[John V.]

GTO has been running well since resto was completed 2+ years ago. Pretty much stock 389 rebuilt during resto.

Recently I had it out and it stalled on me a few times. It has always run pretty cool IMO but that day I was carrying 3 passengers and thought maybe it had gotten a little warmer than usual. So I thought it might have been a bit of vapor lock causing the unusual stalling and ignored it,

A couple days ago, I took it out for the first time since to wash it. Before I did, I made a short cruise up and down the mountain where I live, a round trip of about 20 miles. Got home and washed it. Then drove down the driveway to my barn to put it away. Didn't notice anything unusual during the drive or returning to the barn.

It idled as I opened the doors and I shut it off in the barn. Before walking away, I decided I wanted to see if I could get the vacuum secondaries to open on the Tripower as I was suspicious that they were not opening. I opened the hood so I could see the carb linkage, then restarted the engine. All seemed okay and then rev'd it to about 4k on the tach about 4-5 times in quick succession. End carbs didn't open. Since I didn't quite floor the pedal I still wasn't sure if the end carbs should have opened.

As I released the pedal the last time, the engine kind of gasped and quit.

Every other time in the past when it has stalled, it would start right back up with a quick turn of the key. In fact, I was always pleased at how easily it starts in those circumstances. It has only been hard starting when it has sat for more than a couple days, presumably because the gas in the carb evaporates and takes several cranks for the pump to fill the float bowl and get it to fire.

This time though, when I went to restart it, it coughed a couple strokes but wouldn't catch. Having rev'd it like I did, I thought perhaps I had flooded it. So after a couple tries with the pedal floored, and no more coughing, I walked away so as not to run down the battery.

2 days later I tried again. This time it fired right up but after running maybe 10-15 secs it began to die again. I tried reving it, but it just quit running.

And it wouldn't restart.

Now I'm thinking it is behaving like it is out of gas. The gauge reads 1/4 tank which is no guarantee but I have run it to 1/8 or less and never ran out.

I walked away again and decided I would ask for advice here before tearing things apart.

Couple thoughts running thru my head.

Maybe the fuel pump diaphragm is failing, reducing the flow. How would I check for that?

Float needle sticking almost closed, restricting flow to the bowl? Is this possible? If so, how could I check?

Pickup in gas tank broken? No idea how that is set up but wondering if such a thing could make it act like the tank was empty and the pump unable to draw much fuel.

I haven't done any diagnosis, mostly don't know where best to start but my seat of the pants feel has been that the problem is fuel related. And given that it did run about 10-15 secs, I'm thinking not ignition related.

One additional thought, on occasion the engine will bog when giving it a little gas from idle. This is problematic in my area, hills everywhere and trying to get underway while trying to get the engine to respond can get to be dicey. As I get off the clutch and the engine isn't cooperating, it is difficult to get the rpms I need while trying not to roll backward. Maybe if I was a heel and toe guy but I'm not!

Is it possible that this is a carb issue that has gotten worse?

I'm just throwing as much info out as I can think of. I'm hoping you guys have some good ideas for systematically diagnosing the problem.

[60sstuff]

Just a thought, as this would be an easy diagnosis.

Fuel filter.

Maybe after those multiple high revs, you may have sucked something into that fuel filter?

[ZeGermanHam]

Yeah, can't hurt to check the fuel filter. I'd buy a cheapo clear fuel filter as a temporary unit to verify that you are getting fuel from the pump, and doing so will also let you know if your current filter is clogged.

I agree it does sound like a fuel issue.

[John V.]

Would it be possible to disconnect the fuel pump below the filter and then crank the engine SAFELY and discharge any pumped gas into a container to see if any debris gets discharged? Would I disconnect the coil wire?

Is there another simpler way to clear the line ahead of the filter? I don't have a vac pump but could that be used in some way?

I like the filter plugged idea but I'm thinking if I just replace the filter (it is the repro original type for Tripower without A/C) then couldn't there be something in the line that only hits the filter when the pump is pumping?

And how can I check to see if the filter is clear? Remove it and blow through it?

ZeGermanHam, I follow your idea about the clear filter but as long as I have to open the line anyway, seems like I should be able to check for gas flow without installing a new filter.

