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Join Date: Aug 2014
Location: PA
Posts: 65
Intermitant complete engine power loss / hesitation.

Hi all. Im trying to fix my final (really��) issue with my 80sc USA model.

I have an intermittent (3-5times in 1hr drive) full engine power shutdown / hesitation. 1sec complete 'hickup'.

This issue was present when I bought the car 4yrs ago.

Since buying I have:

Rebuilt engine ��. It smoked , used oil, leaked and wasnt that fast.
Rebuilt the gearbox. I'm nearly sure this is irreverent. But hey.
Refreshed CIS fully. Everything. I can tell you what my system and control pressures are in my sleep. HEGO version with frequency valve. It all works perfectly. 14.8@idle 12.2 at full throttle.
New fuel pump.
I run with Hego disconnected as I'm using the boss for my own wideband. Frequency valve duty cycle checked. %65 cold/%50 hot/65% hot when stamping throttle fully.
Classic retrofit CDI, new coil, wires, disi, arm, green wire, disi coil. I e tried non rev limiter arms and rev limit arms. No difference.

This is the final bugbear. As it's so abrupt I had assumed ignition. However I read that rev limiter on usa models is fuel pump cut. I'm pretty sure I can hear 'something' behind the dash when 'it' happens.

It starts hot and cold perfectly everytime. It's now quite fast. It drives perfectly except for this issue. The same issue has remained unchanged despite all the new components. I didn't do the above to fix this issue btw. I just wanted a 'proper' 80SC.

Thoughts on suspects most welcome!

Last edited by Sub8; 06-02-2018 at 02:38 PM..
Old 06-02-2018, 02:20 PM
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Join Date: Oct 2008
Location: Nash County, NC.
Posts: 6,863
By pass the rev limiter
With a jumper wire remove the red relay and cross points 30 and 87a
This runs the fuel pump steady and nothing else
That would be one doubt remover
Bruce
Old 06-02-2018, 02:39 PM
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Join Date: Jun 2009
Location: St Paul MN
Posts: 2,500
Garage
When it cuts out, what does your tach do? Iím not 100 percent positive, but if itís ignition, tach will drop, but if itís fuel, tach will still read. Can someone else verify if Iím correct?
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Rutager West

1977 911S Targa Chocolate Brown
Old 06-02-2018, 05:56 PM
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Join Date: Aug 2014
Location: PA
Posts: 65
Hi - thought about relay by-pass as I was writing! I guess that eliminates the rev limiter, the relay itself.

As for tach, can't say I've noticed. But will keep a better eye open....
Old 06-03-2018, 12:58 AM
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