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86 k5 No Spark

Justin Fleming

Justin Fleming

1/2 ton status
 Premium
Joined
Aug 24, 2005
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Location
Oxford MI
It has been a while.......I do know that I have gas and compression and now the missing link is spark. The truck has been parked for a few months and ran just fine prior to parking it. I have checked that I have power going to the coil (red wire that plugs in on the Bat term of coil) when the key is in the run position.

What would the next step be? How can I test the coil or how can I test the brain deal that has the three wires going to it??


thanks
 
well if your trying to test for a spark i know you can tak the sprk plug out and put the treads of the spark plug put it against something with exposed metal (ground it basicly) and turn the ingnition and it should spark and if there is no spark could be alot of things coil pack-distributer-battery-ignition-alternator lol it could be alot of **** most of this **** any electronic componets you can take them off and take them to auto zone and they can test them but sence it sat so long it might be your battery try jumping it and if its making no cranking noice at all have some one hit the starter with a wrench while some one is turning the key
 
well if your trying to test for a spark i know you can tak the sprk plug out and put the treads of the spark plug put it against something with exposed metal (ground it basicly) and turn the ingnition and it should spark and if there is no spark could be alot of things coil pack-distributer-battery-ignition-alternator lol it could be alot of **** most of this **** any electronic componets you can take them off and take them to auto zone and they can test them but sence it sat so long it might be your battery try jumping it and if its making no cranking noice at all have some one hit the starter with a wrench while some one is turning the key
 
I will bet it is your module(thats the brain deal) they will go bad with no warning rhyme or reason. You can get them tested at most auto parts stores
 
Or It could be the ESC computer also. Mine went bad not long ago and would not start. I pulled this off 73-87.com


[SIZE=-1]Here is a way to remove the ESC from the distributor without having to change distributors. I recently found this quick fix on the 73-87 truck forum at Chevytalk. It was posted by a member that goes by the name of 86Scottsdale.[/SIZE]

​
[SIZE=-1]I had a problem with my 86 C20 305-H engine. It could start and run fine and just suddenly die out, sometimes start right back up or take a couple hours to get restarted. After several weeks of this nonsense (and getting very good at getting those half turn dist. cap latches off), I did some checking. There is a power feed to the spark control unit under the dash that comes off of the pink (hot) wire to the distributor. The pink wire clips into the connector for the feed, which in turn clips into the dist. cap. What had happened was the feed for the Spark Control was shorting out somewhere, killing the spark. I talked to some Chevy mechanics at my dealer about this and they told me how to bypass the spark control computer and keep the original distributor, something they claim is done quite often.[/SIZE] [SIZE=-1]First thing to do is unhook the spark control computer lead from the pink wire and hook the pink wire directly to the dist. cap. Make sure you plug it into the cap at the BAT terminal. The second thing is to locate the 4 wire connector that feeds into the ignition module. There's a brown (D), green (C), white (B), and black (A) wire there. The letters in () are on the black clip that the wires come out of. You cut the green (C) and black (A) wires between this clip and where they go into the distributor. Then all you need to do is solder the 2 cut leads from the dist/ignition module together, i.e. the green and black ones, (make sure to tape the exposed wires) and now your HEI distributor will function just as a pre ESC model does. I did this and it has been running fine for well over a year now.[/SIZE]
[SIZE=-1]Dan[/SIZE]
[SIZE=-1]Note: Here is a photo I made of the plug which goes to the ESC control and feeds the ignition, which Dan mentioned above. I labeled the wires which need to be cut and showed which wires are A, B, C and D.[/SIZE]
[SIZE=-1]
plug1.jpg

[/SIZE]
moz-screenshot.jpg
 
quick test...

One quick way to test a non EST HEI dizzy is to hook a test light up to the "Tach" terminal and ground the other end,and crank it over for a few revolutions--if the test light flashes,the HEI is getting 12v power,and the pickup coil and module are working..DONT crank it over longer than 5 seconds,or the module might get damged..:crazy:
 
take the cover off of the coil(if the cover is even on there) and make sure the coil is not sitting in water. if the trucks been sitting for awhile, theres a hundred ways water could've got in there for example, sprinklers near by, precipitation, degreasing the engine then rinsing it off, etc.
 
thanks for all the great tips.......I have snese burned out the starter trying to get it to start. The starter has always been a little iffy any how.....
 
So I put a new starter on the truck and my problem seems to have gone away? Does this make sense to anyone? Maybe the distributor was not getting the correct power as I beleive it comes from the same circuit. Maybe there was a short in the starter??

thanks
 
huh?...

I learned right from GM's tech school to use the testlight that way--(actually my brother did,and I inherited all his knowledge and factory repair manuals and procedures..yes,I'm aware it CAN damage the module if you crank too long,and I did make mention of the fact...the manual does reccomend you limit cranking time to a max of 5 seconds..they also tell how to jump the wires on the module to make the spark jump the spark tester..(which can also fry things if left connected too long!)..

I usually assume the module is junk, and just put in a new/good used one,and if it still has no spark,the pick up coil is probably the culprit...90% of the time its the module..sometimes replacing it gets it sparking again,and the pickup coil craps out shortly thereafter...:doah:

I find a light easier to see flashing than watching a meter needle or digital readout..plus most everyone has acess to a bulb (a 194 marker light bulb could be "borrowed" on the trail..) ,but not everyone has a DMM with them at all times..yes,the bulb is a rather "crude" test,but effective..IF you do it according to the book!..:crazy:
 
lol well perhaps you should get one an incadescent test light draws a large ammount of current that can short computer-attached logic leads to ground which hmmm can destroys a vehicals computer? id like to see you test ohms with a test light or perhaps test a fuse that may look fine to you but could really be blown i dunno lol i have maybe i shouldnt of gone to school to be a mobile electronics certified professional :) id love to see the silly redneck school that told your brother as a GM tech to use a testlight maybe your brother was taking a nape during the electronics part of his course
 
Ok...

