[Diy_efi] 928/749

[dgilbert78 at juno.com]

Hello: Had a problem like that , everything was there , but would not
run. final fix, spark wasn't hot enough. Go buy chep spark energy tester
at parts store. If it does not troow a healthy gap, fix that. I went
absolutely nuts. I had spark, everything, just not enough and the damn
thing would not run.
good luck
Darryl..
On Wed, 15 Aug 2007 20:33:37 -0700 "Steven P. Donegan"
<steve at donegan.org> writes:
> Only takes 3 things to go bang - gas, spark and compression - you've
> verified 2 of the 3 below. Compression seems to be the only thing 
> left.
> 
> On Wed, 2007-08-15 at 23:23 -0400, Bill Shaw wrote:
> > I've been chasing a long series of problems with my 928 since I 
> > installed the new motor this spring .  Right now it won't start,  
> it's 
> > having some weird electrical problem. 
> > 
> > A little background...
> > I ran it in a similar configuration for 3 years... Porsche 4.7L 
> v8, 
> > Vortech supercharger, GM ignition module, sensors, throttle body, 
> and 
> > 749 ecu.  Ran great,  had loads of fun flogging the crap out of it 
> on 
> > all the road courses in the northeast.  Last fall it ate 2 spark 
> plug 
> > tips and scored 2 cylinders at Lime Rock.  New motor was in the 
> works so 
> > I finished it up and got it in the car.  The new one is a 5.0L 
> Porsche 
> > v8, '87 big dish pistons,  16 valve ported & extrude honed heads 
> all 
> > adding up to about 8.5:1 cr,   bigger cams, bigger throttle body, 
> bigger 
> > exhaust.  It ran pretty good for about 2 days,  good enough to set 
> me 
> > back in my seat and put a grin on my face,  then it all went to 
> he!! again.
> >  
> > I've swapped ECUs, ignition modules, plugs, cap & rotor, been 
> through 
> > all the plug wires with an ohmmeter, wrung out the wiring harness 
> from 
> > the sensors to the ECU.  I'm getting fuel,  I can hear all the 
> injectors 
> > clicking,  and have 43 lbs of fuel pressure.   The REF signal from 
> the 
> > distributor makes it through the ignition module to the ecu and 
> the ecu 
> > is putting out EST pulses, verified by o'scope.  #1 is firing at 
> TDC 
> > with bypass unplugged.  Everything is great,  it just won't start. 
>  
> > Tonight we checked the cam timing and retensioned the timing belt. 
>  I've 
> > been through all the basics I can think of, all is good but no 
> fire in 
> > the hole. I've reverted to my last known good bin while doing all 
> this 
> > testing.
> > 
> > The only weird thing I can put my finger on is with spark.  I move 
> my 
> > inductive timing light from wire to wire checking for spark on all 
> 8.  
> > I'll find one not firing (it changes some times),  pull the wire 
> off the 
> > spark plug,  insert another spark plug in the wire and ground the 
> tip on 
> > the block and it will fire,  the timing light will light up.  Move 
> the 
> > wire back to the plug in the block and it won't fire.  Pull the 
> plug 
> > from the block,  put it in the plug wire and ground the electrode 
> on the 
> > block and it will fire again.  WTF???  This is driving me nuts.  
> I've 
> > pulled one plug wire off 3 times to check resistance, wiggled both 
> ends 
> > and the whole wire looking for an intermittent break,  everything 
> is 
> > great,  3.1k ohms per spec.
> > 
> > I'm running out of ideas.  Anyone have a thought??
> > 
> > Thanks,
> > 
> > Bill
> > 928s 5.0L Vortech/749
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