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

["DMC Joe" <dmcjoe@xxxxxxx>]

David,

I agree with your comments concerning "giving advice by remote control".

I also wanted to make one correction in your analysis of the operation of
the idle speed motor.

You said: "BTW the idle motor system is also controlled by the RPM relay so
it should go quiet too along with the frequency valve. Reference D:05:03."

In actuality the idle speed motor receives voltage from fuse#1. Therefore it
will operate with the RPM relay removed. 

Happy Holiday's
  

-----Original Message-----
From: David Teitelbaum [mailto:jtrealty@xxxxxxxxxxx] 
Sent: Monday, December 27, 2004 12:18 AM
To: dmcnews@xxxxxxxxxxxxxxx
Subject: [DML] Re: Fuel pressure & RPM Relay




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 









To address comments privately to the moderating team, please address:
moderators@xxxxxxxxxxx

For more info on the list, tech articles, cars for sale see www.dmcnews.com

To search the archives or view files, log in at http://groups.yahoo.com/group/dmcnews 
Yahoo! Groups Links

<*> To visit your group on the web, go to:
    http://groups.yahoo.com/group/dmcnews/

<*> To unsubscribe from this group, send an email to:
    dmcnews-unsubscribe@xxxxxxxxxxxxxxx

<*> Your use of Yahoo! Groups is subject to:
    http://docs.yahoo.com/info/terms/