won't crank after rebuild

[depotdave]

I have a 2005 TB LS. My normal shop returned a report of low compression on #3 cylinder and recommended a replacement head. After reading about the problem of replacing a head in-place, I pulled out the entire engine. I have currently replaced the head and have everything reconnected, all fluids filled, and new battery. Attempting to start engine, only response is clicking noises from power fuse box, without cranking. All systems appear to operate, but no cranking. No security lites, only check engine and battery lites. What is next step? A tow to dealership for reflashing PCM? Please help.

[carriedi]

no, no, don't even worry about reflashing yet. You need to check for your connection at the starter solenoid, If the engine doesn't crank. do you have power to the start terminal on the starter solenoid when you turn the key to start? Just start with the basics first. you need get your engine turning over. Once it is cranking you can check for spark, fuel pressure and injector pulse.

[depotdave]

not sure whether or not last post went through, so again: I get 6+ volts at the solenoid when attempting to start/crank. I can hear relays switching inside the underhood fuse box. I have also noticed that the driver's side headlight doesn't burn as brightly as the other as headlights come on at "start/run". Any other thoughts?

[depotdave]

After further review, the headlight issue appears to be due to driver's side having a foggy/weathered lense. For kicks, I removed and reattached the prpl wire at the solenoid, to no avail. I have also checked the NPPS (neutral/park position switch) which seems to be operational. The gear selector indicator in the instrument panel (IP) is coordinated with the gear shifter.

[carriedi]

you should be getting battery voltage at the starter solenoid. check you ground connections. make sure you have a good body ground and a good engine ground. also make sure you have a good connection for your positive battery connection. If you only have around 6V at the solenoid it won't be enough to hold the solenoid down.

measure the voltage drop between your negative battery terminal and your engine block or your starter assembly. when you go to start the truck the voltage drop should only be about a half a volt or so.

if the starter wire from the ignition switch only has 6V you might want to check your fuses real quick. check from the negative battery cable to all the fuses with the key in the on position. If they all appear to have battery voltage (12V) you may have to check your voltages from your ignition switch through to the starter solenoid.

check the voltage on the fuse that says "IGN A" it's fuse 34. it should be a 40A fuse in the underhood fuse panel. It's the power to the starter relay for the starter solenoid. If you have battery voltage there, compare that to your voltage on the purple wire to the starter solenoid. if you only have 6V on that wire try switching the stater relay with another relay that has the same numbers on it. You could have a bad relay. every time a relay clicks on and off there is a little arc. sometimes the arcing will leave a burn mark on the contacts in the relay. after a period of time the burn marks can cause higher resistance that could take away voltage from the circuit.

[depotdave]

Checked ground connections by checking resistances between Bat (-) to body and to engine block. checked zero/good. checked all relevant fuses visually and/or electrically across fuse(s). relevant by identification on electrical schematic. got to thinking about goodness of ignition switch. checked for bat voltage at injector pink plug with switch turned to "on"; checked ok. still suspect of the ignition switch internals/continuity, especially in the "start" mode. also suffering from TMI circulating w/in my brain. I will attempt to further investigate the switch tomorrow. any pointers? and thanks for your time and effort already spent on my issue. I absolutely hate sparky issues. guess 'cause one cannot see nor visualize those pesky electrons floating around.

[carriedi]

you could always try a remote starter switch, (a jumper to the purple wire from the battery to give the starter solenoid 12V just to see if it will turn over)

[depotdave]

I have tried the remote starter and still no crank. Tonight I removed the console to get to a Trailblazer Park/Neutral solenoid, which is attached to the shifter and prevents shifter movement without the brake being depressed simultaneously. It also will capture the key from being removed if the shifter is not in Park or Neutral. I am at my end and plan to take it to the auto shop as my next step. results will be posted.

[carriedi]

ok, maybe we are talking about different things. you say it won't crank. ok, that means that the engine won't turn over. the remote starter should be hooked up to the starter solenoid or the purple wire that connects to the starter solenoid. That bypasses everything. If you have power on the battery cable to the starter and ground from the negative battery terminal to the block, your starter should turn over. It will turn over even if it's not in the car if you have it hooked up like that. Have you checked your starter relay? The purple wire to the starter solenoid gets it's power from that solenoid. Your ignition switch sends a signal to the crank fuse. from there it goes to the pcm. The pcm sees the signal from the ignition switch and looks at the neutral safety. If it sees the key in the start position and the neutral safety in the correct position the pcm sends the signal to the starter relay.

pull the starter relay and check it. use a 12V test light and find out which prong is from the "IGN A" fuse. Place the clip of the test light on the ground terminal of the battery or a known good ground. Find the one that has battery voltage all the time. verify it by pulling the IGN-A fuse and it will go to open. that's your power to power up the starter solenoid. the prong that is diagonal across the plug-in should be your starter solenoid. It should show a ground connection. the other two prongs are for the connection that engages the relay. check to see if you are getting the signals from the pcm to close the contacts in the relay.

working on the engine, even replacing the engine shouldn't cause a problem with the pcm.

Are you having a problem with getting the key out? or taking it out of park?

[depotdave]

Final score: auto shop 1, shade tree mech 0. Not quite the problem of the nut behind the wheel, but close; the loose screw (bolt) at a ground connection. Continuity check with low powered multi-meter checked ok, but high-powered engine starting didn't happen, because of that loose connection. Thank you mystery mechanic for your thoughts and inputs. They saved me a bunch, not going to the dealership. Best wishes to you.

[carriedi]

Ah yes, the poor ground connection. not the no ground connection that would be easy to find but the poor connection that will show ground but just not enough ground. A voltage drop test is needed to find that easily. Use your volt meter and measure voltage from the negative battery post and the starter ground (like the engine block somewhere, and though it may look good, you must check it when you go to crank the engine. It may show zero volts when not cranking but when you crank the engine it will shoot up and show you how many volts you lost to the circuit when you put the key in start.

glad it was something simple and didn't cost you a whole bunch of money to find. Congrats.