Paul Mitchell wrote:
I seem to have a bit of a fuel problem with my 74 TR6 PI. Sometimes
when
I put my foot down, there is a lull, then suddenly it picks up and
surges away again. I can't find anything wrong with the accelerator
linkage, and the fuel pump seems to be fine, albeit a bit noisy. What
do I do next?
Hi, Paul - this seems uncomfortably familiar to what I've experienced
with my PI saloon, except I had a persistent misfire in there as well
that wasn't electrically biased.
I suspect the problem is fairly simple to resolve.
Try the following as my car had a bit of everything shown below:
- Are all the butterflies adjusted with the same clearance on idle?
Remove the plenum chamber and check the clearances at the top and
bottom of each butterfly with a feeler gauge when the butterfly is
closed.
There will still be a nominal clearance, so find out what it is and
ensure
they are all the same Note the readings. This is a pain of a job in
terms
of time in making sure you are getting the correct measurements.
- Has someone at some stage 'ramped' the butterfly opening sequence?
Some cars with worn linkages respond better if the middle pair open
marginally later than the front pair and similarly with the rear pair
opening just after the middle pair.
- It's possible one pair is opening marginally before the other two
pairs and this is upsetting the vacuum settings to the metering unit.
- You've got a vacuum leak somewhere
- Are you absolutely sure there's no slop in the linkages? Have a good
look at the throttle interconnect bar and especially at the bushings
on either end. If you have slack there, even a tiny bit, fit new ones!
I can give you a tip on how to do it with the hard plastic ones
favoured
by people like Rimmers.
- When did you last have the injector opening pressures checked? You
might have one or two lazy ones. 45-50 psi is the normal operating
pressure.
- Is the pump delivering at around 110psi? You'll need access to a
fuel injection test-bench for this.
- Avoid meddling with the metering unit UNLESS you know what you're
doing. It's just possible one of the datum track setting screws has
come loose and this has confounded the fuel delivery curve. That's
when life can become *really* interesting!
I'm not sure whether the TR Register in the UK has availed itself of
the recently re-printed Lucas Fuel System Training Notes but these are
available from the 2000 2500 2.5 Register as well. Contact me off-list
for the
email of the guy distributing them.
Regards
Jonmac
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