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94' GMC TBI only cranks after rebuild, sputters but no start


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JaymeCDS
New User

Aug 14, 2011, 12:51 PM

Post #1 of 2 (2747 views)
94' GMC TBI only cranks after rebuild, sputters but no start Sign In

HELP! I need a GMC guy familiar with the 5.7L TBI engine. I tore down the motor and rebuilt the transmission. Had the block machined, crank cleaned, new piston rings, same pistons & rods, higher lifting cam (CompCam says install same as factory), new cam gear, new crank gear, double roller timing chain, stiffer springs, same valves just severly cleaned up, new roller rockers, all new gaskets and seals, new cap and rotor on distributor, new plugs and wires. After reassembly, I got the motor to start but the RPMs were all over the place and the idle was just rough, timing seemed off. Reset the mechanical timing at 6 and 12 on the gears and set the distributor in at #1 TDC. Firing order is correct on plugs. I've already unplugged the timing wire to try and set the timing but no luck. Can't even get the thing to start now. It just cranks and sputters a little but won't fire up. I've set and reset the both the mechanical and distibutor timing with no luck. I'm exhausted, any ideas?


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Aug 14, 2011, 7:05 PM

Post #2 of 2 (2716 views)
Re: 94' GMC TBI only cranks after rebuild, sputters but no start Sign In

If you have the cam gear dot 6 and crank gear dot 12 and install the distributor pointing at number 1, you'll be 180 degrees out on the distributor.

If your valves are adjusted too tight, it will idle really rough or possibly not start.

One trick is to get number one TDC on compression stroke and then install distributor with rotor pointing at the number one cylinder. You should be able to draw an imaginary line from the center of the rotor to the tip of the rotor to number one cylinder. That will get you in the ball park for it to start.

Valve has to be closed on the particular valve your adjusting lash on. At zero lash, which you can feel by spinning the push rod, give it 1 full turn to center the lifter plunger.







Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Aug 14, 2011, 7:31 PM)






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