i have a 1974 450 slc mercedes 4.5 v8 . it was runny with a slight idle problem but other then that i couldnt ask for much more out it. I drove it for about ten minuetes and then i let the car sit for proably an hour while i did a few other things. i went back out to start the car.
the car would turn over as if it where going to start. but it doesn't. the car will make a sounds like it almost ready but it doesnt have enough fuel to get it really going.
Ive tested the spark on one of the plugs. i checked the voltage at the fuel pump which is about 6.4 i think. If i spray carberatuor cleaner into the air intake and it almost fired if i heald the gas pedal all the way down. That worked till it started flaming backwards out of the air intake.(my freind burned his knuckle hair off). so thats where i stopped i think ill do a compression test on the engine and check all the spark plugs for sparks. then ill check the fuel pressure throught out the system. I am a beginger mechanic so i have acces to a lot of tools.

Pull the right valve cover and see if the timing chain is still there. If so, set engine to TDC on #1 and see what the valve timing is. If it fires up the intake, make sure the rotor isn't broken.

Also, check for a clicking sound from the injectors, and make sure the fuel pump is running.

6.4 volts isn't enough at the fuel pump, it requires 9. Should run for a second or so when you switch the ignition on, and then while cranking.

You can also check by pulling the relay in the box under the passenger side kick panel -- top one on the front set. Bridge the terminals labled 30 and 87, key on. Pump should run. If it doesn't, and you don't have good voltage, pull the next relay down and bridge it the same way. If pump runs, replace second relay.

If the pump does run, replace the first relay.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!