On a good note (420SEL "mostly" fixed)
Been having a bit of a hell of a time with my newly acquired 86' 420SEL, anyway with a commited attitude and wanting to fix the problems, I've slowly been working away at it.
The car had a bunch of problems, of which the previous owner had masked and having only owned a diesel W124 previously, I didn't know what the symptoms were I should be looking for, anyway we live and learn I guess.
When I purchased the car, it was night time (after work), in Sydney, Australia where it's hot (I live in Canberra, where it's cold) beginning of May this year.
It idled pretty well, even though the idle was a tad high 850rpm hot (but didn't actually notice that till after the purchase).
Ran well, didn't sputter etc. issue with left mirror, power antenna and right rear window moving.
Had a couple of suspension knocks which I thought were some bushings that needed doing (it's an old car and expected).
So, after purchase:
I pulled apart the mirror and fixed the motors.
Pulled apart the rear door and fixed the broken sliding shoe.
Pulled apart the power antenna and fixed "everything in there".
Car had a leak in the boot, was the tail light, fixed that too.
Knock in the front was the right outer ball joint, swapped it and fixed.
Knock in the back is the strut top bushings I believe (they just arrived so I need to do them soon)
Then onto the seemingly high idle I had... ohhh and terrible cold start
This got interesting and involved wayyy more learning then I would cared to have learnt, this is basically the very short version of how events took place.
1) Found OVP fuse blown
2) Replaced it, car would die when hot due to low revs at idle.
3) OVP replaced, no change.
4) ICV pulled, noted it had been gutted and a necked down rubber hose inserted.
5) Non-genuine ICV purchased and fitted, problem made significantly worse (1600rpm idle).
6) Idle Control Module (ICM?) opened and resoldered, no change.
7) ICM changed, no change in problems.
8) Many MANY things tested, temp sensor swapped.
9) Brand new ICV tested, wouldn't close with 5v, spring adjusted, still no dice.
10) Over-priced used OEM (new in 2016) ICV purchased, fitted, idle fixed instantly (550-600rpm in gear, 850-900 neutral) - which I still think at this time is a little high.
11) Strong emmissions smell from car noticed under ANY conditions, idling or at speed (idling would have visible "fog" from the tailpipe) and slightly "bumpy" idle when hot.
12) Injectors replaced with new bosch, no changes noticed... except seemingly by coincidence...
13) Hard cold start condition returned (was resolved after the OVP fuse was initially replaced).
14) Many MANY things checked/tested again (inc. CSV, no voltage was getting to it)
15) Fuel relay replaced, no change.
16) Pins to fuel pump relay tested, instead of 3-5v, 2v was read.
17) Random - seatbelt light begun staying on (constant flashing), globes removed to "fix".
18) ECU replaced with 2nd hand unit after I resoldered the pins.
19) Cold start fixed, bumpy idle fixed, idle in neutral lowered even further (800rpm) AND most notably emmissions smell/fog fixed!
It would seem my issues where casued by a bad ICV which was replaced with a NEW BAD ICV.... AND a bad ECU.
Who would've though a bad ECU could cause such failures!
Idled okay, controlled the ICV correctly, seemingly was working the CSV for "a period of time"...
My old ECU has visible burnt connections, a split open resistor and burn smell (only on the board once removed from the case).
So, while I understand there are many things that cause a blown OVP fuse, it seems another one can be... blown ECU!
Now just onto fixing my strut bushings, a dodgy dash light (have globes), odometer that's broken (have new gears) and spongy seats lol.
It would seem these machines can still be fixed, but by god there is some complications... I like my mechanical diesels much more any day!