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MG MGB Technical - Long Dormant Engine... Revival in Progress

Recently picked up a 1971 MGB. It's been sitting
for about four years, so it's going to need some
love before it's running again. Fortuntely,
it was a suspension issue that sidelined the car,
so the engine was running fine when it last
ran.

I've rebuilt three engines (one v8 and two i4)
but this is the first older car I've worked on.
I've ordered the factory manual, but it's not
here yet and I want to get started!

So, here's the status: I started with just
pouring some oil into the cylinders via the
spark plug holes and letting that sit for
a week. Then I removed the radiator so I could
turn the engine by hand. (It sure would be
handy if the steering wasn't in the way and
I could get a socket on there!!) It turns
without binding or problems. Changed the oil
and drained the coolant.

With the spark plugs out, decided to see if the
starter motor could bring up the oil pressure.
With a new battery, cranked, but got no response
after, oh, ten seconds.

Now, I don't trust that the oil gauge is actually
working (I checked the sensor, it went from 40
ohms still to 70 ohms cranking) so I've taken
the oil pressure sender out, and I'm going to
attach a mechanical gauge I have just for the
moment. We'll see what happens.

All of this comes from a concern that the oil
pump may not be primed any longer.

Next, is the SUs. I would rather not take them
all apart _yet_, although I'm sure I'll do it
later... it can't be much worse than a Rochester
QuadraJet, right? ;) Where should I clean
these out to remove the gum?

And, the fuel pump. Mine is sitting in the
boot, what actually triggers it to run? I plan
to check all the grounds and clean them up, but
does it need some attention? I don't hear any
activity back there when I turn the key on.

Fuel filter: I found one just eight inches
from the carbs, are there others?

Thanks guys!

Anders
arg Green

I have an MGA, but the engines are only slightly different.

To prime the oil pump: There is a pipe on the right side of the block. I do not remember if there is an oil cooler on the 71's. If not, the pipe will run from near the back of the engine to near the oil filter. If it does, it will be a hose running from near the back to the oil cooler. Disconnect the rear connection and pour some oil down it into the block. Also, it will take a while for the filter and cooler (if attached) to be filled when you start cranking the engine.

Pressure gauge: I thought they used a mechanical gauge until they stopped building B's.

Fuel pump: when you turn on the ignition, you should hear a fast ticking from the fuel pump. Assuming the fuel pump wasn't replaced with a NAPA special. The correct one is a cylinder about 5-6 inches long attached to a block that contains the fuel line connections.
Norman Fair

SU carbs are certainly simpler than a Rochester 4 BBL. Try just spraying carb cleaner all over the outside. Pay particular attention to the throttle shaft. This, BTW is leak-prone, as the shaft wears.

They can also stick at the float needle valves. Clearing this would likely involve at least some dissambly. The jets are the spring-like connection underneath that goes from the float bowl to the main body of the carb. This can get gummed up from sitting too long, as well.

When (not if) you do get to dissassemble the carbs, do them one at a time. They're actually pretty simple, but it is nice to have one complete carb to compare the dismantled one to. They are just mirror images of each other.

The piston inside the large vacumn chamber (called a dashpot) should move freely up and down.

Don't forget oil in the dashpot. Unscrew the cap and pull out the plunger. A little engine oil here is used as a damper to prevent the piston from moving too quickly.

I don't believe that the fuel pump was mounted in the trunk on the '71s. The original position is inside the right rear wheel well.

I don't believe that any fuel filters were installed originally in 71. So any that you find are PO-installed. It is not uncommon to find one between the tank and the fuel pump to protect the pump from rust and crud in the tank.
Paul Noble

In addition to what you've already done:

Pull off the valve cover and pour oil all over
the rocker assembly and valve tips. Let some
oil dribble down the push rods (and onto the
lifters).

With the sparkplugs out, spin the engine
some more in order to get the oil pressure
to register. 10 seconds seems a bit short
for an engine that's sat for all that time.
Spin for 15-20 seconds or so, let the starter
rest a bit, spin again. Repeat until the oil
pressure gauge reads up to 40-50 psi, or so.

Spray some carb cleaner directly into the throats
of the SU carbs. Lift each piston (in the throat)
up/down with your finger. The movement should
be smooth and easy. Open and close the throttle
plates. Again, the movement here should be smooth.
Spray the linkage with WD-40. Unscrew the cap(s)
on top of the carbs, withdraw the damper assembly,
and check the oil level there. The level should be
near below the threads. If not, 30W engine oil, or
ATF (Automatic Transmission Fluid) works here.

