Please help! C280 wont start
 

Install a new EGR and EGR pipe to the newer one on my 95 C280. Once completed, I notice the idle was not as usual. During the process of removing/installing the EGR pipe, I had to pull the injector rail and loosen the Intake Mani. When reinstalling the injector rail, I noticed that the seals looked dry but just put some oil on them. Drove the car for a week without improvements.

Thinking the seals was causing my unsteady idle, I ordered a set of upper and lower injector seals. Replaced all the injector seals, let the system prime and attempted to start the car. Car would not start! Got out and looked under the hood to find gas everywhere. The upper seal on Cyl 4 was spilling gas everywhere and all over the garage floor. Cleaned up everything and changed the seal with an extra one purchased.

Now, the car starts for 2 seconds and then stops. Will not start again for 3-5 mins, but only runs for 2 secs. Pulled and tested the spark plugs; they are dry and have spark. Tested at the fuel pressure relief valve and it squirted across the room. Got spark, got fuel, got air = No Start!! What should I try next??

Update:

Checked the fuel relay & fuse = good.

Checked the OVP relay & fuse = good.

Checked EGR valve operation = good..

Still trying to find the source of the problem..

Anyone have other suggestions?? Please help..

Not sure on this, but it almost sounds like an " Anti - Theft " device kicking in.
Can you monitor the fuelpump ( turn key on,listen, start car, listen ) and see if the pump turns off ? :confused:

Thanks Manny for your reply...

Just tried it.. Yes, I can hear the fuel pump come on.. but not if it turns off..

Now, Im resetting the alarm by locking/unlocking drivers door using the key. No start!! :(

Im at my whits-end here!!

Can you put a 12 v. testlight on the fuelpump circuit, to see if the power stays there after starting ?

Where is the fuelpump circuit? The fuse, relay or somewhere else?

Feel the relay with your hand.
Have somebody turn the key on.
You should feel the relay klick in.
Start the engine & see if you feel the relay kicking out.

okay... we might be getting somewhere now!! :)

Turn the key to on position: Feel the click twice..
Start the engine: Feel it click again.. motor stops!! :(

Im guessing its turning off the pump as you described...
I then reset the ECU (removing negative battery post)
Performed test above and same result...

How do I clear this? Whats next?

Maybe have a closer look at the relays ( OVP & fuelpump )?
I've heard soooooo many stories here about cracked solderjoints inside of relays, etc.
Could be worth taking it apart & inspecting it ( burned contacts, cracked solderjoints ).
At this point I don't want to tell you to " jumper " anything.

LOL!! Manny, guess what Im doing right now?? I have a fuel relay open looking for burned connections... I will also look for cracked solders too..

Ive also checked in my box of extra relays (I usually buy extra relays found online on-sale/ebay)... I couldnt find a fuel one though. Its probably this one :)

okay... Found the spare gas relay... I was in a packaged box..

Installed the new relay... But same problem: starts, runs for 2 sec, dies :(

How can I figure out what triggering this?

Boy, we're really getting to the " bottom of the pit " here. :D
On most vehicles, not specifically M-B's, there is a signal ( either tachometer or oilpressure ) that keeps the relay in.
Sorry I can't be more specific or more help. :(
Just looked at my Haynes Manual & see the trigger wire comes from the ECU. ( Not too helpful ).
If you want to try something temporarily, you could jump power from terminal 30 to 87 & see if the engine stays running.
http://img.eautopartscatalog.com/live/P202067087MEY.JPG

Terminal 30 is always hot. As me how I know??
Big time spark between 30 & 87 with car off...
But 85 & 86 activates the relay..but will not keep the engine running..

BTW, all of the connections inside of my fuel pump relay were fine; no burns or solder cracks...

Any other suggestions? Im going crazy here. Changed the injector seals and engine runs only 2 seconds! Why?

Ideas?

Put a FP gauge on the fuel rail test port and monitor the pressure when the car stalls.

