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JohnWayne007

305 v8 TBI has spark & fuel but wont start!

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So i let my truck sit for about a month after replacing the fuel filter and fuel pump in my 1996 GMC K1500. I went to go start it today and it just cranks, plenty of fuel squirting into the cylinders of the TBI and i checked for spark, there is spark so i decided to change my plugs with new ones. But no matter what i do it just wont start. I did have the spark plug caps off of the distributor cap, and as far as i know i put them back on in the correct order.

 

Is there anything i am missing? This truck ran perfectly a month ago. I let it sit while doing some body work and exhaust work and now it just doesnt want to start.

Edited by JohnWayne007

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The essentials are fuel, spark, compression and timing. It doesn't sound like compression would be the problem so double check the firing order on your distributor cap with the #1 cylinder at top dead center.

 

Other things might be the O2 sensor wiring since you were working on the exhaust or possibly ECM wiring harness damage or plug problems depending on what part of the body you were working on.

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The distributor cap should have the position of the plug wires on it so I'd check that first. Driver side cylinder numbers are 1-3-5-7 from front to back and passenger side cylinder numbers are 2-4-6-8 from front to back. Distributor order should be 1-7-3-5 on the driver side from front to rear and 8-2-4-6 on the passenger side from front to rear. That's what I remember from doing mine recently.

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If you messed up the plug wires you'd think you'd at least get a pop or a backfire when cranking. Did you check for spark at the plugs? If your truck has the same rinky dink distributor cap as my 98 Yukon they're kind of a joke and after sitting, especially when the cap gets older and if it's been wet or damp they can be stubborn to start. I think what happens when the cap gets bad is yes you do get spark, but it's erratic and is jumping all over under the cap and not going to the wire it should be going to, hence it won't start. I've had a similar issue in the past and again recently with my Yukon, l put a new cap and rotor on it and the thing fired right up, no issues since.

 

Does your cap look like this? >>>https://www.1aauto.com/distributor-cap-and-rotor-kit/i/1aedk00042?f=699211&y=1998&utm_campaign=gb_csv_br&utm_content=EDK&gclid=Cj0KCQjwierMBRCHARIsAHl9i4HNUcqa2OfCGdwyppmvDtnQAvj4EQnDqNMpyKEVpyvri-AH-ZnFYRwaAjd_EALw_wcB

Edited by ifixedit

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Could be timing chain, usually you'll get a backfire if it's that. Same as crossed plug wires. Cap and rotor, control module.

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Forget the O2 sensor issue, no O2 sensor has the capacity to cause a crank no fire condition. ECM is not the issue either with the TBI injector pulsing because the distributor is sending crank signal back to the ECM to fire the injector.

 

Recheck 2 or 3 random spark boots to see if spark is present. If not, find out what is disconnected / broken at / or in the distributor. Find some either and squirt 2 puffs pass the throttle plate. Quickly crank the motor. Did you hear any combustion noises??? Does the motor pop, spit, or make any combustion noise when cranking??? Or does it crank a little faster than normal???

 

The rule in a crank, no fire situation is:

 

Is there a fuel signal, ...yes

 

Is there ignition, you claim spark is present??? It should be because you have TBI pulses. What's going on in the distributor??? Is there power to the ignition coil itself???

 

Is there spark to the plugs present after you reinstalled the distributor cap??? Unknown

 

Mechanical, does the motor turn over faster like it has no compression??? Unknown???

 

Why did you undo the distributor cap when you were "just" changing plugs???

 

These are some of the questions that need to be answered.

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