It is a beautiful day and you are looking forward to enjoying a nice ride in your collector car. Everything is going as planned until suddenly a problem crops up that has the potential to spoil your time. The engine dies or won't start after being shut off. It is bucking, misfiring or overheating. Depending on the problem you can be stranded on the side of the road or in a parking lot far from home. Not exactly how you planned the afternoon.
It is most important that you are in a safe place and your vehicle is not in a position to cause an accident or hurt another motorist. A car no matter how special can be replaced but a life can not.
The best insurance against a breakdown is proper vehicle maintenance. Though it is not impossible for a part to fail unexpectedly, most vehicles sitting on the side of the road are there because someone ignored the warning signs of trouble and pushed their luck too far.
Clean and tight electrical connections, replacing old belts and hoses along with a common sense approach to vehicle care goes a very long way in reducing the possibility of getting to know the side of the road more than you would like.
There are eight main categories for potential issues. They are: • No engine crank • No start • Rough idle • Stalling • Lack of power • Pinging/detonation • Hesitation • Overheating
Once the vehicle is in a safe place analyze what is happening. It is common to have a problem in one area impact three or four others.
For example, a GM HEI system with a faulty ignition module that has a fixed instead of expanding dwell period. Depending on the where the dwell is locked the engine may experience all of the following: a rough idle, stalling, lack of power, detonation and hesitatation. This can very easily be thought of as numerous or a much more serious condition than a failed ignition module. Thus, when diagnosing an engine problem it is important to take a logical and methodical approach.
A visual inspection of the engine is the first step in proper diagnostics. Is a wire loose? Did a vacuum line fall off? Do not look for a complicated solution to a simple problem.
Before a problem ever occurs and the engine is running fine you should spend a few hours performing a series of tests. Record the results and keep it with the car. This way you will quickly be able to determine what is astray if a problem occurs. You can not know what is bad if you do not know what is good. This data should include base ignition timing and the amount of vacuum and centrifugal advance, cranking compression, cylinder leak down, alternator output, engine vacuum, etc.
When a problem occurs try to get a handle on whether it is ignition or fuel related. Make the mixture richer and leaner (you can choke the carburetor by hand and then pull off a manifold vacuum hose). Add and subtract ignition advance by moving the distributor. You may find the engine responds to a richer mixture -- then you would probably be looking for a vacuum leak or weak ignition. You want to see a positive response. An engine that has a severe manifold vacuum leak will idle better if you choke the carburetor with your hand. The engine's response to the change is what you need to acknowledge not the change itself.
Listening to and feeling the exhaust will tell you a lot about what is going on. True dual exhausts can help determine what side of the engine the concern rests. A problem that is affecting all cylinders such as misadjusted breaker points will impact every firing event. A broken ignition wire or valve spring will produce a rhythmic misfire at the exhaust with smooth pulses in between.
Driving the car is also a diagnostic step. Being able to "drive through" a problem can help to locate the cause. Does the engine run rough at light load or throughout the rpm range? Is the hesitation more pronounced just off idle or can it be felt when the throttle is moved even at a low road speed?
Do not be afraid to get your hands dirty. The spark plug resides in the combustion chamber so it is a window into the engine. Take all the plugs out and keep them in order to identify the cylinder. Look for a major difference in color or wear and then check that cylinder more thoroughly. There are very few mechanical conditions inside the engine that would impact all of the spark plugs at the same time. If they are all fouled most likely the cause is external, such as the carburetor or ignition coil.
The following is a basic guideline for each condition with the most likely cause first.
Lack of power- insufficient ignition advance, secondary butterfly on carburetor not opening, metering rods/power valve not functioning, restricted exhaust, starving for fuel.
Pinging- excessive ignition lead, carbon-laden pistons and combustion chambers, lean mixture, high cylinder head metal surface temperature/coolant, EGR (if equipped) not functioning, ignition timing scatter from worn distributor bushing.
Hesitation- weak accelerator pump stroke, vacuum advance not functioning, idle mixture screws set wrong, vacuum leak, insufficient amount of base timing.
Stalling- idle speed set too low, massive vacuum leak, idle air bleed circuit in carburetor blocked, EGR valve stuck open, choke tension (when cold).
Engine cranks but will not start- no power to ignition coil, failed ignition module or breaker point adjustment, lack of fuel to carburetor, needle valve sticking in carburetor, fuel pump, engine flooded. Engine will not crank- dead/internally broken battery, loose/poor electrical connections, starter binding, neutral safety switch failed (automatic transmission).
