Question about 1990 GMC Sierra

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Changed plug wires now cant start

After changing plug wires cannot get started. Checked firing order it is alright.Maybe I am In wrong location on cap for #1 wire.

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Check for the right location by turning crankshaft till at zero degrees on the pointer scale-the timing scale. Then look at rotor position: should be either pointing to No. 1, or will be pointing directly opposite if you are on the exhaust stroke (TDC) of No. 1. Turn the crank one revolution, and come back to the zero mark. If rotor was pointed opposite before, it should now be directly at the number 1 plug wire tower.

Posted on Jan 03, 2013


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Posted on Jan 02, 2017

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SOURCE: truck turns over but won't start 87 gmc 4x4

Well, if it was running prior to your replacing the plugs, then somewhere you went amiss. Check the firing order. If when you crank the engine over and it pops and backfires then you have a few plug wires mixed up. Other than that the other item to check would be the rotor button in side the cap. Is it lined up correctly or broken? Good luck.

Posted on Feb 07, 2009

  • 1305 Answers

SOURCE: spark plug wiring on distributer cap on firing order

here is the diagram for your engine...
click here

Follow the locations on the cap illustration..

Posted on Jun 09, 2009

  • 850 Answers

SOURCE: spark plug wires diagram for 91 gmc sierra

ok number 1 piston should be a top dead centre & mabe on the top of the cap is a mark or number
if not then there should be a mark on the lip of the dizzy!
if not then just choose one near the front & set the points at that point on the point of sparking! [ready to open points] make sure you have spark or you may have left ou the insulator on the points locating pin!!!
then its a matter of the firing order!
i hope this helps
cheers Rob

Posted on Aug 15, 2009

  • 60 Answers



Posted on Jun 27, 2010

  • 834 Answers

SOURCE: we changed spark plugs &

Here is the firing order diagram for the 5.0 liter (305), 5.7 liter (350) and the 7.4 liter (454) V-8 engines (note position of locking latches/screws between the 3 and 6 and the 1 and 2 terminals on the distributor cap). Let me know if you need the 4.3 liter V-6 engine diagram (hopefully not in a 2500 series truck) or if you require any further assistance.


Posted on Nov 29, 2010

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