Diagnostic Tech: '92 Astro Van, 4.3Z (originally posted March 2008)

 Saturday, March 01, 2008

Diagnostic Tech: '92 Astro Van, 4.3Z

I had a '92 Astro Van come in on the hook for a no-start. The engine was a 4.3 with throttle body fuel injection. The owner said the van had been stalling and sometimes failing to start for some time now. He had replaced the fuel pump and filter because he thought it seemed to be running out of fuel. No testing had been done and the same problem remained after the fuel pump replacement. When I turned the key on I could hear the fuel pump run. Turning the key to start engaged the starter, the engine spun nicely and... it even started right up! It isn't uncommon for a no-start to be towed in and then start once it gets here. I'm sure there is an applicable Murphy's law for that.

What I did notice though was an intermittent engine cut-out. A sure fire sign of a secondary ignition problem. Even though the van owner was still sure he had a fuel problem, I decided to take a look at the ignition system. On the Astro van the ignition system is easy to access once the engine cover is removed. I immediately saw what was probably causing that cut-out symptom I had noticed. There was a burn mark where the secondary spark from the coil wire had been jumping to a vacuum hose instead of following the intended path to the distributor cap. That meant that the resistance in the secondary, downstream of the coil wire was so great that the spark found it easier to jump to the vacuum hose. A mental list of plugs, wires, cap and rotor was forming in my mind.

As I began the work of replacing the secondary ignition parts I began to be amazed that this engine was running at all. The coil wire tower in the cap was completely burned away.

The rotor was burned through and the distributor was severely corroded.

After a cleaning with electrical contact cleaner and penetrating oil the distributor was found to be in good condition. I replaced the spark plugs, spark plug wires, distributor cap and rotor. The van ran very well after that with no more stalling or cutting out. At 264,000 miles I wouldn't be surprised if it did need that fuel pump as well.

Kenny@ggauto.repair