Blake,
Don't rule out the fuel pump just yet. True most of the time they
either work or don't.
BUT-
There is that other 1%. One very good possibility is a worn or
sticking check valve in the pump. Another related check would be for
foreign matter blocking/partly blocking a check valve.
Too, you could have a leaky diaphram in the pump.
Electrically, the pump points could be sticking and/or the pump
condenser is bad.
While checking the pump, you might want to consider installing a filter
on the inlet side of the pump. Dirt and crud are powerful enemies of
Lucas pumps.
It sounds like youve just about eliminated everything else it could be,
with one exception. Have you checked the line between the pump and the
carbys. A partial obstuction could produce your symptoms.
Rick Morrison
72 MGBGT
74 Midget
On Wed, 14 Jan 1998 17:00:22 -0600 (CST) Blake Wylie <bwylie@hiwaay.net>
writes:
>Here's what I did today...
>
>I've already replaced the coil, so I went ahead and replaced the
>condenser
>which is about the only thing that I didn't replace before. The
>problem
>kept coming up, except it happened while the car is idling a number of
>times
>(I kept running it and it would run for maybe 5-10 minutes each time
>before
>bonking out).
>
>I then went to the fuel system (because I would notice that the fuel
>pump
>would pump like the bowls were empty when I turned the ignition back
>on). I
>started watching the fuel filter that I had put in. I watched as it
>pumped
>through, but it stopped after a little while (as if there was no
>pumping).
>I also did this with the gas cap off to make sure there were no
>ventilation
>problems with the tank, but the same problem kept arising. Then, I
>took off
>the fuel filter and put the regular line on thinking that the filter
>was
>causing a sort of blockage making the fuel pump think the bowls were
>full.
>This still didn't fix the problem.
>
>The main thing that is odd about this is, is that after it quits, I'll
>turn
>off the ingnition...as soon as I turn it back on, the pump pumps like
>the
>float bowls are empty (which is I guess true). Sooo...basically the
>car is
>starving for fuel for some reason. Could it be the new float bowl
>needles
>sticking that I put in? (they are new, but when I played around with
>one,
>it seemed to stick every now and then, but I thought that it wouldn't
>stick
>enough to hold back fuel). There doesn't seem to be much gunk down in
>the
>bowls, but that wouldn't be the problem if they empty out.
>
>The problem is somewhere from the bowl needles back. I don't think
>it's the
>ventilation in the tank as I took off the gas cap to see if it was
>getting
>enough ventilation...but that didn't seem to work (as mentioned
>above). It
>wasn't the filter as I took it off. Hmmm...it can either be the pump
>or the
>float needles from what I can tell..because it definately seems like
>it is
>running out of fuel.
>
>I was thinking as a guy had said ealier that 99% of the time, the pump
>either works or it doesn't, so I'm turned off by the idea of the fuel
>pump
>going out intermitently. The needles are new, but it does seem to
>have a
>slight sticking problem when I play around with them...but it didn't
>seem
>like enough to hold back fuel if the float was down. Could my float
>be
>sticking? How would I tell?
>Could it be the needles? Should I get the groose needles instead?
>Could it
>still be my ignition system breaking down (even though it sounds more
>like
>it's starving for fuel)?
>
>Hmmmm...I dunno...any other ideas? :\
>
>Keep the ideas coming, because I'm always open to new ones. :)
>
>Blake Wylie
>70 MGB
>
>At 01:31 PM 1/14/98 -0600, Bill Eastman wrote:
>>Blake,
>>
>>Another thought- electrical components often crap out with heat. In
>>particular, original Lucas electronic ignitions are prone to this.
>Maybe
>>your coil, condensor, or electronic ignition (if so equipped and yes
>I know
>>that 70 MGB's don't have electronic ignition. I used to own one) is
>puking
>>on you once it gets hot. Condensers are cheap and coils aren't too
>be
>>either so you may want to thow one in to check it out. If your car
>>originally had a ballast resistor and it has been removed, your coil
>could
>>be susceptable to overheating.
>>
>>I find it interesting that your old tank was not vented. A 70 B
>should
>>have one of those neat in trunk vapor separators and a charcoal
>cannistor
>>up front as well as an air pump.
>>
>>I would question whether the problem is a fuel pump issue or a float
>bowl
>>issue because of how long it takes to crap out. if the fuel pump
>couldn't
>>keep up, it would not take long to run the float bowls dry. An
>>intermittent issue with the floats would be just that- intermettant
>and you
>>would not see the consistency of the engine bonking after 15-20
>minutes. I
>>suppose that a slight leak in the supply line to the fuel pump could
>make
>>it work hard enough to overheat but I expect that you replaced all of
>that
>>when your replaced the tank.
>>
>>The next time it quits, listen for the fuel pump. If it is still
>running,
>>you may be running the float bowls dry. My bet would still be tank
>vacuum
>>or electrical.
>>
>>Regards,
>>Bill Eastman
>>
>>
>
>
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