[Dick Boneske]

Somehow, it's running out of gas. You can disconnect the line at the front carb and put a hose on it and into a container, crank the engine, and see if there is any flow.

If there is none, disconnect the line at the inlet to the fuel pump. If there is a reasonable amount of gas in the tank, it should flow out of the hose. If it doesn't, chances are the filter sock in the tank is plugged.

[Geoff]

Pour about an egg cup full of gas down the centre carb, equal amount in each bore, then try & start it.

If it runs ok & keeps running ok, maybe it was vapour lock....

If the engine starts but dies after a few seconds, actuate the centre carb & check that has accelerator pump shot. If it has, it suggests the f/pump is working.

The problem then could be flooding from excessive fuel pressure, hole in the float or leaking needle & seat.

[buds56]

In my experiences a bad condenser will give a similar feeling of fuel problems.
The quality of them is not that good anymore.
Good luck

[pfilean]

So you drove it 20 miles with no problem. Sounds like it's getting gas.
But the first time you experienced trouble it may have been getting hot.
The problems seemed to be erratic with not definitive. You thought there was a fuel delivery problem but you never said you looked for fuel delivery from the accelerator pump when it would die. But as you had fuel for the 20 mile trip I would think the accelerator pump is probably good.
The problem starting when it may have been hot suggests to me it may be an old coil. I have seen them short out when hot and then work when cold until they short out completely. Check for spark.. It's an easy thing to do and could rule out ignition as a problem.

[ZeGermanHam]

Originally Posted by Geoff

If it runs ok & keeps running ok, maybe it was vapour lock....

To me, it seems unlikely to be vapor lock because of the following:

Originally Posted by John V.

2 days later I tried again. This time it fired right up but after running maybe 10-15 secs it began to die again. I tried reving it, but it just quit running. And it wouldn't restart.

It died on him when the engine and fuel were both cold as a stone after the car had been sitting for days. That would seemingly rule out vapor lock in my view, which is something I have dealt with in the past.

But regardless, confirming fuel delivery is easy enough to do and should be the first thing to check. Checking the coil for spark would be next on my list.

[aogmitch]

Just went through something similar on my '66. Turned out to be a dying fuel pump. Was only getting about 1.25 psi. New pump and running great now.

[mgarblik]

You have some good suggestions as far as verifying, fuel flow, verifying clean, fresh gas, and checking/changing the fuel filter. If you have access to a fuel pressure gauge it would be nice to verify 3.5-5 PSI fuel pressure as well as flow.
Tri-power specific things to check: I would disconnect the front and rear carb. linkage and get the car running properly on the center carb first. It's possible the front and rear carbs have very old, stale gas in them if you don't run the car hard or it's been sitting a long time with old gas in the front and rear. Gently revving the engine to 4000-4500 RPM's will not open the front and rear carbs with the car in park or neutral. You need a fast vacuum drop, only operating under load will produce, so that's not a valid test of the vacuum secondary operation. A hand vacuum pump could be used to verify front and rear carb. opening with the engine not running, which is safest. Make sure front and rear carbs are not stuck slightly open, that will make the engine idle terrible and run lousy at low throttle openings. Good luck.

[Andre]

I don't know much about anything, but I'll say this. The revving of the engine is something you traditionally have never done before. Whether that has anything to do with this is unknown. It could be as simple as the float being stuck and preventing gas from entering the carb. As a previous poster indicated, you can add some gas to the carb and start and see what happens. Maybe give the center carb a solid tap.
At least that is what I would do before I start tearing into it

[John V.]

I'm indebted to all you guys. I really wasn't sure how to begin diagnosing the problem.

Special shout out to buds56!

The GTO seems to be running fine now.

I was focused on fuel, just seemed most logical based on how it quit running. The advice you guys gave helped my confidence that I could figure it out and I had a plan. I had a scrap fuel line hose and a container. I planned to pull the hose off the top of the filter, install my scrap piece of hose, and with my wife's help to crank the engine, I expected to observe if I had good fuel flow.

