Ditch CIS?

[Matthew Beaubien]

I think I'm at my all time hate level for CIS right now.

It all started a couple of weeks ago.  I was driving home from work (~6 miles) and 2 blocks from home, the engine started running really bad.  I had to use lots of throttle to do anything.  I would crawl along at WOT in 1st gear with the engine running at say 3000 RPM.  It wouldn't pull any higher.

I stopped outside of my house and kept the engine running.  Eventually it cleared up and seemed fine.  I couldn't get it to reproduce the problem.  I drove the car the next day and it seemed fine.  Until I drove home.  At almost exactly the same spot, it started to sputter again.

I did some trouble shooting and it seemed that playing with the relay board could make it run better.  My attention was then focused on the fuel pump relay.  I bought a new relay and did some other trouble shooting, and it seemed like the FP wasn't working.  I even hooked power up directly to the connector and heard nothing until I tapped the assembly with a hammer (this was all done while it was in the tank).

Fine.  Looks like the fuel pump is dead.  Get a new pump, install it into a tank that's full of fuel, and run the new FP relay.  No better.  Runs like crap if I can get it started.  Sounds like it's missing most of the time.  The I/C hits the front of the car when there's intake backfires.  The plugs look quite rich, with the exception of #1 which looks kinda lean.  Start pulling plug wires with the engine running and find pulling #1 makes virtually no difference.  I verify there is spark and compression is good on #1.

Ok, something is plugged and preventing fuel from reaching #1.  To diagnose fuel distributor vs lines and injector I swap #1 & #3 at the distributor.  Start the car up and it seems to be running the same.  I pull #3 plug and it dies.  Pull #1 plug and it dies.  Huh?

I swap the lines back.  Pull out all the injectors.  Find 5 empty beer bottles (easiest part of the whole ordeal), place injectors in bottle, remove the rubber CIS boot and actuate the flapper to various heights (spray pattern looks fine on all).  Inspect bottles.  They're all very close to one another, and if anything, #1 is slightly higher than the rest.

WTF!?!

I'm at a loss as to what I should do.  It sure seemed like an electrical problem at first because it cured itself.  I'm not certain what is acceptable, but it seemed like the end of the injectors could be moved around a fair bit, but actually pulling them out was quite difficult.  All the large o-rings looked fine, but the small black one on #1 was torn.  This could have happened during the removal process though.

I'm really considering putting EFI on.  It sure seems like it would clean up the engine bay, free up some power, and reduce complexity.  I have the inserts that allow the use of electronic injectors in place of the CIS units.  I'm concerned at the lack of space in the area and interference with the throttle body.  I have full access to a machine shop so I was even considering placing the injectors on the outside bend of the intake in a horizontal position.  There's certainly a lot of room out there.

I have an old Haltech F3 (fuel only) box that I would use to control matters.  Tuning won't be a problem as I have access to WB O2 meters and people who do this all day for a living--not to mention that I have a pretty good handle on it myself.

How many people have done an EFI conversion?  Any guestimates on the number of manhours involved, and any major obstacles?

Comments?  Suggestions?  Condolences?


Thanks,

Matt Beaubien
'86 5kt
'73 911E