Double D racing Posted January 31, 2012 Report Share Posted January 31, 2012 ok guys i got one for ya. 1998 chevy 3/4 ton 5.7. wife was coming home last monday, traveling down the road and it just quit. got the truck back home, made arrangements to take to a popular mechanics shop over on eastside san antonio, but nooo.... a buddy of mine said no problem, we can fix it. so...first thing i changed was fuel filter...very dirty,,before installing, turned key on to make sure fuel pump was working... it was... i checked for firing on plug wires, no fire, but the coil was firing...so went back to auto parts and bought a camshaft sensor...still didnt start. then went and bought a crankshaft sensor, even poured a little fuel down the throttle body...no start... that was 3 trips to auto parts (15 miles one way), after 7 hours and only one beer, i gave up....now my gut instinct from the getgo was to not mess with it, you dont know what your doin, LEAVE IT ALONE !!! but being pursuaded by my buddies, i am now 160 bucks less i can spend on race cars...like George Strait would say, im in too deep to pull out now...it doesnt make sense to me, when you turn the key on, the fuelpump activates and shuts off like normal....IDK Link to comment Share on other sites More sharing options...
4cylfordz Posted February 1, 2012 Report Share Posted February 1, 2012 sounds like a distributor problem, since you say you have spark from the coil, start simple check the cap and the rotor. if all appear fine check the wiring make sure no connectors came loose. then check the ignition control module ( little silver box with the fins on the pass side under the air intake tube) id try a friends or a junkyard one first (autozone i think can test them for you) and if then still no workie then the distributor itself is no good or better than that do a koeo test since it's obdII and see what's out of range Link to comment Share on other sites More sharing options...
HiTech Posted February 1, 2012 Report Share Posted February 1, 2012 OK .BEEN THROUGH THIS MESS TWICE THIS YEAR ...........JUST FINISHED A 99 ...... NEED TO LOOK AT THE DISTRIBUTOR CLOSELY .. THERE IS A PROBLEM WITH THE ROTOR PLATE BENDING ......OTHER WISE THE GAP BETWEEN THE PLATE AND SENSOR GET .S OUT OF WHACK .. IF YOU ROTATE THE RELUCTOR PLATE THROUGH THE SENSOR .YOU SHOULD NOTICE THE GAP AT ONE END IS SO MANY THOUSANDS .BUT AS YOU TURN THE PLATE THROUGH ITS FULL MOTION... THAT GAP WILL CHANGE AS YOU GET TO THE END OF THE PLATE .......A GOOD DISTRIBUTOR WILL IN THE CENTER OF THAT PLATE CLOSE THE GAP TOWARDS THE SENSOR ..IF IT OPENS THE GAP ..CHANGE THE DISTRIBUTOR ..OTHER WORDS THE METAL RELUCTOR PLATE SHOULD BE EGG SHAPE ....IF I SCREWED YOU UP HERE ..THEN CALL ME AT 361.290.2096 ....I HAVE A BIG FEELING YOU HAVE THAT PROBLEM. may be someone here can print a pic of the distributor .. Link to comment Share on other sites More sharing options...
Double D racing Posted February 2, 2012 Author Report Share Posted February 2, 2012 OK .BEEN THROUGH THIS MESS TWICE THIS YEAR ...........JUST FINISHED A 99 ...... NEED TO LOOK AT THE DISTRIBUTOR CLOSELY .. THERE IS A PROBLEM WITH THE ROTOR PLATE BENDING ......OTHER WISE THE GAP BETWEEN THE PLATE AND SENSOR GET .S OUT OF WHACK .. IF YOU ROTATE THE RELUCTOR PLATE THROUGH THE SENSOR .YOU SHOULD NOTICE THE GAP AT ONE END IS SO MANY THOUSANDS .BUT AS YOU TURN THE PLATE THROUGH ITS FULL MOTION... THAT GAP WILL CHANGE AS YOU GET TO THE END OF THE PLATE .......A GOOD DISTRIBUTOR WILL IN THE CENTER OF THAT PLATE CLOSE THE GAP TOWARDS THE SENSOR ..IF IT OPENS THE GAP ..CHANGE THE DISTRIBUTOR ..OTHER WORDS THE METAL RELUCTOR PLATE SHOULD BE EGG SHAPE ....IF I SCREWED YOU UP HERE ..THEN CALL ME AT 361.290.2096 ....I HAVE A BIG FEELING YOU HAVE THAT PROBLEM. may be someone here can print a pic of the distributor .. ok i pulled the dist to put the cam sensor in, we spun it around and didnt see anything unusual except the fact that the distributor is plastic !!! it showed wear on the gear but besides that it was in pretty good shape...the cap and rotor had been changed bout a year ago.looked ok.. Link to comment Share on other sites More sharing options...
