To FI or not to FI, that is the question

[andreic]

Hello fellow teeners,

Here is the problem I have. My 1975 1.8L has an engine that runs but has some issues (leaks oil, burns oil, low compression -- 85psi across the board), which is not surprising at 93k miles. I originally had a plan to build a fresh engine, but I fear that project may be a bit too much for me right now so for a while it will be shelved.

A couple of days ago I came across the option to buy a motor which looks like a good candidate for a replacement. 1974 1.8L, with only 30k miles on it, ran last year. It comes with the original L-jet fuel injection system, supposedly complete, including also a 1975 FI harness. The seller gave me the option of either buying the motor as it is, with the FI system, or (at a lower price) without it. The trouble is that my car was long ago converted to a single Weber carb. My original plan was to use a dual Dell'orto carb setup on the replacement engine (I already have the Dell'ortos), but the seller kind of talked me into giving the FI system a try.

I don't know what was taken out of my car when the car was converted to the carb setup. I know that I personally removed the high pressure fuel pump about 3-4 years ago, but I may still have it somewhere. I know that the relay board is still in the car, but without relays. I don't know if the throttle position sensor is still in there, or if the wiring going to the fuel pump is still there. (The car is in storage so I can't check.)

My two questions are:

a) How hard is it to get the FI system to run well if all the wiring is still there, assuming that the engine I get has all good running parts? I would still need to take the fuel tank out, put the high-pressure fuel pump in, buy new relays, and get the engine running.

b) Is the trouble to get the FI system running worth it? Is the FI system running considerably better than a dual Dell'orto carb setup? I plan to use this car only for driving around in the summer, never for racing.

What would you guys do?

Thanks,
Andrei.

[stinkindiesel]

Ditch the single carb. You could make a case for a good set of dual carbs vs. fuel injection, but single carbs belong on lawn mowers, not Porsches. L-jet is not that hard to figure out, and you'll get lots of help here with it.

Gary

[andreic]

Yes, I got that message loud and clear that I should get rid of the the single carb set up. My question was if I should go to a dual Dell'orto carb setup (with the advantage that I don't need to do much electrical debugging in the car, and I can test the whole setup outside of the car, and tune it up) or try to get the FI system back to life.

What do you think?

Thanks,
Andrei.

[Dave at Pelican Parts]

Just a note: The relays on the relay board are not used by the L-jet system. One is used for the heater blower fan, and one is used for the rear window defogger, but the other two spots would just be spares. (Handy place to keep them, though!)

The relay functions are handled by the "dual relay" that hangs off the battery tray. There is also a "resistor pack" that hangs off the battery tray, and it is needed to drop the voltage going to the injectors so you don't fry them.

L-jet is a pretty good system, all in all. But it really doesn't like vacuum leaks; they make it run lean. Since the crankcase is plumbed to the manifold, you even have to ensure that the oil cap seal is in good shape, or you'll get "false air" (unmetered air) and a lean mixture.

I figure it will probably be a pain to get the L-jet working right. But the up side is that there really is a specific "right" for the system--as opposed to "lots of combinations that are about close enough" for a carb setup. And it's likely that once you get L-jet sorted out, you won't have to touch it again until it's time to replace the hoses.

--DD

[andreic]

Am I right in understanding then that all that is needed in order to run the engine outside of the car (with FI) is:

a) install transmission and starter, wire starter
b) wire ECU and fuel pump to dual relay
c) plumb fuel pump to pressure regulator and to a tank of fuel
d) wire a fake starter switch to the dual relay and to the starter solenoid

Anything else I am missing? I would like to have the opportunity to run the engine without modifying my car, it is much easier to spot oil leaks (and to fix them), check oil pressure and compression, adjust the L-jet, etc. Is this a good idea?

[Emo993]

I would go with dual Webers, I had them on a 1.8 bumped to a 2.0+ big bore with mild cam, auto-crossed and drove great for over ten years. Never had to touch them....Best, Mark

[Cairo94507]

F.I all the way. Once it is right, forget about it.