2000 Blazer No Spark

[Oldsmobile Doctor]

Started truck to warm up ran for a while than died. When you cycle the key you can hear fuel pump running. Checked and don’t have spark at coil. Plugged in known good ignition module still no spark.
Plugged in good coil still no spark. Hooked up computer reader and cranked engine no codes or tack reading while cranking. Replaced crank position sensor and still no start. Replaced cam sensor still no start. Checked the power feed to coil, ing module, crank position sensor and cam position sensor all good. Checked all fuses to ignition and computer all good. Unplugged computer isolated EST pin and sent signal to ignition module and it sparked at coil. Checked for power with LED test light at computer pins from crank and cam sensor. Replaced Computer and still no spark. So now I am stumped 20 ½ inches of snow over the weekend and my 4 wheel drive is down. If you have any suggestions it may be a few days before I shovel any more snow to check it out.

[Autopro1962]

Here is something you might want to think about.
Truck was towed in there was no spark. When cranking there wasnt any RPM signal.I checked power at the ignition fuse and I noticed it losing power as it was cranking. I then tried to start vehicle by not turning the key all the way and it would start.I replaced the ignition switch and it started right up with no more problems

[brcidd]

I had a '95 blazer act similar- only it would try to start when I let off the ignition switch -that is it would not fire in "start" position- but it would hit once or twice when I released the switch to "run" position-- so did you check power at coil in "start" position??? -- mine was only hot in "run" position-- so to double check my diagnosis- I jumpered 12v battery hot to the coil hot inout lead-- and it started right up-- the ignition switch would not supply 12v to the coil in "start" only in "run"-- thus the need for a new ignition switch-- But since this was a job for a favor- I opted to install a relay which activates upon start commaned- and jumperes battery hot to the ignition pink wire under the dash- exactly the same thing the ignition switch does-- and the truck starts every time-- so now all I have done is to guaranttee the ignition is hot through a parallel relay circuit- without installing a new ignition switch- the choice was easy a $10 relay or a $100 plus ignition switch- plus the aggravation of installing it....Sounds like you have replaced just about everything in this truck- I feel bad for you- been there done that--

[Oldsmobile Doctor]

Put a test light from the coil battery terminal to ground on while in start position and while cranking and got power. Put a jump wire from fuse inj1 & ecm1 to battery this should bypass the ignition switch completely still no start.

[brcidd]

Is your security light flashing? does it go off after ignition is on for a few seconds?

[Oldsmobile Doctor]

Security light doesn't flash and goes out after a few secounds. Owned it for 6 years and never had a remote assumed that it didn't have a security system.

[brcidd]

How about crank sensor wires- connector- and continuity back to the vehicle control module?? .... also I had one that was blowing me away once- it was a Ford- I had checked with a meter- every fuse in the car- while the fuse was seated- they all worked-- but what I soon found out, was that some bast**d had pulled a fuse- so that the fuse was NOT there, that I needed to run the car-- so check every fuse slot as well-- I lost about 4 hours on that one......

[old_master]

The pink wire at ignition coil should show battery voltage when the ignition switch is in the RUN and START positions. The white with black stripe wire at the ignition coil is from the ignition module and should pulse while cranking. The black with white stripe wire at the ignition module should show less than 5 ohms to ground. The white wire at the ignition module is from the VCM. The VCM tells the ignition module when to fire the ignition coil. If those check OK, the crank sensor, the VCM, the ignition module, and all of their associated wiring is ok. The camshaft position sensor has nothing to do with wheather it has spark or not. Post your results.

[Oldsmobile Doctor]

Just checked continuity for both signal wires from the crank position sensor to the ecm ok. The truck was running than died kind of ruled out a fuse missing. Also the fuel pump is running, the security system shuts the fuel pump down.

[Oldsmobile Doctor]

Checked the pink wires going to the coil & ignition module and have power. Sent a signal to the ignition module from the ecm (white wire pin # 9 white connector) coil fires with big blue spark.

[83cutlass]

1. Disconnect the ignition coil harness connector.
2. Probe the ignition coil connector terminal C with a test lamp connected to B+.
3. Crank the engine.

Is the test lamp flashing while cranking the engine?

[old_master]

Originally Posted by Oldsmobile Doctor

....Sent a signal to the ignition module from the ecm (white wire pin # 9 white connector) coil fires with big blue spark.

explain...you manually sent a signal or the VCM sent a signal while cranking?

[Oldsmobile Doctor]

If a test light was flashing while cranking wouldn't the coil spark? I did do that though no flashing....... No ignition on not cranking to test the coil and ignition module...I am starting to think that the new crank sensor is bad

[Autopro1962]

Inspect the plug to the crank sensor real good may be a connection problem and take a good look at the tone ring that passes by the crank sensor,back probe the connector at the crank sensor and see if you get a pulse while cranking.
. Using a lab scope check for a square wave signal at the Powertrain Control Module (PCM) connector C1 pin 31 Yellow wire.

2. Check for Battery Voltage (B+) at the crank sensor pin A Pink wire cranking.

3. Check for a good ground at the crank sensor pin B Purple wire while cranking.

[old_master]

Originally Posted by Oldsmobile Doctor

If a test light was flashing while cranking wouldn't the coil spark? I did do that though no flashing....... No ignition on not cranking to test the coil and ignition module...I am starting to think that the new crank sensor is bad

The crankshaft position sensor is an input to the VCM and is constantly monitored by the VCM. If there is no signal from the crankshaft position sensor at the VCM while cranking, (or running), DTC P0336 will be set and the SES light will come on. If P0336 is not present, the crankshaft position sensor, and it's circuits to the VCM are ok.

The VCM applies a pulsing ground signal to the ignition module while cranking, (and while the engine is running). The ignition module in turn sends a pulsing ground signal to the ignition coil. To test for pulse at the module and/or the coil, the alligator clip of the test light must be connected to battery positive, and the test light probe connected to the white with a black stripe and to the black with a white stripe wires. You should have pulse to both while cranking. This checks the VCM output for ignition. If there is no pulse from the VCM at the ignition module, the circuit from the VCM to the ignition module needs to be checked for continuity. Ignition output from the VCM to the ignition module is a VCM output and is not monitored by the VCM, so no codes can or will be set if there is a problem.