Help! '90 300E stalled and won't start. OVP?
 

Hello,

I'll try and be brief.

Driving to auto parts store to get oil for fall oil change. Doing about 40 and then braking to stop for traffic. Car dies before I stop. Warning lights come on as the car died.

This has happened three or four times this week but I could always restart it. Not now. It cranks with gleeful abandon but it doesn't start.

OVP, MAS or Fuel Pump Relay? I've heard that the MAS replaced the FPR on the 1990 cars.

Before ordering parts, any advice so I am not flying blind?

Thanks.

chicago124

PS: On a brighter note, I saw a new E500 at MB of Chicago a few days ago. What a nice car!

Typically the OVP won't keep the car from running "at all", just keep it from running correctly. It will run in a so-called emergency running mode.
Fuel pump or relay would be a possible cause if you know it is not running due to no fuel pressure. You could check this but removeing the fuel supply hose from the fuel distributor. If there were no fuel present (or you can't hear the pump running) you can try jumping the appropriate 2 pins at the MAS relay for power in to the relay and power out to the pump. If the engine runs by jumping these 2 sockets (and you prefer to diagnose via parts substitution) then a new MAS relay may be the "silver bullet".
If fuel supply seems adequate, then spark would seem to be the next area of concern. Hopefully you have enough knowledge to do a quick check for spark. If there is no spark, a coil could have suddenly died, or another possiblity is that the driver that screws down to the front of the canshaft that the ignition rotor screws on to could have cracked. They can run for an indefinite amount of time with the rotor cracked off this "bracket" as it is called. Until the rotor and broken piece of bracket turn enough that the rotor doesn't index with the proper area of the ignition cap any longer.

Gilly

Hi Gilly,

Thanks for the quick reply.

Where would I jump the pins on the MAS? And what should I jump them with. Believe or not, there is a radio shack about 40 feet from where the car sits.

Fuel pump is on the right side correct?

Is there a FPR on my car?

Thanks,

chicago124

I KNEW you'd ask that! It's sockets 1 and 2. There is a long row of sockets once the relay is removed, 1 and 2 will be at 1 end of the rows directly across from each other. If you use a light you should see the numbers in the connector. The relay is remove by twisting the knob on top of the relay. Kind of tricky to get the catches in place to put the relay back in. If you operate the knob a few times with the relay removed you will get an idea of how it works, that will help. If you have someone to turn the key on and off a few times, you should hear the fuel pump run for a second or two every time the switch is switched on, this may help you decide if removing the MAS relay is worth the hassle. If no pump runs, then it's the best next step.
Correct, the MAS takes the place of the fuel pump relay and Klima relay in 1990. It also provided the current to run the O2 sensor heating coil. It had a few other jobs also. NO fuel pump relay on a 1990.
Yes, the fuel pumps (there are a pair under there) are kind of ahead of the right rear wheel above a plastic panel.
I don't know what you can buy at radio shack to jump the pins. I think maybe a small electrical jump wire may work if it had small alligator clips. i have jumper wires made up using a section of wire and the appropriate size "pin" that plugs in to the sockets on the connector. There is no one "right" answer, I'm sure you can make something work.I wouldn't use an uninsulated wire though, use some type of electrical wire, not like a piece of wire clothes hanger or something.

Hi Gilly,

Made the connectors from radio shack bullet connectors and wire. Jumped MAS 1 and 2 but the car did not start. I didn't want to crank it for more than 10 seconds.

I'm wary of checking for spark with lots of amps running around that system. Any suggestions so I do not fry myself while doing it?

Will be checking for fuel pump noise today as well. Need a partner for that.

Thanks.

chicago124

Hi Gilly,

Problem solved:-) Although not by me:-(

So it's going to cost about $325 including towing.

The mechanic found a very old vacuum line (from starter) and it was causing a massive vacuum leak.

$150 to replace it.

Towing and a diagnostic fee of $75 added to the bill. Sounds like I could have replaced it myself.

Thanks for the help though. I learned more about the car.

(Seems as if I'll be selling it this weekend. Just when it has been sorted out. Oh well.)

Kind regards,

chicago124

Hi,

As a follow up to this post, I have since found out that the mechanic did not change any hoses that I can find!

I did find some sealant around one of hoses going from the idle control valve. I have forgotten where the hose goes but it's the one on the right as you face the ICV from the front of the car.

I won't be going back to the mechanic. They told me the hose was in the starting circuit and was so old that it fell apart. Little did that mechanic know that I replaced the hose about two months prior so I know it was new. He slathered some sort of grey sealer around the hose attaching to the ICV. Now it's going to be that much tougher to clean it out.

So, if your 300E dies and won't restart, pop the air cleaner assembly off and inspect the hoses to and from the ICV.

Leanring more all the time. Too bad it can be expensive.

chicago124

What is the ICV?

ICV
 

Idle control valve