Ok just to be clear, when the key is turned to run the fuel relay will turn the pump on to prime the fuel system, then shuts off. Then while cranking and getting the crank signal allows the pump to continue to run while engine runs.

I have four pump relays. One from Mercedes that lasted about four minutes. Two brand new unbranded pump relays have done nothing right out of the box. So no, at this time I can not turn the ignition on and get the fuel pump to run.

If I dump half a shot glass of fuel down her throat, she will run. Jump out the FPR and the pump runs but not the car. I just installed new BOSCH injectors with no go.

Tomorrow I pull one of the injectors and see what kind of fuel delivery I'm getting.

ok so you have ruled out likely not ignition, it will run with shot glass of fuel , next as soon as key turn to on the pumps should ren for a couple seconds , your not getting that?

Working by myself, so I can't tell if I'm getting the pump to build pressure or not. The hazard warnings drown it out. I did have fuel in the delivery tubes and injectors when I changed them out.

What shuts down the fuel pump when pressure builds? I can't imagine the pump runs continuously. Even in your question you indicate the pump will come on for a short period of time then shut off. What controls that shutdown?

I have not checked the O2 sensor yet. If it were bad, would this cause a crank/no run failure?

OK, so I just went out and powered up the car. After I shut the system down, my fuel distributor has and holds fuel pressure. If I break the nut on the fuel return line fuel comes out under pressure.

I have the fuel line to cylinder No. 1 removed and when I operate the intake, nothing comes out of the fuel line. Shouldn't fuel come out

Went and pulled the fuel line completely. I can blow air thru it with no issue. Also found and pulled the fuel distributor filter and it also was clear.

I had fuel under pressure when I took off the filter. So I'm getting fuel to the fuel distributor but I don't seem to be able to get any out. So I'm going to guess it is the fuel distributor needs a rebuild or replacement..Or could it be the pressure regulator?

The fuel relays is what controls shutdown, only primes system until it gets crank signal then keeps running as long as it's getting a signal,if you want to see if your getting pressure bridge relay circuit 87 and 30 and depress air inlet Plat briefly, it will chirp at injectors. Which indicate enough pressure to squirt fuel into engine

looking up your car , i found a wiring diagram 126.024 your car designation s class with a 6 cylinder reading via pin id of fuel relay= pin 4 = starting valve ie when car cold it gets the starting valve injecting additional fuel , pin 8 =12 volts from x35 which is a terminal block which in turn receive power via overvoltage relay, pin 7 goes to output power to pumps and o2 sensor heating element , pin 11 is ground side of cold starting injector, pin 10 is td signal a connection from ac control unit n6 to pin 2 of n6 ac control unit , and goes to cis n3 fuel injection brain , pin 12 is crank signal from starter circuit 50 or = started solenoid, pin 2 is from brain cis n3 unsure what signal that is , pin 6 is to kick down switch, usually to disengage ac compressor under full throttle , pin 9 is key on to overvoltage relay ending at overvoltage pin 3 one leg and fuse f1 fuse 7 from ignition switch, f1 is front fuse box

Sorry to be slow in responding. Thank you very much for taking the time to track that all down. Excellent information.



This is just a matter of keeping finding a problem, fixing it, and trying again. The engine control on this car is new to me, even thou it's over 35 years old.