Timing chains can cause grief when worn out

Hey there, time traveller!
This article was published 05/09/2003 (8107 days ago), so information in it may no longer be current.

QUESTION — My 1990 Ford Thunderbird has over 100,000 miles (160,000 km) on it and I have been told the timing chain may cause engine problems if it is not changed. The engine is a 302 CID (5.0-litre) V8. How can I check to see if it needs a timing chain and what happens if I don’t change it?

ANSWER — The timing chain connects the camshaft to the crankshaft and as it wears, the camshaft timing becomes retarded. A worn timing chain can cause performance loss, poor fuel economy, and a rattling sound from the engine. If it is left too long before it is replaced, the chain may “skip” or “jump” a tooth on the drive gear.

When this happens, the least that happens is the engine runs poorly. Sometimes, it may not even start. At the worst, it may bend valves in the engine and require expensive cylinder head work. Usually the vehicle will have in excess of 100,000 miles (160,000 km) on it before a chain is required. Sooner or later the timing chain will need replacement. The question is, when should it be done?

I check timing-chain wear by watching the valves move through the oil filler hole or watching the distributor rotor turn as I turn the crankshaft by hand. Make sure the car is in park and the key is out of the ignition. Then turn the crankshaft front pulley using a large socket and handle.

After you can see the valves or rotor start to move, turn the crank pulley in the opposite direction and note how far you have to turn the crank before the valves start to move again. If you have to turn the crank back more than about 15 degrees before movement is seen, then the chain is worn and should be replaced.

Checking for chain wear when the engine front cover is off is easier. Try lifting the chain up off the big sprocket. If the chain lifts more than 1/2 the height of the sprocket tooth, then the chain needs replacing. Replace the sprockets at the same time as you change the chain. A worn sprocket will quickly wear a new chain!

QUESTION — I need to wire my 1988 Nissan Pathfinder for a new utility trailer I purchased. The Pathfinder uses a red light at the rear for brakes, and an amber light for turn signals. The trailer, on the other hand, uses the same red light for both brakes and turn signals. I tried to wire it already, but the lights wouldn’t work properly. What am I doing wrong?

ANSWER — Wiring a trailer with only red lights to a vehicle with red and amber rear lights is an easy task; you just need the proper part. Go to your local auto parts supplier and ask for a trailer light wiring converter. It only costs a few dollars.

The converter is a small sealed module that contains several one-way electrical valves called diodes. The diodes allow electricity to flow from the red brake lights and the amber turn lights to the red brake/turn lights on the trailer but do not allow the electricity to flow between the Pathfinder’s red and amber rear lights. All the lights should work correctly after the converter is installed.

Be careful with your connections when installing any trailer wiring. Quick-connect wiring clips may be convenient, but usually soon let dirt and moisture into the wiring connection. Then your lights start working intermittently. A better way to connect the wiring is to carefully remove the insulation from the wire, wrap the connecting wire end around the original wire, and solder the connection using rosin core solder. Finish the job by tightly wrapping the connection with plastic electrician’s tape.

Some trucks come pre-wired for trailer wiring so all you have to do is find the harness beneath the truck and run it out to the rear. Install the trailer wiring plug and you are finished. Unfortunately, your Pathfinder doesn’t have a pre-wired harness, so you will have to make your own.

Jim Kerr is an experienced mechanic, instructor of automotive technology and freelance journalist. You can e-mail questions to Jim at the address below.

kerr.jim@sk.sympatico.ca