Depending on the problem that befalls your car there may be a time when it will be impossible to get it running on the road side. The purpose of this primer is to educate you on how to locate and temporarily repair a problem without calling a tow truck. Once you get home then you can correct the issue properly.
A good idea is to be a member of a motorclub that provides free towing, such as AAA. With most collector cars it is usually best to have it brought home since it is very hard to find a modern repair shop that knows how to work on a carburetor or a distributor with a set of breaker points.
For our photos we worked with Gene Ascolese and employed his 1955 Ford Thunderbird. He has owned the car for many years. He acknowledges that it is in need of some mechanical TLC, but he does use it. That makes it a perfect example for our images. A previous owner replaced the Ford engine with a 283 cubic inch Chevy motor but that will not change any of the procedures for getting back on the road.
Our goal is for you to have to never use the information we provide here -- but it may not be a bad idea to keep this issue in the trunk along with your tool kit. Happy motoring!
Source Gene's Automotive 308 Route 46 Great Meadows, New Jersey 07838 908-637-6711
Being prepared is key to getting back on the road. You should always carry a tool kit, jumper cables, flashlight, flares and electrical tape in he trunk. A shop manual along with any other information will help quicken diagnostics if the car is brought to a repair shop that you do not know.
Never panic when a problem occurs -- that will have you make the wrong decisions. What ever the problem may be stay clam and think it through in your mind. The most important thing is to make sure you and others are safe. For example, an engine that is running hot from a partially stuck thermostat can get safely home by running the heater on full hot to help cool it and is no big problem.
Perform a good visual inspection while applying common sense. If the engine cranks over but will not run then obviously the battery and connections are not an issue. If any work was done recently on the engine look there first since a wire or vacuum line could have been accidentally disturbed.
Listen and feel the exhaust for an indication of the problem. Dual exhausts will identify which side of the engine is suffering. A misfire with a rhythm is usually spark plug related or a valve spring. A constant misfire affecting all cylinders can be mixture or ignition such as the breaker point adjustment.
Remove the air filter and while moving the throttle look down the carburetor for accelerator pump stroke. If there is no fuel spray then the carburetor is not receiving any gasoline. Back track from there. If there is fuel and the engine will not run, try cranking it with the accelerator to the floor in case it is flooded.
An engine that will not idle but runs at higher speeds often has a piece of dirt in an air bleed in the carburetor. While keeping the throttle at around 2,500 rpm, choke the carburetor with your hand and before it stalls, remove your fingers. This will increase the pressure differential and often dislodge the piece of dirt.
Make sure that all the ignition wires are secure in the distributor cap and coil. To check for spark, remove the coil wire (center) from the distributor cap and hold it by the insulation with the end about 1/2 inch from a piece of metal. Have a helper crank the engine -- there should be a strong spark. If there is no spark, follow the voltage supply to the coil and then look in the distributor.
A poor running engine could be the result of a distributor that came loose and moved. Try twisting it with both hands. If it is loose, play with the position until the engine runs well enough to get back home. Then you can time it with a light.
For a no crank condition go to the battery first and check the connections by grabbing them. Turn the headlights on to see if there is any voltage. Then try cranking the engine with the lights on while someone watches them. If they do not dim and the engine does not crank, there is no power getting to the starter.
A sudden engine stalling problem can be as simple as the breaker points coming loose and the gap changing. Remove the distributor cap and rotor, tap the engine around to get the rubbing block on any distributor cam and check the gap. If you do not have a feeler gauge, the cover from a book of matches is close enough to get the engine to run and drive home.
If a coolant hose starts to leak let the engine cool off and wrap it with electrical tape. Loosen the radiator cap so pressure does not build up and stress the temporary repair.
If the carburetor starts to run over with fuel or if there is none in the bowl, then the needle valve or float is stuck. Gently tap the fuel inlet of the carburetor to dislodge it. If it was flooded you will need to hold the throttle to the floor to start the engine. If the needle valve stuck closed, then you will have to crank the engine over to fill the bowl back up. If you have spray carburetor cleaner use that in the throat to get the engine started and fill the carburetor back up with gasoline.
A misfire from a spark plug wire that is bare from heat or vibration can be made to function by wrapping the area with a good deal of electrical tape and moving it away from anything it can arc to.
A starter that is binding can often be made to work a few more times by gently tapping it with a small hammer while a helper tries cranking the engine. A neutral safety switch can fail and not allow the engine to crank. If it does, remove the plug and use a cotter pin or paper clip to jump the two wires so the engine starts.