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1967 250SE Cpe, 1979 450SL, 1984 300TDT (sold), 1989 560SEC, 1990 300CE, 1993 300CE cab
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41 Posts
Discussion Starter #1
With brand new Bosch EHA installed on 1989 560SEC, I measured 6.8 bar in upper chamber, 5.0 in lower chamber (!)

The lower chamber pressure should be about 0.4 bar lower, thus in this case it should be around 6.4 bar.

Now I will make measurements again tomorrow, to doublecheck. Gauge I use is good quality MB pressure gauge (borrowed from MB dealer :thumbsup:)



--- Here is my question: I just wonder if there is anything else that can go wrong inside the fuel distributor, and give me the high differential between lower and upper chamber??? :confused:



I know that you can adjust the EHA, but it should be set correctly when new. I am afraid I would mask other problems if I mess with the setting.

All other symptoms point to this problem (rich, flooding, no start, wet plugs, gas washing along cilinders into oil crankcase during many start attempts).


Thanks
 

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1995 E320 (totalled) 91 420SEL W126 (retired) 2002 S500 W220(retired); 2008 C300 Sport W204
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662 Posts
Could also be the Fuel Accumulator. The EHA valves are pre adjusted when purchased new. It is also possible that the Fuel Distributor has an internal leak. There are alot of O rings inside the distributor that can be bad.
 

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1967 250SE Cpe, 1979 450SL, 1984 300TDT (sold), 1989 560SEC, 1990 300CE, 1993 300CE cab
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41 Posts
Discussion Starter #4 (Edited)
I ran the test again this morning, and disconnecting the electrical wires on the EHA dropped it to the perfect 0.4 bar difference, so something was telling the EHA to go rich. I will hunt that after I get the car running.

Now, with new Bosch coil installed, spark is still weak on old plug, and when using new, but fouled, non resistor Champion plug there is no spark at all! You'd think it would at least spark a bit.

Distributor cap, rotor and wires *look* very decent, so I will try new, properly gapped NGK plugs :cool: first.

The ghost hunt continues. :eek:

:) Edit: With new NGK plugs, car starts up, but only when you remove Fuel Pump Relay, and jumper the pump **after** the car starts.

Thus, without the fuel pumps, the car will start on the remaining system fuel pressure (and obviously, would only run for 1 second or two, if you do not turn on the fuel pumps).

If you turn the pumps on right away during start attempt (either by jumper wire, or Fuel Pump Relay), car floods and will not start.

Already have new EHA, and new fuel injectors. Upper/lower system pressure in FD is perfect. Wonder why it can still flood. It is around 100 degrees here, so Cold Start Valve is not operating right now.

----The idle adjustment on top, by the FD, can it be so far out of wack that the car will adjust far too rich during start attempts? :confused:
 

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'95 993 / 2011 F150 Raptor SC / Land Cruiser D4D V8 / 500 SEC
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439 Posts
I think the way it's supposed to work is like this : when you switch on the ignition the pumps prime the system and stop. Then the engine starts, and when it's running the pumps start up again.

It sounds like your system is being overpressurized, hence the flooding. Somethings letting way too much fuel in. What about the FPR ?

I'm a novice at these cars so don't put too much faith in my diagnostic ability.
 

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1967 250SE Cpe, 1979 450SL, 1984 300TDT (sold), 1989 560SEC, 1990 300CE, 1993 300CE cab
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41 Posts
Discussion Starter #6
Yes, you are correct, and in my case, it seems like it is getting just a bit too much during normal cranking with FPR (new or old) installed or pumps turned on manually.

Crank for a bit with pumps off, and it starts right away (1-4 seconds).
Turn the pumps on manually while it starts, and car runs.

I will attempt to measure duty cycles next (it is a California car, and you have to get it in the right mode), to see if the idle adjustment is anywhere close to where it needs to be.

As mvmiller indicated, it could be the FD too, but I will wait before tearing into that thing, especially since it will run after starting.
 

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1989 300SE EURO
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301 Posts
Vacuum leak inside the fuel distributor

Could also be the Fuel Accumulator. The EHA valves are pre adjusted when purchased new. It is also possible that the Fuel Distributor has an internal leak. There are alot of O rings inside the distributor that can be bad.
Hi,
sorry for hijacking this thread. I just got report back from my mechanic who was looking for vacuum leaks that I have a small one inside the fuel distributor. He said it's around the plunger (?). But if I read the comments on the other threads, there's no real vacuum attached to the distributor...
So my questions would be, is that possible to have a vacuum leak at the fuel distributor and is it fixable (besides of buying a complete new unit)?
Thanks, steh-fan
 

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Premium Member
560SEC, 190E, Frontier, 240Z
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1,329 Posts
I personally believe the best way to adjust a new EHA is to watch the Duty Cycle at idle and 2500rpm. They should be similar numerically or you need to adjust the EHA.

Purge the system after opening any part of the system or trapped air will cause problems. Run it some before you check and adjust again.

EHA right out of the box should be assumed to still need adjusting.
Tj
 

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1967 250SE Cpe, 1979 450SL, 1984 300TDT (sold), 1989 560SEC, 1990 300CE, 1993 300CE cab
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41 Posts
Discussion Starter #9 (Edited)
solved, finally

For those of you who stumble upon this thread with similar issues....

After replacing parts, measuring pressures, voltages, fault codes, buying more parts, plugs, FPR, injectors, more parts, and throwing some more parts at the car, car kept flooding badly.

After a long break :eek::D, I took off the whole fuel distributor setup. Found lots of gas, I'd say a coffee cup full of gasoline had dripped/leaked in to intake manifold. You can't look there without removing the whole setup.

Suspect that the Fuel Distributor somehow was leaking fuel into manifold, causing continuous flooding. Tried to inspect that, but aside from complete disassembly, there is not much to check.

Found a complete used setup (FD, EHA, etc all still mounted) installed it, and car started right up, no adjustments needed! :thumbsup: :bowdown:

my car's symptoms:

- difficult to start or no start.
- heavy flooding, running very rich.
- gasoline in oil after many crank attempts (your oil level will rise).
- with fuel pump relay removed, car would start (but of course die soon after).


For my next problem, I will listen to mvmiller's opinions and suggestions more closely!!!
 

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Outstanding Contributor
1989 560SEC, 1989 560SEL, 1995 E420
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4,468 Posts
Peter, did you ever change the little oring at the base of the control piston (on the bottom of the fuel distributor)?

I'm in the middle of something similar to you but on a 300TE. The oring didn't make a difference in my case but it sounds like it might have for you.
 

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1967 250SE Cpe, 1979 450SL, 1984 300TDT (sold), 1989 560SEC, 1990 300CE, 1993 300CE cab
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41 Posts
Discussion Starter #11
Yes, actually I did. But I believe the O-ring visible (size of a quarter???) that I replaced simply sealed the FD from the outside world.

I assume that the problem was internally, with worn out O-rings inside the FD. I never opened it.
 

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Outstanding Contributor
1989 560SEC, 1989 560SEL, 1995 E420
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4,468 Posts
Yes, that quarter-sized oring seals as you mentioned. The oring I'm referring to is internal but very easy to get to. It seals around the control piston. You just unscrew the ring-shaped part with two slots in it, replace the oring and reinstall at the same depth.

Anyway, just wondering it that had been on your laundry list.
 
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