1990 GMC Sierra Won't Start after Plug, Wire, Cap & Rot

JOEF5

MEMBER
1990 GMC SIERRA
V8
2WD
AUTOMATIC
186,000 MILES

The truck was running okay, with some hesitation and occasional back fire through exhaust when accelerating from a stop. Parked truck, changed plugs (.035 gap), wires, cap, rotor. Truck would crank, but not start. It appears to be a timing issue. The distributor is tight and was not moved. We have verified firing order comparing to numbers in the book and on the intake manifold. Checked that the #1 cylinder was at TDC and the rotor was pointing at the #1 wire. We have spark at the plugs. We have fuel spray from the throttle body injector into the manifold. Rotating the plug wires one position either clockwise or ccw caused the motor to backfire through either the intake or the exhaust.

Saturday, July 25th, 2009 AT 11:42 AM

1 Reply

JDL

MECHANIC
16,098 POSTS

Hello, just my two cents, I'd use a gage and check fuel pressure. I've seen tbi injector spray patterns that looked good to me, but the pressure was half, 5psi, should have been around 10. 5psi would not start that v8 I was working on. If I used extra gas or starter fluid down the throttle-body, I could get it started, but, it ran poorly and died quickly. Then I grabbed the fuel pressure gage.

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Saturday, July 25th, 2009 AT 11:59 AM