Tech Articles

Troubleshooting Engines: Do You Ever Feel Like You’re Chasing Your Own Tail?

Troubleshooting engine gremlins can be one of the most frustrating parts of working on race cars.

Racing can be a challenging sport for drivers and crew alike. Much like everyday life, it can be trying and humbling at times, yet the excitement and occasional victory can help smooth the road. One of the most frustrating situations for racers is when the car has taken on a “gremlin” where it just doesn’t quite perform like it has in the past, and trying to troubleshoot engine gremlins can make you feel like you’re literally chasing your own tail.

Tools for troubleshooting engines include a leakdown tester, oil filter cutter, TDC locator tool, and inspection light
Some common tools for troubleshooting engines.

Situations such as these are where accurate, consistent record keeping can be of great help. If a drag racer, for example, has kept a log book of elapsed times complete with weather station data, he’ll know immediately after he makes his first run of the weekend whether the car is performing as it should under the current conditions. Log and set-up books are an invaluable source of information and reference, particularly if a problem arises.

It’s usually best to approach these situations with a “troubleshooting” mentality, the same method that a professional auto mechanic would take when diagnosing a driveability problem with a passenger car. If the car’s performance is in question, it’s best to first check the basics, verifying that the ignition timing and fuel system jetting are correct, and that the air intake or exhaust isn’t blocked or restricted, rather than to just start changing parts.     

Checking valve lash on mechanical camshaft applications or hydraulic lifter pre-load should be one of the first things to check. If valve lash is found to be out of spec on a particular cylinder, it is best to determine why it loosened up rather than just resetting it, only to find out later that you have a cam lobe going flat.

Another important check when troubleshooting engines is to inspect the oil filter to verify that something isn’t awry in the engine. After removing and draining the filter, cut the filter open with a oil filter cutter, such as the Longacre LON77750, remove the element from the canister and thoroughly examine it. If the element is loaded with bearing material, you’ve obviously found the problem and it’s time to pull the engine.

A leakdown test can be performed to verify piston ring, head gasket and valve seal integrity. If this test is done periodically, using a tool such as Total Seal‘s TOT14MMLDT, you’ll know what readings are considered normal and which aren’t. Leakage readings can vary, due to piston ring type, but cylinder-to-cylinder consistency is what’s important. For example, if all of your readings are 8-10% from cylinder to cylinder, it’s probably time to look elsewhere. While leaking the engine down, it would be a good time to examine the spark plugs with an inspection light, such as the Powerhouse POW301080. A plug that is soaked with fuel, oil or water should set off a red light that there may be a problem in that cylinder and further diagnosis is needed. More than a few racers have fallen victim to problems such as a cracked cylinder wall.

It should also be confirmed that sufficient fuel flow is available. Simply disconnect the fuel line at the carburetor or fuel injection unit (after the regulator) and place it so that it can flow into a fuel jug of sufficient size. If the car is fitted with an electric pump, simply turn the pump on for 30 seconds. It is important at this point to have a helper present to prevent any possibility of fuel spillage. The system should deliver a minimum of one gallon in 30 seconds. Applications using a mechanical or belt drive pump will, of course, require spinning the engine over to determine that proper fuel flow is evident.

Another common problem that has caused more than a few racers to literally pull their hair out is a “spun” harmonic balancer. Most OEM-type balancers feature an outer ring that is bonded to the crank hub with a special rubber. If the rubber bond deteriorates, the outer ring can spin on the crank hub, effectively putting an end to accurate ignition timing readings. For example, it may appear that you have 36 deg. of ignition lead, when in reality it may be only 28 deg.. The balancer’s integrity and true TDC (Top Dead Center) location can be quickly checked using a TDC Locator tool, such as the Proform PFM66792.

Race cars that are stored in non-climate controlled conditions are subject to moisture, condensation and corrosion, which can lead to excessive rust build-up inside the exhaust headers. This rust build-up not only hurts exhaust flow and performance, but can also be sucked into the engine during starting, harming the pistons, rings, cylinders and valves. After removing the headers, a cleaning tool can be fabricated from a trimmed down drain snake that is then covered with sand paper, and then used to effectively clean the inside of the tubes.

Electrical system issues such as insufficient voltage and “voltage drop” have plagued racers as well. The electric fuel pump, for example, cannot perform correctly without the proper voltage. For example, if a volt meter reads 14 volts at the battery with the engine running, it doesn’t necessarily mean that the same amount of voltage is present at the fuel pump. A condition referred to as “voltage drop” can exist due to improper power wire sizing, causing voltage to drop to below 12 volts. To correct the condition, a relay may be installed to prevent the lead wiring from being overloaded.   

Negative grounds are a critical component on any race car and it should be ensured that the components that they attach to such as the engine block, heads or frame are free of corrosion, grime or paint. Due to the advent of today’s powerful ignition systems, one of the most common causes of electrical system problems is often tracked down to a bad ground.

There are literally a myriad of other mechanical or electrical issues that have caused many a racer sleepless nights, but taking a steadfast, thorough approach when you troubleshoot engines can often help you find the solution, rather than panicking and literally becoming the cat that runs around in circles, chasing its own tail.