Getting An Old Car Running

Starting an automotive engine that's been sitting for several years requires extra procedures and precautions. Before trying to get an old car running, care needs to be taken to ensure internal parts aren't needlessly damaged or broken.

getting an old car running

If the vehicle in question is new to you and you have no history on it, there's no guarantee the motor will start. Getting an old car running again will not only depend on your efforts, but factors such as mileage on the engine, mechanical condition, etc. And if it's an original engine in a classic car, you may consider not even trying to start it, and instead make plans to remove it from the car and rebuild it.

Read: Does My Engine Need A Rebuild?

Before you begin, remember that an internal combustion engine is essentially a large air pump. Aside from any mechanical issues that it may have, given fuel and spark in the correct timing the motor will start and run.

To more easily understand how to diagnose a non-running engine, let's break it down into four basic categories; fuel, air, ignition, and starting system.

Reading Spark Plugs

Start by taking out the spark plugs, keeping them in order when you remove them. This will help you determine if only certain cylinders have issues. Also, don't assume that the plug taken out is correct for that year, make, and model car. Check the plug number with a catalog or an auto parts store.

spark plug

A spark plug is exposed to more stress than any other engine component, yet has no moving parts.

Reading the firing end of the plug reveals what kind of tune the motor was in when it last ran. There's probably dozens of various plug end appearances, but here's the ones most commonly found.

  • Black, sooty plugs indicate carbon fouling, caused by a rich fuel mixture.
  • Oil deposits on all plugs reveal worn piston rings and/or valve guides.
  • Oil deposits on one or several plugs indicate worn or broken piston rings on those particular cylinders.

The last thing you want to see on a plug tip is a broken insulator (the white ceramic part). This usually characterizes detonation, brought on by lean fuel/air mixture, engine lugging, over-advanced ignition timing, and/or incorrect engine modifications. Light tan to grayish color on the electrode of all plugs is normal.

Change Oil And Filter

An important step in getting an old car running is draining and changing the oil. Automotive engine oil degrades with time and can start losing its lubricating qualities in less than a year. You don't want to risk damaging something internally.

If possible, take the valve cover(s) off and pour fresh oil over the valve-train components while performing the oil and filter change. Pour some Marvel Mystery Oil (or WD-40, or similar fluid) into the spark plug holes. This will help free up the piston rings in the event they're stuck. One cap-full at a time is all that's necessary, and remember it takes a while for the oil to penetrate.

Remember, you don't want to damage anything internally. Overnight is a minimum time to wait for the penetrating fluid to work it's best. After the draining is complete, install a new filter and refill with the correct amount of fresh oil.

Check Engine Coolant

If you have no history of the car, drain and refill the engine coolant as well. I usually refill with straight water first, then if all goes well, drain and replace the water with a coolant mix afterwards.

Diagnose Ignition System

Begin with a freshly-charged battery. If you have an automatic shut-off battery charger, great. If not, make sure you don't cook it by leaving it on charge too long!

Digital Multimeter

A multimeter is a test tool instrument designed to measure electrical values such as voltage (volts), current (amps), and resistance (ohms). There are two main types of multimeters, analog and digital. Digital is by far more common, they have an easy-to-read numeric display, and one can be had for less than $20.

electrical multimeter

Shop: Digital Multimeter

To check if a wire is good or bad, connect one test probe to one end of the wire, and the other test probe to the other end of the wire. With the multimeter on ohm setting, it should read .02 or less. Anything higher than that, replace the wire and/or the terminals.

Check the resistance of your positive and negative battery cables with your multimeter. If bad, throw them away and replace with new ones.

Next, check the secondary ignition system, starting with the spark plug wires. These can be tested with a multimeter, or simply replaced if they feel stiff or hard to bend.

Read: Old Car Ignition

On cars with points-style distributors, take the distributor cap off. With the car ignition turned on, you should be able to 'rock' the distributor rotor back and forth and see if the points are sparking. The ignition coil can also be checked with a multimeter.

If it looks like the distributor can be removed easily, take it out to examine it closer. Inspect and/or replace the points and condenser (yes, you should change the condenser, too). On many automotive engines, you can prime the engine with oil with a drill attachment on the oil pump shaft. This would pre-lube the engine with oil, and also let you know the oil pump is working. After this is done, reinstall the distributor.

Crank The Motor Over By Hand

With the spark plugs still removed (you may want to stuff a paper towel in the plug holes) crank the motor slowly by hand, if possible. This is easier on a stick-shift car, but if yours is an automatic you can put it in neutral and it may work. Use a large wrench or 1/2" drive socket on crankshaft balancer bolt.

Read: Best Oil for Classic Cars

If the motor doesn't turn, something is preventing it from spinning freely. Do not try starting an engine that will not turn over by hand - forcing it will very likely break something!

Once the motor turns over freely, continue on to the next step.

Fuel System

Sitting unused for several years, gasoline will turn to varnish. This was the case on my old Jaguar engine. The Jag had sat for nearly 20 years before I bought it, and when the carburetors were disassembled, the old gas had hardened into varnish in the float bowls (see picture below).

Rebuild Carburetor

What's required here is disassembly, removing gum and varnish, cleaning, and careful re-assembly with new gaskets. Depending on the type, your carb may also require new diaphragms, seals, or o-rings, too. Air passages should be blown clear with compressed air.

varnished carburetor float bowl

If your old gas has turned to varnish, slowly and carefully scrape and clean the carb bowl before the rebuilding the carburetor. I cleaned the left side of this fuel bowl first to show the difference of the before and after cleaning.

rebuild Zenith Stromberg carburetor

It's nice to have a second carburetor to use as a reference as you're disassembling the other, but keep in mind that front and rear carbs can be different from each other.

Once the carb rebuild is done, remember to replace the fuel filter with a new one, and replace any old or dry-rotted rubber gas hoses.

Rusty Gas Tank Alternative

I am always hesitant to pour good gas into a 20+ year-old gas tank, so I usually substitute a plastic gas jug as a temporary gas tank (if the fuel pump is operative). On several occasions, I rigged a 'gravity-feed' gas container, which hung from the top of the open hood and connected right to the carburetor inlet, thus bypassing the need for an operative fuel pump. This is allow you to see if the engine will run before investing too much time and money in it.

Crank The Starter Motor

With the spark plugs removed and primary coil wire removed (you don't want to start the engine yet) see if the starter motor will crank by turning the key. If it does, you can check to see if the mechanical fuel pump is working.

Install new spark plugs, properly gapped, or clean and re-gap the old ones. Re-attach the primary coil wire. With good spark, fresh gas, and a fully-charged battery, you're now ready to see if the engine will fire up. The carburetor choke, whether it's automatic or manual, should be closed.

Starting Fluid

Crank the starter, but limit starter operation to a maximum of 5 to 10 seconds, and wait about a minute in-between tries. If it doesn't start up right away, a squirt of starting fluid into the carburetor may help.

Automotive engines can be kept running by repeated squirts of starting fluid into the carburetor, but that's never a good idea. Do not mis-use starting fluid, there is the likelihood of washing the engine oil off of the cylinder walls, causing internal damage.

If the engine fires after starting fluid was sprayed, but doesn't continue to run, that tells you the ignition is O.K. You can then concentrate on the fuel system.

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