Intermittent Start Issue, Fuel Pump? 93 300CE - PeachParts Mercedes-Benz Forum

jlostlen · #1 08-19-2009, 02:10 PM

Hi,

I have intermittent starting issues due to lack of fuel to engine. Sometimes the engine fires up in 1 second, others it takes up to 30 secs with foot on gas pedal.

Ive been researching fuel pump issues in the forums for a couple hours this morning.I will list some symptoms:

When cranking for longer periods (up to 30 secs) it cranks for a while then starts to caugh faster and faster till runs the caughing last sometimes 15 secs until it will start.

With key in on position no fuel pump noise ( I have read that this specific pump system does not prime in on position, only comes on when cranking/running. Please verify)

When jumpering K38 pins 30 and 87, the pump aubible whirrs, sounds strong.

New OVP

Rebuilt ETA

Thanks!

James

jlostlen · #2 08-20-2009, 12:22 PM

bump

Oracle12345 · #3 08-20-2009, 12:25 PM

I would check fuel pressure then check back with your results. Sounds like you have some issues with the fuel pumps or power source to them. Do you know how to check fuel pressure?

jlostlen · #4 08-20-2009, 12:48 PM

no i do not, please advice when and how to check. thank you

ps2cho · #5 08-20-2009, 03:11 PM

You'll need a CIS fuel pressure tester to check it.

Here are the steps + info you need
http://www.ps2cho.net/downloads/MB%20CD/W124/w124CD1/Program/Engine/103/07.3-1603.pdf

Oracle12345 · #6 08-20-2009, 04:31 PM

http://www.sjdiscounttools.com/ta33865.html

jlostlen · #7 09-04-2009, 01:59 AM

After cranking for more than a minute it would not start, I finally realized there is a valve on the fuel rail, I removed the safety nut and pressed the nozzle and fuel shot out about 7 feet.... I assume I can skip the fuel pressure reading test... I now suspect ignition, have 3 new plug connectors on the way, any other ideas?

Thanks all

Oracle12345 · #8 09-04-2009, 09:54 AM

Quote:

Originally Posted by jlostlen

After cranking for more than a minute it would not start, I finally realized there is a valve on the fuel rail, I removed the safety nut and pressed the nozzle and fuel shot out about 7 feet.... I assume I can skip the fuel pressure reading test... I now suspect ignition, have 3 new plug connectors on the way, any other ideas?

Thanks all

wrong

you need to see if it holds the fuel pressure for at least 20 minutes. If it cant hold it for 20 minutes you have a external/internal leak somewhere.

tinypanzer · #9 09-04-2009, 11:29 PM

Yeah, that means you are getting some fuel pressure, but not necessarily enough nor necessarily for long enough.

After cranking for a minute (your poor starter motor!) you should notice the smell of unburnt fuel coming from your tailpipe. If not, then back to fuel system testing.

jlostlen · #10 09-05-2009, 02:58 AM

I am moving beyond the fuel system and here is why: It has enough pressure to shoot 7 feet from the test needle on the fuel rail and still will not start. I do smell fuel while cranking.... Im very sure this is an ignition issue now.
Yesterday had the car up to 105C driving, turned off for less than a minute in town, came back and would not start. tried and tried to crank the car , it would not start, jumped it with a diesel truck and thick cables and it started immediately.... Im wondering if it is just a weak battery. That is my next test.

Oracle12345 · #11 09-05-2009, 04:49 PM

Quote:

Originally Posted by jlostlen

I am moving beyond the fuel system and here is why: It has enough pressure to shoot 7 feet from the test needle on the fuel rail and still will not start. I do smell fuel while cranking.... Im very sure this is an ignition issue now.
Yesterday had the car up to 105C driving, turned off for less than a minute in town, came back and would not start. tried and tried to crank the car , it would not start, jumped it with a diesel truck and thick cables and it started immediately.... Im wondering if it is just a weak battery. That is my next test.

Do you what want then

Oracle12345 · #12 09-05-2009, 08:06 PM

Quote:

Originally Posted by ps2cho

You'll need a CIS fuel pressure tester to check it.

Here are the steps + info you need
http://www.ps2cho.net/downloads/MB%20CD/W124/w124CD1/Program/Engine/103/07.3-1603.pdf

actually thats wrong since the car has LH injection system but I have the bosch book on their fuel injection systems and hard starting is caused by incorrect fuel pressure or poor fuel delievery. Obivously since gas is squirting all over the place then it has to be incorrect fuel pressure.

bsmuwk · #13 09-05-2009, 09:23 PM

Crankshaft position sensor.

jlostlen · #14 12-15-2009, 01:51 PM

I had someone crank the engine while I sniffed the exhaust and it is a strong gas odor when its cranking over, it seems to me that this can rule out the fuel delivery, is this true? what do you guys think? what should i try next?

thanks guys

jlostlen · #15 12-15-2009, 01:52 PM

bsmuwk,

I read about CPS faults and they seem to cut out during operation, this does not happen with my car. I think I can rule that one out...