My beater work van. 07 chevy express 1500 5.3 4l65e automatic. 428k on van, question marks on engine. Has a reman tag.
It cranks for a long time before starting. Like up to 15 seconds. Once started it runs incredibly, pulls hard and sounds great.
In an attempt to fix this, the van has a brand new fuel pump/regulator/filter assembly, blew the lines through with air, changed out to low mile injectors, used hptuners to tune out the anti theft and scanned it to verify cranking rpm to eliminate crank sensor as a culprit.
Also the van came with bosch plugs, which in my experience suck with gm, so it has brand new ngk plugs and denso wires. Also changed map sensor because it was easy and i had a known good low mile one here. All grounds cleaned and good condition. Also it does it with maf plugged in or not.
Fuel pressure is 60 key on, 58 cranking and running, and steady.
Where would you go from here? I have the ability to scan every parameter, so if someone has a clue what to look for i'll plug the laptop in and go.
What's the cam signal like?
It seems to me that gm's resort to long cranks when a cam sensor fails and goes batch fire as a failsafe.
You seem to have already hit all the common problems.
Check your crank and cam sensor sensor signals. Any change between hot and cold starts?
Ranger50 wrote:
What's the cam signal like?
It seems to me that gm's resort to long cranks when a cam sensor fails and goes batch fire as a failsafe.
Will check that sunday, going to jersey tomorrow
Actually have the doghouse off and another known runner sitting here, may try it tonight
The Hoff wrote:
You seem to have already hit all the common problems.
Check your crank and cam sensor sensor signals. Any change between hot and cold starts?
Doesn't make much difference hot or cold. Rarely it fires right up but that's pretty uncommon
I have another 07 express and it fires immediately like any other ls/lq vehicle i've had
Actually we have 3 2007 ls engined vehicles, not sure that ever clicked with me. Weird
Give it a shot of starting fluid and see if it fires right away. At least then you'll know if it's a fuel or a spark issue. Do you have a noid light?
Starting fluid doesn't help it start quicker, forgot to mention that. I do have a noid light set
I'm convinced its spark related since i can smell raw gas in the exhaust as it cranks
It sounds like cam and crank sensors are the next thing I would check also. I'm guessing you already checked for any trouble codes.
p0342 cam sensor circuit A low.
replaced with known good sensor just now, cleared codes, still cranking long time and still setting the p0342 immediately.
probably have to probe the cam sensor wires next to see if it's getting power and signal
Just had the multimeter out. Red wire is ignition voltage, pink/black is ground through pcm, brown/white is signal and it should be live 50% of the time as its a 1x signal.
I have ignition voltage at red(to ground). I have ground at pnk/blk confirmed to battery power and ignition voltage line on connector. I stripped the signal wire and clipped it to a test lead and then to my multimeter, and spun engine by hand. 8 ratchet spins zero volts, 8 ratchet spins ignition volts. So the sensor is good(so is the one i took out), it's producing signal half the time so the cam wheel is good. Now I'm at bad signal wire, bad connection of signal wire to pcm, or bad pcm. Going to bed. Easy button is pull the pcm from my other 07 express and see if it fired immediately with no cam sensor code.
I read that when pcm sees no cam signal it changes firing order between normal and 180 off trying to see where tdc is until it starts, sure sounds like that's happening while cranking. Will have to break out the schematics to see which wire on pcm connector is cam sensor signal and probe it. Should be good, harness is in excellent shape. Would hate to have a bad pcm at this point but it sure is getting closer to looking that way.
I may eat my words, i stripped cam sensor signal wire at pcm connector and while i was reading voltage at the sensor, i was getting nothing at the pcm. I jumped the stripped sections together with my test lead and it fired up almost immediately. Going to run a new permanent wire tomorrow now that i found a fault. Still have to fire it hooked to the scanner to verify the code isnt being set, but hopefully this one is licked. Life can continue if this is fixed and behind me, can move on to making sure the datsun is going to be ready for the challenge
Cam sensor issue fixed, fires right up now.
Next issue popped up, rev once and then the pedal quit moving the throttle. Threw tac module and pedal communication loss code. I wiggled the wires and plugged/unplugged the module and throttle body repeatedly in an attempt to clean the connections. The last time i was able to keep revving it and didnt set the code. Tomorrow should be able to run it longer and hope that cleared up. It's been sitting since February when i got the other van.
still losing com between tac module and pedal. it's not the number of revs, it's about 25 seconds into running.
