vance500a

GMC Savana van problem. Van wouldn't start after lunch?

2005 GMC Savana van 2500 with 4.8 liter motor
VIN # 1GTGG25V451226506 116,000 miles

I have a service van with 2 doors in the back and 2 on the side, motor oil and coolant levels are fine and the oil was changed 2 weeks ago. The problem started last Friday the 16th, in the morning after a couple of calls I tried to start the van and it wouldn’t, it just turned over and made a funny ping like the timing was really off or something bad was happening inside the engine. I waited a second and thought that was strange. Then I turned the key again and it started normally and I drove off. Took 2 or 3 other calls then got something to eat. When I came out of the restaurant and tried to start the van it did the same thing. I tried again and the motor would not turn completely over (at least that’s what is seemed like it was doing 4 or 5 times), then it tries to start it makes a loud ping and shakes a lot when I turn the key the 6th time. If I continue to turn the key and let go it the engine won’t rotate much and sort of bounces back. Then, after several tries, it will turn over again and shakes a lot while it misfires like it’s badly out of time then stops with a ping noise coming from inside the engine again. Figured something is bad- wrong. Had it towed and the tow truck driver checked the battery and it had 650 cold cranking amps. I recently changed the starter and since it was under warranty I swapped it out again. No change. Talked to someone I know that works on engines and he said sounds like a timing chain, valve or lifter problem, etc. So I took the spark plugs out and turned the motor over and over with the fuel pump fuse pulled and the power ignition coil packs unplugged. The motor spins and spins, everything sounds great and no pings. No OBD codes either. Put the plugs back in and hooked everything back up and tried to start it again. I doesn’t run and does the same thing. Took it apart again and removed the plugs. Pulled the valve covers and turned the motor over and over, watching the springs, rockers and stuff. Everything looks good and it spins fine. Nothing looks bent. Put in the spark plugs one by one and it’s still spinning great so it wasn’t the plugs either. The problem only happens when I connect the power packs and replace the fuse to the fuel pump. No OBD codes, did a scan when motor torn apart as described – hopefully, that’s not a problem. Does this sound like it could be caused by a crank or cam shaft position sensor? Thanks

canucklehead

What are you using to scan for codes? Some of the the small hand held unit miss things. It sounds electrical to me. The newer engines are way more complex that the older ones. Could be any of the many position sensors causing a timing issue.

vance500a

It's an Actron OBD II autoScanner model CP9175
BTW, thanks for replying.

SnlpeR

what is your fuel pressure like?

vance500a

I'll check it and get back to you.

Ron6519

Turn the ignition on to auxiliary and see if you hear the fuel pump start. I have a 2001 GMC Savana van whose fuel pump just died.

chevy55

the way it sounds is you may have a bad crank sensor,if its going bad it could throw your timing off while cranking.the ecm uses the crank sensor for no 1 timing sequence for ignition firing.if it goes bad it might not be firing on the right cylinder and cause a no start to a hard start.i have come across the older vortex engines where antifreeze leaks from the waterpump weep hole,run down onto the crank sensor and in the plug.when that happens it causes the timing to go out of wack,cause a back fire and bust the nose off of the starter.hope this helps.

canucklehead

Vance never got back to us.....lol.

greenfire

As usual... Should be a 5 post minimum before you can start a new thread. Most people just want free advice, rather then to be part of the community.

canucklehead

I don't mind the questions. I like to help if I can, but its the OP posting the actual result/fix that cements it.