This case study will help you to diagnose a ‘Spider’ fuel injector that is stuck open due to the PCM having fried and causing one of two things: A misfire condition or an engine hydrolock condition (a no crank condition caused by gasoline filling up an entire engine cylinder).
This isn't something that happens everyday to a ‘Spider’ CPI or CSFI fuel injection system equipped vehicle, but it does happen enough that I thought it would be helpful to a lot of folks to write about it in this case study. Hopefully this case study will shed some light on what the symptoms are (when it does happen) and how to diagnose and repair this type of issue.
Before I go any further, let me tell you that the info in this case study article complements the info found in the two articles below (that also deal with testing the ‘Spider’ fuel injection system):
One last thing, the way I've organized this case study article, I'm gonna' jump into the story itself, which will detail the complaint, symptoms, diagnostic and repair solution. At the end of the case study story, I'm gonna' offer you specific safety precautions that should ‘round out’ what you just read.
When one of the 6 or 8 ‘Spider’ fuel injectors stays stuck On all of the time, you'll see the following symptoms:
Right off the bat, I'll tell you that the most common cause of this happening is usually the PCM (Powertrain Control Module = Fuel Injection Computer) going BAD.
Even though this is a case study of a 1997 CSFI ‘Spider’ equipped GM Suburban (with almost 200,000 miles), the core testing tips of this article will help you whether you have a 4.3L with CSFI or CPI ‘Spider’ or a V8 with CSFI ‘Spider’ (no matter what the year of the vehicle)... if indeed this is the problem you're having with your vehicle.
For your info, these are the core differences between a CPI and CSFI system:
Like a lot of folks, in this tough economy, my buddy Charles doesn't take his older vehicles to a repair shop anymore. He does most of the repairs that he possibly can himself (tune-ups, alternator replacement, starter replacement, etc.), in order to save money.
Every now and then a problem pops up, in one of his two vehicles, that gets him stumped. He doesn't give up easily though... since he does a lot of research on the internet (not to mention that he has a whole library of repair manuals) and/or calls me to find answers and/or testing tips.
On this occasion, he called me on the phone and told me his 97 5.7L GMC Suburban was giving him a headache. His complaint was that the Suburban was running rough. The check engine light was on and the PCM was spitting out a P0306 diagnostic trouble code (DTC) and that he could smell raw gas coming out of the tail-pipe (when the engine was running).
He had already replaced:
...and the Suburban was still misfiring and giving a P0306 diagnostic trouble code.
Let's turn the page and find out how I diagnosed the issue to get his Suburban back on the road.
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Kevin Costner in The Postman