Changed fuel distributor, car won't start. - Mercedes-Benz Forum

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post #1 of 5 (permalink) Old 10-08-2007, 04:31 PM Thread Starter
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Changed fuel distributor, car won't start.

I am looking for any advice on how to get to a starting point with idle screw and the idle mixture adjustment to get the car running again.

I have a 1976 450sl. After working on this car for quite some time I got it running however it did not seem to have the power it should and would sound like it was missing a tiny bit at idle. When trying to go up a slight hill it would almost stop, but running on city streets it was ok. I was able to set the timing at 5 btdc and the idle did hold between 7 - 8k. The previous owner told me that his mechanic said that it needed a fuel distributor so i picked one up and decided to put it on the car. We put it on today and tried to start the car. No luck. We played with the idle screw and the 3mm hex screw adjustment next to the fuel distributor but still could not get it started. ( I did notice that the plate next to the hex screw is very hard to push down. Don't remember it being like that before.)

Could anyone tell me how to put these two adjustments back to a general starting place?
Right now I don't know where to go next to start to get the car started again.

I have replaced distributor, wires, rotor, coil, all sensors, all vacuum fittings and hoses, all belts, k&n air filter, alt. brushes, rubber boots under intake manifold, rubber hose on throttle plate, injector oring and seals, injectors have been sent away for cleaning and insuring that they are opening within spec of each other, set timing, set idle (to information plate by radiator), timing chain, rails, timing chain tensioner, put on 73 exhaust manifold,
cleaned every connector and electrical joining point, new battery, fuel tank removed and re surfaced, all new rubber fuel line from tank to fuel distributor, distributor advance and retard mechanism checked for correct operation, all vacuum actuators for locking system replaced and locking system works good. I've done more but i think this is all that may pertain to my problem.

One other thing. The replaced fuel distributor is not brand new but I was told that it is in working order. The car was idling and running fine (lest low power and slight lope) then it
developed a condition where it will not accelerate beyond 1400 rpm. Beyond 1400 rpm the engine bogs down and acts like it is going to cut off. This was the last problem before replacing fuel distributor.

Thanks in advance for any help you can give.
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post #2 of 5 (permalink) Old 10-12-2007, 12:52 AM
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I take it from your post that it has a Kjet injection?
First of all,throw the used distributor somewhere where you cannot use it.Replacing Kjet parts with shite is foolish.
next ,' why are you trying to diagnose any fuel injection without a pressure guage?'
It foolish trying to even begin to tune a kjet or even djet without a cannot do it as you have found out.
How do you know it's the distributor and not the warm up regulator?
what if it is the fuel pump not delivering enough volume?
if the air flap can't be pushed down easily it means the spindle valve is seized and that makes the distributor junk.
In future you should only used a MATCHED distributor and Warm up regulator from a reputable rebuilder or use. new parts.
Also,you MUST NOT attempt to alter the idle mixture with out a CO meter.From 'too rich' to 'too lean' is only a 1/3 of a turn.any more and you altered the setting of the airflap completely.
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post #3 of 5 (permalink) Old 10-13-2007, 08:47 AM Thread Starter
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Thank you for the reply. Looks like i've got tools and possibly parts to buy. Jerry
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post #4 of 5 (permalink) Old 10-13-2007, 08:58 AM
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You probably need to find a qualified mechanic to run a series of tests, including a CIS pressure gauge test to check the warm-up regulator, a volume test on the fuel pump (930 cc is the desired result), and check the air flow sensor plate height. If these all check out, you may need a fuel distributor.

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post #5 of 5 (permalink) Old 11-10-2007, 04:02 AM Thread Starter
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Update to problem.

1) Found and performed adjustments for plate height and plate arm to fuel distributor.
2) Bought fuel pressure gauge and discovered that accumulator was defective (leaking). Replaced it.
3) Performed fuel pressure tests - now all ok.
4) Cold start valve not working correctly - replaced it.
5) Warm up regulator pressures not correct - rebuilt wur and set pressures to service cd specs.
6) Went through linkage adjustments.
7) Car starts right up now and has good reving. Only thing is I have to push the accelerator pedal down just a hair before starting.
Reviewing adjustments to locate and identify this problem.
8) Bought Bosch CIS Fuel Injection Book, very good info.
Thanks, Jerry.
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