RE: [DML] Re: RMP Relay woes?

["John Hervey" <john@xxxxxxxxxxxxxxxx>]

Adam, 
Your correct. The RPM relay is a safety device so if the car got hit in the
back and the engine stopped turning the fuel pump would shut off. 
Hence no more fuel. As Adam described it is how it's powered. #7 fuse is the
FP fuse. It will get extremely hot. If you don't have a fuse extender then
the fuse may melt without blowing and mess up the fuse box. 
John Hervey
www.specialtauto.com



-----Original Message-----
From: dmcnews@xxxxxxxxxxxxxxx [mailto:dmcnews@xxxxxxxxxxxxxxx] On Behalf Of
Adam S.
Sent: Wednesday, July 08, 2009 11:02 PM
To: dmcnews@xxxxxxxxxxxxxxx
Subject: [DML] Re: RMP Relay woes?

The RPM relay runs the fuel pump as long as it gets ignition pulses, which I
believe come from the distributor by way of the ignition computer (someone
correct me if I'm wrong). Power for the fuel pump runs through the relay
socket. 

When they go bad you can get the symptoms you describe, though there's
always the possibility that the pump itself is flaky. If you want to test
it, make a jumper from two male spade terminals and a length of wire and
jumper the socket as shown here:
http://specialtauto.com/delorean-parts/images/rpm-relay-jumper.jpg

(This is also a handy trick for diagnosing the fuel pump circuit without
having to run the car.)

Be advised that the jumper WILL continue to run the pump even if the car is
off, so make sure to remove it when you're done! I *think* (not 100% sure)
that this will also disable the Lambda system since that also depends on the
RPM relay, so you may have some weird fuel mixture changes until you replace
the relay.

If you duplicate your failure conditions with the jumper in place and the
problem doesn't reoccur, especially after multiple tests, then your relay is
probably bad. 

If it IS bad, on DMCTalk there is a person named Dave, his handle is
Bitsyncmaster. He sells an upgraded RPM relay (you'll need to send in yours
as a core or pay a bit extra) made from solid state components. It's
generally regarded as a superior product in just about every way. I think
the price is $75 with your old relay. Buy one of those, it's the last RPM
relay you'll ever need.

If the relay isn't bad... then 

-Adam S.

--- In dmcnews@xxxxxxxxxxxxxxx, "roller822" <roller822@...> wrote:
>

> 
> The next day I took another drive and the same thing happened: I found
fuse 1 to be getting warm(rmp relay?). My question is this.  What exactly
does the RPM relay do, and does it rest itself when it cools after about 10
mins of sitting, will this relay also take out the fuel pump briefly? or is
there a circuit breaker that is giving me a hint that it is heading for the
trash?
> 
> Thanks in advance for any info and help.
> 
> John Kennedy
> 11196
>




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