Q: My '96 Blazer with 161,000-plus miles on it runs great. It has a good, strong 4.3L Vortec V-6 engine. It's mechanically sound and runs and sounds like an engine with half the mileage. I purchased the truck this past February from a smart guy that had done all the work on the truck himself. He replaced parts at proper intervals and took great care in performing scheduled maintenance. One problem he could not figure out was a problem starting the vehicle. He replaced just about the entire ignition system. Sometimes when you go to crank the engine, it will not start right away. Sometimes you have to hold the ignition in the start position until it catches. Sometimes it takes multiple tries to get it to start. But the truck always starts.

When I bought the truck, he said it could be the one part he did not replace, the ignition coil. But a friend of mine said it could be a problem with oil leaking and covering the spark plugs causing there to be a spark problem. I was not overly concerned about it as the truck is my second vehicle for daily driving and winter driving. Do you have any ideas? I don't know what you think, but it's one of the best SUVs ever built. There are many still on the road with 100K+ or 200K+ miles. Mine still gets about 20 mpg on the highway. That's better than some of those "fuel-efficient" crossovers on the road today.

A: B.B., I don't think your Blazer's problem is a faulty ignition coil or oil getting on the spark plugs. That's because ignition coil and spark plug problems usually act up with moisture or high temperatures. You didn't mention those as conditions when the problem occurs. Also, if the ignition coil or spark plugs were acting up, the problem would not only affect starting, but the engine would misfire or shake at idle and on acceleration. If your engine runs smoothly and accelerates normally from a stop, it's likely the ignition coil and spark plugs are not your problem.

I'm thinking that your truck's ignition switch could be worn out. There are several contacts inside the ignition switch with separate circuits for the starter motor and ignition/fuel systems. It's possible that the contact for the starter motor could be okay, while the contact for the ignition/fuel system has excessive resistance. Using a multimeter and schematic diagram, a technician can determine if the circuit through the ignition switch for the ignition/fuel system is acting up. If the ignition switch tests okay, then there's likely a poor electrical connection either at the Powertrain Control Module (PCM) or somewhere between the PCM and the fuel injectors or ignition coil.

Q: My 2002 Toyota Sienna has 92,000 miles on it and the maintenance book says that the belt should be replaced at 90k. The dealer also suggested that the water pump (which is driven by the timing belt) be replaced. What do you think? Do you know if this is one of those interference engines where engine damage can occur if the timing belt breaks?

A: E.R., I'm in agreement with the dealer. No, the 3.0-liter V-6 in your Sienna is not an interference engine. But if the timing belt breaks, the engine will stop running and you'll need a tow-truck.

Questions for Ira Siegel? Call the Auto Adviser Hotline at (708) 633-6839 or e-mail Autoadvisr@aol.com. AutoAdviser: Ira Siegel is an Automotive Instructor and ASE Certified Master Auto Technician.