6 Tips for Starting an Old Engine

By: Christopher Neiger & Talon Homer  | 

old engine
If you've ever tried to start an old car that's been sitting for a long time, you know that it isn't always as easy as just turning the key. NurPhoto/Getty Images

If you've ever had an old car sitting around for a while, you know that getting it started and back in running condition isn't always easy. Engines were made to run regularly. The longer they sit idle the more they can develop problems you'll have to deal with later.

Think of an old engine like your body. The less exercise you get the more your body gets used to not exercising and the harder it is to start working out. Your body may even be more likely to suffer injury because the muscles aren't used to that level of physical activity. A car works in a similar way. When the moving parts of an engine sit for too long and aren't used or properly lubricated they have a tendency to get stuck and become resistant to movement.

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But the mechanical parts aren't the only things that go bad when a car sits around. Old oil, antifreeze and gasoline don't hold up well when sitting in an engine for months or even years. Fluids break down, seals leak and corrosion sets in on various parts of the engine. And the delivery systems that moves fluids like fuel and oil pumps, hoses and filters can all cause problems when starting an old engine. When your vehicle has been sitting unused, all of the fluids that once made the vehicle run may now be working hard against it.

An old engine may be difficult to get started, but it's not impossible. Every engine is different, but there are a few general techniques that can be used to get almost any engine in running condition once again. Just remember, it's likely that you'll have to use more than one technique listed here to get your engine started.

6: Lubricate the Engine

When an engine is really old or has been sitting unused for a long time, the internal components are going to be less likely to get going. You can liken it to Newton's first law where he said that an object at rest tends to stay at rest. This just means the engine will need a little coaxing.

Since the engine hasn't had any oil running through it in a while it will need to be lubricated. You can do this using a product called Marvel Mystery Oil to lubricate the cylinders, pistons and rings. You can do this by taking out the spark plugs and pouring a small amount of oil directly into the cylinders. The plugs will probably need to be replaced anyway.

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old engine
You might need to pour a small amount of penetrating oil directly into the cylinders to get things moving.
Barrett-Jackson/Getty Images

There are two different ways to get the engine to turn over at this point. In some cars you may be able to turn the engine over using a socket wrench on the crankshaft nut or you could hook up a battery to the ignition. Any oil that's in the cylinders will come out when you do this. If the engine turns over after you crank it then it may start up once the spark plugs are replaced. If your engine has a carburetor, some people recommend spraying starting fluid into the carburetor to aid combustion.

Getting the engine to turnover is a good sign, and if you've already corrected some other problem areas then the above suggestions may be all you need. But even if everything is working properly with the engine, there still are several other factors that you need to inspect before you can get the engine running for good.

5: Replace the Fluids and Filters

One way to start up that old engine is to make sure the fuel, oil and engine coolant are all flowing properly. We already talked about lubricating the engine before you turn it over, but another major factor that causes old engines not to start is old gas. Regular petroleum fuel has a shelf life of about three to six months. If it's left sitting for longer than that, it can easily cause problems in the fuel system.

Gasoline is a highly refined product that vaporizes and combusts easily. The same chemicals that give gas these properties are also the ones that allow it to evaporate over time and cause the gas to lose its ability to ignite easily. In addition to evaporation, a process called oxidation can occur, when chemicals in the gas mix with oxygen. This produces deposits in the gas that can clog fuel lines, fuel filters, and the carburetor or fuel injectors. Gasoline that has ethanol in it also tends to draw moisture out of the air, and corrode the fuel system even faster.

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To start an engine that has old gas in it, you may need to pump fresh fuel into the system from an external source. You may also need to completely remove the old gas from the tank and fuel lines before trying to start the engine. Fuel filters and injectors that have been sitting for months or years may need a good cleaning, or to be replaced entirely.

old engine
It's important to check and, most likely, replace the filters in an old car.
Portland Press Herald/Getty Images

Before putting a car into storage, also consider adding a product known as fuel stabilizer to the gas tank. This stabilizer slightly changes the chemical properties of the fuel, preventing corrosion while sitting for a few months. In addition to replacing the old gas, the antifreeze will likely need to be flushed as well. Antifreeze breaks down over time and forms acids that can hurt your engine.

