Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
Hi everyone. My 1993 Mercedes 400E has ~140K miles and I've owned it one year. During this time, it has run great - smooth, power, fairly fuel efficient, with an occasional, temporary rough idle on startup. I attributed those instances to using regular fuel when the 11-1 compression requires premium. While running using regular, it has been smooth. I've been using premium since. Fuel filter recently replaced.
The major symptom appeared suddenly while driving slowly through the city with no traffic and light throttle. The engine began sputtering and power died immediately which required its first tow in my ownership. Attempts to start the engine saw it turn over easily with a rare indication of firing. (Fuel pump and/or fuel accumulator?) Once towed home, it started immediately once off the truck and ran smoothly for a few minutes while parked.
How do I diagnose this car? What tools do I need? Thank you.
Hi william,
Based on the symptoms you describe, I would begin by testing fuel pressure. I'm no Benz guru, so It may be easier said than done!
I've seen cars die out and then restart after a tow with failing fuel pumps. All the jerking and bumping onto the truck can kind of jostle the pump like when you might strike the tank with a hammer to wake up a lazy fuel pump.
BUT, if prior Mercedes experience serves me, then your tank is in the trunk and the pump is mounted on the frame. Still, I'd want to know about fuel pressure.
What was it a particularly hot day ? Fuel system problems tend to show up in particularly hot or cold weather. Also what was the fuel level ? if the level was low it can show up fuel pump problems before they become apparent in normal driving.
It would help to know what model of injection system was on the car.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
Hi Noah,
The tow truck driver (FWIW) thought the same about jostling the car during loading, transport, and dropoff. The tank is in the trunk and the fuel pump is mounted underneath. Thank you.
UPDATE: Car is running well. I went the ignition route and replaced plugs, each plug wire, two distributor caps, and one rotor. It's running well. I wasn't able to replace the ignition coil wires due to unfamiliarity with disconnecting the wires from the coils. Each coil is enclosed in a cover and access to each is limited. I wanted to replace the second rotor but the hex head of one of its mounting screws stripped. A low profile screw remover did not work. Cleaning the fuel injectors is next. Thanks for your help!
Hi all,
The new plugs, rotors, caps, and wires fixed the major issue and appear to have fixed or improved two other electrical issues:
1. the auxillary electric fans would run randomly and when obviously not needed. They appear to run only as needed now.
2. some sort of electrical switch that sounds to come from behind the left side of the driver's dash would randomly switch on/off often. I presume it's a temperature sensor connected to the aux fans. I rarely hear it now.
Topic Author