I don't have a pressure gauge and never have witnessed a mechanical pump to know what "good flow" should look like, but I figured it would be obvious once it started pumping.

Meanwhile, buds56 threw out his comment about bad condensers mimicking fuel problems.

Plan was to check the fuel flow yesterday. But first I googled how I might test a condenser. Got a couple variations. None seemed particularly definitive.

Now, it is getting close to 50 years since I last replaced points and condenser but my recollection was it's an easy job. So I figured I would at least test the condenser before checking fuel flow. It wasn't quite as easy as I remembered, must be getting old. I pulled the cap and rotor. Both looked brand new. Out came the condenser.

I put my multimeter to it according to the googled advice. I started with my cheapo free Harbor Freight digital multimeter. But I didn't seem to get any reading. Maybe a bad condenser? Or maybe me not being the best with a multimeter. So try another meter. None of my meters can check capacitance, so all I was trying to check was whether it would store and drain voltage according to a video I watched.

I have a couple other meters but I decided to try my best but old Radio Shack auto ranging digital. Pulled it out and was bummed, the LCD screen has developed a dark spot right in the middle. That wasn't there last time I used it, maybe 6 months ago.

I got some readings that didn't really make sense. And after a few attempts, my meter stopped responding, New batteries didn't help. There were nos. being displayed but the on-off switch was non-responsive (it worked when I first pulled it out) and the auto off after 10 minutes also didn't work. I couldn't shut it off except by pulling the batteries and it was immediately on when batteries were reinstalled. And the low battery indicator is on even with multiple new batteries tried.

Maybe I fried it while trying to test the condenser so that has me bummed. If it was just its time to die, I'll never know. I took it apart and see what looks like a watch battery in a sealed plastic case with red/black wire leads from it soldered to the board. Apparently not intended as a replaceable part. This thing is maybe 25-30 years old now so I wonder if that watch battery has finally quit and the meter not working as a result? Anyway, I'm way off track here.

So after getting no real info about the status of the condenser, I decided, what the heck, I'll just replace it and see what happens. If it didn't fix it, I'd proceed with my fuel pump test. So this morning I picked up a new condenser, came home, and installed it.

I then pulled the air cleaner off the center carb, For yucks, I pulled the throttle open while I peered down the carb. I saw no spray of fuel. Not sure why and I suspected that the float bowl was dry. Put the air cleaner back on for "safety".

So I got in expecting it would have to crank for several seconds to get fuel. And I was not at all expecting that the condenser was going to be the answer anyway.

But when I hit the key, it immediately fired up! Just like it usually would as long as it hadn't sat for weeks.

I let it idle for maybe a minute and it ran as smooth as could be. I gave it just a little gas and it responded without hesitation, After about a minute, I shut it down. I was shocked and more than a little ecstatic.

I let it sit for a couple minutes, then got back in and fired it right back up. I'm still in a little disbelief.

It is pouring rain here today (and has been off and on for days) so I didn't take it for a drive.

So there is still a bug in my brain saying that this isn't over yet. But the way it started and ran today, I couldn't be happier.

Lesson learned. I plan to heed the advice of one of the guys that described how you can test a condenser. He says ALWAYS carry a spare and be prepared to install it on the road.

Like buds56 suggested, the quality is just not that good anymore. I can now testify to that, this one has just less than a 1000 miles of driving on it.

Could the high revs have killed it? Or just the final straw? If the voltage regulator was allowing too high a voltage especially at higher rpm, would that kill the condenser?

I do have a Voltmeter as part of my Autometer gauge set. Never noticed any high voltage spikes but haven't actually paid very close attention to it either.

Just wondering if I need to be looking elsewhere for a root cause rather than blaming a low quality foreign made part.

[Kenth]

Oxidation on electrial parts sitting for 50 years is not unheard of.
For the condenser most times it helps unscrew the condenser, clean the surfaces some and remount it.

FWIW

[John V.]

The tune-up parts in the GTO were brand new, well maybe 3 years since they were installed and 900 miles since the restore was completed. I didn't install them. My original '64 distributor was professionally restored at that time. Didn't mean to imply the points and condenser were 50 years old, just that I had not installed points and condenser in nearly 50 years, the last time I owned a running car with points distributor!

