All In The Timing
I have a unique (or perhaps not so unique) starting problem on my '73 Q-code Mustang convertible. I recently added the following to an otherwise stock 351 Cleveland 4V engine: a Pertronix electronic ignition, an Edelbrock Performer intake manifold, a Holley 600-cfm carburetor, and a Paxton supercharger. The spark advance is set at the factory-recommended 16 degrees before top dead center (TDC), the battery cables are fresh and the correct size, and the battery is new and rated at 1,000 cold cranking amps (CCA). My problem is, the engine turns over too slowly to start after the engine is thoroughly warmed up, especially after a long run on the interstate, for example, and a stop for fuel, then the problem presents itself. It doesn't happen every time-maybe 50 percent of the time. The only way to get the engine to turn over is to keep turning the ignition switch until it finally turns over properly, then it starts right away. Any ideas?
Jay Harris
Fallbrook, CA
P.S. The engine started perfectly before I added the speed equipment.
Any engine cranks harder when hot, therefore, many cranking problems are only obvious following a hot soak. Most hot-cranking problems can be traced to either over-advanced timing or high electrical resistance in the cranking circuit.
A quick "backyard" test can be performed by touching the various cable connections from the battery to the solenoid, the solenoid connections, and the connection at the starter itself. Any hot seals indicate high electrical resistance and will contribute to your problem. Of course, the correct method is to use a voltmeter to check for voltage drops, as these connections should be within 1 volt of battery voltage during cranking.
Solenoids tend to increase resistance with age, because every time they are actuated, their contacts arc and burn slightly. Check the new battery cables carefully; I've had new cables with high resistance where the lead joins to the copper cable. This must be checked with a voltmeter, since the lead connector will absorb any heat created with one backyard test.
The ignition timing can contribute to a hot-start problem, even when set to factory specs. Make a mark on the distributor housing and the engine block to create a reference. During a hot-start incident, retard the timing by rotating the distributor counterclockwise slightly, making 11/48-inch increments. Should normal cranking begin, leave the distributor in that spot until a timing light can be used to note the new timing setting.
Running The Circuit
I recently put a repop radiator in my '66 hardtop, 289 A-code. It has no air or power features. I used a top-quality, new correct cap and repop hoses. When I run the car to warm then shut it off, within 30 minutes the upper and lower radiator hoses collapse. Is air in the system or is it another serious problem?
Now for the real problem. Recently, I was running about 50 mph in Third gear when she stumbled, sputtered, and shut down. I thought the fuel pump diaphragm had blown out. I replaced the pump and the inline filter. She gets plenty of gas (maybe too much). I even replaced the voltage regulator and the coil. I also replaced the intake manifold gaskets. Still, the motor bogs very briefly at the first tickle of the accelerator. When the rpm exceeds 1,300 or so, she runs like a bear. I must set the idle up to about 900-1,000; otherwise, it will stall. It has a new air cleaner element. I've run out of time and money from trying the process of elimination, but at least my car received a good five-year makeover. In your opinion, am I experiencing a fuel or electrical/spark problem? The Flamethrower coil and the intake gaskets seemed to help. Thanks!
Randy Hedrick
Bear, DE
The radiator cap is most likely your reason the hoses are collapsing. The cap is supposed to allow air or coolant from a recovery bottle to fill the void created as the hot liquid cools and contracts. Try removing the cap the next time the hoses collapse to see if they return to normal. If they do, obtain another radiator cap.
I believe your engine problem is fuel-related, because the hesitation you describe is typical of a weak or malfunctioning accelerator pump or a vacuum leak. The high idle speed suggests you have a lean condition: either an internal carburetor problem or an external vacuum leak. Did the engine idle properly before you rebuilt the carb? If not, perhaps the accelerator pump doesn't deliver a strong squirt of fuel as the throttle is opened. The pump should deliver a shot of fuel every time the throttle linkage is cracked; even the slightest movement of the linkage should create fuel. The pump can be adjusted by relocating the pump actuator rod into different locating position holes provided for this purpose on the carb throttle linkage. The instructions included with the carb rebuilding kit or any Ford shop manual will provide an illustration. Almost all hesitation problems can be corrected with attention to the accelerator pump circuit.
Try covering the top of the carb or close the choke slightly as the engine is idling to observe the effect on the engine. Should the idle quality improve, it's probably an internal carb problem that's creating a lean idle circuit.
Send your questions to: Beyond the Basics c/o Bob Aliberto P.O. Box 205 Salt Point, NY 12578e-mail us at mustangm@primediacmmg.com