63 _ Engine dies after warm up _Part II

[Steve D.]

The saga continues. (Short history of the long previous thread _engine dies after warm up and I was trying to identify a carburetor problem in an Edelbrock 1406.)

To try to eliminate the carburetor as the culprit, I removed the Edelbrock and installed a Holley 4160 (600 CFM) that I had on the shelf. The result was the same; after warm up at idle, the engine stumbles and dies. It can still be kept running by opening the throttle to an RPM above idle. I previously observed that with the Edelbrock, when the engine started to stumble, I could pull the hose from the PCV connection and the engine would not die. On the Edelbrock, the PCV connection is in the front by the primary throttle plates. On the Holley, the PCV connection is at the rear by the secondary throttle plates and removing the hose at stumble does not keep the engine from dying. Is this significant? My first thought was that since the same problem occurs with two different carburetors, the source of the problem must lie elsewhere. But the fact that it only dies at idle leaves some doubt about that. If it is not the carburetor, then the new question is ... what in the ignition system could stop functioning after warm up, but only at idle?

I replaced the coil because it can drop out after heating up, but got no change in result. (I have not tested either coil, but probably should do that)

I checked the vacuum advance can after warm up with a mity-vac, and it holds vacuum and provides the specified amount advance.

In the previous thread, when I recounted changes that were made before the problem started, I don't think I mentioned that I removed a Petronix unit and replaced it with points and condenser. (The replacement came about after I broke the Petronix ring) The points and condenser are new (recently inspected, no pitting) , and dwell is set at 28 deg.

The only items left are the rotor, cap wires and plugs and it hard to see a connection for them to a heat related idle only problem.

[Frank D.]

Re: 63 _ Engine dies after warm up _Part II

I'll apologize in advance for not going back to the original thread to see what you've already done but here are some thoughts...

How long after idle does the engine shut down ? Is it a long time or right after the choke 'pulls off' ? I've been running down a similar perplexing problem in my '63 which still occasionally occurs on super hot Orlando days. I've changed the coil, cleaned up the bulkhead connectors, found that the wire to the distributor breaker plate was badly frayed (now fixed) and have run the car without the ignition shielding for a week or more.

I'm just about convinced its fuel starvation under certain conditions.... Perhaps vapor lock.

Be SURE to check the fuel pump actuator rod pin; there has been a crazy spate of these pins 'walking out' of the pumps and causing inexplicable problems both running and at idle (see red arrow in picture).

To completely eliminate the cockpit side of ignition wiring you could try running the car to the point it starts to stumble then immediately put a jumper wire (already connected on one end to the "+" battery terminal) and connect it to the "+" ignition coil terminal (don't run this way long). If the car picks up and stays running you have an intermittent electrical problem in the ignition wiring. I had such a problem on my '61 after I first purchased it; took me a couple of weeks to track it down to a corroded ignition switch harness connector.

[Gene M.]

Re: 63 _ Engine dies after warm up _Part II

Try setting dwell at 31, chevy does not like short 28 degrees. I don't think this is the source of your problem but it should run smoother.

[John D.]

Re: 63 _ Engine dies after warm up _Part II

Lately there seems to be a lot of engine fuel pump problems.
I have a customer who has a midyear FI car. My pal FI Art restored the unit. Car would start and run a minute of so and die. Wasn't the distributor as Don Baker restored it. Wasn't electrical. And it wasn't the fuel injection.
It was the engine fuel pump.
Car owner went to NAPA and bought a pump and car runs fine now. Whew!!!!
I know some of you don't like Airtex pumps but the car is running fine right now and that gets Fi Art off the hook

[Domenic T.]

Re: 63 _ Engine dies after warm up _Part II

Steve,
I also just joined thread and would like to pass on a similar problem I had years ago with a 283. Wouldn't run right after it reached temp. I went thru about everything and found my problem under the carb at the exhaust crossover. It had a hairline crack that would open up when hot and mess up the mixture. It was not easy to find but after removing the carb time after time I saw the exhaust trace around the crack, it had turned grayish.

Dom

[Steve D.]

Re: 63 _ Engine dies after warm up _Part II

Dom

I have the crossover partially blocked with inserts (with a hole in the center) in the intake manifold gaskets. I could try using the full blank inserts. How did you solve your problem?

