Weird Driveiabiilty Problem

SteveStromberg · 10-02-2001, 05:52 PM

My 72 914 has a strange problem its a 2.0 Twin 44 Idfs, 009 with Coumpufire, when insalling the motor I put in a New Coil, Cap, wires ect these items have maybe 3k. Heres the problem: While driving the Tach will swing from 1k to 7k wildly and the motor will start to miss. My battery reads 12.6 without the motor runnings , 13.4 with it running,I checked the ground strap,and made sure that the spark plug leads were not close to each other or the Coumpufires coil to dist., I have Cleaned the Carbs,adjusted the valves, Checked the ground on the fuel pump (I have 4 psi). Could it be that the Coumpfire is Bad? its the only thing I have not changed. Any Ideas? I have swaped the tach out for another, no change.
Also it comes and goes the car will run really strong then wild swinging and missing.
Steve

DDS · 10-02-2001, 05:56 PM

Intermittently grounding tach wire?

scotty914 · 10-02-2001, 06:25 PM

check the grounds to the compufire and the dizzy, also the ground braid in the dizzy

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scott thacher
75 1.8 on the road again
75 under rust
(fine german rust)

John Rogers · 10-02-2001, 06:35 PM

Check the Compufire wheel with the four magnets in it (in the distrib) to see if it has cracked? I've had that happen and I have several spares now. Good luck.

SteveStromberg · 10-02-2001, 07:13 PM

I tried it with the tach wire disconnected at the coil,it made no difference. The part I dont get is the wild swinging of the tach. I will check the magnet in the morning, John did you tach act this way when the magnets were cracked? It will run perfect the wham missing and swinging tach then it will run prefect again. Steve

[This message has been edited by SteveStromberg (edited 10-02-2001).]

John Rogers · 10-03-2001, 05:55 AM

If I remember correctly, the tach did bounce around a lot, but it's been a year or so.

Dave at Pelican Parts · Dave at Pelican Parts's Garage

The tach runs off of the signal from the points. (Or whatever has replaced the points.) So if it swings around wildly, your main suspects are that the tach is bad (unplug the tach), the tach wiring is bad (unplug the tach wire at the coil), the points or replacement are bad, or the wiring to the points or replacement is bad.

--DD

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Pelican Parts 914 Tech Support

A few pics of my car: http://www.pelicanparts.com/gallery/Dave_Darling

SteveStromberg · 10-03-2001, 07:57 AM

The first thing I did was swap out the Tach, alas it did not change a thing .It did the same wild Swinging. Steve

Dave at Pelican Parts · Dave at Pelican Parts's Garage

So you're left with the compufire and the wiring to and from the compufire as your suspects. Swap in some points--does the problem go away?

--DD

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Pelican Parts 914 Tech Support

A few pics of my car: http://www.pelicanparts.com/gallery/Dave_Darling

John Rogers · 10-03-2001, 10:42 AM

My memory has gotten better it seems. I remember the guys at Compufire said the distributor had to have 0.005 or less of axial motion and if it goes over that the round fiber plate with the magnets will flail up and down and cause missing which will also show up in the tach. That is what finally caused the round fiber plate to get cracks. I measured the 009 I had been using and it was like 0.125 inch or so! Give them a call to verify this. Good luck.

clubracr · 10-03-2001, 12:59 PM

If you find that your dizzy is suspect then I'd recommend putting in an 050 dizzy instead of the 009.

SteveStromberg · 10-03-2001, 07:06 PM

Well I swaped out the Dist. for an 009 with points,She runs sweet I drove home 20 miles and the tach was as solid as a rock not a flicker to be seen. The Dist. had some vertical play,I suspect this was the problem I am going to put the Compufire in another dist. and see what happends. Thanks for all the input. Steve