Distributor replace/align

[RawbDidIt]

Ok... weird thought here. I wonder if your harmonic balancer has failed. That would cause your timing mark to be off, and cause issues with timing resulting in weird bouts of running lean and rich, as your plugs are indicating. I'd verify the cylinder is at TDC when the timing mark says it should be. I used a boroscope when I did mine, but you could use your glove finger, should start deflating when you rotate past the mark. If that checks out, the only other thing I can think of is the distributor gear being worn out. I'm guessing that's not it since you've pulled it, and hopefully inspected it for wear.

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[Schurkey]

The magnet is visible once you take the rotor off, although it's mostly covered-up by the rest of the mainshaft assembly.

One of these days, I'm gonna take pictures and start a new thread...

https://www.gmt400.com/threads/tbi-hei-small-cap-hei-ignition-problem-areas.52686/

 

[Schurkey]

Now she'll turn over and over but no start. Have checked plug wires (I labelled them all) and firing order (also labelled cap). Ignition coil is connected, pickup coil is connected...

Did i put the distributor in 180 degrees off?

Make sure all the fuses are good. Install a grounded spark-tester in the coil-wire terminal of the ignition coil. Crank engine while watching spark tester and watch the fuel injectors also.
Do you have spark at the coil wire terminal of the ignition coil?
Do the injectors spray fuel when cranking?

No spark, fuel sprays = ignition problem (ignition coil problem, wire harness problem)

No spark, no fuel spray = Pickup coil problem, module problem, wire harness problem, failed ECM

Spark and fuel, but won't run = ignition timing problem, or cap/rotor/plug wires, which may have fouled the spark plugs.

Does the engine run when you disconnect the "Ignition Timing" connector? If so, I'm thinking failed ECM or broken wires in wire harness between ECM and distributor.

 

[pmndlt]

Interesting read @Schurkey I will have a look at the two I have (new/used) in the AM and compare. Wonder if it was weakened/cracked before it left the factory floor? @RawbDidIt I'm not sure how that would happen this is already deeper than I like to go lol.

I did try two more things - 1 back to TDC (no cylinder confirmation) and swapped the distributor 180 per another suggestion - My father-in-law. Man was a great mechanic/bodyman but had a stroke 5 years back so he's tough to understand sometimes.

Anyhow no change. So for the sake of it I went back to the initial distributor and swapped it as is - I've got it marked on the intake and distributor plate. And thats as close as it got to firing again, backfired once but at least I know it's firing as my timing light was flashing.

I'm thinking now I may be on exhaust stroke? I should've tested it properly but my poor wife is tired of me for one day so I thought it'd be easier to just swap directions on the distributor.

tl;dr I'm swapping distributors and directions in the hopes I can at least get this POS out of the garage this long weekend. Thanks again for all the help you guys! Cheers.

 

[pmndlt]

@Schurkey just caught last post after my novel. I will try the EST plug in am. And confirm spark/fuel. Thanks!

 

[pmndlt]

Morning guys. So here's what I did. After second guessing myself for the last day and evening I went right back to the original distributor, cap and rotor and marks. Fired right up. Code for EST (42) registered which was fine as it was unplugged. Couple questions for you just so I can learn from this painful experience.

1) Is it possible the new distributor failed before I got it - it is a reman.

2) GM tech reported no injector pulse when engine stalls (I have no idea how this is tested - scoped?)Is it possible no distributor pulse was from weak spark plug connection? I noticed yesterday a couple of the wires on the plugs need almost an extra push - they click in twice, seemed odd but wonder if this was part of the issue?

3) Should I run the truck with the EST disconnected to see if there is any change in the stalls?

4) Will pick up a spare ignition coil today and if the stall continues I will replace that first to see if it betters.

I'm not into frosting this pig with new parts if I dont have to but as we're using it for a an old camper I'd like it to run half decent.

Have a great day everyone. Thanks again for your responses and suggestions.

 

[JeremyNH]

Question: your first post is "no pulse from distributor" and your last is "no injector pulse". That's two different things. On the Vortecs the distributor controls firing by mechanical timing but the PCM controls fuel to the cylinder by pulsing the spider injector to each cylinder with which one being determined by crank position. The cam position sensor on the distributor is simply used to tell the PCM when it is the #1 cylinder at TDC compression since the 4X reluctor on the crank can't resolve crank position fine enough to know if the #1 (and therefore the other eight) cylinder is on compression or exhaust stroke but only that it is at TDC. The pcm can therefore tolerate a bit of slop on the cam position sensor but the distributor rotor itself needs to be precise since it directly fires the cylinders. If the spider isn't getting the fuel pulse then it could be wire or PCM. It's also possible you're not getting fuel from the spider poppet when it's pulsed since they are well known to clog (so PCM sends pulse to fuel a cylinder but no fuel delivered). So it depends on what the tech meant when he told you "no pulse".

 

[PlayingWithTBI]

On the Vortecs the distributor controls firing by mechanical timing

Sorry, we're talking about an 88 with a TBI system.

 

[JeremyNH]

Sorry, we're talking about an 88 with a TBI system.

Apologies. I had misread it as a 98 not an 88. What little knowledge I have is only on the 96+ trucks.

 

[PlayingWithTBI]

I had misread it as a 98 not an 88