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Mercedes Benz E320
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Discussion Starter #1
Hi guys!

It's been a while since my last post about the AC...I'm waiting for a few parts and hopefully this week it will be ready. I will post back the results.

However, another problem appeared: I noticed it today and a couple of days ago: I tried to start the car, it cranked pretty long and nothing! After I tried again, it finally started, but it seemed to run a little slower and then normally. Also, yesterday when driving on interstate, I got some hesitation around 2500 rpm, during acceleration. It feels like the engine misfires.
I have a new fuel filter and no CEL on. Any idea what this can be?
The problem is that I am supposed to leave this Sunday and I need the car running...and these things always happen when you need the car :mad:

Thanks!
 

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'01-E320 & 02-ST2
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31,633 Posts
Hi, razvu.

CEL or no CEL, I would check for codes. Pending codes can store without a CEL and the bulb itself could be burned out, too.

If there are no codes post up the mileage as well as any other details you can think of... that can help in trying to diagnose over the internet. :)

Take care and enjoy the ride,
Greg
 

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1994 E320 Wagon,1999 E320 Wagon,2000 E 320 Wagon, MGB Track/Rally, ,1988 300E ,more....
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6,019 Posts
You

can always test the cel bulb at start up.When you start the engine a good check engine light bulb will always stay on for a few seconds and then go off.
Check for pending codes per greg,clean your maf per the diy.Check battery charge and output.
ohlord:bowdown:
 

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Discussion Starter #4
Thanks for the reply!

I just checked it tonight, there was no pending code, all systems passed!
The car has 81k miles, L6 engine.
the starting doesn't happen all the time, tonight it started OK, but the hesitation happens all the time after 2500 RPM.
I will do some more testing tomorrow.
 

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Discussion Starter #5
OK, here is what I got today:

first thing in the morning, it took forever to start! I cranked it first time, and it didn't start. Then I had to do it at least 5-6 times and it finally started.

I hooked up a fuel gauge. Here are the results:

idle, fuel pressure regulator connected: 46 psi (in the manual it says it should be between 46.41 - 52.21 (the original measurements are in BAR)

idle, FPR disconnected: 55 psi (should be between 53.66 - 60.91 psi)

slowly accelerating, the pressure dropped to 45psi, even a little below.

engine off: the pressure dropped suddenly to about 37psi, manual says it should be 43, if it drops quickly, replace the check valve in the fuel pump. After a while the pressure started rising to approx 47-48 psi (then I had to leave). I have to run a fuel rest pressure, to see if after 30 min the pressure will be at least 36 psi, will probably do that late tonight.

Also, when I turned the key on, I didn't seem to hear the fuel pump, I think it usually whirs...
I had some whirring noise from the throttle actuator, with the key on. I moved the throttle cable, pressed on the pedal, but it didn't open more than maybe a quarter??? of course this was with engine off, ignition on, and the air intake disconnected. is this normal? I double checked with a scan tool, and it shows TPS 25, I cannot really drive the car at WOT, because of the hesitation at 2500...

Any more thoughts?

Thanks!
 

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Mercedes Benz E320
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Discussion Starter #6
I did some more testing today and I hooked up 2 cables to the fuel pump.
I turned the ignition on and sometimes I have 12V, sometimes not. whenever I have 12V is just for 1-2 sec, then it goes to 0.
If I try to crank the car, I have 12v. I checked the wires, they are good. i'm thinking maybe the fuel pump relay is going bad, but it's in the relay module under the hood. I found the connector, but the relays are soldered on the board.
Anybody had this problem?
 

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2001 SLK 320(217K Miles), 2002 E320 Special Edition(183K Miles)
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3,467 Posts
Just a though - could it be the CPS that's going bad?
 

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Mercedes Benz E320
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Discussion Starter #8
how would you check on that? there are no error codes on the CEL...
 

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2001 SLK 320(217K Miles), 2002 E320 Special Edition(183K Miles)
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As far as I've seen from other posters, the CPS about never stores a code. Not sure how you can test it however.
The reason I'm not sure about your fuel pump, is that as far as I know, the pump does not run the whole time if you only got the key turned. I think it does an initial priming run, but after that the engine needs to crank/run for the fuel pump to continue runnig. But of course my understanding may be wrong - maybe somebody can pitch in with a more definite description?
 

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Discussion Starter #10
yes, I think that's how it should be. It's the same in any car I think...you turn on the ignition, the pump creates pressure and then it stops. My concern is that I didn't seem to have 12V every time I turned on the ignition :confused:

The other thing is that according to Alldata manual, the pressure at idle should be at least 46.something psi. At parts throttle there is a graph and it should be higher, and at WOT should be even higher! I don't think it's possible when you accelerate the pressure to go down, otherwise why would there be a pressure regulator, which BTW I still didn't have time to check it...)

I tried in a Honda which has a electrical pressure gauge, very accurate. The pressure stays constant at 42 psi when you slowly accelerate.

Anyway, it seems that I have to postpone the whole thing for 2 months as I will be out of town, so the car will stay here :crybaby2: I would then send the injectors for cleaning and do a whole fuel testing again, maybe with another pressure regulator, and if it's still low, then I'll probably change the fuel pump.
I still didn't have time for the fuel rest pressure...
 

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Discussion Starter #11
hesitation and starting problems again

Hi guys!

It's been a long time, been very busy in the meantime, and the car still gives me trouble...what happened so far:

I got rid of the oil leak: there was some minor leak in between the timing cover and the upper cover. There is a U kinda shape gasket, and it was broken, there was a lot of sealant when the head gasket was changed, but as I figured out the gasket was not in place.
There is a groove where it should stay, but it doesn't when you put the upper cover. I put a few drops of glue in the groove so it wouldn't move out of place, then a little oil on the gasket and some sealant at the corners, and then install the cover. There is no leak whatsoever! Also the AC problem was fixed, look for it in the AC post.

Now, the bad part: the hesitation is still there, around 2700 rpm. What I noticed, and I really need some help here:
Ignition ON: (do not start the car). There some whirring noise from the throttle plate, it doesn't stop. I took the air pipe off, looked straight down and I moved the throttle cable, from closed to WOT. the throttle plate moved only about 1/4! It was still whirring, but not moving more than 1/4. Can somebody confirm this? Best is if somebody can listen/look in there so I can be sure...

The starting problem: the long cranking and no starting was due to the lack of spark! I checked for spark with one plug out, and I can confirm 100%. It seems to come from the ignition switch. I noticed first that if I move the key slowly and not to the end of CRANK position, it would start faster. Also, today I saw that the rings around the ignition switch were moving, I took them out, and I saw that one of them is an anti theft device, it has some magnet or something with a wire coming out of it. I tried to start the car with the ring out, the same symptom: cranking but not starting. I put it back and it started. I need to check back on this some more, and then post the results.

Thanks for your input!
 
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