With the ignition "On", check the wire at the fuel pump
for 12v with a voltage tester. If OK, often, a long-dormant
SU fuel pump can be awoken with a couple of well-placed
smacks with a hammer. Seriously. This unsticks the
points which may have become frozen by corrosion.
DO NOT hit the pump directly. Hold a piece of wood
(ie: broom handle) up to the pump body, switch the
ignition on - and give the piece of wood a few, good,
sharp, smacks (...hard enough to scare yourself ...but
don't get crazy, either). Whatever you do, DO NOT
hit the black plastic end cover (points housing) on the
pump - or you'll bust it open. You'll know it's working
when the pump begins clicking softly. It'll stop clicking
when the fuel pressure is up and steady. If it doesn't
stop clicking within 5 seconds or so...check for fuel leaks.
Sticking float needles on the carbs are the usual culprits
for this.

Originally, there should be only one fuel filter near
the carbs. Some owners choose to install another
filter between the tank and the fuel pump, however.
Daniel Wong

Your MG should have a mechanical pump. If you have no plugs in the block and have oiled cylinders and poured oil in thru the top getting the valves ect., I would try it again. It can take a little while(definatelly less than 30 seconds) to get pressure up. Make sure your oil level is correct, but I have had similar old engines that have taked 30 seconds to pressure up. If you want to test oil pressure, unscrew the oil pressure line on the engine block above the radiator. oil will shoot out and be highly noticable.
As for the carb clean out, I'd:
A-Drain the tank and flush it with some new gas.
B-Throw out the fuel filter and get a new one. There is only one.
C-While the filter is disconnected pump some gas thru the line to get rid of and gunk in there.
D-i think you still have the SU's with external bowls to the side. You want to carefully remove the tops and clean out the bowls and also the jets. They will be in the top of bowl under the float. The float is removed by a screw in the side of bowl. Try not to bend it as it is set at an exact measurement. Then reassemble. This is all documented in any good repair manual.
E-Then reconnect everything.

As for the pump it should be an SU pump. it'll tick loudly while it builds pressure up. Check to make sure it;s grounded and that it is getting a 12V supply with ignition on. If it is the correct type it has points inside of it. Give it a whack with a hammer with power on it. This will normally surfice to get the points moving again. If not take the plastic and off and you will see some points. Just clean em and try again.

you also might want to grease the front end. There are 3 nipples on each side, and also take the wheels off if it has wire wheels and regrease. They can stick something fierce when left unmaintained. Probibally want to flush the cooling system with the heater valve open and replace the thermostat too.
J Arthurs

Here's the update:

Unhooked the hose to the oil cooler. Held
it up, and poured about 1/4 a quart in.
Reconnected to the oil cooler, and, with
no oil pressure measuring device
connected (system is open) cranked using
a remote starter watching the open port.

A couple of 15 second cranks later, oil
started oozing out. Hooray! Hooked up
my mechanical gauge. After several more
attempts, it comes up to 35 PSI after
about 15 seconds.

Now, I put 10W30 oil in which is a little
thinner than what is specified, so I
expect it will climb a little bit with
the proper oil. I don't plan to run it
with this oil, I just had it around and
figured I would replace it after running
the engine a few minutes.

Next issue: dash gauge. Now that I knew
there was oil pressure, I connected
the regular sender, and wired it up.
Within 15 seconds, it was reading at
the first bar on the oil gauge. Good. :)

Carbs: haven't messed with them yet.

Electrical: took the ground strap off,
cleaned it up, Dremel'd the metal where
the strap connects. This turned my very
weak spark issue (main wire to the block)
right around: now getting a very good
size spark where before it had to be a
hair's width away before it would jump.

Fuel pump: located, as expected, just
near the battery, in the right side wheel
well. Checked voltage and cleaned
connectors, solid 12.x volts. No clicking
though. It is a SU model, and seems
new(er). Gave it some whacks, but still
nothing. Perhaps I'll need to open it
up...

This does leave me with a mysterious round
canister, grey metal, perhaps five inches
in diameter and 2.5 inches deep, mounted
in the boot just near the right rear tail
light, that the fuel goes in and out
of. Ideas?
Anders Green

The round canister is a fuel evaporation canister. Fuel vapors from the emmissions go thru this and then back into tank. There should be no liquid in this at all. I would not worry about it at all. I'd remove the fuel pump (real easy), and then it is easy to take the cap off and clean the points. You can use some real fine sandpaper. Just wedge it in with the points closed and you can clean both sides at once. You can bech test it while it's out too.
J Arthurs

Ah hA! Fuel pump is now working after an early morning garage session.
Very nice start to the day. The points were all corroded and needed to be
scraped.

Next issue is cleaning the carbs up a little, and then it will be time for the
starting attempt!
Anders Green

This thread was discussed between 01/07/2002 and 02/07/2002

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