'74 280se won't run after heater rebuild

[Wassermann]

Guys I'm in for some help.. I've got a very nice 74 280se, with the D-jetronic system. Last week I had to rebuild the heater box after all the foam came of and jammed the valves. I put back the fresh heater box and hooked every thing up. Nice. But... Now the engine won't run. The starter is working fine. There is a spark and when I hit the accelator I can hear the fuel injectors. But: the fuel pump will not run any more. When I put direct power on it thru the relay next to the heater box, in the passenger footwell, it will run. But, when I turn the ignition key on nothing happens. No relays are clicking, and the fuel pump won't run. Not even for a few seconds. Nothing.

So. I messed up I think. I desperately need some help: is there some plug or connection behind the heater box I forgot? Is there a hidden fuse?
The relays are all ok. But I seem to miss some power coming from the ignition switch some where?

Thanks very much!

[daantjie]

Did you have water coming into the instrument cluster area?  Could be you shorted out the ignition switch and it burnt out.  I did this due to the previous owner having a start button wired in and the thing shorted out, crisped my ignition.
So this might be an option.  They are cheap to replace but access is tough, you have to pull the whole instrument cluster to access the switch at the back of the key/tumbler assembly.  Then you can open it up and check if it burnt, you will smell it and see blackness inside if it is toast.

[Wassermann]

No water in the car or near any of the connections. How ever: I found that if I put 12v on pin 30 of the relay next to the heater box the fuel pump will start running.  Just don't get it... How is the who thing switched? Thru the ECU?

[s class]

The D-jet cars have a plug under the dash, quite high up on the cabin side of the firewall, where the internal harness connects to the engine bay harness.  CHeck it hasn't been dislodged.  on my RHD cars, its on the passenger side.  Not sure if the LHD cars will have it on the opposite side. 

[Wassermann]

That sounds interesting. Can I find a picture of this plug somewhere? It sounds like that could be the problem, but I can't see a plug like that. I did find a five pin plug though near the heater blower in the right side passenger footwell... However the electrical wiring diagram says there should be a six pin plug?

[Wassermann]

Still thinking of my no more running problems... One more question:

The main relay, should that be plugged in to the 5 pin plug on the bracket hanging on the firewall?

Any advice or pic would be very welcome 

[UTn_boy]

If this plug you speak of is the same one you made mention of two posts ago, then it's unlikely that there wasn't ever a relay at that location.  There really isn't a "main" relay.  There are several relays for all systems that require a relay, and the relays are mounted either in the fuse box or behind the side panels in the front floors.  The wiper relay and turn signal relays are the only ones that I can think of that are mounted under the dash.  If you have automatic climate control, the a/c compressor relay will be behind the glove box, but that's about it.  I'd go back and double check anything you unplugged or had apart.  If you've already done that, then do it again.  Also, the plug on the back of the ignition switch is indexed so it can't be turned around, but sometimes the indexing pin will break off, and the plug can be dislocated and you not know it.  Check that, too. 

[Wassermann]

Ok, problem solved. The "main"  relay and the main plug got mixed up.... After putting everything where it should be the car is running as she should. Thanks for the info.