JamesHigdon Posted February 2, 2012 Report Share Posted February 2, 2012 Up until recently my daily driver was an L31 Yukon and between the drivers we have at the shop ours have a combined total of over a half million miles. On that motor if your getting fire to the coil but not the wires it can be a few things. As HiTech said the flatness of the rotor plate is important but if you've got fire at the coil then typically the camshaft sensor is good. First thing I'd do is check and if needed replace the cap and rotor. Those distributor bases are plastic and over time can crack at which point moisture can get in the rotor and cause fouling. From there you need to check to see if you have any codes that may be causing or caused by the injectors not firing. You can also give us a call at 210-287-8564 with any questions. James Link to comment Share on other sites More sharing options...
Double D racing Posted February 2, 2012 Author Report Share Posted February 2, 2012 Up until recently my daily driver was an L31 Yukon and between the drivers we have at the shop ours have a combined total of over a half million miles. On that motor if your getting fire to the coil but not the wires it can be a few things. As HiTech said the flatness of the rotor plate is important but if you've got fire at the coil then typically the camshaft sensor is good. First thing I'd do is check and if needed replace the cap and rotor. Those distributor bases are plastic and over time can crack at which point moisture can get in the rotor and cause fouling. From there you need to check to see if you have any codes that may be causing or caused by the injectors not firing. You can also give us a call at 210-287-8564 with any questions. James when we first started this my buddy cleared all (old ) codes...then unhooked battery.hooked back up and it had no codes til later.then it was a code from the transmission sayin it was not in park or neutral,but it was still turning over...i was told by a friend with a well known auto shop on the east side of san antone to try the ignition module next.so far a few others agreed...if this doesnt work then i will pull dist and look at the plate you are talking about.. Link to comment Share on other sites More sharing options...
JamesHigdon Posted February 2, 2012 Report Share Posted February 2, 2012 Typically if you're getting for at the coil the module is good, but if it's sporadic or weak fire it could be the module. What kind of spark are you seeing at the coil wire and how often? Link to comment Share on other sites More sharing options...
Double D racing Posted February 2, 2012 Author Report Share Posted February 2, 2012 Typically if you're getting for at the coil the module is good, but if it's sporadic or weak fire it could be the module. What kind of spark are you seeing at the coil wire and how often? it is constant as long as the motor is rotating.. Link to comment Share on other sites More sharing options...
HiTech Posted February 2, 2012 Report Share Posted February 2, 2012 Typically if you're getting for at the coil the module is good, but if it's sporadic or weak fire it could be the module. What kind of spark are you seeing at the coil wire and how often? it is constant as long as the motor is rotating.. question ..when you let off the starter .does that motor kick back ...like its out of time ....if so change the distributor ......another thing ..the crank and cam sensor could be out of correlation and be caused by the timing cover among other things like a bad plug at the crank sensor .......push lightly up on the crank sensor .spin the motor over .if it starts ..the cover is junk..i had fire through spinning the motor over at that time ....throwing some stuff at you i went through last year with a yukon alot of folks here know about ..i found nothing is impossible with this typ of sorry system .... good luck .. Link to comment Share on other sites More sharing options...
JamesHigdon Posted February 2, 2012 Report Share Posted February 2, 2012 Just out of curiosity how many plugs did you check for spark? Link to comment Share on other sites More sharing options...
Double D racing Posted February 3, 2012 Author Report Share Posted February 3, 2012 ok...i bought a ignition module,installed it,and i have come to a conclusion....im done.....still no start.so what you think next,distributor? how much is a new one.... Link to comment Share on other sites More sharing options...
HiTech Posted February 3, 2012 Report Share Posted February 3, 2012 ok...i bought a ignition module,installed it,and i have come to a conclusion....im done.....still no start.so what you think next,distributor? how much is a new one.... I KNOW HOW YOU FEEL .WENT THROUGH THREE MONTHS LAST YEAR WITH ONE ..BUT I NEVER GAVE UP ...... DID YOU READ POST 9 AND 10 .IF SO ....LETS US KNOW ...SOME OF US HAVE BEEN THROUGH THIS CRAPPY SYSTEM MORE THAN ONCE .. I BOUGHT A DISTRIBUTOR AT AUTOZONE ...129.00 IS WHAT I PAID .BUT I GET A DISCOUNT . I WORK THERE .159.00 OVER THE COUNTER .BUT COMES WITH CAP .SENSOR AND ROTOR....... I PULLED UP 96 YUKON NO IGN ...... Link to comment Share on other sites More sharing options...