I appreciate your input,but I was referring to non-computer HEI's from the 70's and 80's,not the later EST ones and trucks with computers and TBI..I'm still in the stone age,and I kinda like it there!...:D ...

I do have an old "needle"meter stlye multi-tester for checking resistance and voltage readings,but I let my friend deal with any troubles I have with later vehicles..he's got all the fancy digital meters,code scanners,ect..I wasn't saying you were wrong,though my post may have sounded that way,now that I re-read it!..:blush: ..dont take it personal!..:wink1:
 
lol just trying to help you out so you dont try your test light on a newer car and fry their comp :P and an analog meter those things are crap lol you have to get them calibrated like every time you use it i dunno i do quite a bit of car eletrical in my field DMMs all we use
 
Justin Fleming said:
It has been a while.......I do know that I have gas and compression and now the missing link is spark. The truck has been parked for a few months and ran just fine prior to parking it. I have checked that I have power going to the coil (red wire that plugs in on the Bat term of coil) when the key is in the run position.

What would the next step be? How can I test the coil or how can I test the brain deal that has the three wires going to it??


thanks
Click to expand...

Ok

So the problem that I thought I had fixed has come back. Here is what I do know.

1 New cap,rotor,coil,plugs,wires
2. ignition module in the dist. tested good
3. I have 12v to the terminals when cranking the motor over and or when key is in the on position
4. I have no spark


Things that I wonder or need explaination on:

1. Does the key/ignition switch send a signal to the module or does it just send the 12v to the terminal?

2. I noticed that when cranking the motor over it does not fire, but sometimes when I let go of the key and turn it back one click it fires for a split second. So I wonder if something is getting messed up from the ignition switch?

3. Is there some sort of pick up on the dist under the rotor that tells the module pulses or something like that

4. where do the 4 wires go to from the module (out the back side of the dist)


Thanks
 
my ghetto spark tester...

I use an old burned out headlamp to check for spark!..hook one terminal to the plug wire,and jump the other one to ground with a jumper wire..it gives a good veiw of the spark,and unless your touching the wires,you wont get "poked"...;)

The fact your truck seems to want to fire up as you let off the key does sound like it might only be getting power to the HEI in the "key on" position,and not while cranking..that could indicate the ignition switch is faulty,or not adjusted properly...

The ignition delivers 12V to the HEI..the pick up coil inside the distributor,where points used to sit in older models,is what "tells" the module and coil,and the TBI(if so equipped) when to fire...it often craps out intermittently,and gives you tons of grief,because often it wont do it for days or weeks,or when you want to diagnose the problem..many times the wires that go into it and go to the module get broken inside,and cause it to lose spark intermittently,or a hesitation..

Replacing it requires pulling out the distributor,and removing its drive gear and mainshaft..its kind of a pain in the butt..but replacing it is about the only way to really tell if its defective--you can measure its resistance with a multi-meter,but they often test "good", but still act up and cause a no spark problem,or a hesitation when the vacuum advance unit moves it to advance the timing..

If your HEI was installed in a NON HEI truck,be sure it has a 10 ga wire that is hot only when the key is "ON" powering it,preferably right from the fuse box..many guys just use the old coil wire from the points,and it wont deliver enough juice--it has resistance,and wont let a full 12V go to the HEI--and it will run,but poorly,if thats how its wired up...:crazy:


:crazy:
 
TheSunDanceKid said:
lol well perhaps you should get one an incadescent test light draws a large ammount of current that can short computer-attached logic leads to ground which hmmm can destroys a vehicals computer? id like to see you test ohms with a test light or perhaps test a fuse that may look fine to you but could really be blown i dunno lol i have maybe i shouldnt of gone to school to be a mobile electronics certified professional :) id love to see the silly redneck school that told your brother as a GM tech to use a testlight maybe your brother was taking a nape during the electronics part of his course
Click to expand...

Maybe before pulling out the smarta$$ comments we should ask what redneck school told you that you can't use a test light?

When I see comments directly contrary to what GM puts in it's technical manuals used to make comments such as you did, it makes one wonder exactly where your attitude comes from? Just because you learned one thing means everyone else is wrong?
 
For what its worth...

The school my brother went to was an authorized GM service tech center in Dedham MA..lets not forget this was around 1980,when digital multi-meters were NOT in every mechanics tool chest yet!...:rolleyes:

While I'm sure a test light CAN hurt a computer in newer cars,it was the tool of choice back then,when vehicles HAD no computers yet!....and yes,the GM service manual DOES state to not leave the test light hooked for more than 5 seconds,or the module could be damaged or ruined..

Please don't think I'm "arguing" with you!--I'm not,I'm just stating what I learned back when..neither of us are "right" or "wrong"--we just learned two diferent ways of doing something,thats all!..nothing to get upset about!..:crazy:
 
Actually,the late 80's Camaro manuals (for example) specifically dictate using a test light for certain ignition tests. "Momentary" is the key word used for using the light.

I responded because I very much dislike seeing someone berated and insulted for posting something. There are ways to say "you are wrong" (even though you weren't) without trying to make someone feel bad. It doesn't help the forum or anyone here. Use attitude, get attitude, and you never do, so why should you be on the receiving end?
 
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