Souk - good thoughts...not sure though , how the "load vs no-load" part figures into an ignition problem.
I'm pretty sure that it's a lean-burn issue, since unloaded, the engine needs less fuel to rev, than loaded.

Razor - if you're willing to do this: how about let's just assume that it's running lean - so, to fix, we'll just crank a slight bit of richness into the fuel distributor?
Go to your Bentley book - look up how to adjust mixture - but instead of trying to set a CO level at idle, just give it exactly 1/2 turn rich. (I think this is 1/2 turn clockwise)
Then take it around the block and see if there's any difference. If not - try 1/2 turn more....test drive again.
If NO GO - then just back off the mixture adjustment exactly one turn, and you'll be back where you started, no money spent.
(the good part about this test, is that you're out no money - and just a little time and it's easy to return the adjust ment to exactly where you started)
This should allow you to "test" the problem, with only fuel mixture as a variable.
Whay say you?
(weekend's coming up - this should only take about a half hour?)

jcat, I tried adjusting the mixture 1/2 turn and 1 full turn clockwise, but nothing seemed to improve.

I've got about 20 guys giving advice on my $50 at p-parts if you solve my problem thread.

Say...I think the problem might be the plunger in the fuel distributor. When I lifted the air valve it seemed easy for about 1/2 way up then was harder to lift. It seemed that the plunger was offering some resistance to lifting the air valve. Is this normal, or could it be a gummed up plunger?

Not normal. Per Bentley when lifting:
Later under "Mixture Control Unit" it says :
Tom

Razor,
Tom is correct - action must be silky smooth...no perceptible change in resistance, throughout the range of motion.

If you've got resistance as you describe, then it's time to take a hard look at the air flow/fuel distributor device.

I believe that there's a good teardown/inspection section in the Bentley book - Also there's some good info in the Haynes paperback manual (much maligned, but helpful in some areas)

john

I really hope this means that I am close to solving this problem. I am suspecting that the plunger has varnish or rust on it. I plan to take the plunger out this weekend and have a look. A new fuel distributor is $500+.

There was some resistance about 1/2 way up on the air vane travel. This could be why the engine hesitates, right?

I really hope this is it!

Razor, I took the fuel dist off my motor a couple of weeks ago (think) and cleaned the pooper off of it with two cans of carb cleaner. Mine was not gummed up, but I still feel good about doing it.

Remove CIS boot and all there obstructions. Undo all your fuel lines to and from the dist. Use rags to soak up the fuel that will come out of the lines. Remove one line at a time and put the banjo bolts back on with the washers so you don't lose them or get more crude in the dist.

Once the dist is free of attached lines, undo the three screws on top of the distributor. Now you are ready to take the dist off, BUT!! BE CAREFUL OF THE PLUNGER. It will slide out. Don't drop it or knick it on the lower housing. It is a very precise piece and you won't want to scratch it if you can help it. Slowly lift the dist and with a slight angle to try to hold the plunger in the dist. As you clear the lower housing use your other hand to hold the plunger to the dist until you have it in a safe place.

There is an o-ring that seals the distributor to the lower housing. Don't lose it if it is good. If it is dried and rotted, replace it. You should be about to find a close replacement at the Ace Hardware store. Don't lose it in the grass like I did. The neighborhood kids will circle and ask why a grown man is on his hands and knees with his face 2 feet from the ground.

Once you have the dist off, get a small deep pan from your wife's kitchen, but do it when she's out shopping. You can use one of those disposable aluminum baking pans too, if you get a small one.

Take the banjo bolts off and let them soak, just to clean, not that important unless there is crude in the holes of the bolt. Try not to lose the soft sealing washers.


Soak the plunger!!! The spray carb cleaner into all the orifices on the distributor. Leave it in the pan to soak with enough carb cleaner to cover the holes.

After a good soaking, remove all parts and drain the dirty solvent and repeat as needed.

I used an air hose to blow out the orifices in between soaking. Don't use too much pressure or you might damage the guts (not sure this is that important, but it's a good precaution).

Clean the lower housing and air box while you're soaking. Clean the mating surface. Clean the air plate air with the carb cleaner, place a towel in the airbox to soak up the solvent.

When installing. Place plunger in the dist and make sure it moves freely. Be very careful to ease the plunger into the dist. Hold it to the dist and install with a slight angle tot he dist to hold the plunger in the dist. Make sure you've put the o-ring on the lower housing in the groove, use a little grease or vasoline to help seal.

Without fuel pressure and varnish on the plunger, the air plate will move up very easily, but you will hear air shooshing into the dist as the plinger slides back down. I had to reinstall a couple of times before I realized everything was good.

You're done with the tough part, now reiinstall in reverse. Pressur eup the distributor and bleed it by lifting the air plate.

Good luck and have fun. Don't get high off the solvent fumes, do this in a well ventilated area free of ignition sources. And keep the dogs out of the garage!!!!
SmileWavy

I have a 78SC coupe guards red but I am afraid that I cannot directly help. Assuming that you have standard cams I would guess it is a distributor advance problem. However this is just my guess. In your situation I would take my car to a dyno operator and get them to log ignition advance and the exhaust hdrocarbons whilst you simulate the problem. With this data you should be able to narrow down the offending part. My car is a euro version which initially had the vacuum connection on the distributor plugged. However reconnecting this did not have any noticeable impact.