got an 05 blazer that stalled and will not start ,tach signal lost , i have ground and power to ckp but no 5v ref , then i unplugged a bunch of sensors and no change , then found i have lost 5v at every sensor on the engine .

anyone have a diagram of pcm to ckp sensor and all attached to the 5 v ref

and nay advice would be awesome .

so just an edit , I’m thinking I need a diagram of the connector at pcm and PIN number for the 5v ref wire for the sensors does that even sound right

also what’s the best manual that would have these diagrams even digital manuals

 

Your crank sensor does not use a 5V ref, only a 12V ref and lo ref (signal ground). See the attached circuit diagram. We need to start here and figure out what is going on and then move to other sensors if you have a more global problem

 

okay i have signal it wouldnt light my test light but shows .18 on multimeter , no tach movement ,cranks but wont start ,bright spark ands i can smell fuel

and your gonna love this , just finished teh intake on my 01 blazer and have the exact same issue but cant see anything i did to cause it on teh 01 the 05 happened randomly while wife was going to work .

 

So the power to the crank sensor is 12V ref on lt green and purple. The signal is seen between . yellow and purple but crank sensor output is difficult to check without a scope.

1. How are you testing for crank signal out and where are you measuring it?
2. Do you have spark while cranking?
3. Do you have proper fuel pressure?

George

 

I just used a dvm , I got 10.56 on the power
0.18 v on the yellow reference wire with dvm no scope here .

I have a new spare crank sensor but no change

yes I have spark it just floods when I crank and no tach movement and no start

 

so just out at the car i have signal on pin 12 yellow signal to ckp test light on when ckp plugged in and off when unplugged , when i plug the ckp in i can hear everything energize , but still no tach movement and no start even with cmp unplugged so maybe i should change the title to cranks ,no start , no tach movement new ckp sensor no change . can passlock be causing this ? it gets spark and fuel but no tach and no start

 

One of the more common Shadetree mechanic tests of the crank sensor is key on engine off a voltmeter on the yellow wire to signal ground and then turn the engine at the crank pulley and you should see the voltage output go from zero to around 10 and change up and down repeatedly as you rotate the engine. Make sure the engine is disable so it cannot start.

If you have spark then you do not have a failed crank sensor. Not to say that it or its circuit may not be marginal but it’s not a hard failure.

With a pass lock failure the truck will start in a few seconds later the PCM will disable the fuel injectors and it’ll die. You really need to test the fuel pressure because it can be not enough pressure or too much pressure which may be why you’re flooding. If that’s not it then we got to get fancy and probably start looking at mechanical problems or spark timing


George

 

Ok so what I thought couldn’t be true actually is … I had replaced the lim gaskets and decided to do the mpfi upgrade with a standard auto products fuel spider that was actually 50 bucks more than a delco , that one misfired on most and dumped fuel into cyl 1 ,

got a replacement on warranty from rock auto and this is what is causing my issue , i didn’t catch it on the koeo pressure test but on cranking it dropped pressure to zero and stayed their after turning key to off , it literally leaked every drop of fuel in a second on the 2nd brand new injector in a week .


Is delco really the only brand that works ?

so back to rock auto and see if they will
return and exchange for a delco .

 

That sucks! I would do an oil change before running the engine.

 

It used to be Delco or Delphi on spiders like fuel pumps. Then as I understand it, Delco was no longer available. I see recently that they are listed again, not sure if that's still the gold standard for quality or if they are just private labeling the same stuff you already have.


George.