Intermittent won't start/no spark problem - HELP

143K miles on 2-dr full size blazer. Just had dist cap, pick-up, fuel filter, and module (not sure which one but it was a $78 part) replaced. About once every 2-3 weeks it won't spark. Wouldn't turn
over with ether/choke cleaner or gas poured into throttle body so I'm assuming it's electric related. I've pulled a plug wire when it won't crank and i get no spark. Intermittent problem occurs most often after sitting for 6-8 hrs during a day at work after driving it to work and it sits for the day. Let it sit for 2-8 hours or overnight (walmart lot, work lot, home depot lot) and it starts first attempt. It hasn't hasn't occurned in the mornings.
Is there a best sequence for trouble shooting intermitt ignition/no spark prob? I volt tested the main coil lead wire from the dist cap to the ignition coil and it's good. Should I test for spark further 'upstream'? Thanks in advance.
/neil
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I should have mentioned it's a '92 5.7L V8 TBI. /neil
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. Re: Intermittent won't start/no spark problem - HELP Group: alt.autos.4x4.chevy-trucks Date: Thu, Oct 9, 2003, 2:39pm (CDT-2) From: snipped-for-privacy@doctordirectory.com (NeilSpencer)
I should have mentioned it's a '92 5.7L V8 TBI. /neil /////////////////////
yes, you should have.
marsh monster ~:~wonders if neil wuz talk'n to himself~:~
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~ Intermittent won't start/no spark problem - HELP Group: alt.autos.4x4.chevy-trucks Date: Thu, Oct 9, 2003, 9:25am (CDT-2) From: snipped-for-privacy@doctordirectory.com (NeilSpencer) 143K miles on 2-dr full size blazer. Just had dist cap, pick-up, fuel filter, and module (not sure which one but it was a $78 part) replaced. About once every 2-3 weeks it won't spark. Wouldn't turn over with ether/choke cleaner or gas poured into throttle body so I'm assuming it's electric related. I've pulled a plug wire when it won't crank and i get no spark. Intermittent problem occurs most often after sitting for 6-8 hrs during a day at work after driving it to work and it sits for the day. Let it sit for 2-8 hours or overnight (walmart lot, work lot, home depot lot) and it starts first attempt. It hasn't hasn't occurned in the mornings.
Is there a best sequence for trouble shooting intermitt ignition/no spark prob? I volt tested the main coil lead wire from the dist cap to the ignition coil and it's good. Should I test for spark further 'upstream'?
Thanks in advance. /neil
~ your welcome post script
Ignition Distress No-Start Diagnostics, Address:http://www.babcox.com/editorial/us/us80124.htm
marsh monster
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Intermittent won't start/no spark problem - HELP top post... IM kind of confused i understand your not getting spark but you mentioned two things you gave one example where it wouldnt crank then you gave another where it wouldnt turn over..well pal which one is it dont crank or it wount start? If it is cranking and your not getting spark listen to marsh but if its doing nothing let us know... Steve
Group: alt.autos.4x4.chevy-trucks Date: Thu, Oct 9, 2003, 9:25am (CDT-2) From: snipped-for-privacy@doctordirectory.com (NeilSpencer) 143K miles on 2-dr full size blazer. Just had dist cap, pick-up, fuel filter, and module (not sure which one but it was a $78 part) replaced. About once every 2-3 weeks it won't spark. Wouldn't turn over with ether/choke cleaner or gas poured into throttle body so I'm assuming it's electric related. I've pulled a plug wire when it won't crank and i get no spark. Intermittent problem occurs most often after sitting for 6-8 hrs during a day at work after driving it to work and it sits for the day. Let it sit for 2-8 hours or overnight (walmart lot, work lot, home depot lot) and it starts first attempt. It hasn't hasn't occurned in the mornings. Is there a best sequence for trouble shooting intermitt ignition/no spark prob? I volt tested the main coil lead wire from the dist cap to the ignition coil and it's good. Should I test for spark further 'upstream'? Thanks in advance. /neil
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(Neil Spencer) 143K miles on 2-dr full size blazer. Just had dist cap, pick-up, fuel filter, and module (not sure which one but it was a $78 part) replaced. About once every 2-3 weeks it won't spark. Wouldn't turn over with ether/choke cleaner or gas poured into throttle body so I'm assuming it's electric related. I've pulled a plug wire when it won't crank and i get no spark. Intermittent problem occurs most often after sitting for 6-8 hrs during a day at work after driving it to work and it sits for the day. Let it sit for 2-8 hours or overnight (walmart lot, work lot, home depot lot) and it starts first attempt. It hasn't hasn't occurned in the mornings. Is there a best sequence for trouble shooting intermitt ignition/no spark prob? I volt tested the main coil lead wire from the dist cap to the ignition coil and it's good. Should I test for spark further 'upstream'? Thanks in advance. /neil
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Thanks all for the posts. Doc, sorry to give you a headache. Is this not a CAR forum? I'll put in a few more periods if you'll work on using the apostrophe key when you're supposed to (see those little ' in my words that correctly establish subject possesion? Try them sometime!) Didn't know I needed to pass a test here. I'm not a nazi and get enough criticism from my wife.
