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Need more ideas for a no start blazer...

jjlaughner

jjlaughner

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Hey all, back to get some ideas on my 2000 ZR2 blazer, 4.3Vortec, $wd, ac all the goodies

Symptoms - Ran Lousy, hesitated often, died occasionally, now it won't start. new alternator, battery and fuel pump (other issues), replaced in the last 18 months.

First no start:
Cleaned the Cap and rotor, reinstalled started but ran lousy down the road under load. Seemed to run ok under full throttle. Had a scanner on it, only code thrown was Multi Spark Discharge, once it was cleared no more codes, but still ran lousy.

The Distributor had a plastic ear broke off which kept the cap from screwing down tight so I replaced the Distributor, cap, rotor with a Summit Metal body. Still no start, swapped out the pickup in the distributor and still no start.
Checked plugs, re-gapped, all fired.

Checked fuel pressure, 60+ PSI at the back of the throttle body (on fuel pump #3).

Thought maybe a clogged Catalytic converter but it has decent pressure at the tail pipe while turning over.

Tried spraying starter fluid in it doesn't even act like it wants to start but did backfire. Tech said try starter fluid, if it started then died it would be the injection spider system; if it didn't it would be a computer issue.

Picked up Computer off ebay for $50 swapped it, still no start, stole the neighbors computer swapped it in, still no start, mine worked in their truck...

What else can I try? I'm stumped... probably something electrical or something stupid I'm forgetting...

When the Hazzard lights/ turn signal was replaced under recall about a year ago they put in a new ignition switch in the column as well as relays and turn signal level... so I ruled out ignition switch since it ran after it was replaced and was running poorly before it was replaced...

:dunno:

Coil maybe? It has fire at the plugs...

Ideas?
 
couple questions,


- the spark plugs are firing right? If I read it right you say they are.

-crank position sensor if they are not firing would be a tree I would bark at.

-are the dash lights now working? When you crank do they not light up? If the switch and ignition switch harness are bad or one of them it can cause a crank but no start.

- any corrosion on the screws inside the cap?

-wiggle the coil. Is it loose? if so replace.

-fuel pressure relay, swap it with a relay next to it to rule it out.

-fuel pressure regulator.. you may have 60 psi but is it before or after the pressure regulator you are getting this measurement?

-check and see if you are getting the correct voltage at the alternator and battery.

-check where your injector circuit and plug is, pull it apart and make sure no fuel is inside.


-trans... Might sound odd, but you should have an electronic controlled trans. my 07 had the wiring plug come loose/off and it caused a no start situation. On this note next tree to bark at or consider is a neutral safety switch and that could be in the trans with the newer electronic versions?

lastly the starter to battery cable and grounds.. they could be corroded even under the insulation.


added more thoughts
 
Last edited:
HEY SUPERSIZE!
Question for you,
crank and cam position sensor if bad wouldn't relay timing info the computer so the plugs wouldn't fire would it? Mine have fire, and the cam position sensor is in the distributor, that was replaced. The Crank Position sensor is on the front of the motor, That I think I ruled out because if it where bad there would be no fire (timing info at the computer)... It's on or off basically...

Am I wrong on that one?

As far as the spark plugs, they are firing, seem bright, I've checked my order a couple times on the wires, all looks good (on firing order). This was a steady decline in how the truck ran, so I assume the wiring order was right before... I blamed it on the distributor ear being broken and cap/rotor corroding originally, but all of that is new and tight now!

I have not checked the transmission plugs, that didn't cross my mind although I did check the Neutral safety switch and tried starting it in Neutral.

I have noticed since its not been starting, in the run position and in the acc position the windows won't roll down... Thats just odd. I've checked all the fuses several times also.
 
jjlaughner said:
HEY SUPERSIZE!

I have noticed since its not been starting, in the run position and in the acc position the windows won't roll down... Thats just odd. I've checked all the fuses several times also.
Click to expand...


dash lights acting funny?

what your saying makes me wonder if it is the ign harness or switch.

go check that injector harness too, I helped diag one of these a couple years ago and there was fuel that had made its way where it did not belong.
 
Sound slike a couple more things I can check...

Yes the dash lights work with nothing more than the service engine light on, while sitting in the on position, not started. Hand held scanner does not show any codes currently, but the engine is not started so it may not. *NOTE: about two years ago I did have issues with the dash going blank then popping back on but the engine performance never failed at that point or during the "blackout", its was like someone just turned the dash off and back on.

Fuel pressure, I'm measuring the PSI off the inlet line to the back of the throttle body, its has a pressure valve/release/inj cleaning bung on the line itself. Gauge reads 60-62psi in the on position. I'm not sure where the regulator is I'm guessing inside the throttle body or on the pump in the tank.

I've sort of ruled out fuel delivery since the truck did not even try to start on starting fluid. Since I have fire, I have been leaning toward electrical gremlins but I have yet to track them down!

