Hello Malcolm,
Can we assume that your engine is in generally good condition (it passes
compression and vacuum tests) and is in a proper state of tune (with
distributor advance & retard systems OK at all rpm and carburetors
carburating well at all rpm.)
You can test both volume and pressure of the fuel pump. I think the output
volume should be about a pint per minute.
You mentioned that this occurs during highway driving. Does it occur after a
few minutes of such driving, or does it take an hour or more? Is the car
running overly warm when this happens?
Does your car have the charcoal canister? It may be blocked with fouling. I
believe this can cause fuel vapors to build up over time and cause fuel
delivery problems. Test this by disconnecting the hoses temporarily. If it
is a problem, it is very easy to take apart and rebuild.
Our friend Paul Hunt would likely remind us that a systematic approach
should be used to identify that cause of the problem, saving time finding
the cause and money buying parts not needed. Paul is entirely correct, he
usually is.
Going up hill produces more load as the car fights gravity going up the
hill. The power fade being more prevalent in this situation sounds more like
a carburation or fuel delivery issue more than an ignition issue, unless
your dizzy springs are weak and your total advance is very low. Could the
pistons in the carbs be sticking?
Others chime in please!
Eric in Florida
'74 MGB
-----Original Message-----
From: mgs-bounces@autox.team.net [mailto:mgs-bounces@autox.team.net]On
Behalf Of Malcolm Jeffcock
Sent: Sunday, July 12, 2009 7:20 PM
To: mgs@autox.team.net
Subject: [Mgs] sputter
Hi all:
I have a 74 B that has a irritating problem. When at highway speed, not
around town , I get this period loss of power, I thought fuel starvation or
something related to ignition. It is especially prevalent if I am going up
hill. It does happen on the flat and if I take my foot off the gas it
sometimes helps when I apply the foot again. I changed the fuel filter
thinking it might help and it did insofar as the frequency of these
occurrences. I noted that it was much easier to blow through the new vs. old
so I wonder about the fuel pump pressure. I don't have an SU but rather an
after market low pressure pump as per the rating in our workshop manual...is
there a method to test the pump?
Anything else it could be? Like I said I have fuel delivered to engine
without trouble through all revs except if I am on highway with the revs at
say 3k for a while and then try and accelerate-nothing. If going up hill I
just lose power gradually to the point of needing to pull to the shoulder
because I am a hazard...
Any helpful thoughts?
Malcolm
You are subscribed as ericemarkley@bellsouth.net
Mgs@autox.team.net
http://autox.team.net/mailman/listinfo/mgs
http://www.team.net/archive
Checked by AVG - www.avg.com
Version: 8.5.375 / Virus Database: 270.13.12/2233 - Release Date: 07/12/09
08:20:00
_______________________________________________
Support Team.Net http://www.team.net/donate.html
Mgs@autox.team.net
http://autox.team.net/mailman/listinfo/mgs
http://www.team.net/archive
|