An engine oil change with a new oil filter replacement is also a must-do. Most manufacturers recommend replacing oil after 12 months, at the maximum. You may also want to consider more frequent oil and filter changes after the engine is running just to flush out any sludge that has been sitting in the engine block.

If changing the gas, coolant, oil and filters doesn't work for your engine, you may need to try a different approach.

4: Inspect the Electrical System

The newer your car the more electrical components you'll probably find under the hood, but even old engines can have electrical problems. If all the mechanical parts seem to be working properly and you still can't start your old engine, you may have an electrical problem.

The easiest problem to diagnose and fix is the battery. Car batteries are made up of a lead-acid or lead-calcium system that converts chemical energy into electrical energy. Batteries go through a recharging cycle when the alternator sends a current to the battery's internal plates and back into the electrolyte mixture inside the battery.

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When a battery isn't being used, the chemical reaction in the battery breaks down and causes it to lose its energy. If the battery sits long enough it will be ineffective for starting up the engine. Corrosive green slime can also take over the battery's terminals. If more than a little corrosion is present, that's a sure-fire sign it's due for replacement. Also be sure to clean from your car's wiring contacts before installing the new battery. Another product great for car storage is a battery tender. This device provides a small, constant charge to the battery, which prevents it from draining and maintains electrical component health.

In addition to checking the battery, inspect the ignition coils and coil wires. Use a multimeter on the coil to see if the resistance reading matches the recommendation for your vehicle. If it doesn't, then the coil may be bad. If the coil and its wiring work, use a current reader to see if the starter motor is receiving a current. Corrosion or bad wiring can inhibit the starter motor and prevent the engine from firing up. If the starter motor gets enough current and still doesn't engage, then it may need a rebuild or replacement.

If your electrical systems are working and the car still won't start, you'll have to look elsewhere for the problem.

3: Check for Vacuum Leaks

Your engine creates a vacuum when the intake valve is partially closed in the intake manifold. The vacuum is then used to help power other components on the car. It may help reduce your effort in pressing down the brake pedal or, in older cars, it may even power the windshield wipers. If enough vacuum hoses have leaks, or you have one big leak, it may keep your old engine from starting.

In newer cars, some vacuum leaks can cause engine sensors to report incorrect readings to the engine's computer system. When this happens, even minor leaks could keep your engine from starting. A few trouble spots for vacuum leaks may be the throttle body, the manifold seals, the positive crankcase ventilation (PCV) valve or the PCV hose. Although those may be some trouble spots, there are numerous vacuum hoses in each car.

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old engine
Even minor vacuum leaks can keep your engine from starting.
CLEMENT MAHOUDEAU/Getty Images

When the engine sits for a long time the hoses can deteriorate and develop cracks. A few small leaks won't keep your car from starting but large leaks, or too many small ones, may be too much. There are several ways to determine if you have a vacuum leak, but the most effective is using a smoke generator. This smoke-out tool generates smoke in the engine so you can see where the vacuum leaks are coming from in each hose.

This tool is somewhat expensive and usually used by professionals, so it may be a better idea to locate a diagram of your engine's vacuum hoses and replace them all instead. Replacing all of the hoses in an old engine isn't a bad idea, considering you could spend a lot of time trying to track down a leak and you'll be replacing several hoses either way.

Old engines may also have compression leaks in their cylinder heads. Low compression can stop fuel from combusting in the chamber and keep the engine from starting, so a compression test at your local mechanic may be in order.

2: Replace Timing Belt

Timing belts, or chains, are the part of your engine that keeps the camshaft, distributor, crankshaft and pistons in sync. When the timing belt breaks or is damaged it can keep the engine from starting up. Most timing belts will last about 60,000 miles (96,561 kilometers) but if your engine has been sitting for a long time it might be a good idea to inspect it.

