Engine brain racking

josh912 · 06-06-2001, 08:31 PM

OK, the engine runs really strong, smooth, and wonderful. However, it has a few glitches, so let's see if you guys can help me out!

1. The car starts really hard in the mornings or after it has sit for a couple of
hours. The car starts right away but it will not run above 800 rpm and the only way to keep it running is to pump the throttle, while its running for about 30-50 seconds. After that, it idles and responds just fine. This lead me to think that the carbs were leaking. I just rebuilt the Webers and I checked today and found no gas leaking out of the accelerator pump or fuel inlet, even when running. Could it be evaportating? But where? Also is there another place where the gas can leak out that I don't know of? Or is it something else beside the carbs?

2. When at highway speeds the engine pops up through the cars intermittenly. When I say intermittenly I meen that I can go 30 miles without a pop then it starts popping quite often. The pops normally come in spurts of 2-3. This is happening between 3000 and 4000 rpm at steady speeds, no accelerating or deaccelerating. I sync'd the carbs not that long ago and it runs very strong so I don't think its because the carbs are out of sync, but a possiblitiy at higher rpm's. I have new Bosch W5AC plugs, and that didn't solve the problem. And the car is tuned up. It's nothing major but every little sputter, pop, rattle, jurk, or ping annoys the heck out of me so I'm trying to get to the bottom of this. Any ideas?

Well, thanks in advance for the help as all of you have been great!

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Joshua Harrison
1968 912 Coupe

Steve F · 06-07-2001, 06:26 AM

Josh, this is just a shot in the dark, but my wifes "66" bug had the same problem and it was driving me nuts!As it turned out it was a intermitent condenser.Good luck!

Steve

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1967 912 "in progress"

Ads912 · Ads912's Garage

Hi Josh,
From my limited knowledge of Webers; they do not have a choke, so when the engine is cold, the only way to keep it running is to pump the acc. pedal. Your foot is the choke.
I have to pump my gas pedal to keep it running when it is cold.
Re the popping, it could be timing. I know that you run the 050 distributor. Is it new? Is the advance good and consistant? Hold the rpm at 3000 and use a timing light. Does the advance stay in one spot?
I hope this helps.

Adam.

josh912 · 06-07-2001, 08:05 AM

Adam, I've always had to give the car gas when cold but now it won't run past 800 rpm???? It keeps trying to die.

For the timing, its been hot here in California and with my high compression I had to back the timing down to 30 BTDC. Maybe thats the problem. I'll give it a few more degrees and see what it does.

Steve, what is an intermitent condensor?

Thanks guys

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Joshua Harrison
1968 912 Coupe

Steve F · 06-07-2001, 08:14 AM

Josh, it's the the little tin can attached to ignition points on the distributor(sp).Should be about $3-$4 for a new one and is an easy swap out with no adjustment.Good luck.

Steve

Rich G · 06-07-2001, 08:44 AM

Josh,

I read all the great replies and offer you one more. Although my past problem was a little different; my '76 912E would pop after driving a while, especially when the engine was pulling up hill. My buddy has a 928 Calloway turbo and told me to replace the coil. I replaced the coil with O.E. and the car has run fine ever since (over a year now). I know you said you were tuned up, but it is possible that even new equipment can be faulty sometimes. Good Luck .. Rich

josh912 · 06-07-2001, 11:44 AM

Hmmmm, I bought a new Bosch Blue coil when I rebuilt the carbs, and it has been popping since. Time to grab one of my 3 spare coils and give it a shot. Right now I'm waiting for the engine to cool down for 3 HOURS so I can adjust the valves, again. I had to replace the condenser when I got the 050 (sorry Steve, intermitent condenser didn't click in my brain). If all else fails I'll order a new condensor as I'm using my spare. After the valves I'll up the timing and see what happens.

Still have the cold engine starting problem. Bugging the heck out of me. It must be fuel starvation because while my fuel pump rebuild kit was on backorder I temporarily used a electric pump and had no starting problems. Any ideas???

Thanks

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Joshua Harrison
1968 912 Coupe

Steve F · 06-07-2001, 01:18 PM

Fuel pressure???Maybe....

Steve

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1967 912 "in progress"

Roland Kunz · 06-07-2001, 06:42 PM

Hello

Do you have thermal insulators between manifold and the carbs ?

Grüsse

josh912 · 06-11-2001, 06:39 PM

OK, after adjusting the 7 too tight and 1 loose valves, adjusting the out of sync at higher rpm throttle arms, fixing the BIG exhaust leaks, and leaning out the too rich carbs that were set too rich because of the out-of-adjustment valves and exhaust leaks, and replacing old, leaking, rubber fuel lines, I finally got the car to start up right away in the mornings and have eliminated the pops, I think. With the valves and throttle linkages adjusted, the car runs better and is VERY reponsive, even with the low timing due to pinging problems in the summer. No more reving up the car to 3K at stop lights just to be able to take off. The car responds instantly off of idle, even with the hot cam! Ahhh, the joys of owning a Porsche that runs good.

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Joshua Harrison
1968 912 Coupe
www.geocities.com/jkh912