On to my car now, if that's ok with Professor, er Doc - i did incorrectly use the words 'wouldn't turn over' when i meant wouldn't crank. Battery, starter, alternator are working fine. Thanks Marsh for the diagnostics article.
/neil
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.. Re: Intermittent won't start/no spark problem - HELP Group: alt.autos.4x4.chevy-trucks Date: Fri, Oct 10, 2003, 7:57am (CDT-2) From: snipped-for-privacy@doctordirectory.com (NeilSpencer) Thanks all for the posts. Doc, sorry to give you a headache. Is this not a CAR forum? I'll put in a few more periods if you'll work on using the apostrophe key when you're supposed to (see those little ' in my words that correctly establish subject possesion? Try them sometime!) Didn't know I needed to pass a test here. I'm not a nazi and get enough criticism from my wife. On to my car now, if that's ok with Professor, er Doc - i did incorrectly use the words 'wouldn't turn over' when i meant wouldn't crank. Battery, starter, alternator are working fine. Thanks Marsh for the diagnostics article. /neil ========= ========= Neil, I'de be willing to bet that if Marsh Monster could have read what you just scribbled about "the Doc"......he would'nt of helped you....
I could be wrong on that.......
Scrib Abell ~don't thunk he is thoe~
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. CDT-2) From: snipped-for-privacy@doctordirectory.com
(NeilSpencer) Thanks all for the posts.
Doc, sorry to give you a headache. Is this not a CAR forum?
I'll put in a few more periods if you'll work on using the apostrophe key when you're supposed to
see those little ' in my words that correctly establish subject possesion?
Try them sometime!
Didn't know I needed to pass a test here. I'm not a nazi and get enough criticism from my wife.
On to my car now,
if that's ok with Professor, er Doc -
i did incorrectly use the words 'wouldn't turn over' when i meant wouldn't crank. Battery, starter, alternator are working fine. Thanks Marsh for the diagnostics article. /neil ========= ========= snipped-for-privacy@webtv.net (ScribbAbell) spewed forth this.....
Neil, I'de be willing to bet that if Marsh Monster could have read what you just scribbled about "the Doc"......he would'nt of helped you.... I could be wrong on that.......
Scrib Abell ~don't thunk he is thoe~ .......................... ......................... hey Scrib, how's it hang'n dude......
yep......wander if I can go back and use my eraser button?
Marsh Monster ~wonders if Scrib has any of that shroom juice left from last night......~ .......................
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. Re: Intermittent won't start/no spark problem - HELP Group: alt.autos.4x4.chevy-trucks Date: Fri, Oct 10, 2003, 7:57am (CDT-2) From: snipped-for-privacy@doctordirectory.com (NeilSpencer) Thanks all for the posts. Doc, sorry to give you a headache. Is this not a CAR forum? I'll put in a few more periods if you'll work on using the apostrophe key when you're supposed to (see those little ' in my words that correctly establish subject possesion? Try them sometime!) Didn't know I needed to pass a test here. I'm not a nazi and get enough criticism from my wife. On to my car now, if that's ok with Professor, er Doc - i did incorrectly use the words 'wouldn't turn over' when i meant wouldn't crank. Battery, starter, alternator are working fine. Thanks Marsh for the diagnostics article. /neil ................................... ...................................
