Help with Diagnostics

[wubie317]

Over the past few days, I've set about doing a tune-up on my recently-acquired 77 Spider.

It was running fairly well, though occasionally missing (on #3, I think) and it had a lag (basically almost stalling) at low RPM and intermittent bucking. I guessed that it had something to do with fuel getting into the carbs. So...

I replaced plugs, plug wires, distributor, rotor (the one I got to replace the old is quite 'sloppy'...is that normal?), points, condensers. I put a new fuel filter in (though not one 'made for' the car...the one I got from Ricambi was too big for the hoses...so I grabbed a cheapo see-thru one from O'Reilly). Also, I tested the coil and it seemed like it was out of spec for resistance, so I put a new one in.

Of course, now it's really bad.

It seems to run nearly perfectly on the cold points, but when it warms up things go south. At 3000RPM, it starts skipping and missing badly. I stopped at a station when it started happening and then she wouldn't start...until it cooled down somewhat (though not all the way down to 'cold'). After getting it started I could drive enough to get it home, but now I don't know where to begin to diagnose what I did that was so wrong.

NOTE: I'm a newbie mechanic...been years since I worked on my '77 Toyota pickup!

• Could it be the points? This seems like the most likely culprit, but I've checked the gaps twice...I have a dwell meter but I don't know how to hook it up and don't know what I'd do with the information, even if I did get it working. Also, I couldn't be absolutely sure which were the cold and which were the running points...which one is closest to the front of the car?
  Could it be the cheapo fuel filter? Too much back-pressure or something?
  Could it be the sloppy rotor? I put it in before I did the points, coil and plug wires and the car ran ok, but unchanged from the same low RPM bucking and missing

I'd love to hear your ideas of a process to figure it out and get it back to running well...even if I can't fix the low RPM chugging and bucking. I'm guessing there might be a valve issue somewhere, but I'll need a little more experience before I try to tackle that.

Help!

[wizard124]

The rotor should not be "sloppy". I would try the old one (and the cap too if there is any doubt).

Then be systematic. How is the idle? Maybe some carb ajdustments. Check the timing at idle. Does it advance with RPM? Check for vacuum leaks and poor connections

I don't remember the last time I delt with points and condensor?? Cant help you there.

[msrichmond]

I didn't see where you checked the timing with a timing light. Spec says 10 degrees BTDC on the cold points. What a lot of us do before we ditch points altogether is just use the same points for hot or cold. The hot points time to 0 degrees BTDC which is actually an emissions play to reduce combustion temps and oxides of nitrogen. But it makes the car run really doggy. If you use one set of points and set to 10 degrees BTDC you will have much better part throttle response.

Yes, it's a little bit too much advance at the top end, but with the low compression stock motor and decent gas, you should not get any engine pinging.

MikeR ('77 Spider that once had points)

[wubie317]

I didn't see where you checked the timing with a timing light. Spec says 10 degrees BTDC on the cold points. What a lot of us do before we ditch points altogether is just use the same points for hot or cold. The hot points time to 0 degrees BTDC which is actually an emissions play to reduce combustion temps and oxides of nitrogen. But it makes the car run really doggy. If you use one set of points and set to 10 degrees BTDC you will have much better part throttle response.

Yes, it's a little bit too much advance at the top end, but with the low compression stock motor and decent gas, you should not get any engine pinging.

MikeR ('77 Spider that once had points)

So, you ditched the points. I've looked at the "stealth" Ignitor that's available on Autoricambi for $88...Is that something others have used with good results? Or do I have to go all-in with the $500 one?

[azruss]

the point condensers could be bad. If they are bad, you get a weak spark and almost no spark at start. These are cheap and can be bad right out of the box. Dirt in the carb could do this, but it would have to be really bad. check all your hoses for air leaks, particularly the hose going to the brake boost.

[carl]

In regard to the dual points, what Mike meant was to remove one set of points and just run one set. You run a wire from the set of points you keep directly to the coil and thus bypass a ton of wiring and stupid thermal switches. Any spider should run just fine on a properly set up set of points.

[So Cal Mark]

I'm still trying to figure out why you have changed the entire ignition system if you thought you had a fuel issue. The ignitor-type kits merely replace the points with a magnetic pickup, no improvement in spark intensity. If your new rotor is sloppy, it's probably missing the metal insert that secures it to the distributor shaft.