I think for now I'll rule out the tranny issues since it was a steady decline in engine performance leading up to the no start. But I will still check the plugs/connections.

I think I'll start today checking that wiring harness, anything specifically to look for beside nicked or cut wires and corrosion?

Connections at battery and alternator look good, I have not checked the starter end yet.

Headed out now.

One other tid-bit, oddity, The day I got it to start and run it was about 20deg that morning, went inside got ready for work and was leaving about noon, it had warmed up to about 30-35deg and thats when it did not start. That night it started in 16deg weather, but the next morning at about 30deg it did not. If it where an electrical connection you would think that the cold would retract the broken connection and it would start when it was warmer, but its just the opposite...
 
hmmm


google

vortec blazer injector harness or vortec blazer no start harness

should bring up lots of hits.


The plug im talking about was the injector harness gm push lock plug, the wires had corroded to hell it was junk inside. I see this online too with others.


do not just rule out the dash issues it is common
 
Friend had a later small blazer with the vortec 4.3 and had a bad spider injector thingy, we checked alot of things then finally replaced the spider thingy and it fired right up first crank. We had decent fuel pressure also.
 
Just trowing this out have you checked the body to battery gorund wire and motor to body ground wires?

Had a Chevy Astro that had bad ground wire and would not start.:dunno:
 
Well I have an update, it still hasn't fired up. But it did some whispy blow backs and a back fire with pouring fuel into the Throttle body. I unhooked the battery and pulled every harness plug, all them where still clean and shiny, easy to pull and replace, no corrosion (surprisingly). I cleaned all the power, ground, starter, fuse panel connections and alternator (all popped off easily and showed no signs of major corrosion, just a little green on the wire ends but the connectors where good). Pulled the fuses and wire brushed them, swapped around the ignition relays, pulled the TPS off to see if it was oily or had fual in it, it was clean and dry. Hooked the battery back up after letting it charge, put the battery charger on and set it to 100amp jump just for the boost, and still no start!

I think I'm back to my first thought... Timing belt. Tech told me that the belt couldn't slip if it did there would be lifter noise. With the whispy blowbacks through the throttle body and the big back fire, along with the steady decline in the trucks running, I'm thinking the belt slipped a couple notches, the computer adjusted, slipped a couple more and now its so far out that the computer cant adjust. Which might explain why when it was below freezing it would start, idle, but not pull its weight down the road. If the belt shrank it might have been holding tight enough to start.

So timing belt? Thoughts?
 
supersize75k5 said:
put the fuel injector plug/ harness at the top of your list
Click to expand...

I checked this while pulling all the connectors, it was clean, dry, shiny as where all the connectors in the intake. Only thing that looked funny was a oily substance in the TPS connector but I cleaned that, pulled the TPS off and the inside was clean and dry. I did find the fuel pressure sensor on the intake, it was clean also.

The neighbor guy came over and helped listen to noises while turning it over and he noticed the whispy blow backs in the throttle body / air intake, I couldn't hear them before, but I think the timing is off. With the new distributor, installing it top dead center on #1 and the rotor pointing the same way as the old distributor that came out I'm confident its back in correct.
 
The 4.3 does not have a timing belt, it is a chain and that is easy enough to figure out if it has jumped teeth (never in my career have i seen a chain jump, they usually break). Pull the #1 spark plug and crank engine until you get compression coming out of the cylinder then slowly rotate the engine until the timing mark lines up and now pull the distributor cap and see if the rotor is pointing to the #1 wire in the cap, if so no problems there (unless you reinstalled the distributor wrong when you put it back in.
 
Yeah I was looking at parts online this afternoon, all showed Chains. Well then I'm not sure what to do now! Might have to break down and take it some place. I need to get this truck running and or sold before the snow flies so I can get my K5 floors and exhaust done to drive it.

I know when we took the distributor out (the truck was not running at this point), we did do the compression/tdc test and it was pointing to #1, we pulled the old out and put the new dist in pointing the same direction.
 
my guess would be an ignition module. Seems like a lot of 4.3 I have seen had some problems with these going out.
 
My father always reminded me ... You need three things for a car to run:

1. Compression
2. Spark
3. Fuel

In your case, I would remove the spark plugs and rotate the crank until you can check the timing marks line up.

I would then put the plugs back in and hook up a compression tester and check against the specs. The important part to remember about this is that the valves are opening at the wrong time or are not fully closed you won't have compression.

Then check fuel pressure and flow. Do it right, pull an injector and measure the flow per the shop manual. Your injectors may be flowing too much if they are worn out causing an over-rich condition.

Then check for spark.

Then check to be sure you have the correct firing order. (I've never messed this up! :lol: )

The backfire tells me you're firing while an intake valve is open (timing) or you're running way too rich (fuel pressure/delivery).
 
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