912E Questions

[DLANG]

Does anyone know why Porsche installed the L-Jetronic on the 912E 2.0L when the 914 2.0L used the D-Jetronic? I used to own a 914, and now own a 912E and am wondering about the differences, and the advantages/disadvantages of these two sytems. Does any of the D-Jet tuning information transfer to the L-Jet? Would I be better off converting the 912E to the D-jet system? It seems that there is much more information avalible on the D-Jet. I've also recently had the problem of completely losing spark while driving. I cleaned all of the ground conections and it seems to have fixed the problem for now, but I don't know if this was indeed the problem. Any ideas? Thanks in advance for any help that might be offered!

[WFBowen]

DLANG:
I hope I can help a little. I have a 912E and a 67S, but I recently had to learn just about everything about 912E injection, as my car wouldn't pass smog here in Calif. (It finally did).
The L-Jetronic system is a later development of the earlier (D) systems and, as far as I understand, has "fewer moving parts" and is more "controlled" and tamper proof, for smog reasons. Differences include (L vs.D) no injection trigger points in distributor, much less complicated throttle-position sensor(full or no throttle sensing); non-adjustable fuel-pressure regulator;manifold pressure read at air-flow meter; and L-jetronic firing injectors twice in one group (as opposed to once for two groups.)
The problem you mentioned sure sounds like improper grounding, but make sure all grounds (even the main ground strap under the car) are absolutely perfect. The small clip-on grounds at the rear (fan) side of the motor often corrode, even when they look okay, and sometimes the spade fittings (which attach to the engine) are the cause. You didn't mention how often the problem occurs, but keep in mind that just about everything on this system goes through the "Brain Box". Also, check and double check all fuses and relays on the left side of the engine compartment. There are varions covers under which are wires which often corrode (these are all under the large black plastic cover.)
I'd suggest you get a copy of "Bosch Fuel Injection & Engine Management" by Charles O. Probst, SAE;Robert Bently, Publishers. It's softbound and saved my life when it came to troubleshooting this system since there isn't a lot of documentation on this particular car. Don't waste your money on the "factory" supplement - it just tells you which special tools you'll never own and to use high quality motor oil and Porsche approved wax.
Also: don't forget the basics: Distributor and points/coil wiring and grounding.
Hope it helps. WFBowen

[JP Noonan]

I've conveerted my 912e to D-jet if you want the low down, just ask.

Pretty simple. Two relays that fit is stock empty holes. a couple of wires here and there... Works like 914 does, 100hp vs. 88.