1965 300SE Revival - Page 2 - Mercedes-Benz Forum

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post #11 of 18 (permalink) Old 09-22-2009, 10:43 PM Thread Starter
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Date registered: Sep 2009
Vehicle: 1965 300SE 2 Door Coupe
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I haven't been able to post on the M-100 forum yet. I guess the administrator needs to accept me still. . .

I'll continue to post here until I can post on the M-100 forum. Maybe I can pick your brains a little longer

A few more thoughts:

I haven't actually tried to crank over the engine yet, but I'm wondering if the aftermarket fuel pump is insufficient. My service manual says the the pump needs to supply a minimum volumetric flowrate of 1.0 Liters in 15 seconds and a minimum pressure of 1.3 atm at the overflow of injector pump. I converted these values to English units, and if my math is correct, this means the pump must deliver roughly 63 gallons per hour at roughly 19.1 psi. Carter doesn't make a rotary-vane type fuel pump that delivers both the required volumetric flow rate at the required pressure. The most likely one installed (I haven't had time to actually look at it yet, but I know it's a rotary-vane type) might deliver 100 gph at 18 psi (these values were obtained from the latest Carter specs). Could this slightly lower output pressure cause the engine not the start, assuming everything else works? Based on prior experience (at least on American engines and fuel systems), the required pressure and flowrate really matter at high load and wide-open throttle, not starting nor idle conditions. Is this also true for the M189 enigne? Or does the fuel flow rate and fuel pressure count at all loads and all throttle positions? If this is true, I really don't want to spend $500+ on an OEM Bosch pump (unless I absolutely HAVE to in order to obtain the ideal flow rate and pressure), so I'm wondering if an in-line type aftermarket fuel pump (roughly half the cost) with somewhat higher flow rates and pressures (say, around 75-100 gph at 30-40 psi) will work. What do you think?

Once I clean out the fuel tank, fuel pump, injector pump, and replace all the fuel lines and fuel filter element, I'll measure the fuel pressure at the injector pump to confirm the feed pump's output. Then, I can further diagnose my fuel problem.

One more thing: I heard these engines can tolerate unleaded, premium fuel. Is this true? Dad always used a lead-substitute, but I heard a rumor somewhere that all Mercedes engines are able to safely run on unleaded fuel without damaging the valve train. Any thoughts or information?

Any othe advice? Tips? Online, free resources? Like I said, I REALLY love this car. It is beautiful: the paint is spectacular, the interior is luxurious, and the chrome is stunning! Except it doesn't start. . .

Thanks again,

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post #12 of 18 (permalink) Old 09-23-2009, 01:05 AM
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Vehicle: 73 450 SE Euro
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Ive got a 67 300 sel, same engine also try 300se.org they have lots of good info.
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post #13 of 18 (permalink) Old 09-23-2009, 05:01 AM
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I guess you have seen that thread on the M100 board where they explain that cleaning the fuel system before trying to start the engine is important for not bringing into the injection pump all kind of undesirable stuff. They also describe how to clean the injection pump with toluene I think.

From what I understand the fuel pump feeds the injection pump and from then pressure to the injectors is created by the injection pump itself. Once you have cleaned everything you can try the system with the fuel pump which is currently in the car. Pull an injector out and see if it vaporises fuel when you crank the engine. If not check if fuel reaches after the injection pump, by disconnecting a pipe between the injector and the injection pump. Original fuel pumps are rebuildable. You could give it a try if you still have it.

Before cranking, change the oil and put some oil on the camshaft and in the cylinders. When you crank the engine make sure oil gets everywhere. Disconnect the hose that goes from the engine to the oil pressure gauge in the dashboard. If you've got oil there, you may be ok, as it is towards the end of the circuit.

Of course, First thing to check after cleaning the fuel system and changing the oil is the ignition.

There may be other things to do to avoid unnecessary dammage. I will try to get some people from the M100 board come here and help you.

Last edited by GGR; 09-23-2009 at 05:20 AM.
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post #14 of 18 (permalink) Old 09-23-2009, 09:17 AM Thread Starter
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Thanks, GGR! My registration at the M100 forum was accepted. I'll post all the info I did here.

I'll keep in touch.

Thanks again for all the help!

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post #15 of 18 (permalink) Old 09-24-2009, 08:37 PM Thread Starter
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Pictures anyone?

Hello again,

I've posted pictures on another forum:

'65 W112 Coupe revival - Mercedes-Benz Club of America Forums

Check it out!

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post #16 of 18 (permalink) Old 10-10-2009, 05:50 PM Thread Starter
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I've made some progress!

Here's what I've done thus far:

1. Cleaned out, sealed, and repainted the fuel tank.
2. Cleaned each injector.
3. Cleaned out each fuel line from the injector pump to the injectors.

Pictures of my progress can be found here:

Eric Rushenberg's Photos - Mercedes Revival | Facebook

Immediate fuel-related jobs to come:

1. Clean out the injector pump.
2. Replace the rubber fuel lines
3. Replace the fuel pump.


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post #17 of 18 (permalink) Old 10-10-2009, 09:10 PM
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Date registered: Aug 2004
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I bought a 63 300SE many years ago that was declared dead. Someone had put the wrong rotor in the distributor (too long), and the ditributor shaft was turning, but not the rotor. I had great spark at the coil but, in checking, found spark at only one plug wire! You should be so lucky!

Meanwhile, I had aquired another 300SE for it's low mileage doner engine. The fuel pump was stuck due to gumming in the fuel system. I was able to free it by imersing the suction and return lines in diesel fuel ( gasoline would also work but dangerous around sparks), then putting 12 volts to the motor and rocking it by reversing the polarity.

Finally, the fuel rack, which runs the length of the fuel injection pump, will also gum up from sitting. If stuck in the off position, no fuel will be sent to the injectors. There is a cap, on the front of the injection pump, over the end of the rack, which can be removed.
the rack is threaded internally for a small diameter screw, which can be inserted and then used to excercise the rack while the electric fuel pump is running.

Shortly, I was able to drive both cars by pumping up the air suspension with an external air compressor. There is a Schrader (tire)valve in the driver's side, front, fender well for this purpose, but you need a minimum of 130 PSI to raise the car. A knob on the dash enables you to "lock" the air suspension to prevent using up the air Leakage excepted, of course.

Jim Friesen
Phoenix, AZ
98 ML320
79 300SD
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post #18 of 18 (permalink) Old 02-07-2010, 04:33 PM
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Any progress ??
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