HELP. LT4 swap won't start.

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Oct 11, 2007 | 09:14 PM

grogetter

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Heel & Toe

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From: Georgetown Texas

HELP. LT4 swap won't start.

Swapped out the lt1/4l60 for an LT4/ZF6 speed, now the LT4 won't start.

Double checked the cam installation and it's good. Using the same sensors and harness, except for the trany connection. Had the PCM reflashed by PCM for Less and looks like the spark timing is about 80 degrees AFTER TDC.
I've checked the plug wires, I have spark , fuel pressure and the injectors are firing. WTFO!!!

Thanks in advance!:o

Oct 11, 2007 | 09:58 PM

96GS#007

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Joined: Apr 2000

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From: Texas

Quote:

Originally Posted by grogetter

Swapped out the lt1/4l60 for an LT4/ZF6 speed, now the LT4 won't start.

Thanks in advance!:o

Probably installed the Opti wrong.

How do you know the spark timing is 80* after TDC? If you watch it with a scanner, all you'll see is what's programmed into the tables in the PCM.

Oct 12, 2007 | 08:10 AM

grogetter

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Joined: May 2007

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From: Georgetown Texas

Can it be installed wrong? It's keyed to the cam drive pin.
I used an OLD tool called a "timing light".

I had previously marked the harmonic balancer, so I could see where TDC of #1 piston was to check the cam install.

Oct 12, 2007 | 11:39 AM

0Paul Ruggeri

Former Vendor

Joined: Nov 2006

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From: Carmichael ca

With the engine at TDC #1 cyl., where's the rotor pointing? If its 40 degrees (80 degrees of crank rotation) past the #1 cyl. terminal on the cap as your timing light suggest then something is misaligned. I can't think of what it could be though if the cam timing is correct.

Paul

Oct 12, 2007 | 05:36 PM

hgh pwr

Racer

Joined: Nov 2002

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From: palm harbor fl

yes it can be installed wrong ask me how i know. I would check it first,you can start the car without the water pump and the sensors installed to see if it starts then you just clear any codes later.

Oct 12, 2007 | 07:05 PM

96GS#007

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From: Texas

Quote:

Originally Posted by grogetter

Can it be installed wrong? It's keyed to the cam drive pin.
I used an OLD tool called a "timing light".

I had previously marked the harmonic balancer, so I could see where TDC of #1 piston was to check the cam install.

Yes, even the later Opti's can be forced into place wrong.

Timing light....went to the auto parts museum huh?

Oct 12, 2007 | 10:40 PM

grogetter

Thread Starter

Heel & Toe

Joined: May 2007

Posts: 19

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From: Georgetown Texas

As a great philosopher once said, DOHHHHHH!
Yes, it can be installed incorrectly. Amazingly, it took hardly any force at all.:o :o :o

Yeah, the timing light is an antique, but for an old guy like me, it's just about the right speed for psychadelic lights. OOPS, I think my age is showing
Far out, man.
Thanks to all.

Oct 13, 2007 | 02:52 AM

kylebuck89

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Joined: Apr 2007

Posts: 10,215

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From: Lafayette LA

St. Jude Donor '09

Quote:

Originally Posted by hgh pwr

yes it can be installed wrong ask me how i know. I would check it first,you can start the car without the water pump and the sensors installed to see if it starts then you just clear any codes later.