1994 Chevrolet S-10 cranks, will not start

Tiny
FUELISH62
  • MEMBER
  • 1994 CHEVROLET S-10
  • 2.2L
  • 4 CYL
  • 2WD
  • MANUAL
Replaced the PCM, replaced the crank sensor, coil packs, plugs & wires, spark plugs. Replaced fuel pump and fuel pressure regulator. I'm wondering about the cam sensor. It has 3 wires - one is "HOT" (12.6) even with the key off. Key on it stays 12.6 but the middle wire reads 8.84 and the third wire is. A ground? Any ideas?
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Tuesday, June 17th, 2014 AT 2:59 PM

3 Replies

Tiny
CARADIODOC
  • EXPERT
Have you actually diagnosed anything? You've installed a bunch of variables that are going to make it a lot harder to sort out. If you haven't figured it out yet, throwing random parts at a problem is the most expensive and least effective way to figure out what's wrong.

For your camshaft position sensor, it sounds like you're grounding your voltmeter on the battery's positive terminal. That will give you the 12.6 volt reading on the sensor's ground wire. You should have 0.2 volts on the ground wire when the ignition switch is on, and either 5.0, 8.0, or 10.0 volts on the power wire. The signal wire will vary between approximately 0.2 volts and the supply voltage, depending on camshaft position. Regardless, you don't need to test the sensor. Professionals never do because they have to charge for their time, and doing those kinds of tests takes too much time. The Engine Computer does that for you. It's too late now, but if a sensor had failed, there would have been a diagnostic fault code stored in the old Engine Computer. That got erased when it was disconnected. If you're lucky, there may be a code set now if the computer was able to detect a problem during engine cranking. Some codes only set when the engine is running and coasting to a stall.

Here's the page that will tell you how to read the fault codes:

http://www.2carpros.com/articles/buick-cadillac-chevy-gmc-oldsmobile-pontiac-gm-1983-1995-obd1-code-definitions-and-retrieval-method

You've replaced parts in a couple of different systems so I can't tell which one has the problem. The place to start is by listening for the hum of the fuel pump for about one second after turning on the ignition switch or while a helper cranks the engine. Next, check if you have spark. We'll figure out where to go once we know which of those is missing. Also be aware that on GMs, there can't be any leaks in the fresh air tube between the mass air flow sensor and the throttle body. If any air sneaks in that doesn't go through the mass air flow sensor, the Engine Computer won't know about it so it won't provide the needed fuel to go with it.
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Tuesday, June 17th, 2014 AT 11:46 PM
Tiny
FUELISH62
  • MEMBER
All of the above mentioned parts were already replaced prior to me. There has never been any codes in either the old or new PCM nor does the check engine light come on when you turn on the key? I don't believe it's the original motor. Here is something I found - there was no continuity on one of the crank sensor wires. (The copper was dust inside the insulation). Doesn't this indicate there is a ground issue someplace? I replaced the wire, still no spark? Fuel pump hums when you turn the key on. Also none of the fuses or fusible links are blown. I had the ignition model tested twice and both times tested good.
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Wednesday, June 18th, 2014 AT 2:52 AM
Tiny
CARADIODOC
  • EXPERT
GM tried using aluminum wires on some of their vehicles, and that dust you described was what would happen to them if the insulation was pierced to take a voltage reading. They'd corrode in that spot within a few weeks, but I don't think you have aluminum wires under the hood.

Since we know you have no spark, start with the cam and crank sensors again and measure the voltages on all six wires. Turn the engine just a little by hand, then measure them again. You should see a change on the signal wires at some point.

The next step would be to connect a scanner that displays live data so you can see what the Engine Computer is seeing. That will tell you instantly if the crankshaft and camshaft position sensors are working.
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Thursday, June 19th, 2014 AT 12:46 AM

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