Thanks Arthur.. I dont have a fuel pressure gauge installed on this car. My other cars all have pressure gauges installed in the fuel lines.

Going to the store to pickup one tonight.. What type of reading should I expect...

Im now thinking that I have triggered a non-ODBII fuel shutoff code when I spilled gas everywhere. What you think?

You are thinking too much..
Take a FP reading and see what you have ...if the reading drops off , you have a fuel problem..if it doesn't , you have a possible ignition problem .
If their is no ignition on HFM/SFI systems, the injectors shut down for cat protection.
Do a FP test............and check your wire harness...

FP specs for 104/HFM :

At idle
3.2-3.6 bar with vac line connected to FP regulator
3.7-4.2 w/o vac
2.5 bar after 30 min shut down of engine, key OFF.

okay.. I know Im thinking too much.. but nothing has worked..:confused:

Purchased the Fuel Pressure tester. Hooked it up to the test port and got a reading of 7 psi. Had someone turn the car on and turn start the car. Nothing changed. Needle didnt move..

What next?

<<Had someone turn the car on and turn start the car. >>

turn the car on and turn start the car ?????...

you want to tell me what that means

Yep.. someone turn it on and then tried to start it.. It ran for 2 seconds and died...
no fuel.. Freaking 8 month old fuel pump is fried?

But the relay is switching it off!

My question was ..What does "turn the car on and turn start the car ..." mean ??

Are you telling me Key ON , engine OFF 7psi, and then same with engine running????

What does "turn the car on and turn start the car ..." mean ??
Turn the key to on and turn the key to start.. turn on ignition... But it has spark and no gas..

Okay.
The pressure is remaining the same at all key positions: off, on, start. It runs until gas is gone: 2 seconds..

I just drained all of the pressure using the pressure kit.. And did the test over.. All 3 positions: no pressure... and no run this time...

What do you think is going on? Im not experienced with MB's. But Im willing to learn. Im taking off work tomorrow and hopefully fix this (while the MB parts shop is still open). So, what are your recommendations...

Check fuses first..give them a spin.

The ecu needs a TN speed signal to operate the FP relay..
..but you want to check the FP and filter for flow by themselves ..so, make a jumper wire with a fuse in-line and jumper pins 87 and 30 at the FP relay connector while you have the gauge on the fuel rail..do not run the car, just run the pumps so you can verify that side of the fuel delivery..you should see 3-4 bar pressure and it should hold after you remove the jumper.........
....if still low/no pressure , the problem is FP or filter. If pleanty of pressure, then the relay is not seeing a TN signal and dropping the pump circuit..could be a poor connection at fuse feed to ecu , unplugged cam sensor, or bad OVP feed to ecu...tap the ovp a few times ,, the fuse can look fine , but the OVP can be bad and that will cause no feed to ECU, which in turn means no feed sigto FP relay.
Isolate/verify pumps w/jumper first...

Thanks. I will post my results tomorrow morning..

On the Jumper wire, what size fuse, 30amp?
Pin 30 has 12v constant (even with the ignition off). Just connect the jumper to the relay pins or to the actual connector base holes?

This may seem like a stupid question, but is there any gas in the tank? Maybe you lost it all on the garage floor!

Richard could be correct.

I would add at least 2-3 gallons of fuel before going any farther

Richard & Doc..
The tank is 3/4 full.. Plenty of gas.. But thanks for asking..

You can have a good reading BUT still be low on fuel on the pick-up side of the tank.

Don't be fooled.

The W202 chassis has 2 sending units. 1 can give a bad reading.

Good point Doc.. Leaving now to pickup 5 gallons of gas to add.. And I will start testing within an hour.. Conference calls all morning.. :rolleyes:

Testing Update.
1. Added about 4 gallons of fresh fuel. Tank is now full

2. Checked the Fuel filter for blockages.
Results: Looked clean (changed 8 months ago with pump)

3. Checked the FP with a fused jumper wire and gauge on the fuel rail. Ignition off.
Results: Gauge went to 54psi and could hear fuel returning to the tank. Removed jumper. The test gauge leveled off to 50psi after 5 mins and holding.

