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GMC VAN...IGNITION PROBLEM?

 
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piperxxx piperxxx
New User | Posts: 26 | Joined: 01/11
Posted: 01/28/11
09:23 PM

I GOT A GMC VANDURA AND IM GETTIN SPARK AND FUEL..JUST WONT START..THE SPARKING SEEMED WEAK AND ERRATIC...BUT DOESNT EVEN TRY TO START...THROTTLEBODY INJECTION...GETTIN PLENTY OF FUEL....TRYED TO TEST THE IGNITION COIL BTU NOT SURE  HOW TO USE THE MULTITESTER...THANK YOU FOR ANYONES SUGGESTIONS  

waynep7122 waynep7122
Addict | Posts: 4561 | Joined: 08/09
Posted: 01/28/11
10:11 PM

knowing what year.. would have helped...  and which motor...


ignition rotor.... take it off... toss it.. put a new one...  5 bucks.. they get holes burned through them.

take the coil from the cap.....   examine it for signs of high voltage leaks...  look around the outer edges of the center core next to the coil laminations...   see any white dots... dust circles...    coils break down.. loose their ability to create high voltage sparks...   if it was a remote coil HEI.. i would say to see if you can get it to toss a nice crisp blue spark at least 3/4 inch...

weak spark will show an Orange spark. but it won't throw a spark more than a quarter inch.. and thats NOT enough to jump 2 gaps.. (rotor to cap and spark plug gap)  along with flowing through the high resistance spark plug wires...

in cap hei coils are under 25 bucks at AZ...

you might also want to climb under the van...    with a 5/8" six point socket.. a 3 inch extension.. and a breaker bar...  rock the crank back and forth...    you can feel when the slack in the timing chain is gone and the cam start to turn.. if you get more than about 5/8" of movement at the outside of the damper.. you might be needing a timing chain...   some years were equipped with a nylon toothed aluminum cam gear...  

can you turn the crank and the damper till the timing mark lines up with TDC mark on the pointer.. some engines is hard to *** as the timing marks are only visible behind the water pump.. straight down..    if you line up the damper mark at TDC>> or at the base timing mark as indicated on the emissions label.. then look at which way the rotor is pointing.. it should be pointing at either the number one wire.. or the number six wire.. remember. the crank turns 2 turns to one of the distributer..


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


a few tests with the digital volt meters...

set meter to 200K ohm scale.(200,000 ohm scale)..    measure the spark plug wires...   a 24 inch wire should read less than 24 on the meter... probably 12 to 18...   that would be 12,000 ohms to 18,000 ohms..    1,000 ohms per inch max...

i would also look in at the pick up coil connections where they plug into the module...  if there is green showing.. you might have corrosion happening..   so you might end up needing to replace the distributer pick up coil...

you can also disconnect the pick up coil from the module..  set the digital volt meter to the 2K ohm setting.. measure the pickup coil resistance..   500 to 1500 ohms of resistance...

before you disconnect.. flip the meter to 2 volts AC or 20 volts AC...  spin the distributer shaft or crank the motor...  you have to see close to ONE volt AC...   if you don't get close to 1.0 volt AC.. there will not be enough seine wave height to turn on the power transistor to charge the primary windings of the coil...   if the distributer passes ohms resistance... and fails the AC output test..  you have a bad reluctor..   this is NOT a problem on large cap HEI...  but it is a problem on small cap HEI distributers along with ford and mopar distributers..

imagine.. i have just shown you how to test a solid object for proper operation in a magnetic field..  with a volt meter...


you will also want you  to monitor the voltage on the red wire to the bat terminal on the HEI...  should be full battery voltage...  

waynep7122 waynep7122
Addict | Posts: 4561 | Joined: 08/09
Posted: 01/28/11
10:16 PM

a bit more info about year. and which motor...  there are a LOT of differences.. even though they all work in a similar manner..  

piperxxx piperxxx
New User | Posts: 26 | Joined: 01/11
Posted: 01/29/11
06:33 AM

thanks so much you guys...im usually pretty good on autos...except the electronics..i hate buyin parts if i dont need them..still learnin....i got a 1987 350 5.7 liter,,,also is remote ignition coil  

piperxxx piperxxx
New User | Posts: 26 | Joined: 01/11
Posted: 01/29/11
06:36 AM

i was also gettin a weak blue spark on one plug and a brite orange spark on the other  

waynep7122 waynep7122
Addict | Posts: 4561 | Joined: 08/09
Posted: 01/29/11
10:31 AM

almost every one of those i have worked on.. needed a new coil...