Neil, you really should apologize to Doc for making that sound like a flame.
MarshMonster ................................. .................................
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Neil,
Are you new to USENET? If you'll scroll up a few messages you'll see that my smart-assed commentary was in response to Steve Cook, who writes small novels without a single period or comma and NOT your postings. Your post<s> are quite easy to read and your explanation of the problem is quite clear as well.
Yer' (uh-oh, innappropriate use of apostrophe!) pal,
Doc
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I suppose I'm not using the right terms here - let me do it again. She turns over but won't start. She always turns over fine if 'turning over' used correctly means she cranks but doesn't catch, run, start, go, etc. Sorry. She always turns over, but frequently doesn't start. When she doesn't start, I check for spark (at the plug) and get none. She'll then decide to start (and spark) just fine several hours later.
/neil
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Lord, if I've offended anyone here please accept my apology. The Doc hopefully saw the humor....because that sure was the attempt. A flame it wasn't - and now I see that perhaps the doc was referring to steve cooks posts as causing headaches...and not mine. After all, The Doc felt inclined enough to poke at someone's particular writing style without adding a thing to the actual thread discussion.
Doc, the way your post came through it looked as if you posted what steve cook wrote.
Since Marsh is out, would anyone else like to lend a hand?
/neil
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Neil,
First let's clarify yer' terms. When you turn the key to "Start" and the starter kicks on, the motor is cranking. When the fuel makes it to the cylinder and fires up that is what is referred to as turning over. So, you have a motor that will crank but will not turn over.
The ignition system on these trucks is relatively simple. A few things before we can go any further:
1) When you're cranking the motor in a no-start situation, is there fuel spraying from the injectors? Pop off the air cleaner and watch for fuel spray as someone else is cranking.
2) In a no-start situation test for spark at the coil, which eliminates the possibility of a bad distributor terminal or wire causing you to not "see" any spark. Ya' follow?
3) When you're getting a no-start, test for voltage TO the coil. Your coil will have two harness connectors running to it. One harness will have afat red wire (+12V) and the other (white or green) is a tach lead. The other harness leads to the ICM (see # 4 below). If voltage to the coil doesn't read around +12V with the key turned to RUN, you know your problem lies before that (ignition switch, loose wiring between switch and coil lead, etc.)
4) Do this ASAP. Remove the distributor cap. There will be a black, flat, rectangular module under the cap with two wire harnesses on the outside, one or two on the inside. This is your ICM (ignition caontrol module). Yank it and take it to Autozone for a free test.
5) Do this ASAP as well. The ECM (engine control module) has two grounds. If one (or both) of these grounds are bad weird shit will intermittantly happen. The grounds are located on the front of the intake manifold, one on the front left corner, one on the front right corner (usually on one of the waterneck studs). Remove these wires, use a wire brush or steel wool to polish the studs and connectors, apply a light coating of dielectric grease to the studs and connectors, then reassemble. You could ohm them out and test for resistance to ground, but due to the fact this is intermittant it probably won't help.
Regards,
Doc
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Hmmm....I see a huge potential for mass confusion here. Where I'm from, *cranking* and *turning over* mean the same thing. Early engines needed a crank to turn them over, and you often had to turn them over several times before they would fire. Must be a regional thing.
Dave

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Re: Intermittent won't start/no spark problem - HELP Group: alt.autos.4x4.chevy-trucks Date: Fri, Oct 10, 2003, 3:23pm (CDT-2) From: snipped-for-privacy@doctordirectory.com (NeilSpencer)
Lord, if I've offended anyone here please accept my apology.
The Doc hopefully saw the humor....because that sure was the attempt.
A flame it wasn't -
and now I see that perhaps the doc was referring to steve cooks posts as causing headaches...and not mine.
After all, The Doc felt inclined enough to poke at someone's particular writing style without adding a thing to the actual thread discussion.
Doc, the way your post came through it looked as if you posted what steve cook wrote. Since Marsh is out, would anyone else like to lend a hand? /neil ------------------ ----------------- Neil, Your a class act.....good show of character.
I wouldn't worry too much about Marsh Monster......he doesn't know anything about engines anywhoooo....he's a drunk yuh know.