Still, I get your point. In my case, I'm pretty sure the condenser has failed and from the numerous posts on the internet, it seems new condensers are low quality and fail much more often and with much shorter life than those from 50+ years ago. Back then, I remember the debate was whether you should ever replace the condenser if it was still good. I always replaced them with each new set of points but lots of guys thought that was a waste. Some even believed you might replace a known good condenser with one that would crap out, so they thought replacing it was not smart.

Today, from what I read, it seems like guys are lucky if the condenser lasts at all. And lots of guys recommend looking for an NOS condenser that is old vs. buying foreign made new ones.

[rohrt]

John you may want to invest in a decent Fluke meter.

[John V.]

Looking for more opinions.

Just to recap, my engine had always started easily, idled well, ran smoothly since the resto was completed about 2-1/2 years ago. But recently, I began to experience stalling at idle after driving for some distance and an unsettling "no throttle response" off idle. Finally, it culminated in a no start condition even after sitting for a couple days and engine cold.

Replaced the Ignition Condenser and the engine immediately restarted and idled well, responded to the throttle without issue.

So a couple weeks went by and I took it for a long ride, out to dinner about 50 miles away. It ran good almost all the way there most of it on 50 mph rural roads (I purposely avoided the Interstate). It did stall making a turn but restarted and seemed okay. A few stops along the way. Ambient temps were 80+.

Then a short distance before the restaurant, it started to idle very poorly, just like before. No response off idle, multiple stalls. Always able to restart.

Once I got it running, as long as I could get the revs up, I could get underway while burning up the clutch to avoid stalling.

I only had one hill to negotiate at a light just before the restaurant. Managed to get it thru the light and into the parking. Continued stalling but got it parked and proceeded to dinner.

After close to 2 hours, came out with my fingers crossed, hoping that the engine had cooled and would run well for the 50 mile return trip home. It did, for the most part, although I tried to avoid stops especially on uphills. Seemed to respond to the throttle, no serious stalling. Idle might have been a bit less smooth, but even when I got home and left it idling while opening the garage doors, it didn't stall. It was a good bit cooler out by the time I arrived home.

As my issue now seems related to excessive engine heat after running for an extended time, I am focused on a couple things.

1. Bad coil? Heat can affect them right? However, wouldn't that make restarting difficult or impossible once the coil got hot enough to cause a stall?

2. Vapor lock? Diagnosing that seems about impossible. But I had an epiphany one night. I have original '64 log exhaust manifolds with the Heat Riser Valve on the RH manifold. I have never checked its operation before so not sure how it has been functioning.

Today I finally got around to checking it manually to see if it might be stuck. I recall it having a couple springs. When I operated the external weight/arm, I didn't feel any spring tension in either direction. The weight seems to settle at about a midway point. IIRC, one of the springs is just an anti-rattle spring.

I am not sure which direction is fully open or fully closed. I didn't crawl underneath to look but I'm wondering if the spring has disappeared. The main spring is a thermostatic spring right? So I'm not sure if it is supposed to be fully closed when cold or is partially open normal? Should I feel spring tension when moving it manually?

Anybody can tell me which direction the weight/arm is supposed to move as the thermo spring heats up?

I will get under it to see if the spring is still there but I'm tempted to wire it so that it stays open. But will need to know which way is open and which way is closed.

If the Heat Riser Valve is functioning correctly, I might still be getting vapor lock right?

What advice does anybody have for avoiding vapor lock?

Could it be I need to run richer? Can timing help with avoiding vapor lock?

Temp gauge never seems to read too high. Maybe 190 when it starts to run poorly but that is only maybe 10 deg more than when it has no symptoms.

Help!

[Tom Vaught]

I believe having the weight move upward (due to the spring) opens the valve.
Weight needs to move upward, if I remember wiring mine open 50 years ago.

Tom V.

And yes, the engine could have fuel vapor issues if the valve remained closed.

[Goatracer1]

Instead of guessing diagnose it. Get a helper and first check for good spark and then fuel flow. Find out what is actually wrong first before just replacing things.

[Geoff]

Check that your fuel tank vent is not blocked.