Coilhighvoltageleakareas



distributer caps...  ignition rotors... are WEAR items....  they need to be changed as they wear out ...  cars with points got the points changed once in a while...  yes.. you could sand the contacts... but the high voltage burns holes through the plastic...    the carbon button spreads out conductive carbon around inside the cap...

spark plug wires are also wear items..  they need to be changed once in a while...

while in there changing the coil...  the rivets are aluminum..  you can knock the heads off with a sharp scraper.. and a few hits with a hammer..   the brackets DO NOT come with the coils.. there are too many variations...


while in there with the cap and rotor off...   look straight down the top of the distributer shaft...  you will see the top layer of the reluctor riveted on..  there is a small gap between that and the second layer.. a black ceramic magnet..   if the magnet is cracked...  you really need to change the distributer also....

the nice clean seine wave put out by the reluctor passing the tips of the pick up coil when the magnet is cracked.. has additional random patterns that also generate out of phase seine waves..  this messes with the electronic timing control... causes the timing count down clock that when the computer shortens the clock count.. the timing advances.. when it lengthens the clock count.. the timing retards...  when these ghost waves appear.. it tosses additional count downs into the system causing random ignition coil discharge events..  making the engine run weird...

this is the picture of the top of a reman V6 distributer.. these are sold at AZ stores.. along with others.. compare your reluctor to this IMPROVED reluctor.. you won't believe how much better your truck will run if your original reluctor magnet is damaged...

4Pointthreetbidistributer

you should also OHM or carefully replace your spark plug wires if you have not already replaced them...

there is NO wire in them.. just bits of carbon usually ...  this reduces the radio frequency pulses created by the high voltage running down the wires...   do you get engine noise on AM radio???  or on a portable radio when the engine is running..  the carbon burns out eventually...  increasing the voltage needed to send a spark down the wire..  this increase.. causes the tip of the rotor to burn away slightly.. the carbon button in the cap to get hotter and burn away.. and for the high voltage created in the coil to work its way over time to leak to the grounded frame of the coil as noted above...

with a full size gm van...   i would probably use just ac delco wires...      that van will probably also use a special spark plug... from delco...


Ac-Delco Copper/Spark Plug
For your 1987 GMC Truck G2500 3/4 ton Van 5.7L TBI 8cyl
Part Number: CR43TS

many parts guys may hand you a R43TS... its the same heat range.. but the CR43TS center and side electrodes are far thicker...  will last a much longer time than a conventional R43TS...


you will also want to pick up a 99 cent package of spark plug BOOT LUBE....    wipe a tiny amount of this around the inside of the boots.. but NOT into the metal contacts...  this stops the high voltage from leaking between the boot and the spark plug insulator..   there is a small package of this with the wires.. sometimes its not enough ...  

piperxxx piperxxx
New User | Posts: 26 | Joined: 01/11
Posted: 01/29/11
01:07 PM

excellent...it ended up bei n the ignition coil...thanks alot! i neede a second oponion on that ...as far as reluctors go...do u think i should get the improved one for my van? it runs good now but im always lookin for improved performance...i changed my rotor too just for good measure...nto the conventional rotor it was not the flat kind but round and hollow..also under that it has a copper looking sleeve that goes down around and over what ur photo shows,,,i have no idea what that is...thanks again wayne ...u sure know ur stuff!  

waynep7122 waynep7122
Addict | Posts: 4561 | Joined: 08/09
Posted: 01/29/11
02:36 PM

take the rotor back out.. look straight down the shaft..  under the first plate were there is a gap around the plate to clear the shaft.. the second layer is a magnet.. if cracked.. replace the distributer with the improved version..


the copper sleeve tries to prevent stray RF from getting into the windings causing the Ghost wave forms like i describe..

when / if the module ever fails... swap in a reman unit.  

one thing... make it easy to ***

with the cap off.. bump the engine around till the rotor is pointing at the number one spark plug wire location in the cap ..  if you can get someone to work the crank back and forth till the reluctor tips line up perfectly with the pick up coil tips... you can yank the old distributer out.. drop the new one in.. making sure thats it's down on the oil pump shaft properly.. then turn the housing so the reluctor and pick up coil tips line up again perfectly. lock the distributer down.. it will start on the first try..

be sure to check once you get the reluctor and pick up coil tips to line up.. where the timing marks line up with the pointer on the front of the motor...

you can make you self look like a genus ...

l love to preset the engine like i described..  yank the distributer out..  work on it... shove it back in..  lock it down.. reach through the window and turn the key and have the engine start on the first try..   i have had people just stand there with the mouths hanging open when they first see it..  its really simple... the base timing is when the tips line up exactly...  set the damper to the proper base timing marks.. everything lined up... it starts on the first try without having to twist the distributer to get it to run...  

piperxxx piperxxx
New User | Posts: 26 | Joined: 01/11
Posted: 01/30/11
08:48 AM

i did that on my old van and worked just like u said...thanks for the info on the electronics on the distributors...that gave me alot of insight and now i understand how it works...the manuals dont tell much about that stuff  

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