Now, Im checking the relays again. New FP relay installed yesterday & fuse is new.
I do have a backup OVP relay in my box somewhere. Will install and test for OVP failure.

Where is the Cam sensor located?

New Update: After 30 minutes, the fuel pressure has dropped to 42psi. Im loosing pressure slowly. Would the injector seals cause this?

Removed the Injector rail and repressurized it again.

No visiable leaks at the injector rail seals, No leaks from the injector tips, and No leaks from the vacuum line of the fuel pressure regulator.
But its still not holding pressure.

<New Update: After 30 minutes, the fuel pressure has dropped to 42psi. Im loosing pressure slowly. Would the injector seals cause this?

--------------------------------------------------------------------------------
>

Normal.

Thank you Mr Dalton..

Update.
1. Reinstalled the Fuel Rail

2. No signal to the Fuel Relay as you described..
Changed the OVP relay. And my goodness, it STARTED! ! ! :D :D

3. Currently: the idle is bad and missing some. It cut off a few times. Have white smoke. Is this normal? Should I take for a test drive to correct this?

But, THANKS to all for your help thusfar.. Big Progress made today!
Especially You Mr Dalton!! :thumbup:

Very Good..
The OVP was dropping power to ECU..
Run it for a hard run up a hill to clear the lines of air and stuff.
Then if it still misses , change the 3 plug connectors under the 3 coils...they fail terribly on that engine and are worth change regardless..

Will do! I will order the Plug connectors today along with a new OVP (as Im using my old backup OVP)..

Update:
Test Drive was successful..
My vacuum pump is still on under the hood.. Dont know whats causing that pump to stay on but I will check that over the weekend...

Im all good here guys!! :vbac47679

Thanks again for your help!

Make sure you also have F8DC4 plugs in that motor.
Plats don't like that 104 engine. The F8DC4 are cheap, too..standard Bosch plug. Can get them here with the plug connectors.

http://catalog.worldpac.com/mercedesshop/sophio/quote.jsp?clientid=catalog.mercedesshop&cookieid=21H0MN3YU2A910G9G7&baseurl=http://catalog.peachparts.com/&partner=mercedesshop&year=1995&product=F1010-84561&application=000357354

Also, check the connector plug the OVP plugs into..they can get burnt up from the OVP not being completely plugged in all the way..you have to hold the plug from the bottom with your other hand to make sure there is a good snap connection b/c the socket is not secured to the chassis panel as one would expect....common mistake made when one changes the OVP .

Believe it or not, I do regular maintenance on this car..

Yes, I have the el cheapo Bosch F8DC4 plugs (after reading the post by Phil; changed out the month old expensive BKR5EIX NGK Iridium plugs) . I changed them in the fall along with changing all coolant lines & some engine vaccum hoses. Also I removed the dash and changed all of the hvac control vacuum elements. Im in the process of replacing the door lock elements (rear doors are done, fronts door are more difficult).

My OVP connection did not snap. Rechecking now for a snap.

Unplugged and replugged.. No snap.. Tight but no snap.. I dont even see a groove for snapping.. R U sure it snaps??

What I mean by snap is that it is fully seated and plugged all the way in......that's all.

Arthur,
For future reference, can we determine what caused the OVP to burn out (& the fuse not blowing).

I know you are probably saying I think to much again, but I would just like to understand the sequence of events that triggered this. Im assuming that the OVP relay was thrown by the ECU due to dropping fuel pressure.

Which sensor(s) monitors the fuel pressure?
I never got a Check Engine light. Was a code ever stored? Where, SRS system?
Is there a writeup thread here somewhere that decribes (at a high level) the sequence of events during startup?

