Question: I have an intermittent starting problem with my 1995 ZR1 Corvette that鈥檚 been unsolved for years. The car has 106,000 occasional kilometres on it and is kept in the garage. Once a quarter (every tenth drive), it won鈥檛 start. It always occurs after the engine has been warmed up first and then sits for an hour or two. When the key is turned to start, the dash lights come on brightly but not a hint of starter or click of solenoid. Within an hour or so, it usually starts the normal way. It never occurs when cold (off for a day). And it never happens for the mechanic. I replaced the ignition key (new resistor) and replaced the battery (unrelated). Can you help?
S.T.
Great job observing the symptom pattern: This is referred to as a hot soak issue, although with the length of time you鈥檙e indicating, it鈥檚 more of a warm soak.
Your starting system, like that of other vehicles new and old, has two circuits: control and power. The control circuit includes the ignition switch, clutch or park/neutral switch, theft deterrent relay, central control module and connecting wires. If these all do their job, a 12-volt starter request signal can be sent to the starter via a purple wire, through connector C-100 (a busy pass-through at the firewall). The power circuit includes the battery, battery cables and the starter assembly.
How about picking up an unpowered incandescent 12V test light (under $10 at any auto parts store or other) and the next time your 鈥橵ette is safely elevated, perhaps for an oil change, securely connect the test light鈥檚 insulated alligator clip to the starter鈥檚 鈥淪鈥� terminal (purple wire connection). Thread the test light鈥檚 lead up into the engine compartment, avoiding contact with exhaust parts 鈥� perhaps securing it with a zip tie or two, and prepare to temporarily lay or attach the test light body in a safe place on or near the engine.
Try testing the starter control circuit request signal a few times as normal starting occurs by touching/nesting the test light鈥檚 icepick-like tip to bare engine metal as you crank the starter. Looking through the windshield, note the brightness of the test light鈥檚 bulb as you practice this several times. Then secure the test light to a safe place and wait.
The next time the starter fails to engage, check for the request signal again. If it鈥檚 strong (a bright test light), the control circuit is good and the fault must lie with the starter assembly or battery cable connections. If the test light鈥檚 bulb is dim or not illuminating, the fault lies in one of the control circuit parts or wire connections. With the exception of the front half of connector C-100, these parts are all inside the house, likely unaffected by engine compartment temperature. I鈥檓 thinking starter or battery cable connections.
Should the fault lie in the control circuit, testing will be needed before and after each of the circuit鈥檚 parts to see where there鈥檚 voltage (during cranking) and where there isn鈥檛, during an episode. The test light would work fine for this, this time with the alligator clip grounded and probing the desired places with the tool鈥檚 sharp tip. Component locations make this a bit of a challenge, but this would be big fun to track down and conquer. Also, you might try wiggling the wires near C-100 and check for a change in symptom.
Q: I received a 12-volt, plug-in heated seat pad for Christmas. I seem to remember that you shouldn鈥檛 have anything plugged in while starting the car. It was something to do with the extra drain on the battery, especially in these subzero days. Does it matter if that is plugged in or not when starting the car in winter?
J.B.
If your battery has not already gone dead overnight, the accessory socket you are using is probably on a switched circuit. In other words, the accessories do not continue drawing any current when the ignition key is turned off. When that is the case, the accessory circuits are also bypassed during cranking, so you should not have any problems.
Q: I thought that on newer cars pumping the gas did nothing in regards to helping the car start.
J.T.
Jamming the gas pedal to the floor usually prevents the fuel injectors from spraying during startup. You can do this if the engine is flooded so as to not worsen the problem by introducing even more fuel and increasing the flooding problem. But you should never pump the pedal on fuel-injected engines.
Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, California. Readers can email him at [email protected]..
