Hi first post here! I bought an 83 240 dl 2.3l yesterday in non running condition. The engine turns over, but does not fire. The fuel pumps are new as are the relays. fuses 5,7,13 intact 25A fuse on fender cleaned and intact. The fuel pumps do not operate at the turn of the key but do operate when the relay is bridged. the relays test good. There is fuel at the fuel rail under pressure. The wire harness to ECU is the good replacement harness, nothing appears hacked.
I believe the problem to be electrical and want to begin wire tracing. I have a haynes and chilton manual that came with the car and have ordered the bentley manual online. The manuals I have are not very clear on electric diagrams.
I am looking for help in where to start fault tracing for this issue. I am also looking for an ECU pinout if anyone would share one for an 83. Any help would be much appreciated- thanks.

 

I would check for spark next, maybe a broken timing belt.

 

there's diagrams for an 81 and 85 240 here, K-Jet.org | 200 Series

it kinda matter which engine/injection system is in the 83, is it K-Jetronic (CIS) or LH (EIS) ? I'm not clear what years they switched, my experience is mostly with LH systems. The 85 is a LH II system, while the 81 is a K-Jet. the differences year to year with the same configuration are almost non-existent.

 

Open the hood and check carefully everywhere if any thing has loosened like an airpipe or something.Many years back I had such a problem in a 240 and it was just a loose pipe under the air intake.I pushed it back and the car started.

 

if the fuel pumps aren't running a second when the car is turned on, then either the relay is bad, or the signal from the ECU to the relay isn't getting through. I believe thats pin 17 on an LH2 ECU connected to relay pin 86/2. on a K-Jet, I'd have to dig deeper.

 

Thanks for the link, The car is running the LH II system, It has the separate relays for system and fuel pump. I performed some of the component/ wiring checks. On the pump relay check grounding terminal 17, there was no relay switch nor fuel pump start. System relay grounding terminal 9 and 21 showed no battery voltage or relay switch. The air control valve showed ~3ohms should have been 20ohms connecting pump terminal 87 to to control unit terminals 10 then 23. I did not get a good reading on the AMM grounding terminal 21 then using voltmeter between terminals 9 and 36 on the AMM connector and 9 and ground on the AMM connector. (I'm going to retry this)
The car did run tonight with the fuel relay bridged and AMM disconnected. The system relay buzzed a few times between starting attempts. The idle hunted some, but smoothed out after 10-15 seconds. It ran quiet and smooth overall, stumbling lean sometimes when throttle was depressed. My impression was that combustion was soft, though. I used a shot of ether to initiate starting.
I plan on cleaning up the grounds and electrical connections generally and finding the source of a hissing leak after shutdown. I would like to continue the wire and fault tracing. I will eventually suss out the diagrams but would definitely appreciate some real world input on the issues I have identified.

 

with the AMM disabled, the ECU is in limp mode, and will idle poorly, but not give it nearly enough gas when you try and accelerate, since it has no idea how much air the engine is sucking in. there's no throttle position sensor on these.

 

I would also clean the blade fuse and holder by the coil.

 

The no-start, no relay activation was caused by corrosion on fuse #12, a/c microswitch I believe. Car starts now, exhaust smells, bad fuel or?

 

I'd not worry too much about the exhaust smell until you take it out and drive it 5-10 miles, get it nice and hot to fry any spiders who moved in, burn off any residual moisture that accumulated. for sure, a tank of fresh gas would be a good thing.