just removed both injector rails on my project car Highline from 03/1990. E32 750 V12 M70 engine.
I decided with my friend Take to rip everything out and renew as much as possible.
Have taken out the intakes for later sealing and cleaning, throttling valves, MAF's, fuel lines (I can only suggest you to check them, I was really surprised to see hoses in the fuel return line from the DK's which broke like glass, they were hard like stone. Very dangerous!!!).
Valve cover gaskets, all rubber in the intake lines, coolant hoses, Thermostat, new radiator (made in Japan with aluminium tank instead of plastic. We use the rest from an radiator from my grey 750 for that. I do not want to have the plastic connector neck broken again) washwater tank etc.
Now coming back to the injectors. As almost everything like the oxy sensors, spark plugs, distributor caps, -rotors they are the original ones from 1990. because of the damaged distributor caps, the oxy sensors were damaged, the spark plugs are black and to be replace, all injector are black and covered with a kind of carbon, one was even completly blocked from outside.
Of course they need new gaskets/seals, but if they still work 100% I cannot check with my limited tools. Seals cost here about 5 $ per piece, at autohauaz.com 0.65 $. Sending them for example to cruizin performance it will cost per injector approx. 20 $ at least with shipping to/from Japan-USA.
http://www.cruzinperformance.com/fuelinj.html
Here in Japan they charge for one injector abt. 200 $, in Germany 130 $, in USA 42.31 at autohaus, and these are the latest version type
Of course, as usual, the V12 is more costly, 42.31 x 12 injectors = 507,71 for new ones.
20 $ x 12 = 400 $ for repair and testing.
So the difference is not that big. And as usual on the V12 engine it is a PITA to get to them.
Intake manifold system has to come off, the gaskets cost a fortune if damaged, in total about 400 $. Usually I use Hylomar to seal them again.
So, it is not a money question, just: how long last injectors and is it worth to repair and test them or waste of money after 15 years use.
The engine has 130K km = 80K miles. But of course a lot in traffic jam here without moving, so the actual "no-moving miles" the engine has run is maybe 150 k miles.
Your opinions please.
Thank you.
Edit: for sure I will find 12 injectors on my parts cars which finally work, but that involves a lot of work by installing and removing and installing again, as no suitable test tools for injectors in my garage.