Re: [DML] Fuel system questions
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Re: [DML] Fuel system questions


Don't you have a shop manual?? First thing you should do is get a set of manuals from a vendor.? The section on the fuel system is surprisingly well-written and easy to understand.? If you need more info, you can get a copy of Bosch Fuel Injection and Engine Management by Charles Probst (see This book covers some tuning details and other variations of Bosch FI.? Between these two books, there isn't much else to say.

As for your idle surging, it is not normal for the engine to do this when it is working properly.? It sounds like you have an intermittent vacuum leak.? Since it happens in all sorts of conditions, I wonder if there is a problem with your idle speed motor pipe that goes into the bottom of the mixture unit.? It could be vibrating itself of place, and will result in a large leak if it is not secure.? If you haven't done it yet, I would spend an afternoon replacing every vacuum hose in the engine compartment, and make sure the other things like W-pipe gaskets and o-rings are present.? Feel free to email me off-line if you need some help with this.

Re: Your example 1 - Not sure why you would need this.? On a hill, you just hold the brake,let up on the clutch until you just hit the friction point, then let off the brake and hit the gas while letting off the clutch.? I've never killed the D on a hill.? 

Your example 2 - Are you talking about down-shifting or up-shifting?? That would make no sense when upshifting, but when you say 'drop RPM's' I am confused.? If you are talking about downshifting, you are supposed to match rev's by blipping the throttle.? No need to watch the tach if you are experienced.

Your example 3- OK that can be your own project!? Luckily, the DeLorean engine is really pretty simple and doesn't need much attention once you have gone through it with a fine-tooth comb.? 


-----Original Message-----
From: Michael Conrad <mike@xxxxxxxxxxx>
To: dmcnews@xxxxxxxxxxxxxxx
Sent: Wed, Sep 9, 2009 10:13 am
Subject: [DML] Fuel system questions

Hello all.

I've been having some trouble with engine revving while idle, which I
understand is somewhat common.  On advice of some club members, I tried a
different CPR, and it seemed to improve my problems, so I ordered a
rebuild from Hervey and it also worked, but I do still have occasional
revving.  I can't really seem to establish a pattern.  Sometimes it drives
perfect, other times it revs with a 700rpm amplitude (from about 500 to
1200) and loses power when accelerating.  Once I even had a cloud of smoke
coming out the exhaust.  But again, other times it runs perfectly fine.
Sometimes even on the same day.  The problem most often happens when the
car is first started, but sometimes it doesn't happen until I've been
driving for a half hour or so, and once in a great while it will still
happen after hours of driving.  The intermittency is making it really hard
to diagnose.

Rather than the usual "whats my problem" email, does anyone have a nice
write-up of how the fuel system works?  And not just how it works, but why
it was designed the way it was and which components are supposed to solve
which problems?  I'd also like to hack around on it some day, so I figure
I might as well learn to understand it inside-out.

Example fun hack #1: wouldn't it be cool if you had a little servo on your
idle adjustment screw that would raise and lower the idle based on
conditions?  For example, when you're stopped on a hill it would be nice
the car was idling at maybe 1500 so that you didn't need to use gas and
brake and clutch all at the same time.  You could determine this with an
accelerometer and a speed and rpm measurement.

Example fun hack #2: wouldn't it be cool if taking your foot off the gas
while shifting caused the engine to drop rpm to exactly the rpm needed to
drive the next gear ratio?  I know this can be done with manual skill, but
it would get rid of those annoying lurches when you're changing lanes and
don't have time to look at your tach.

Example fun hack #3: put a sensor on every sense-able thing you 
possibly think of, and get real-time monitoring and logging of the
engine.  It would make future diagnosis a snap.

Thanks in advance.
Mike Conrad
vin 5732


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