Many cars use reinforced rubber belts, but older cars and many newer luxury cars still use metal chains. Timing chains typically last much longer than belts, but may still become stretched out and loosen over many years of use. In either case, a broken timing belt (or chain) will inhibit your engine from starting.

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Although it may take only a few minutes to actually slip the belt on, getting to the belt might not be all that easy. It's likely you'll have to take off multiple hoses, move electrical wiring and remove other engine components to gain access to it. Once you're able to access the belt you'll have to make sure to align the crankshaft and camshaft markings and ensure the number one piston is at top dead center (TDC). If you don't get this exactly right you can throw the entire engine off its timing and probably cause some serious internal damage when all of those metal parts start crashing into each other.

While performing a timing belt, or chain, replacement, you may as well put on fresh accessory belts at the same time. Accessory belts are also made of rubber, but sit outside the engine, exposed to air. For this reason, they are likely to become dry-rotted after long periods of disuse.

Needless to say, changing the timing belt isn't for everyone. It requires a high level of skill, and in some cases, it might even require taking off an engine mount to gain full access while suspending part of the engine as you work on it. If your timing belt or chain is old, stretched, worn or broken though, you'll need to replace it to get your engine started. Consider taking it to a mechanic if you don't have the tools and skill required to replace it.

1: Care and Maintenance

It's important to remember that getting an engine started is only half the battle to ensure longevity. Regular maintenance is the most important thing to mechanical health, and a neglected engine requires even more care. If your car has been sitting for a few months, then all it may need is fluid and filter changes to run right again. If it's had years or even decades without use, then more drastic repairs will be required.

Gaskets, the seals that sit between engine components, can dry-rot and leak after disuse. Running an engine for too long with bad gaskets can cause oil and coolant to leak outside, or back into the combustion chamber. This can then lead to worse problems like overheating, corrosion and eventually a seized engine. Other drivetrain components like the transmission and differentials also have fluids and gaskets that may need changed.

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old engine
Regular care and maintenence is the most important part of the mechanical health of an old car.
Barrett-Jackson/Getty Images

In an old engine, oil passages may be blocked by sludge deposits, causing piston rings and crankshaft bearings to be denied proper lubrication. If these small metal pieces are run dry, they will definitely scratch the components they rub up against, requiring more repairs. Worst case, they will scrape off metal shavings that fall into oil passages and contaminate the rest of the engine.

If you're dealing with an antique engine that hasn't run in 40 years, the safest bet is to have a professional tear it down and inspect each component before it even starts. They'll be able to check the block for warpage or scoring, replace bearings and gaskets, and clean out carbon deposits. A full engine rebuild will be an expensive operation, but it's really the only way to be sure an old car will run like new.

Originally Published: Jul 20, 2012

Start Old Engine FAQ

How do you start an old engine?
You can get an old engine running by lubricating the engine, replacing the fluids and filters, inspecting the electrical system, checking the timing and fixing any leaks.
What happens if a car is not driven for a long time?
Car engines are designed to run regularly. If it sits for a long time, the moving parts become stuck and fluids such as oil, gas and antifreeze corrode parts of the engine, causing problems with the fuel pumps, radiators, hoses, filters and more.
What causes a car not to start if the battery is good?
If your car won't start despite a working battery, inspect the ignition coil and coil wire. Use a multimeter to check if the resistance reading reads the same as your vehicle's requirement. If it isn't, the ignition coil is bad.
What do you do if your engine won't turn over?
You can try two different methods to get your engine to turn over. The first involves using a socket wrench on the crankshaft nut. If your car has a carburetor, you can try spraying starter fluid into it to help start the engine.
Will starter fluid help my car start?
When your car sits for a long time, the engine might get too cold or its ignition system may become faulty. In such cases, starter fluid might help start your car.

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