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  #1  
Old 06-11-2004, 10:19 AM
RKS RKS is offline
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Pierburg pump and check valve ?

I'm in the process of correcting a fuel pressure leak down problem on my 84 500SEL, and thought I'd found the answer upon removing what I believed to be the check valve at the fuel pump. The piece I removed from output side of pump is wide open from one end to the other. After purchasing a new check valve, whose pump end threads are different, (it's for a Bosch pump) I started wondering if I need one attached to the outside of the pump, or if Pierburg has an internal check valve. The picture has the original piece on the right, the the non fitting replacment on the left. Hope some can shed some light on this for me. Thanks...Bob

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Pierburg pump and check valve ?-ckvalve.jpg  
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  #2  
Old 06-11-2004, 01:54 PM
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Pierburg does make many aftermarket pumps for many cars including that one. I believe that that series does have an internal check valve.

The most common fuel bleed off problem is the fuel accumulator!
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  #3  
Old 06-11-2004, 04:49 PM
RKS RKS is offline
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Thanks for the reply, I have the new accumulator to put on, guess I'll put it all together and see if the system will hold pressure. I've had the beast for 4 years, it has always had a warm start problem, finally decided to do something about it.
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  #4  
Old 06-11-2004, 05:51 PM
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Of course the fuel pressure regulator in the fuel distributor could be leaking as well. Try removing the return fuel line at the distributor & see if fuel leaks out.
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MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
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  #5  
Old 06-22-2004, 01:36 PM
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90 300E WON'T START-M.B.DOC HELP

M.B. DOC

I desparately need your help.

My car cranks but won't start either cold or hot. Once I add few ounces of fuel in air intake, it starts & runs on load till I shut down. I ran it more than 45 minutes. But, once I switched off, it won't restart.

I have replaced fuel accumulator. My both fuels are running. MAS relay & OVP are okay.

My initial thoughts are: fuel filter, pumps & ignition system are working.

Question: What else should be checked which can cause restarting problem?
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  #6  
Old 06-22-2004, 01:39 PM
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90 300E WON'TSTART

M.B. DOC

I forgot to mention that I have checked fuel at regulator & is there is fuel. There is no leakage from the plastic vent tubing on the regulator.
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  #7  
Old 06-22-2004, 02:52 PM
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Re: 90 300E WON'T START-M.B.DOC HELP

Quote:
Originally posted by benzidude
M.B. DOC

I desparately need your help.

My car cranks but won't start either cold or hot. Once I add few ounces of fuel in air intake, it starts & runs on load till I shut down. I ran it more than 45 minutes. But, once I switched off, it won't restart.

I have replaced fuel accumulator. My both fuels are running. MAS relay & OVP are okay.

My initial thoughts are: fuel filter, pumps & ignition system are working.

Question: What else should be checked which can cause restarting problem?
Hi

You may be experiencing an ignition problem, try inspecting the distributor cap and rotor first. On the cap remove the coil wire & look where the boot bottoms out. You may notice a carbon ring running around the perimeter on the center terminal. When the build up is excessive it can create rough idles and or hard/difficult/no start issues. Another problem may be the ignition coil itself, a basic visual test displays voltage output but it will not help you determine if the coil has maximum output. A low budget secondary voltage tester can help you determine maximum output, you should be able to purchase one of these little gems from your local parts supplier.

My .02
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Old 06-22-2004, 02:59 PM
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90 300E FOR MRCJAMES

Since the car starts & runs by adding fuel into air intake, doesn't it mean that ignition system working? I am puzzled. Could you shed some light about your reason? Thanks
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  #9  
Old 06-22-2004, 06:15 PM
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A weak spark has fooled many a technician. It is the first place I start as I was fooled once, and only once!! After I have ruled out the ignition system as a possible problem then I will pursue the injection system as a possible cause.

If you feel you are having a fuel injection problem than what is helpful is to post any pressure readings that you may have taken from the car. As I did not see any hint of that being performed I was merely suggesting a path to eliminate possible causes which ultimately save you time, as well as money.

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