<Which sensor(s) monitors the fuel pressure?>

None..No FP sensors..that is why there is the Test Port.
The FP regulator keeps the FP at a constant specified operating pressure so that the fuel supply to each injector is always the same. The amount of fuel to each piston/cyl is controlled by the electrical pulse width/time the injector is held open. That is ECU managements job and it uses many sensor inputs when doing these mix/load mapping calculations. The system is fully Electronic. If the fuel pressure is not at correct pressure spec zone to begin with, then you could get a Fuel Trim code b/c the ECU could not correct for FP too high or low..which is why one of the first checks with a fuel trim code is fuel pressure regulator.
[ the other being possible vac leak]
The mapping parameters of the ECU injector width sig needed to satisfy the required engine fuel demands are calculated by design with the known factor of the fuel pressure being in spec..this pressure is not controlled by ECU, it is a design spec of the fuel pump and regulator flow.[Fuel delivery system] The ECU simply EXPECTS that pressure spec to be maintained constant by that system.. and those specs are the ones I listed for you to verify with your TEST PORT and gauge chart. Those spec have to be verified FIRST on a suspected fuel flow complaint/diagnosis.............as you can see, if the Fuel Pressure is not kept in the spec zone at all times , then the AMOUNT of gas flowing thru an injector with a certain time width sig will be higher or lower than the engine is calling for b/c of too high/low of the FP pressure. The ECU can correct for this in a small % amount using it's sensors feedback Engine Management control system, but that has its trim limitations...One can easily verify this by taking a scope reading at the 02 sensor and watch that signal go instantly Overly-RICH by simply taking the vac line off the FP regulator..what has changed ??? nothng, except the fuel pressure has now increased beyond spec b/c of no regulation and that increase has allowed too much fuel to go thru the injector at the same injector open time...see what I mean??? [ look at FP chart and notice the pressure spec is HIGHER with vac line disconnected] This higher pressure test in included in the chart b/c that test is used to check the FULL capacity of the pumps/system, not the running/regulated pressure. Note that there are 3 test on FP..one is with regulation, one without, and then one for holding pressure. All must be met. The first two are with/without vac activation of Regulator and the last is check valve sealing/holding test at the pump outlet check valve . [ or leaking inj./lines/etc]
As far as OVP is concerned, the FP had nothing to do with OVP failure.
OVP is nothing more than a voltage spike protection device [ smart fuse] that uses Zenier Resistor/diode circuits to limit ECU voltage feed specs. Most OVP failures on that engine are manufacturer component defects and the new modified OVP will be sent to you when you order it.
The original over-voltage relay MB # 000-540-52-45 is to be be replaced with 000-540-67-45. MB issued info (internal bulletin) on that problem back in 1996
OVP can also blow from improper jump starting the car... a bad fuse will be indicated by ABS lamp, but a bad OVP does not always have a blown fuse , as that is an amp feed protection and not a part of the voltage spike protection circuit. I believe I posted that info for you before, which is what it turned out to be.
The FP relay turns on for 1-2 secs when the key is turned just to get FP to the rail of a car that has lost the residual pressure from long standing...your problem is the relay got NO signal from ECU once the engine had started ..that is where the ECU and rpm sig mapping come into play, but with no OVP feed to ECU, nothing would work .
That's about all I can tell ya.....
I can see you have an interest in understanding HFM/SFI system operation, so , for more technically detailed and accurate system specific info, you may want to check into the Service CD set ..these systems are in there and I think you can get one here ..see them sometimes on Ebay , too

Thanks for the great explanation Arthur. BTW, the blown OVP relay was a new one installed 2 years ago 000-540-67-45. My backup OVP relay is also a new one with the same part number. Just strange that it blew coincedently during this event.

I will read more about HFM/SFI system operation. I do own an old CD set (WIS_09_2004) but it always comes up in German and I have never taken the time to corret that. I will take the time now!

BTW, I found another relay for the Aux Fans thats exactly like the green Fuel Pump relay.. These relays can be swapped for testing possible relay failure.

Again thanks for your help..
Ending this thread..