R107 will not start

[JOF]

I own a 1978 350 SL that has sat for a few years. Trying to get her going again, but she will not start. I replaced the fuel pump which wasn't working and new filter. I think I might also have a problem with the fuel pump relay so I wired the fuel pump up to another battery and could hear the fuel being pumped back into the tank; so I know fuel is going round the system.

Turn the key and the car starts for a second and then dies. Leave it for 5 mins and it will start again very briefly before stopping. I poured a little fuel into the air suction box and it did start, a quick rev before dying again - so I know it could go!

I am getting a spark at each plug.

I would be very grateful for any views on what might be the problem or what my next steps should be?
Thanks

 

[Druk]

After you proved the fuel pump on the battery did you then revert it to it's engine supply feed or leave it connected to said battery when you went for engine start?

 

[logman]

Just a thought did you put in fresh fuel in tank ??

 

[Terry_]

So you have good fuel pressure at the metering head? Have you had a gauge on it?

 

[JOF]

After you proved the fuel pump on the battery did you then revert it to it's engine supply feed or leave it connected to said battery when you went for engine start?

Druk - yes, I left the pump running on the separate battery.
Logman - yes, new fuel. I actually removed the tank and cleaned it out a month ago.
WG M-B - not sure about the actual fuel pressure, but I know it is being returned to the tank.

This morning I checked the relay and all seemed ok, so wired up fuel pump properly and it worked, i.e. running for a couple of seconds after ignition turned on.

I have turned it over a few times this morning and actually had it running for 10 seconds or so a few times. However, the engine only gets to approx. 500-1000 rpm with the accelerator pressed about half way. If I take my foot off (or push it to the floor), the engine cuts out. It sounds rough, like the timing is completely wrong, but I haven't changed anything since it was last running.

I was going to clean the spark plugs, check gaps and try again tomorrow. If that doesn't help, I thought it might be worth removing the injectors to see that they aren't blocked?

 

[roastbeef]

I would clean or replace all ignition parts ie dizzy cap rotor arm plugs if ignition leads look crusty replace as well

 

[JOF]

Thanks. Have started to test, clean or replace all of these parts. Not a lot of time (young family), but will report back.

 

[Sp!ke]

There is a very informative thread on these here including jetronic test procedures.

The Comprehensive Illustrated Djet (72-75 350-450SL) Thread - Mercedes-Benz Forum