98 chevy suburban 5.7 won't start

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biggy-p

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My burb has been down since Thanksgiving, this is what happened I went to go to work on a Monday and it sat all weekend and when I tried to start it it slowly turned over kinda like the battery may have been almost dead I tried 3 time and got nothing, so I decided to take our other vehicle and mess with it when I got home, so I got home and tried to start it and got the same result, tge first time and on the second time I heard a pop noise and smoke coming from under the hood, popped the hood and it backfired through the intake and blew it to peices, so I bought a new intake manifold replaced it and nothing my uncle said it was the crank sensor and same result, so since then I have replaced, fuel pump and filter, injectors, map sensor, crank sensor twice, distributor, plugs, tested the wiring for the injectors, plug wires, and what not, so this is what I have now, strong spark on cylinders 1,7,2,8 and I have a weak spark on 3,5,4,6 any help would be greatly appreciated thanks!
 

SAATR

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Do you have any codes stored?

Have you checked compression on all cylinders?

You said you replaced the distributor and the intake. Was this a new distributor? Is it timed correctly? Are you absolutely certain that it is timed correctly?

If you have spark and it is weak on some cylinders and strong on others, it is possible that your cap is no good. I know you just replaced it, but there have been issues with caps straight out of the box. May be worth your money to swap it again, or get the other replaced under warranty.

I see no mention of an ICM. Have you pulled the ICM and had it tested? Or better yet, swapped out with a known good unit?
 

michael hurd

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From your description, the timing was way, way out to lunch. There could have been many causes, from a distributor cap issue, severe wear on the distributor drive gear, or the timing chain jumped.

Unfortunately the upper intake manifold was the weak link in the system when it backfired.

Check the compression on all the cylinders and report back.
 

biggy-p

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I installed a brand new distributor from summit all aluminum deal and I am going home tonight and making sure the timing is absolutely correct, and I'll check compression on all cylinders tonight I checked 6 of the 8 I figured if 6were good all 8 would be good, but I will check all 8 tonight
 

biggy-p

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Do you have any codes stored?

Have you checked compression on all cylinders?

You said you replaced the distributor and the intake. Was this a new distributor? Is it timed correctly? Are you absolutely certain that it is timed correctly?

If you have spark and it is weak on some cylinders and strong on others, it is possible that your cap is no good. I know you just replaced it, but there have been issues with caps straight out of the box. May be worth your money to swap it again, or get the other replaced under warranty.

I see no mention of an ICM. Have you pulled the ICM and had it tested? Or better yet, swapped out with a known good unit?
I dont have any codes stored
 

Ironhead

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The firing order on the Chev V8 is: 1-8-4-3-6-5-7-2. Distributor rotates clockwise when viewed from the top. It is not unusual to mix up some spark plug wires when working on the cap/wiring replacement job.

I know this sounds kind of real basic, but I posted it just in case it is something this simple. Timing the distributor is the next basic issue.

The backfiring could have been caused by the engine getting fuel with no or weak spark. When it did get a spark, the unburned fuel in the intake could have popped off.

Hope this is helpful when you are trying to diagnose the problem.
 
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