This problem has actually been creeping up slowly lately. On days after it has rained, and is extremely humid, my 97 Tahoe (5.7L V8) is hard to start. It cranks for a few seconds and in some instances has semi-backfired. No loud bang, but it sounds like a huge burst of air being spit out under the hood.

A couple days ago after a bad rain I went out and it would not start at all. It'll crank all day long but just would not turn over. Unfortunately I didn't have a spark tester or fuel pressure gauge at the time, so I don't know what was happening there. I did hear the fuel pump running fine, and there was pressure at the rail when I pressed the valve with my finger. All day long it wouldn't start. Waited 24 hours for it to "dry out" and it started right up - some smoke indicated that it was getting fuel.

During the no start condition I removed the distributor cap, looked for condensation, hosed it down with WD40, checked the coil, sprayed those connections with WD40 - nothing. Cranked, but would not start.

Since it hasn't rained it's running fine. I checked the fuel pressure and its a good 55 - 60 psi. I've pretty much ruled out the fuel pump. Plugs, wires, cap and rotor are new about 8k miles ago. It did set a code P0430 about 3 weeks ago, Catalyst System Efficiency Below Threshold (Bank 2), but I cleared it and it never returned. Battery and connections are also new, and were checked.

Its obviously something related to water and humidity, but I'm at a loss to think what else it could be. Any suggestions?

Mark

Hook the fuel pressure tester back up and start the engine. What does the pressure do when the engine is turned off? It should hold pressure and maybe drop a pound or two every few minutes. If it drops fast, the fuel pressure regulator is bad and should be replaced.

//2000CAYukon