Re: Flat running

["Harold McElraft" <hmcelraft@xxxx>]

More than few DeLoreans have messed up the fuel system adjustments by 
turning the fuel mixture screw in order to compensate for some other 
problem in the fuel system. I mention this because the mixture can 
only be set properly when you know ALL fuel system components are 
functioning correctly. It was sealed originally to prevent tampering 
and was set with everything working correctly. So, correct adjustment 
is critical to proper overall performance. Spark, etc. has to be in 
good order too and no vacuum leaks.

There is a dwell meter, voltage process set out in the operating 
manual that can get the fuel system adjustment very close if not 
right-on without using the CO taps. A critical piece in the fuel 
regulation is the pressure regulator mounted on the valve cover. You 
MUST know if that is working correctly. About the only way to know is 
with fuel pressure gauges, or just put a new one. The Lambda is a 
fuel enrichment machine that must also be functioning correctly for 
adequate engine performance. That can be checked fairly thoroughly 
without special tools by just listening to hear if the frequency 
valve is buzzing. If it isn't you need to find out why not.

If the engine was stumbling when cold but fine when hot then the cold 
engine enrichment cycle is messed up. Either the pressure regulator 
or some other component. Not the fuel adjustment. A DeLorean with a 
proper functioning fuel system does not hesitate or stumble, ever.

I would start by methodically checking all major pieces for proper 
function and see if you can get the fuel system adjusted - engine 
hot - with the dwell meter process; then check the other stuff.

Harold McElraft - 3354





--- In dmcnews@xxxxxxxxxxxxxxx, "cruznmd" <racuti1@xxxx> wrote:
> I agree that the WOT wouldn't be the sole cause of this.
> I put the timing light on the engine and the timing advanced as I 
> revved it up. It appeared to be in spec with what the manual 
required.
> The advance solenoid clicks when I open & close the idle 
microswitch 
> but that doesn't necessarily mean it's working does it? 
> 
> Vacuum lines are routed in accordance with the diagram in the 
engine 
> cover.
> 
> Initially, the car idled roughly and would hard start cold and I'd 
> have to feather the gas to keep it running. It appears that the 
cause 
> of this was incorrectly set CO screw. I started richen the mixture, 
> and keep the idle sane by adjusting the throttle linkage (which was 
> on an extreme end anyway by P.O.) and re-setting the timing. 
> 
> Now it starts and idles like a dream from stone cold. It has more 
> power, but still not enough. I feel I have a little more play with 
> the fuel mixture but when I reach the point of diminishing returns 
> I'll have to put a pressure gauge on the system and check control 
> pressure.
> 
> Rich
> 
> --- In dmcnews@xxxxxxxxxxxxxxx, "Harold McElraft" <hmcelraft@xxxx> 
> wrote:
> > The WOT on has a minimal impact so I doubt if that is not your 
> > problem. Does it start and idle OK? If so, I would suspect 
failure 
> > in the vacuum advance system somewhere, the throttle plate is 
> > sticking or, the idle motor switch that operates the vacuum 
advance 
> > solenoid in unison with the idle motor is stuck too, like your 
WOT 
> > micro switch. Are the vacuum hoses routed properly? Double check 
> > this too. Timing light is a tool that can tell you if the advance 
> is 
> > operating.
> > 
> > Harold McElraft - 3354
> > 
> > 
> > --- In dmcnews@xxxxxxxxxxxxxxx, "cruznmd" <racuti1@xxxx> wrote:
> > > My suspects are: timing advance failure, combined with the 
> absence 
> > of 
> > > the WOT microswitch, and/or maybe some smaller vac leaks. Any 
> > > additional suspects are welcome.
> > > 
> > > Rich
> > > #5335