Engine stalls under load

[Forrest]

Hello,

Over the last 4 or 5 months every electrical and mechanical component of my 1956 Coupe de Ville was completely rebuilt, replaced or repaired. The engine and transmission were completely rebuilt. This included the carburetor as well. After starting it and running it at the shop and making any necessary adjustments, it was time for a test drive.

Everything worked flawlessly. The car ran smoothly and quietly, and the transmission shifted as it should. (I should point out that there were no modifications made - everything is by the book per 1956) After driving local roads for a while, it seemed ready for the highway. This too went well with no indication of trouble.

While ascending an exit ramp hill of moderate grade, the car suddenly quit running. This happened without warning and while the engine was under load - not coasting.

The car could not be re started and had to be towed home. Immediately after sliding off the flatbed, the car started instantly with the touch of the key - just as it had before the trip.

During the drive, the temperature gauge remained between 1/4 and 1/2. Fuel level was 1/3 to 1/2 full of fresh premium gas.

After checking all the usual and obvious things I'm at a loss to explain this. Fuel and spark are both present. Timing is correct (brand new working vac advance, etc.) Fuel filter is clean with no evidence of debris. Fuel pump inlet is clear. The fuel tank was removed and inspected. no rust or debris was present inside and the pickup tube was also intact and in place. Air was blown freely through the fuel lines.

Can anyone give me any suggestions as to what might have caused this? Vapor lock entered my mind but the car was driven as a daily driver for the past 7 years without incident.  No re routing of fuel lines or any changes were made to the exhaust system. In fact, the engine used to run hotter than this with the gauge reading about 1/2 to 3/4 most of the time.

If it was a carb problem under load (fuel starvation), why couldn't it be restarted immediately after there was no load?

Any ideas, comments or suggestions will be appreciated. Nothing is too obvious or crazy to be considered.

Thanks for your help.

[35-709]

Check the ignition coil!  One coil failure mode is that when the coil gets hot it quits working, once it has a chance to cool it will function again.  I had two vehicles experience this type of coil failure.  A third was on a 1962 Cadillac with less than 10,000 miles, on that car the coil failed completely.  Good luck.

[walt chomosh #23510]

Geoff gives a good suggestion in regards to checking the coil. Problem is,coils should be heated to be property checked. Static resistance checks with a reliable ohm meter will provide basic checks,but theres no real substitute for heat. I would suggest trying another coil.(it won't hurt to have a spare anyway) Also,carry a spare spark plug so you can remove one of the plug wires and,grounding the spare plug,crank  and check for spark should the motor quit again.
  The fuel system is also suspect.The outlet of my 55 was clogged so bad that I couldn't push a coat hanger thru it!(I had a hint when my motor began to get hot,the result of a lean mixture because of the tank outlet clogging)Cars coming out of major overhauls take quite a bit of massasuging to become roadworthy again.Even when the work had been performed to the highest standard, problems occur.Good luck!....walt #23510

[John Morris #23947]

One other thought is the condenser. It can act up like the coil.

[Otto Skorzeny]

In case any of you guys wanted to know what the problem turned out to be....

We took the plugs out of the side of the carb to make sure the float was set correctly. It was. After testing the freshly rebuilt fuel pump (rebuilt by a reputable pro) we found that it pumped only 4 oz of gas after 9 squirts. The manual says it should pump 8oz in 9 squirts!

How aggravating! The thing that bugs me even more is that that fuel pump is available brand new, from the local CarQuest auto parts store for $45.00!

Amazingly, the starter, which is the same one for late 1956 thru 1960 Cadillacs is also available brand new from CarQuest (I imagine from other chains as well) for under $50. That's a lot better than spending $350 for a thorough professional rebuild.

Anyway, thanks for support.

Forrest

[The Tassie Devil(le)]

Thanks for the update Forrest.

Glad to see that the problem is now solved, but sorry to read that it cost you so much in the first place.

Bruce.

[35-709]

Yes, thank you for letting us know how it turned out.