getting gas up to engine, but won't start.
 

Can anyone shed light on this 280se 1972 We are getting gas up to the injectors,but the car still won't start. Mechanic is giving up. He mentioned relay. Can't be sure. It has spark, gas, timing right, filters changed, spark plgs new, everything, timing etc. Could this be a relay? Help :confused:

Does the engine fire at all? I had a similar problem where the engine would fire only when the starter was cranking it. There is a connection from the starter to the ignition coil after the ballast resistor so that the plugs will spark only when cranking. Try putting a jumper across the ballast resistor.

Which model? 6 or 8 cylinder engine, mechanical or electronic FI?

Peter

thanks, iwill try that one

hi peter, Its a 6 and also mechanical

On the intake there is a colds start valve. Get a 12v test lamp and see if there is power at this single wire when the engine is cranking..
If not , you have a cold start circuit problem.
Report that back and I will tell you the next test..

Thanks, I'll give it a try and report back.

You are taxing my memory, but you may have a fuel shut off soleniod on the back of the injection pump that is supossed to shut off fuel during decel. Sometimes the circuit fails and keeps the fuel shut off. I will have to check my 72 year model manuals to see if your car has the shut off.

Peter

I just had a similar problem, 280se 4.5 suddenly just wouldn't start. Turned out to be the ballast resistors - a couple ceramic pieces bolted to the body right next to the ignition coil. The MB tech mentioned that these tend to decay over time. Anyway, replaced 'em and it started right up.

You say it has spark - where did you check the spark at? All 6 plug wires, or just coming off the coil? There could be moisture in the distributor, a broken contact in the cap, a bad rotor, or just a bad connection somewhere in there.