This truck will not start, No cross firing, New plugs and wires

Tiny
MIKEY300ZX
  • MEMBER
  • 1997 CHEVROLET S-10
  • 2.2L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 89,585 MILES
This truck came to me for repairs over the last weekend. It has proper fuel pressure, spark and engine timing. New intake gaskets. New ICM, CKP, and CMP. I have a 5 volt reference voltage to most of my engine management sensors. This truck will not start. No cross firing. New plugs and wires. Also coils are new. Scan tool data says calculated load at 100%. And rear 02 has no voltage and is new also. Also has new FPR. Any help would be greatly appreciated!
Saturday, October 1st, 2016 AT 7:53 AM

19 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Check security system or try another key maybe a bad key don't use a new one.
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Saturday, October 1st, 2016 AT 1:05 PM
Tiny
MIKEY300ZX
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  • 10 POSTS
No security light on. Also there is spark and fuel. If it was passlock related there would not be either.
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Saturday, October 1st, 2016 AT 1:12 PM
Tiny
MIKEY300ZX
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I do appreciate the reply though.
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Saturday, October 1st, 2016 AT 1:13 PM
Tiny
HMAC300
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  • 48,601 POSTS
How about a bad map sensor I remember a while ago that a bad map would not let a vehicle start. Or try to start with in open loop with sensor disconnected. Also some ECT sensors would do that. One last thing how about compression?
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Saturday, October 1st, 2016 AT 1:34 PM
Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
Just to add to this one what we're the compression readings?Also what is etc readings is it within10 degrees of actual coolant temp verus ecm temp readings?Also we have injector pulse?SO you don't have voltage to the rear o2 sen
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Saturday, October 1st, 2016 AT 6:29 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
Yes, unplugging each vital sensor one at a time might help, It sounds like the ECM is bad if all sensors are not getting the 5 v reference though.

I would start with a pin to pin on the ECM to make sure all power and grounds are right, then I would replace the brain, it sounds like one of the drivers has gone out

Please let us know what you find so it will help others.

Best, Ken
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Saturday, October 1st, 2016 AT 6:30 PM
Tiny
MIKEY300ZX
  • MEMBER
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Ecm is fine. Not all sensors get 5v reference some use 10-12 v that's what I was saying. Also have not checked compression. I don't suspect a compression problem as it was running earlier today just fine. Have swapped a known good ecm and had same issues. MAP readings are 29.5 HG KOEO. Omv to rear o2 sensor. 5.5 degrees ignition advance. Calculated load 100% all the time. Front o2.450 mv. Injector pulse is fine. All grounds that I have seen check out. From what I can see its related to the rear o2. No voltage means its inactive. The injector pulse seems too long to start cold. Way too rich. Also tried un plugging things while looking at engine load. Nothing changed. I appreciate all the input guys.
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Sunday, October 2nd, 2016 AT 5:11 AM
Tiny
MIKEY300ZX
  • MEMBER
  • 10 POSTS
Also temp sensor is within 2 degrees of outside temp so its good I have seen them fail at-20 though. I'm going to test compression next. Seems like either spark at the wrong time or too long injector pulse. The engine will backfire. But wont start as if the timing is off. But its dead on. And the valves are all operating correctly.( Camera inspection tool).
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Sunday, October 2nd, 2016 AT 5:16 AM
Tiny
MIKEY300ZX
  • MEMBER
  • 10 POSTS
I just unplugged the front o2 sensor and it has 0.450mv even unplugged. Rear o2 has no 12 heater power at harness. But no code for that. Gonna look into the harness for now. I've done everything else I can think of.
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Sunday, October 2nd, 2016 AT 5:25 AM
Tiny
KEN L
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Good call, the o2 must have 12 volts, please let us know what you find

Best, Ken
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Monday, October 3rd, 2016 AT 8:58 AM
Tiny
SATURNTECH9
  • MECHANIC
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So did you ever check the compression?
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+1
Monday, October 3rd, 2016 AT 12:23 PM
Tiny
MIKEY300ZX
  • MEMBER
  • 10 POSTS
O2 sensor has 12v to heater and heater ground is good. When I apply voltage to the signal wire scan tool still doesn't pick up voltage. I'm going to trace it to the ecm and find a break. Has to be grounding out. At least that's my guess. Any ideas? Still can't get calculated load to come down. In my experience koeo calculated load should be 0% and I checked other cars I own to back myself up. Also going to check ecm grounds. Can't get my hands on an ecm pinout for some reason. All data doesn't have one.
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Tuesday, October 4th, 2016 AT 8:49 AM
Tiny
MIKEY300ZX
  • MEMBER
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Also have not checked compression but did a leak down test had little to no leak at all.
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Tuesday, October 4th, 2016 AT 8:50 AM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Here is pcm pics best I can do you'll have to piece together because of size.
Images (Click to make bigger)
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Tuesday, October 4th, 2016 AT 9:33 AM
Tiny
MIKEY300ZX
  • MEMBER
  • 10 POSTS
Ok so I checked compression and did a leak down test. No compression on three cyl and 15 on one. Leakdown blowing air through all spark plug holes. Changing the head and gasket tomorrow via the customer. Thank you everyone have a grew weekend. Not sure why I didn't check compression first. What a dip shit moment.
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Friday, October 7th, 2016 AT 2:59 PM
Tiny
HMAC300
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Hey it happens sometimes you forge the simplest things.
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Friday, October 7th, 2016 AT 3:16 PM
Tiny
SATURNTECH9
  • MECHANIC
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I had a feeling about compression that's why I kept asking about compression. Sometimes we just over think things and think it just can't be that.
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Friday, October 7th, 2016 AT 3:21 PM
Tiny
MIKEY300ZX
  • MEMBER
  • 10 POSTS
The only reason I didn't was because it was running fine and shut off on me but I took the head off and it has a crack on both sides along with a bad gasket. Thanks for the input. Untill next time. I'm out. Thank you everyone!
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Friday, October 7th, 2016 AT 4:40 PM
Tiny
HMAC300
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Hey it happens to everyone done that several times
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Friday, October 7th, 2016 AT 4:48 PM

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