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300SE Crank no start. What to check?

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Hello everyone.

My 300SE M103 currently cranks with no start & I'm in the process of trying to find out why. I just want to make sure I'm checking every component that could be responsible for this. This is where I'm at so far.

Fuel pump, filter & pressure regulator have been replaced
Leads, Rotor cap & button replaced

Fuel appears to be reaching the FD, but not reaching the injector rails whilst cranking. (Unsure if this is normal)

Any advice/suggestions is greatly appreciated.
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1989 300SE 247k+ miles
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Oh boy. Checking every component... That's gonna take time. First, what year car are we looking at? Not that it really matters, but it would be nice to know.

Do you know why it stopped running? Or what was done to try to repair it? If someone adjusted the: air flow plate resting height, EHA, 3 mm (CO) tower, or the gland nut on the bottom of the fuel distributor, you're looking at restoring those to original before it'll start.

It's unlikely, but it could be the crank position sensor's bad.

Do you know how to jump the fuel pump relay and depress the air flow plate to get fuel to flow to the injectors? And, have you checked that you have spark at the plugs?
 

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Discussion Starter · #6 ·
Oh boy. Checking every component... That's gonna take time. First, what year car are we looking at? Not that it really matters, but it would be nice to know.

Do you know why it stopped running? Or what was done to try to repair it? If someone adjusted the: air flow plate resting height, EHA, 3 mm (CO) tower, or the gland nut on the bottom of the fuel distributor, you're looking at restoring those to original before it'll start.

It's unlikely, but it could be the crank position sensor's bad.

Do you know how to jump the fuel pump relay and depress the air flow plate to get fuel to flow to the injectors? And, have you checked that you have spark at the plugs?
As per my sig, it's a 1986 model.

Only basic attempts were made to repair it, such as the pump, filter, leads, etc. I was told that it momentarily sputtered into life when its pump was done but then nothing since. He thought it was the pressure regulator which i've since replaced with new.
I would not know if any of the fuel system was adjusted. I was going to replace the crank sensor, since it's not difficult or expensive (and most likely still original).

I haven't checked for spark yet, I plan on doing that next.
I do not know the fuel relay jump trick, I'll find out.
 

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90 420SEL, 00 BMW X5, 00 Lexus RX300, 01 Chrysler Town and Country
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Jump Pins 7 and 8 in the Fuel Pump Relay. Crack open a line foing to the injector. And press down on the air flow meter plate. Does fuel come out?

Also there is a filter in the fuel inlet to the Fuel DIstributor. Is that clean / not clogged?
 

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1989 300SE 247k+ miles
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I don't look at signatures for vehicle info. I look under your name. Signatures let people put all sorts of irrelevant things in there. Like pictures.

Are you aware there are 2 "crank sensors" on this engine? The one that is readily available runs from the harmonic balancer to...well... nowhere. It doesn't do anything. The other one runs to the bell housing. It's not bad access on the m103. The v-8's though, it's impossible. I looked to replace the latter on mine (the one that actually affects the engine). I can't remember if it was basically NLA, or super-expensive. But I left it alone.
 

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1989 300SE 247k+ miles
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The "real" crank shaft sensor rarely goes bad on the m103. I'd start elsewhere. 1) did you replace the gasoline? Did you run all the old gas out of the system? 2) do you have spark at the spark plugs? 3) jump pins 7 and 8 as mentioned above, unscrew one of the fuel injector lines at the FD, press down on the air flow plate. Do you have gas coming up out of the FD?

John's question of how long has it been sitting is a great one.
 

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1989 300SE 247k+ miles
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This is the filter on the FD. Me, I wouldn't go near that yet. There's a whole lot of other possibilities.
Bicycle part Automotive tire Engineering Auto part Gas

For example, is your EHA leaking? A bad EHA would make a car not drivable. And cause a no start.
 

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Discussion Starter · #14 ·
My EHA doesn't appear to leak, I was considering just replacing it. Are they correctly calibrated out of the box?

I didn't even know there was a "fake" sensor on the front 😅. I only knew of the rear one. Old fuel was drained & new fuel put in. No idea how long it had been sitting.

I will be checking for spark, should that pass, move onto the fuel jump test & go from there.
 

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1989 300SE 247k+ miles
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The EHA is properly calibrated out of the box. If you replace it, just do that. And never touch it again until you replace it. ...says the guy that stupidly adjusted his and took over a year to get it back to close to original and now sent it off to be calibrated with a being rebuilt FD.
 

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Discussion Starter · #18 ·
Okay, passed the spark test, however failed the fuel jump. There is no fuel getting to the injectors.
So I'm guessing I need to rebuild the FD?
 

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If you're not getting any fuel to the injectors I'd first look for something more basic than the fuel distributor. Are you getting fuel in the return line?
 
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