99 e300 won't start - PeachParts Mercedes-Benz Forum

ballsie · #1 10-09-2012, 05:22 PM

Hi,Need input.The other day I started my e300,drove approx. 1/2 mile and the check coolant message appears .I drive back home and while I'm adding coolant the car shuts off.Now it won't start.Up till then it's been running fine.I did notice that the fuel line from the prefilter to the fuel heater had no fuel in it.Awhile back,I replaced the prefilter &o ring ,the spin on fuel filter,k40 and the plastic fuel lines.I do hear a click from the shut off valve when I turn the key to start. Any input will be appreciated......Thanks!

Jeremy5848 · #2 10-09-2012, 06:07 PM

When you replaced the fuel pre-filter did you get a new o-ring? Pre-filters don't come with o-rings, they are a separate item. If you threw the o-ring out with the old pre-filter then the new one won't seal properly, air will get into the fuel lines and you'll have the problem you describe.

Jeremy

TMAllison · #3 10-09-2012, 06:15 PM

The short line from the prefilter to the fuel thermostat drains back at shutdown, so thats not a problem.

Are there air bubbles in the lines when you crank it?

Any possibility you got the computer box soaked when you filled the rad and a fuse or two on top of the K40 relay popped?

ballsie · #4 10-09-2012, 06:55 PM

Hi,o ring was replaced in pre filter and no coolant got onto the k40.No air bubbles in fuel lines.

KarTek · #5 10-09-2012, 07:27 PM

So it cranks but doesn't fire? When you're cranking (or an able assistant cranks) can you see the fuel come up into the line from the fuel heater to the pre-filter? Oh, and the "tok" sound you hear from the injection pump is the fuel rack cycling. I'm not sure if the SOV makes an audible sound.

Here's a dumb question and please don't take offense... Are you switching off the key, removing it and re-inserting it when you try successive times to start?

ballsie · #6 10-09-2012, 07:42 PM

Hi,Yes I switch off the key,but don't remove it.I plugged in my OBD and get a code of po725 (engine speed sensor circuit)Could this be my problem?....Thanks

KarTek · #7 10-09-2012, 07:52 PM

OK, how about the other question? Do you see the fuel rise in the pre-filter line? Can you do the "key flick" start test. Turn the key like normal, wait for the pig tail to go out, then flick and release the key to the start position. The engine should crank for about 7 to 10 seconds then quit. If it doesn't that may reinforce the bad CPS indicated by the OBDII.

The CPS is located on the left side of the engine block at the junction between the bell housing and the block. You may check the wiring is good, trace the lines and check for shorts.

CPS is not a common problem that I'm aware of.

I just walked outside and looked at mine. You can see the CPS if you shine a light in the space between the oil filter housing and the intake manifold. It has a cylindrical snap on connector about 3/4" or so in diameter. See if it came loose and you may be able to take a dowel or long screwdriver and press it back on.

TMAllison · #8 10-09-2012, 08:18 PM

When the key hits pos 2 you should hear the click of the electromagnetic SOV openning with the hood up. No click, no fuel, no start.

As Evan pointed out, check the connection of the CPS, and if its good, replace it.

ballsie · #9 10-09-2012, 08:20 PM

Evan,did the flick test,engine cranked for several seconds the stopped.Fuel did rise in prefilter line.....Thanks

KarTek · #10 10-09-2012, 08:27 PM

OK, that's good. I'm not sure what the ECU use to determine how long to crank but I was guessing that if the CPS is dead, it would not crank normally.

Next, I would check the CPS and wiring integrity. The wire runs from the CPS and joins another wire (sensor maybe) and those are taped together and run through a hole in the bulkhead directly behind the rear of the valve cover.

From there, they go around and into the ECU housing. If you look at the left side of the housing (right as you face it from the front), it's the rear, smaller bundle of wire of the two bundles you see there.

ballsie · #11 10-09-2012, 08:52 PM

Hi Evan,Wiring from cps looks good,I will check ecu wiring tomorrow.If the cps is dead,would this prevent the engine from starting?.....Thanks

KarTek · #12 10-09-2012, 09:24 PM

The ECU determines engine speed and controls rack position based on that. I don't know for sure but I would say that without a RPM reference signal, there's no way to calculate a rack position and the engine won't run.