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1989 3500 GMC truck WONT START!


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bigchillenhustla
Novice

Mar 9, 2009, 11:11 PM

Post #1 of 4 (2425 views)
post icon 1989 3500 GMC truck WONT START! Sign In

1989 GMC TRUCK 7.4L

History
Working truck, recent oil change, and spark plugs.
My dad says he was driving, switches lane, he hears two POP noises coming from the muffler and then the truck shuts off.

Problem
It's a throttle body injector type. It's cranking, but wont turn on. There was green corrosion around the module inside the distributor. There is no spark going to the spark plugs. Also, the fuse box is all messed up. Wrong fuses and broken plugs for it. Some missing.

Elimination of problems
Got new spark plugs, wires, and a module. Cleaned off the green corrosion off of these two wires that connects to the module. Replace some fuses with the right number in its spot. No smokes, no weird or loud noises..Tested the coil, it works (sparks) Tested the distributor, ITS TURNING...but still no start!??

HELP

..and i did post another one about the pontiac ...i need help on both right now please!


(This post was edited by bigchillenhustla on Mar 9, 2009, 11:15 PM)


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Mar 10, 2009, 4:40 AM

Post #2 of 4 (2420 views)
Re: 1989 3500 GMC truck WONT START! Sign In

Presumed spark at plugs so now let's check for fuel. Prime throttle body - starting fluid, carb cleaner may work and see if it will react or start for a couple seconds.

How many miles on this old 454?

T



bigchillenhustla
Novice

Mar 11, 2009, 7:40 PM

Post #3 of 4 (2415 views)
Re: 1989 3500 GMC truck WONT START! Sign In

Okay I got the truck to start.

The PROBLEM was the rotor inside the distributor cap wasn't working so I bought a new one for three bucks and that did the trick. The truck turns on, BUT it's no right. It's idling very rough and shuts off. I'll turn on, rev it, seconds later it'll shut off again. The FIRST time I got it to run, rev it and fire shot out of the engine from the throttle and almost burn my face. It's not back firing anymore, but it's very weak and drive horrible. Every red light, it'll shut off and I have to turn it on again.

Whats the deal???

Is it bad timing?? I think I gapped the spark plugs a little too much at a little more than .60 idk

Help


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Mar 12, 2009, 2:40 AM

Post #4 of 4 (2407 views)
Re: 1989 3500 GMC truck WONT START! Sign In

! Just found spec (can be wrong) for plug gap of .035 and if so the .060 is a bit much.
What type of plugs did you use?

HOW MANY MILES IF KNOWN?

Timing is in question as is dist. cap, wires and the rest of a tune up. Don't try to adjust it and if you touched it say so.

Timing should be where it was when last operating properly and decal has specs/procedure for that but if you would just check a few cylinders for compression it would help.

Reason for asking miles: Timing chain may have jumped. That would initially cause the odd backfires or the pops in exhaust if so. You could check for the timing marks, leave on TDC, turn engine by crank bolt while watching the rotor you just replaced. Go forward and back just to see how many degrees the crankshaft turns before the rotor moves. That's critical info for the age of this engine!

T







 
 
 






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