Need help! Autocross tomorrow and my car is running like @#!*

[david c.]

Hi guys,

After months of suspension and exhaust work, I finally thought my 912E was ready to go. As usual, I was wrong.

The car is a 76 912E (you know, 2.0 flat four just like a 2.0 914).
My car has points, a Permatune, 40mm Webers, Bosch coil, 050 distributor (new last year, along with the points, rotor, etc.) The cap and wires are about two years old. I installed brand new spark plugs last night, after gapping them to the specificied plug gap (should it be altered from stock if the car no longer has FI?)

Here's the problem. The car runs, but rough. The cylinders on the driver's side are doing all the work. The cylinders on the pass side are not combusting as much, I can feel a dramatic difference in the exhaust temp of the two cylinder banks at the tailpipe (my exhaust is completely split with no crossover).

With the car running, I can disconnect either, or both, of the spark plug wires running to the suspect cylinder bank. There is no audible change in the engine note.

I cannot do the same, of course, with the good side.

But, I do know that I have spark. I can get spark to jump at the plug end of the wires-visibly.

Now, I did check the plugs first, before I replaced them with brand new ones. They were clean on the good side and caked with black soot (not oily at all) on the bad side.

Also, I disconnected the cross bar on the carb linkage. With the car idling, I opened the throttle on the bad bank. It did have an effect, but not as much as the same movement on the good side.

My thoughts are these: I'm looking for a big problem, but it's probably a bunch of small problems.

I'm thinking part of the problem is spark. I swapped in one old ignition wire to one of the bad cylinders, and it sounded better and the exhaust got hot.

Although that is good news, the problem is that I couldn't really smell a lot of unburnt gas in the exhaust before I tried swapping the wires. I would have thought that if the problem was spark, I would be smelling a lot of unburnt gas in the exhaust from the bad side.

Does anyone have any ideas? I really want to participate in an autocross held both days this weekend. Im willing to work all night on the sucker, so fire away with your suggetions.

Thanks guys, I really appreciate any thoughts!

David

[rkyrdrcr]

I know this may sound a little to easy, but I had the problem with my 1.8 with webers. It turned out to be a combination of clogged idle jets and mixture screws ajustments. I adjusted the carbs after cleaning out jets and everything went back to normal.

Richard

[david c.]

Richard,

Please don't think I'm crazy, but I've never really been "into" my carbs, beyond taking off the top and making sure the floats were okay and the needle valve wasn't sticking closed for some reason.

How would I go about checking out what you've suggested?

Perhaps your observation is part of the problem. Maybe I've got a limited amount of both spark and fuel-which would explain why (a) I get better combustion with a different spark plug wire, and (b) why the car is combusting a little bit, but not stinking of unburnt gas-because there really isn't a lot of gas getting through to the combustion chambers.

With regard to (b), I did spray some starting fluid into the carb on the bad side of the engine when it was idling. It had no audible effect on the engine note. I don't know if that would add further confusion to your suggestion, but I throw it out there for further consideration by the gurus.

Thanks,

David

[si2t3m]

Hi,

Had a similar problem with my webers (40ida3c).

After thinking it was spark it was finally clogged idle jet circuits.

Are both banks synched? Needle valves doing there job (Any gas in the bowl)

If you press on the linkage on that side do you see gas squirting out of the accel pumps? If so by doing a little ride and nailing it you should feel that bank coming to life.

If both banks are synched and nothing seems to be going on at idle it's something to do with the idle circuit.


Pull the idle jets out and blow air in them

With the mixture screws (the ones with the springs on them) turn them in by counting the number of turns then take them out. Blow some carb cleaner in the mixture screw hole and put the mixture screws back in (turn them in then back them out by the number of turns you had taking previously).

Same thing with the air bypass screws. Unlock them, turn them in, count the turn and take them out. clean the ports and air bypass screws and reinstall them.

If no change take a propane torch (don't light it) and let propane go in the top of the barrel. Idle speed should increase. If not, i'd guess an air leak somewhere. Bring the propane torch to the joint between the manifolds and webers. Same thing between the heads and manifold. If idle speed changes you found the source.

So again, if they are synched, no vacuum leaks, and the propane torch is changing idle speed when introduced in a barrel it might just be a clogged idle jet circuit in the carbs.

Take that bank of and start squirting carb cleaner to find the blockage. check for blockage in the passage that goes from the idle jets to the mixture screws. Check for blockage between the passage from the idle jet to the bowl.

On my Weber 40IDA3C carb cleaner would squirt out the emulsion tube wells but didn't in the 2 clogged ones. Idle circuit was blocked between the idle jets and the bowls. Had to drill 2 little lead plugs out on each barrel to clean up the passage. I replaced the plugs by using lead pellets and epoxy.

HTH

Marc-Andre Morin
70 914-6 conversion 3.0 Webers

[david c.]

Thanks Andre! I'm printing out the info now. My only question is how to get the jets out. I'm not really sure what "jet" looks like, as I've never done this before. I have no fear, I'm just carb-ignorant like I was suspension ignorant before I ripped the whole thing apart last winter. You just gotta do it!

So, how do I remove and clean the jets?

David

[si2t3m]

What's the stamping on those webers (should be located on the float bowl under the WEBER word).

assuming that these are 40IDF and by looking at:

http://www.webercarburators.com/40IDFXE.pdf

Idle jets are 22-23-24 (idle jet, o-ring, idle jet carrier) and located at the top of the carb just beside the bowl.

Air bypass screws are 37-38 (air corrector, lock nut) and located at the base of the carb. The air bypass screws have a lock nut on them.

Air mixture screws are the ones with the springs on them 23-28-29-30 (o-ring, o-ring holder, spring, mixture screw).

So with a flat screw driver you should be able to do the work and check the idle jets. What out for those o-rings not to loose any. I put a dab of glycering on the o-ring when reinstalling them.


Also here is a good post from a fellow lister on the 911 list on ajusting webers:

Weber rebuild

[david c.]

Andre and Richard,

I'm going to work! As soon as I get home from my day job, I will begin work with your suggestions. No girlfriend tonight! She will have to understand.

Thanks for the tips. I will let you know what happens on Monday. Thank you very much.

David