTED CAR AND PULLED OF VACUUM LINE ON EGR (RUBBER PIPE WITH THIN SILVER METAL LINE GOING TO FRONT OF MOTOR)
MADE NO DIFFERENCE. PULLED FUSE FROM OVP WHILE RUNNING AND ABS LIGHT CAME ON ..MADE NO DIFFERENCE.PUT FUSE BACK AND LIGHT WENT OF.

DROVE THE CAR AND CHECK ENGINE LIGHT CAME ON. STOPPED AND RESTARTED CAR AND LIGHT WAS OF.
I THEN CHECKED THE CODES AS YOU DESCRIBED AND FLASHED 5 TIMES.(EGR INOPERATIVE)

WHAT NOW? EXACTLY WHERE AND HOW DO I CHECK THE EGR. CAN I SPRAY SOME WD 40 ON IT VIA THE VACUUM LINE?????
HAS THE EGR ANYTHING TO DO WITH INITIAL COLD START? DRIVING IT TODAY AFTER START UP IT IS SMOOTH EVEN WITH EGR VACUUM DISCONNECTED.

WOW A LOT OF QUESTIONS ! WE ARE DEFINATELY KEEPING THIS FORUM ALIVE.

THANKS
SPIKES

 

The number you listed "..... 52 45" for the OVP is the old number. This is a very high failure rate item. Change the part to the new #. The dealer will only carry the new OVP.

Code #5 is egr. When you pulled a vacum when you removed the line, the car should've idled rough. Since nothing changed, your metal hot inlet pipe is plugged.

You should change the egr valve anyway as there was a TSB (technical service bulletin). The old part was updated with a new part #. The old part were prone to sticking anyway.

You can either clean out the old pipe just like I described (with a long wire - old speedometer cable- attached to a drill motor , or better yet just buy a new one and install it.

Yes, the egr is probably affecting the cold starting becaues it is likely stuck in the open position, when it should be closed.

 

KOOLY2,

I'm not really a technician. I just stayed at a Holiday Inn Express last night.

I have an E320, so I'm very familiar with the characteristic problems the M104 engine has.

But my advise on your car would be the same. I'd check the harness to see if the insulation is flaking off. I know that the early 400E's had bad harnesses.

I'd check the condition of the distributor cap, rotor, and wires. I'd make sure there was a good connection between the wires and the resistor boots. Other than the wiring harness problem on some engines, 90% of the time the usual source of idle problems is a bad connection between a spark plug wire and its resistor boot.

I don't think your OVP is bad, but you should still check to see if you have the old # (..... 52 45). On your car, the OVP is under the Hood. It is right over near all the other fuses just ahead of the main fuse box. There are another couple of 1" square relays near it. But it not like the other fuses/relays. Its a GM type 20-30amp plug-in fuse. It has a little black or clear cover over it so prevent the fuse from accidently being knocked out. Here is a picture:

 

THANKS SUGINAMI
I WILL GO AHEAD AND REPLACE THE OVP.
WHERE DOES THE PIPE GO TO FROM THE EGR VALVE? I SEE THE THIN SILVER ONE GOES TO FRONT OF ENGINE.
THE ONE TO BE CLEARED IS THE PIPE GOING TO BACK OF MOTOR?

SOME SILLY QUESTIONS BUT MY KNOWLEDGE OF THIS CAR HAS GROWN EXPONENTIALY IN THE LAST FEW DAYS.

LAST QUESTION....... AM I TO EXPECT ANY OTHER PROBLEMS WITH THESE CARS? SEEMS LIKE A LOT HAS BEEN SPENT ON THIS CAR IN THE LAST 2 MONTHS!

THANKS
SPIKE

 

The metal tube goes out of the back of the egr valve on the left side (passenger side) of the engine near the firewall. It's not the very thin shiney metal tube you are looking at. The tube exits the egr valve, curves around the back of the engine, and comes back around and enters the intake manifold.

Open the steel line at the EGR valve and feed in a long section of old speedometer cable. It must be flexible all the way to the end because it needs to bend 90 degrees around the back of the engine and again at the intake manifold. Spin the cable with a drill motor and run it through the whole tube into the intake manifold. Usually the last 1 to 2 inches of the pipe at the intake manifold is where the most severe blockage is.

I gather that most mechanics used to perform this every 30,000 miles, but now most technicians find it easier to just replace the metal tube.

Regarding the car needing a lot of work, what else have you done to it?

You are experiencing some small things that should have been taken care of before. You have the old OVP and the original EGR valve, and that hot inlet pipe has never been cleaned out like it should've been every 30,000 miles.

Other things that are frequent failure items are oil seepage at the head gasket. The original gaskets had a bad design and were eventually updated. If yours hasn't been changed, believe me it will leak.

Last, 93-95 E320's have bad engine wiring harnesses which will eventually fail because the insulation on the wires is defective and will flake off.

After these things, you'll have smooth sailing...

 

1644 I have the exact same problems on my 1995 E320! Same problems to the tee. I havent been driving the car that often, but I will definately fix this annoying bug.