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Old 10-23-2006, 05:49 PM   #1
davsmitty
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Timing problem=STUMPED

Ive got a headache for all you mechanics. My 86 GMC 1500 305 w/ a Q-Jet is doing some very strange things. It was driving fine until I turned it off, then it never started again. We checked everything in the timing assembly and ended up replacing all of it, reset the #1 cylinder to TDC and set the distributer to the number 1 tower. Now it cranks but wont start. We checked the plugs and they're all good, made sure the rotor is where it should be at TDC and it is, checked all lines and the're good. The carb was flooded so we cleaned it out and put it back together CAREFULLY. We finally checked the voltage at the distributer and it sits at 13.3 until we crank it and it DROPS to ~9vdc.

Do any of you (wally, hobo, any other mechanics) have a direction to point me? Repost if I missed something.

Thanks, David
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Old 10-23-2006, 10:53 PM   #2
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So when you crank it, does the timing light flash? Have you tested compression pressure? Have you tried rotating the dizzy a tad while someone is cranking? Are you sure it's not flooding (drain bowl, cut the fuel and put a teaspoon of fuel down the gullet to test for signs of life)?

I assume if you timed the spark 180 (cam) out of phase you would at least be getting some decent backfire through the carby.
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Old 10-24-2006, 03:41 AM   #3
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Yeah, we tested compression and all 8 are at 180psi. We made sure to install the timing gears correctly and didnt move the cam. Yes, we tried adjusting the distributer a little at a time while cranking. The timing light does flash, and we reset at TDC and pull the dist. off ->the rotor is seting right where it should be. The carb was flooded so we drained it out and pluged the feed and poured a little in, didnt help.

Could the starter be going bad and building resistance? The batt is weak at best but we have it pluged into a charger, tested the voltage at the dist. and its at 13.3vdc but drops to 8~9 when cranked. The starter and spark plugs are the only things left to change.

We've all been having dreams about it and they're starting to turn to nightmears.
thanks
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Old 10-24-2006, 05:19 AM   #4
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Are you absolutely sure both No1 valves are closed when the rotor is pointing at No1 cap electrodes? I guess the timing chain cogging would be out of the question?

OK next test should be to make sure your coil or ignitor isn't dying. What resistances are you getting on the primary and secondary of the coil? If you have an ignitor is it getting hot? If you have points, what is the dwell angle or gap? If you have points you will have a capacitor (aka suppressor), have you replaced it? Do you have a ballast resistor on the coil:- if so is it open cct?
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Old 10-24-2006, 12:00 PM   #5
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look in the carb and make sure the accel. pump shoots gas in when you open the throttle, which would mean the bowl is filling. get the module checked. check the coil. is it still the original semi-computerized setup?
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Old 10-24-2006, 03:13 PM   #6
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We checked for TDC with a blow-off so the valves should be closed. We checked the coil and it seemed like an intermitent open so we replaced it and the cap. Found the computer module, the fuse block didnt have any fuses in the ECM spots so I dont think the comp has been opperating at all. The batery will barely hold a charge even while its pluged into the charger, deff need a new bat.
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Old 10-24-2006, 04:49 PM   #7
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does the truck have spark???? if not change the ignition module located under the cap in the dist. i had the same problem when i was trying to start my monte carlo for the first time. they are cheap, so even if you dont need one, its always nice to have a spare.
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Old 10-25-2006, 02:29 AM   #8
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Quote:
Originally Posted by Wally
Are you absolutely sure both No1 valves are closed when the rotor is pointing at No1 cap electrodes? I guess the timing chain cogging would be out of the question?

OK next test should be to make sure your coil or ignitor isn't dying. What resistances are you getting on the primary and secondary of the coil? If you have an ignitor is it getting hot? If you have points, what is the dwell angle or gap? If you have points you will have a capacitor (aka suppressor), have you replaced it? Do you have a ballast resistor on the coil:- if so is it open cct?

if he was 180 off, i think he'd get an occasional eyebrow trimming backfire.... seems like i always do...
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Old 10-25-2006, 02:30 AM   #9
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Quote:
Originally Posted by davsmitty
We checked for TDC with a blow-off so the valves should be closed. We checked the coil and it seemed like an intermitent open so we replaced it and the cap. Found the computer module, the fuse block didnt have any fuses in the ECM spots so I dont think the comp has been opperating at all. The batery will barely hold a charge even while its pluged into the charger, deff need a new bat.

so what you've got is a coil-in-cap hei w/ one wire hookup and vac advance? no est plug?
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Old 10-25-2006, 10:21 AM   #10
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Fuses
Battery Connection or battery (probably already checked)
Electrical Connections for the alternator, starter, and necissary engine control modules.

