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1994 Mercedes-Benz 300 Series Base 4dr Sedan 3.2L Auto

1994 Mercedes-Benz 300 Series
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June 14, 2011, 10:38 am

Albert C

Question: Ignition ON vs CRANCK

I disconnected fuel line fron entry point injector house and stuck line into bottle......
turned ignition ON (did not cranck) and fule pump BUZZES 5 seconds and a small amount fuel fills bottle during buzing period.
Again its a small amount not under a lot of pressure..............
if I cranck engine a few rotattions, then would see what you describe Copious amounts
screaming into my bottle ???
At least this test has proven no clog in the if cranck should determine pressure bulids up as expected ???

June 15, 2011, 11:38 am

Elizabeth K

Yes, you don't get the pressure in ON that you would in CRANK. Here's a website with a great description of how to test your fuel system, scroll down to the paragraph that starts with "Checking the pump is simple." (and don't worry that it is describing an L-jetronic system, for the basic fuel pressure, it's close enough):

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June 16, 2011, 11:42 am

Albert C

Thanx for reply.
In fact I tested first ON and then CRANCK.....with same result....
there is no obvious increase pressure......
so from clog...would point to defective fuel accumulator..
from quick checking, accumulator in this K jettronic in fact critical to create the pressure required to push through injection distributor till flows out injectors in to pistons....
would you agree my conclusion...???
will check website you indicate.

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June 16, 2011, 2:03 pm

Elizabeth K

If the fuel pump comes on, but the pressure is not sufficient, then it sounds like the fuel pressure regulator or the fuel pump are bad, not the accumulator.

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June 23, 2011, 3:05 pm

Albert C

Hie E
Checked that website hoping would tell me how to measure proper voltage for pumps...
does not.
this model 300te has dual pumps,,,,one next to tank...other floating rack mid under chassis next to filter and accumulator (regulator)

pump has two brown skiny other thick multicolor...
which would i disconnect and with voltmeter (key ON position) check voltage ??

is it voltage feeding in to pump I am measuring or voltage pump is receiving in order to operate properly ??

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June 23, 2011, 4:00 pm

Albert C

I checked both least make sure running....
both upon turning contact ON....they HUM few seconds and had hand touching them....felt vibration while hum lasted.....

what is causing low pressure yet to figure out........

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