I expect you'll be hearing from him again, now that you got Doc on your side.
now...on to your problem....
sounds like for some reason the thing isn't getting the signal from the crank sensor.... telling the thing to fire.
why.????.......I dun't knows rite this sec... I wuz so overwhelmed with your post to Doc that it's erased my ignition diagnosis memory bank......
I'll git back to you though....
scrib abell ~thinks ole neil will get more help now~
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(Neil Spencer)
Lord, if I've offended anyone here please accept my apology.
The Doc hopefully saw the humor....because that sure was the attempt.
A flame it wasn't -
and now I see that perhaps the doc was referring to steve cooks posts as causing headaches...and not mine.
After all, The Doc felt inclined enough to poke at someone's particular writing style without adding a thing to the actual thread discussion.
Doc, the way your post came through it looked as if you posted what steve cook wrote. Since Marsh is out, would anyone else like to lend a hand? /neil ------------------ ----------------- Neil, Your a class act.....good show of character.
I wouldn't worry too much about Marsh Monster......he doesn't know anything about engines anywhoooo....he's a drunk yuh know.
I expect you'll be hearing from him again, now that you got Doc on your side.
now...on to your problem....
sounds like for some reason the thing isn't getting the signal from the crank sensor.... telling the thing to fire.
//////////////////////////////////////////
No crank sensor on 87-95 TBI motors.
Doc
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Re: Intermittent won't start/no spark problem - HELP Group: alt.autos.4x4.chevy-trucks Date: Fri, Oct 10, 2003, 3:23pm (CDT-2) From: snipped-for-privacy@doctordirectory.com (NeilSpencer) Lord, if I've offended anyone here please accept my apology. The Doc hopefully saw the humor....because that sure was the attempt. A flame it wasn't - and now I see that perhaps the doc was referring to steve cooks posts as causing headaches...and not mine. After all, The Doc felt inclined enough to poke at someone's particular writing style without adding a thing to the actual thread discussion. Doc, the way your post came through it looked as if you posted what steve cook wrote. Since Marsh is out, would anyone else like to lend a hand? /neil ============ ============ Neil, sounds like the coil isn't getting a signal to fire when the engine is spinning over for the first few seconds.
You tried using gas down the throttle plate, and it didn't start...so you are most likely on the correct trail on chasing an ignition problem.
It sounds like the signal from the ignition pickup may be getting bad.
If it's firing by just "snapping" the ignition key, but takes longer when holding the key forward.........I would suspect the ignition switch or the ignition module first AND pickup.
Check the ignition module first. You really can't check the signal the pickup out.....without a scope...or a really expensive meter at minimum.
ALWAYS CHANGE THE PICKUP AND MODULE AS A SET.
I think you'de be well advised to go ahead and invest in a new module and pickup.....if it's the original set on the truck.
This is all ASS U ME ing that I am understanding the starting condition correctly.
1) Starts....on quickly "popping..snapping" the ignition key 2) Extended Cranking.....on holding the ignition key forward.
KEEP IN MIND....it could be the ignition switch....but I really don't think so.
as a side note.... good deal on clearing up the posting controversy......
leave it to steve to get something started without even trying.....lol
marsh monster ~takes a slug off the jug.......and pass's it to Neil.....wonder's if Neil wants some shroom juice...~
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What doc didn't say, you MUST coat the metal part of the bottom of the ignition module with heat sink compound, when you reinstall it, or it will fry in short order. The white stuff from Radio shack is fine, if they don't have what you need at the auto supply store. Clean all surfaces well. Renew the cap and rotor, if you haven't already. You need the coil from your old cap. It is the round thing under the 8 toothed wheel, with 2 wires coming out of it. Also, the reluctor may be bad, but that's more involved to test, or change. You can ohm it between the two wires, though,
Dan
On 9 Oct 2003 09:25:53 -0700, snipped-for-privacy@doctordirectory.com (Neil Spencer) wrote:

Colorado Springs, CO My advice may be worth what you paid for it.
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Inline.....................

Yeah I did forget about that.................

What the hell are you talking about???? The pickup coil? It isn't part of the cap but part of the distributor, and cannot be replaced without yanking the entire distributor.
Doc
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