Engine load could be it but I doubt it. Simple way to test it is to pull the belt system and see. Don't let it run too long though; the water won't be pumping.

The starter could be going bad, but if it is it wouldn't cause the engine not to turn over due to pressure. Anything that draws a lot of current pulls voltage down; happens in nearly every electric motor I can think of that pulls more than an amp and a starter pulls several thousand. A washing machine can pull house voltage as low as 100 volts when it's first starting up, for example.

If the crankshaft is spinning and fuel is getting into the engine then it's probably the sparkplugs you're having an issue with and not timing. If it were timing, two things would happen; you'd blow a rod through the block or it'd run shitty. You can check to see if the distrocap is getting power by pulling the top off and trying to crank it; you'll hear and see sparks on all the leads. From there, bad spark plug wiring wouldn't cause anything bad and I doubt all 8 plugs died however a loose connection or bad cap or bad cap wiring could cause what you're talking of.
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Old 10-25-2006, 12:00 PM   #11
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Quote:
Originally Posted by Gwokable
Engine load could be it but I doubt it. Simple way to test it is to pull the belt system and see. Don't let it run too long though; the water won't be pumping.

it doesn't run, remember?

Quote:
Originally Posted by Gwokable
happens in nearly every electric motor I can think of that pulls more than an amp and a starter pulls several thousand.


oh, yeah. that's why i have a 40,000 cca battery in my car! dude.... no. not several thousand...

Quote:
Originally Posted by Gwokable
If it were timing, two things would happen; you'd blow a rod through the block or it'd run shitty. You can check to see if the distrocap is getting power by pulling the top off and trying to crank it; you'll hear and see sparks on all the leads.

wtf are you talking about?!?! just stop...
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Old 10-26-2006, 01:21 PM   #12
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Quote:
Originally Posted by dodger65
so what you've got is a coil-in-cap hei w/ one wire hookup and vac advance? no est plug?

coil-in-cap HEI, it has a hot plug labeled 'bat' and a 3wire plug that comes from the distributor to the cap, and a plug from the distributor that seems to go to the comp. All are connected just like before it stoped working. Since Im getting a big drop in voltage, and my baterie is weak at best, could the starter be drawing more amperage than the bat and charger can supply->causing the voltage to drop and a weak spark?

The only thing left to check/change is the starter motor and the spark plugs and wires. We keep checking the position of the rotor with the harmonic balance at TDC and its right where it should be.

Has Hobo posted lately? I was hoping that he would have some insight as well.

Thanks again
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Old 10-26-2006, 01:33 PM   #13
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Well if the voltage drops too far the electronics will not work. Have you tried a fully charged battery?
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Old 10-26-2006, 03:14 PM   #14
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Quote:
Originally Posted by davsmitty
coil-in-cap HEI, it has a hot plug labeled 'bat' and a 3wire plug that comes from the distributor to the cap, and a plug from the distributor that seems to go to the comp. All are connected just like before it stoped working. Since Im getting a big drop in voltage, and my baterie is weak at best, could the starter be drawing more amperage than the bat and charger can supply->causing the voltage to drop and a weak spark?

The only thing left to check/change is the starter motor and the spark plugs and wires. We keep checking the position of the rotor with the harmonic balance at TDC and its right where it should be.

Has Hobo posted lately? I was hoping that he would have some insight as well.

Thanks again

see post #7, have you tried that yet? as i said, i have had this problem and changing that solved it. get a good battery for it as well
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Old 10-27-2006, 01:15 PM   #15
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Quote:
Originally Posted by glagon1979
see post #7, have you tried that yet? as i said, i have had this problem and changing that solved it. get a good battery for it as well

yes, as Ive already said, the entire distributor assembly is brand new. Timing chain and gears=replaced, distributor and all electronics=replaced and checked, rotor and distributor cap, coil=replaced.

Basically its between the battery and starter being weak and dropping the voltage too low to get good spark (which is my idea)...And us not installing everything exactly right (my dad's idea). Problem is, we could both be right which means an a$$ load of work for me.
If we matched up the marks on the timing chain gears exactly, and didnt skrew anything else up installing the new ones, it cant be the cam-crank ratio could it?
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