Re: [DML] Re: Fuel pressure & RPM Relay

[Rod Dillman <rhdillman@xxxxxxxxx>]

David, I have always been impressed by the "top of your head" advice you give to those of us who need assistance and who are trying to gain a better knowledge of our cars in order to repair them ourselves or who pass on the information to our service tech. I frequently print off postings and file them when the in formation is likely to help me on a future project or repair. Without the free advice on the DML and the free calls to our vendors and service facitities DeLorean ownership would be much more challenging and for some unappealing. I appreciate those such as yourself who share experience and knowledge with those of us who seek to be better informed about our cars. Rod 10921

David Teitelbaum <jtrealty@xxxxxxxxxxx> wrote:


Actuallly it is not quite that simple. Yes, all these engine systems
are controlled by the RPM relay. It is *supposed* to prevent these
systems from continuiously operating if the ignition key is on and the
motor is not running. In practice I have seen cars where it does not
quite work this way. For instance when first powering up the RPM relay
is supposed to pulse so the fuel pump can run enough to provide some
fuel pressure to get the motor started. In many cases it stays powered
a lot longer than a "pulse". BTW the idle motor system is also
controled by the RPM relay so it should go quiet too along with the
frequency valve. Reference D:05:03. I think one of the points to be
made here is when working on old cars (including Deloreans) we
(mechanics and technicians) start to assume that many things are
hooked up and working the way they are supposed to except for that one
problem that the owner/driver has identified. We have to start
somewhere and assume that SOMETHING is correct or we might never get
anything done. The problem with that is that from past experience you
really can't trust everything, I have seen things like the wrong
relays in the wrong places, wrong fuses, things unplugged, jury-rigged
wiring, (especilly in the fuel pump circuit and cooling circuit). When
giving advice by remote control you are in an even worse position.
>From my many years of experience I could spot something that would be
obvious to me but someone else may never see but I can't see it
because I am not there. There was one car that wouldn't start and run
properly. It finally was mentioned that he had the hot-start relay. As
soon as he pulled it the car ran fine. Now, in a quick visual
inspection I may have spotted that and fixed it in a minute. Instead
we guessed at many things and sent the poor guy down a lot of blind
alleys. We all do the best we can. I am not in this for money but to
only help get as many Deloreans running as good as possible. I am not
perfect but I do the best I can. I appreciate that many people read my
posts and think I am helping them. Anyway the short answer is that the
frequency valve will buzz if the motor is not running but after a
short while (if the RPM relay is working correctly) it should stop
buzzing and the idle motor should be quiet. Same goes for the fuel
pump. The time does vary a lot. Another quick point to be made. The
origional RPM relay has a failure rate. It isn't high but it is
significant. Every owner should be aware of this and know how to
jumper it so the car can be driven home. It is not safe to drive
continuosly with a jumpered RPM relay but it is OK to do in an
emergency for a limited time. You must be very aware that the key is
OFF if the motor is not running. In my defense I do not research every
question and sometimes I do give answers "off the top of my head".
David Teitelbaum
vin 10757 




--- In dmcnews@xxxxxxxxxxxxxxx, "endotex23" wrote:
> 
> 
> --- In dmcnews@xxxxxxxxxxxxxxx, "Elvis Nocita" 
> wrote:
> > 
> > David - I don't think so !
> > 
> > the lambda relay is powered from the RPM-relay.
> > When the engine is not running - the frequency valve is quiet.
> > 
> > What he hears probably is the idle speed motor.
> > 
> 








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