95z28camaro

iTrader: (15)

Car was running great then a valve spring broke. Ended up just pulling the motor and had valve job done, new cam bearings and had to replace 1 bent rod. Car is Put back together and everything looks to be hooked up correctly but when trying to start it turns over and just pops and back fires out the exhaust. It sounds a lot like how if you put distributor 180deg wrong direction in an old sbc. Just put a new crank position sensor and planning on putting a new cam sensor tomorrow but car was running good pre hand so I doubt this will fix it. I am stumped.

gMAG

iTrader: (1)

Do you have proper fuel pressure at the rail?
Are you sure that when the coil harnesses were reinstalled, that the correct color coded wires for each coil are connected to their matched coils?
It's quite easy to have the harness on, incorrectly.
If not, you could have the symptoms that you've described.
How long have the injectors been sitting, unused? It doesn't take long for fuel to gum up the internals..

crainholio

iTrader: (2)

During cam installation, was the dot-to-dot alignment of the cam & crank gears verified with a straight-edge or just eyeballed?

95z28camaro

iTrader: (15)

Fuel pressure is good. Injectors have only been sitting 2 weeks.harness is on correctly. Eye balled the two dots. But even if they were one tooth on it should still try to start but just grumble real bad. This is a pretty consistent pop pop pop bang. It's a double roller timing chain. Someone said that the dots may need to be 180 from each other? Both on top?

gMAG

iTrader: (1)

Thanks to "LS1Tech Mod, "Joseph"...

Not many people know the valve events for all 8 cylinders and when they happen. You would naturally assume with the dots aligned it would be the firing position of cylinder #1, when its actually the start of the intake stroke as far as the piston/intake valve is concerned. With the dots aligned cylinder #6 is the one to set preload/lash/ or for installing rockers.

Each 90* (720* / 8cyl = 90*) on the crankshaft gear is another cylinder firing, while each 45* (360* / 8cyl = 45*) on the camshaft gear is another cylinder firing. Having the timing cover off helps to watch the sequence.

Here's a copy/paste of a manuscript I'm working on that may help also:


Quote:
Originally Posted by Joseph
LSX Firing Order 1, 8, 7, 2, 6, 5, 4, 3

TDC Cyl. #1) Camshaft dot at 12:00 / Crankshaft dot at 12:00
TDC Cyl. #8) Camshaft dot at 1:30 / Crankshaft dot at 3:00
TDC Cyl. #7) Camshaft dot at 3:00 / Crankshaft dot at 6:00
TDC Cyl. #2) Camshaft dot at 4:30 / Crankshaft dot at 9:00
TDC Cyl. #6) Camshaft dot at 6:00 / Crankshaft dot at 12:00
TDC Cyl. #5) Camshaft dot at 7:30 / Crankshaft dot at 3:00
TDC Cyl. #4) Camshaft dot at 9:00 / Crankshaft dot at 6:00
TDC Cyl. #3) Camshaft dot at 10:30 / Crankshaft dot at 9:00

If you have that and the timing cover off you don't even half to measure how far you turned the engine over, just line up the dots to the correct orientation and install.


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95z28camaro

iTrader: (15)

Replaced cam and crank sensor with no luck. All grounds are good. All connections are good. I'm completely at a loss on what to do. I just notice that the radio says "loc" does that mean anything? I would think that I wouldn't be back firing if it was lock like its trying to be a kill switch.... Any ideas!?

crainholio

iTrader: (2)

Pull your timing cover and use a straight-edge to verify the dots (crank at 12 o'clock, cam at 6 o'clock) and the cam & crank shaft centerlines are all lined up.

95z28camaro

iTrader: (15)

guess ill be doing that tomorrow night. was just wanting to avoid pulling damn thing back apart if was just something else simple i could have possibly missed ya know. thanks. ill report back with results