Fuel Pump-Does it just go out??? Plus----- - PeachParts Mercedes-Benz Forum

Tims450SL · #1 08-25-2008, 09:14 PM

Does anyone know if the standard electric fuel pump act up to the point of like working and not working which makes the car stumble and pop and Bog down until you mash the accelerator and it revives, but continues to stumble ? And would a bad fuel filter really possibly clog up the flow and cut it off and make the car run like it is half cocked? Please thank you for your help...I havent changed anything on the car it has 103K miles and I also checked the OVP which is a double fuse part and all ok...finally - what about this fuel pump relay?? Does it work and then go off sporatically? Or just completely quits? I know some one has these answers- And can you test the COIL to see if it is weak or going out?

Thanks everyone sorry to ask so much...I am going insane!

Oracle12345 · #2 08-25-2008, 09:21 PM

what car in question?

JEdwards · #3 08-25-2008, 09:59 PM

The fuel pump relay can be removed and you can bridge the connection to test if the relay is the issue. Do a search for "300E fuel pump relay" and you should come up with something related to the diagnosis of the fuel pump. There are 2 fuel pumps on these cars (I assume this is the 300E you were referencing in the other post).

From your description, it seems like the issue is more electrical (e.g. ignition) and not fuel related. My car experienced similar symptoms and the major culprit was a bad ignition coil. On a side note, if you do change the ignition coil, make sure you unplug not only the battery, but also the plugs in the EZL ignition unit. My local mechanic said that if you leave them plugged in, you can possibly damage the crank position sensor, something that is not an easy replacement/fix.

Good luck

Tims450SL · #4 08-26-2008, 12:53 AM

1988 300 E if the fuel pump relay is removed and the bridge is done and it tops then it is the issue. please explain how do I bridge the relay? Also the ignition coil sounds the most favorite issue here because it seemed to be giving me lite issues before i drove car in water (just enough to now make it run this way) would a fuel filter be a culprit? Is the Coiul testable?

JEdwards · #5 08-26-2008, 07:29 PM

I asked my mechanic (saw you dug up many of the old posts on this issue, good work) if the coil was testable. He said that in his experience whenever you ohm out a coil, it always comes back as being ok, but is usually the culprit. The best way to test the coil is to replace it with a known good coil. Pick one up online, if not at fastlane, try www.foreigncarpartsonline.com - I've used them many times and they are quick with shipping and competively priced. I believe the coil is somewhere around $96 + shipping. Like I said before, its well worth the investment if you plan on keeping this car for any length of time.

Tims450SL · #6 08-27-2008, 05:44 PM

Thank you for all the help- I have been graced by good fortune...After hours on hours of researching this issue, and looking for a real qualified person to help me make the repairs, here is what solved my issue...I bought a CPS (Crankcase Position Sensor) Paid a pro to replace it...I know the secret how to do it if you plan on it- let me know I will be happy to share with all- then when he was finished we started the car up, and then it started boggin and sputtering like before. He then took a allen wrench, and adjusted the air mixture screw on top of the fuel sending unit. Now it runs almost perfect. No more stalling or stumbling. I plan on replacing the Coil and the fuel filter- I also am going to check the spark plugs to make sure they are all NON Resitors. Thank everyone for responding and offering goodwill advice. I couldn't have solved my dilema with out everyones assistance! :0)