912e L-Jet, keep it or not? + Idle speed?

[Mr_SpongeWorthy]

Hope this is a quick one. My just purchased 912e has the L-Jet fuel injection. My understanding is that these were a pain in the neck to keep tuned, a bit unreliable, and that many of them have been replaced with a carburetor setup. Then again, as far as fuel-injection goes, I've got the Technical Manual on this puppy and it looks pretty simple (which is good). I think I could probably figure out a lot of it myself, and with the manual I'm sure one of my better local shops could help me out with it.

Is my understanding correct? Is this system a pain? Should I just forget about it for now, drive it as is, save my pennies, and do a carburetor refit, or should I work out the kinks and stick with the L-Jet? What are the major pros-and-cons (fuel economy is important to me).

Current symptoms:

The car starts pretty well, then idles up and down nastily between 400 and 1000 rpm. Occasionally it will stall, especially during the "warm-up" period (it idles and runs best when either completely cold or completely warm). If the engine is fairly-warm-but-not-hot it can sometimes take quite a bit of cranking before it will start. But it has so far always started, and starts well most of the time.

Also, from what I can tell, you don't adjust the idle speed directly with this kind of setup. Makes sense. But, is there a way to do this? If I could ratchet that up even 100 rpm for now, just as a temporary measure, I think it would do wonders for the drivability. Right now I'm fighting it a lot to keep it running at stops during the warm-up phase. It feels a LOT like I have a vacuum leak, but I'm really not sure if that's the case (none of my other classic cars have been fuel injected, so it is new to me).

[WFBowen]

L-Jet systems, once sorted out are pretty trouble-free. I've owned two of these cars and both had problems with the airflow meter. Back when these cars were new, customers complained about lack of performance and many shops "adjusted" the airflow meter (the petentiometer inside) for richer running.
As for your current problem, once you're sure you don't have a vacuum leak, check the auxiliary air meter and the cold start valve ("5th injector") for leakage.
Your idle speed can be adjusted with the large screw on the throttle valve, but do it in very small increments.
As for keeping or dumping the system, here in Calif. (and other "smog states") there's no choice - it has to be on the car and these cars will always have to be smogged.
If you don't have this manual, check it out for good info:
http://www.texas912.org/912E%20Tech%20Data/912E%20FI%20Technical%20Manual.pdf
Bill.

[CRNT918]

As for options, I would google Jake Raby and check out his website.

[Mr_SpongeWorthy]

Originally Posted by CRNT918

As for options, I would google Jake Raby and check out his website.

Thanks. As a long-time VW guy I'm very familiar with Jake Raby. His reputation in the VW world is excellent. In your opinion, is his reputation in the Porsche world also excellent?

[hcariss]

Keep the system
sounds to me like you have a vacuum leak. I would ask over at 912BBS.org LOTS of experience and knowledge over there.

[Mr_SpongeWorthy]

Originally Posted by hcariss

Keep the system
sounds to me like you have a vacuum leak. I would ask over at 912BBS.org LOTS of experience and knowledge over there.

Thanks. I've looked around over there a bit, but their forum software is so out-of-date it is almost impossible to use. I guess I'll give it a shot though!

[CRNT918]

I don't think Jake is as well known in the Porsche world as in the VW's, but I think it's getting better. I've driven a Raby enhanced Boxter at the track and it's great!

[hcariss]

Originally Posted by Mr_SpongeWorthy

Thanks. I've looked around over there a bit, but their forum software is so out-of-date it is almost impossible to use. I guess I'll give it a shot though!

The search function is a bit primitive however post a direct question and you will get many helpful answers.
I like really like Pelican a lot but for 912E tech knowledge the 912 pelican site does not compare to 912BBS.
Let me post gratuitous pic of my car, I have had much help from the 912bbs.org crew my FI is intact.

[Dave L.]

Spongeworthy knows Raby's rep in the Volks-fun world, and so is familiar with RAT Type-IV development work, and I guess the quality that this company represents. Go to Raby's site, and at least until recently you'll see a Bitter Chocolate 1976 912E engine shot. Hmmm...that looks familiar! Wait- it's MINE! Long to short, excellent work, better today even than a few years ago when I purchased a rebuild to 2056cc preserving stock EFI. Car runs very nicely thank you- now on about 45K miles since the job. Not cheap, but do really want the best? P.S. Mr. Raby is also apparently quite involved in 911-ville and is developing flat-6 solutions apart from his early VW/Porsche work. See several references in recent editions of Excellence. An idiosyncratic character who really knows his (our!) stuff. Urrah! All my humble opinions, R/Dave L.

[kejaj912]

I have a 912E with a carb set up which the PO installed due to similar problems. The car would simply not run right at all. Since then, I've rebuilt the carb, changed the fuel pump (he had installed one with incorrect pressure causing flooding), replaced all gaskets and the thing is still occasionaly tempermental.

I was lucky that I got all original injection parts with the car. The second I have a moment I will put the FI back in.

Prior to doing so though, I will check every component and especially replace rubber hoses. As some of the fellas mentionned, vaccum leaks are probably the biggest culpret on these cars. As they are getting up in age, the hoses tend to dry out, especially at the connections.

Download the link which Bill attached for you, there is pretty much everything you require to troubleshoot your system.

If you are bent on putting carbs on, the people at Redline /Weber are quite knowlegeable and have a couple options for the car.


Although the car will not be a rocket with the FI, it is a very good system and usually very reliable and troubler free. I think once you narrow down your problem you'll be quite happy with it.

[Mr_SpongeWorthy]

Thanks everyone, I'm taking your advice and keeping the FI. Obviously I decided I didn't need a rocket or I would have continued my search for a 911 instead of hopping into this 912e, so I don't mind if I can't get quite the power with the FI as I could with carbs.

[Papermaker]

Hi-

Double check for vacuum leaks. I had a similar problem that I traced to air leaks that passed right through the wall of the hose so a visual inspection may not be enough. I'd replace all of the vacuum hoses as a starting point. Also, a complete tune-up helps eliminate problems associated with engine tune.

--John

[Befree]

I agree on the vacuum leaks. Test one more thing! Look at the air mixture controller, it sits right by the air filter. Behind it is a large electrical plug going into the controller. Start your engine and then see if your engine cuts out if you touch the plug or the wire.
Mine had the same problem and I discovered on accident that the plug was nit correctly seated and some of the soldered wires inside the plug got loose and send a bad signal to the air mixture controller. At least it's worth a try.