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25D [I think] Vacuum Advance

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Atrus

Atrus

Jedi Warrior
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I'm having problems with my 1275...car wouldn't go above 30 mph...messed around, found out the wire on the fuel pump was loose, not getting enough fuel. Fixed that, car runs great at low RPM's. It just won't go above 3k or so.

I admit, I broke the vacuum advance tube coming off the distributor. I assume this is my problem (I plugged the engine port). My question is, can I repair this somehow? The tube broke right at the nut on the distributor. Also, is this most likely the problem? I know some Sprites don't have vacuum advance distributors, I figure they have a more sensitive mechanical advance system. Am I correct in assuming this is my problem? The car just stumbles and doesn't want to go. I can get up to maybe 40mph in 4th with my foot to the floor and that takes a long time.

Thanks in advance!
 
Kevin, I don't think your vacuum advance is the problem. You should have full mechanical advance by 2500 RPM or so, and the vaccum advance is totally out of the picture. It sounds suspiciously like the point gap has closed up. Check to see if the point gap is .015", like it should be. Sometimes the little rubbing block that runs against the distributor cam wears, allowing the points to close up.
That would be where I would start.
Jeff
 
Thanks Jeff, I was hoping you'd reply. I'll check the point gap, but I am fairly certain it's set properly - I just checked it 80 miles ago. Sadly, that's all I've driven it since July.

Does this sound like a fueling issue still? Maybe the floats aren't set properly and it's starving for gas? Pump not flowing enough?

My wife's uncle is fairly good with LBC's...It's a 5-6 mile drive to his house, and I'd like to do more than 30...40 with the gas pegged the whole way.

I'm looking just to get it running for the remainder of the driving season, I know it won't be near optimal. Honestly, the wiring and other aspects of the car are rigged and not done properly...I'm hoping to drive it this summer/fall and if I can get through next year I hope to do a nice custom rebuild on it, make it the car I really want it to be.
 
My guess is the mechanical weights in the distributor are stuck. They do rust up. I have found this to be the problem on numerous dizzys. Or the advance springs broke or came off.
Or you timing is way off. Start by advancing the timing, turn the dizzy towards the front of the motor about a 1/4" and see if it helps. If it does, it's time to tear into the dizzy and clean the weights.
 
Thanks Spritenut, I'll check that this weekend. I honestly don't think they are frozen - took the distributor apart in July, made sure everything was free. There could be the possibility that the timing is off somehow I suppose. I'll check that. Have to borrow a gun from a friend as mine isn't working.

Thanks, I'll report back if that's not it!
 
Take it step by step. I don't think it's your vacuum advance unit either. Check the points, plugs, plug wires, cap and rotor. Make sure the points and spark plugs are clean and properly gaped as mentioned above. Then, since you're working on the ignition system, check and set the static timing. If that fails to address the problem, you may indeed have a fuel problem. The first thing I'd check in the fuel system is that you are getting sufficient flow. After that, check the level of the fuel in the float bowls and adjust the float valves as necessary. Is there an extra fuel filter or two on the line? If so, check and replace as necessary.

Once you've sorted out the problem, go back and fix the advance tube. Depending on how and where you broke it I'm sure you'll figure out a way to make a repair.
 
Advance tube repair, small peice of copper pipe from any shop that just fits over the outside of the orginal. Now you have a sleeve, clean all well and solder. Make sure the break is cut off cleanly and line is free.
 
It's definitely not the vacuum advance.

So then, I would start with double checking the wire order. Sounds like maybe miswired, running on two cylinders.

If that's not it, then I would say it is almost certainly the timing.

In any case, it sounds like ignition is not happening in all cylinders at the appropriate times.

I think a fuel problem would be more erratic or lead to a more "dead-in-the-water" situation.

This of course all assumes the engine was in fine order before hand i.e. good compression, proper valve settings.

JACK
 
I am going to say vacuum leak at the manifold or where the carbs bolt to manifold. Have you had either off recently? Have you or someone else used RTV on the carb or manifold gaskets? If so, gas will eat it away and cause a leak.
 
My guess is that the condensor is going out- this sounds very much like the symptoms I had when mine went out.
Bill
 
Wow, lots to look though here. I'll try and explain more.


I have 2 new HS2's on the car. There was an intake manifold leak, the nuts were loose. I tightened them up, and the car seemed to run better. Maybe I should get new ones as these may be leaking?

Anyway, new cap, rotor, condensor, wires, plugs. I checked them all in July to make sure everything was gapped/set properly, and then timed the car. Set the carbs, seemed to be running decent. At this time, I also made sure the mechanical advance was free.

One day driving, it just wouldn't go at all. Foot to the floor, and it'd just sputter and putz along. I believe this was the fueling issue...it did the same thing yesterday when I noticed the wire was intermittently connecting on the fuel pump. I fixed that and the car was cruising like a champ.

Now, when I try to put it above 3k or so (best guess, tach isn't working right now), the car just has no power and won't rev past that point. It sputters, either like a small rapid backfire or like it's missing. It's not a rythmic sputter, it just won't go.

I've checked the rocker clearance and all seemed well.

So, based on this thread:

1) Vacuum leak at the manifold still
2) Condenser bad
3) Timing is off now
4) Float not set correctly
5) Pump not flowing enough.


I have an inline glass filter, looks clean and flowing to me. Also, for vacuum advance repair, the tube broke flush with the nut, so I think I am SOL and will have to get a new unit or something. I'm certain I don't have spark plugs out of firing order as the car runs great up to 3k or so. Idles and cruises nicely below that point. It just hits a wall and won't go any farther.
 
Had an MGB did that to me once, turns out I had crud in the fuel line. When the car was at low RPM (low fuel requirement)everything worked well. As soon a I put a load on the system, the restriction became very obvious. Was a bear to figrue out. You may want to throw some HP air at the fuel lines.

Don
 
I had a buddy that had a big leave in the gas tank of a tr3. Talk about a hidden intermitant problem. Good luck.
 
One other thought is possible (but not probable) Point-float. The points may be new but possibly the spring is weak or cracked and allows the points to float above 3K. You may try cleaning up the old points and putting them back in to test and then putting the new ones back in when nothing has changed /ubbthreads/images/graemlins/smile.gif.
Bill
 
Since it looses power above 3k RPM and starts to backfire then... I modify my earlier suggestion. Focus on obstructions to the fuel flow. You know about the glass, inline filter. Could there be others? How about in the tank? Have you checked the pump's flow when you disconnect the fuel line at the carb. (BTW, mechanical or electric pump?) Don't forget to look for debris in the bottom of the float bowls. You mentioned a lot of new electrical bits, did you check the condition of the carbs when you did this? Are the jet tubes open without varnish (from long sitting)? How about the needles, are they relatively clean? Lastly, how about the dashpot oil, is it topped up?
 
Well, thought I'd give an update. Crud in the fuel lines. Cleared the lines out with air, cleaned the fuel filter, and it's running good. I just need to tune the carbs.

Thanks for the help everyone, it felt great to go for a ride today!
 
Congratulations! It's always a good feeling to sort out a problem. I hope you have lots of good driving weather before winter returns.
 
Does your vacuum advance line have a compression nut on it where it attaches to the vacuum advance unit? If it does, you can obtain a new olive at the hardware store cut the broken line off, slide the new olive on, and tighten the compression nut. An olive is the brass compression sleeve. Phil
 
Sidebar question: British car forums are the only place I've heard the compression sleeve (a.k.a. ferrule) called an "olive". Apart from a shape comparison to a pitted olive, does anyone know where the term comes from?
 
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