Steve

[Domenic T.]

Re: 63 _ Engine dies after warm up _Part II

Steve, I just changed manifolds. I think blocking the ports would work but I was living in the mid west where the crossover was necessary in the winter.

Dom

[Frank D.]

Re: 63 _ Engine dies after warm up _Part II

Steve:

Are you saying you have the intake manifold heat runners on each side blocked by a fuel injection gasket or metal shims ??
If so, did you wire open the passenger side exhaust manifold heat riser valve or replace it with a spacer ??

Read John Hinckley's post (#3): http://www.corvetteforum.com/forums/...strictors.html

[Timothy B.]

Re: 63 _ Engine dies after warm up _Part II

Steve,

From your description I am thinking about the fuel pump. Now don't get carries away and throw more parts at it. If the car runs until hot then runs with the throttle blades opened or more air from the pcv inlet on the carburetor that seems to suggest to much fuel.

If I understand you both carburetors act the same so they both can't be bad. Next time it quits get a test light and see if there is power at the coil primary + termiinal. That eliminates everything in the primary wiring, seems like you have replace most everything on the secondary high voltage side. Have you noticed any fuel or wetness inside the carburetor after it quits. You don't suppose the fuel line could have a hole and the pump sucks air. Something stupid like that and a PIA to troubleshoot so think about that. Maybe get some fuel in a can and run a dedicated line from the can to the pump to test.

[Steve D.]

Re: 63 _ Engine dies after warm up _Part II

Frank _ The riser has been replaced with a spacer. _ Steve

[Steve D.]

Re: 63 _ Engine dies after warm up _Part II

New data points _ The engine started promptly for the test. It ran 18 minutes then died. I had clipped the test light on the positive side of the coil it, and grounded it at the stumble; it stayed on during the dying event. I also checked temperatures with my trusty HFIFRT (Harbor Freight .......)_garage ambient 93 (summer in Texas); after warm up_ thermostat housing 197; intake manifold 160; throttle body 125; bowls front 145 rear 135. Tried to start after dying but it would not start or even fire intermittently while cranking. When I first started this troubleshooting exercise, it would start (with a little coaxing)after dying.

[John D.]

Re: 63 _ Engine dies after warm up _Part II

Steve:

Are you saying you have the intake manifold heat runners on each side blocked by a fuel injection gasket or metal shims ??
If so, did you wire open the passenger side exhaust manifold heat riser valve or replace it with a spacer ??

Read John Hinckley's post (#3): http://www.corvetteforum.com/forums/...strictors.html

Frank, Fuel Injection intake to head gaskets do NOT block ports. Various repro catalogs & forums are confused to what is correct on these gaskets.
To repeat: FI gaskets ports are alll open. Not blocked. John D

[Steve D.]

Re: 63 _ Engine dies after warm up _Part II

I inspected the fuel pump; no loose pin; no sign of leak in lines or pump.

[Frank D.]

Re: 63 _ Engine dies after warm up _Part II

Frank, Fuel Injection intake to head gaskets do NOT block ports. Various repro catalogs & forums are confused to what is correct on these gaskets.
To repeat: FI gaskets ports are alll open. Not blocked. John D

I don't doubt you at all.

But the point is that Steve has done the right thing with the PS exhaust manifold riser....so that's off the table as a problem.
I had considered that this part was still installed as on a carbureted car and perhaps sticking...

[Steve D.]

Re: 63 _ Engine dies after warm up _Part II

OK team, here's a new data point _ I installed a 1/2" phenolic spacer under the carburetor. The good news is that it did not die after 15 minutes, but it did die after 30 minutes. That seems to indicate that cooling the carburetor helped, but I am hesitant to draw any hard conclusions. Following the "reduced heat is good" theory, my plan is to replace the crossover restrictors in the intake gaskets with blanks (i.e. replace the inserts that have a hole in middle with ones that do not have a hole). Any tips or cautions about this procedure?

Correction to previous comment about "no start" after dying: this time after it died, I sat in the car and tried to restart instead of using the remote. I found that if I hold the accelerator all the way down, it restarts quickly. I did the let-die-then-restart cycle several times in a row. I guess that is further indication that it is dying rich. The primary blades are dry immediately after dying.