JamesHigdon Posted February 3, 2012 Report Share Posted February 3, 2012 Ok, if you're getting spark at the coil but not the plug it is in either the cap, rotor, the disributor, every single wire or your tester. Do a quick resistance test from the coil input on the cap to the button on the bottom of the cap, no resistance means its bad. Press on the button on the bottom of the cap and make sure it returns. Those trucks are infamous for getting a whitish corossion on the cap and causing no fire, check the contacts in the cap. Next check the rotor for a short. Compare it to a known good rotor for wear issues. Make sure the rotor is spinning when cranked and that there is no wobble or lash in the rotor mount plate. You have isolated A problem, maybe not THE problem but A problem. Something between the coil and the end of the spark plug wires has gone bad, that's only 4 possible parts (cap, rotor, distributor or wires) Link to comment Share on other sites More sharing options...
Double D racing Posted February 4, 2012 Author Report Share Posted February 4, 2012 ok,i willget a cap and rotor but,another friend of mine still thinks its the fuelpump.... Link to comment Share on other sites More sharing options...
HiTech Posted February 4, 2012 Report Share Posted February 4, 2012 ok,i willget a cap and rotor but,another friend of mine still thinks its the fuelpump....run a fuel pressure test ...some auto part store loan with a deposit a pressure guage .....if you poured some gas down the throtle body and it did not start .i would not be wanting to change the fuel pump on a guess ..costly ..good luck. Link to comment Share on other sites More sharing options...
Double D racing Posted February 4, 2012 Author Report Share Posted February 4, 2012 ok hi tech,i jus spent the last hour reading your post on the 96 yukon....heres what i got ....the motor was replaced 15,000 miles ago,after about 3000 or 4000 miles it started an oil leak from the front of the motor....i couldnt afford to be a vehicle short at the time so i kept it full of oil and monitored it.finally i put it in the shop and found out that the motor was put back together with the original cover and that was causing the oil leak.now i dont recall if a new one was put back in or did we jus silicone it...now..i changed the crank sensor,cam sensor,ign. sensor,almost the same (not as mch time on fuel system) as you went thru. i will contact the shop and ask him about the cover,reluctor and sensor thing.also....to my knowledge nobody threw sand in the tank but...i did notice when i changed the fuelfilter it had alot of dirt/water/junk come out of it....but like i posted earlier when you turn the key on the fuel system cuts in like it should and shuts off in the same time and manner...when the motor turns over it acts like it almost will start and about every third rotation it acts like its out of time....now i jus bought 10 gals of diesel to burn a few brush piles ....i might jus drag this P.O.S. in the middle of the pile and walk away...R.I.P. Link to comment Share on other sites More sharing options...
HiTech Posted February 4, 2012 Report Share Posted February 4, 2012 .........PUSH ON THE CRANK SENSOR SEE IT WILL START ..THAT WOULD ANSWER THE COVER QUESTION AS TO WHAT I HAVE FOUND BEFORE .. NOT SAY IT ISNT THAT .........AS YOU READ /I TESTED EVERY THING ON THAT YUKON .AND THEN SOME ...I LOST A LOT OF HAIR AND SLEEP .................................NOW I AM GOING TO GIVE YOU THE RUN DOWN ON THAT 99 SUB...........I TESTED EVERYTHING JUST LIKE I DID THAT YUKON ......THE FIRST SYMPTOMS ..WERE WITH THIS SUB ..WAS FOR AWHILE IT STARTED COLD LIKE IT WAS 30 DEGREES ADVANCED .....THEN IT TOOK OUT THE FLEX PLATE ....6 OR MORE TEETH GONE ..AFTER CHANGING THAT ..IT WOULD TRY TO START .BUT JUST NOT QUITE GET THERE ....SO AFTER CHANGING THE CAP AND ROTOR .IT WOULD THEN GO TO KICKING BACK AS I LET THE KEY OFF FROM SPINNING IT OVER ..STRANGE ..THATS WHEN I PULLED THE DISTRIBUTOR ..AND PAID ALOT OF ATTENTION TO THE GAP BETWEEN SENSOR AND ROTOR PLATE ...DID NOT SEE THIS PROBLEM I FOUND WHILE LOOKING AT IT IN THE TRUCK.......IF THE GAP OPENS IN THE MIDDLE OF THE ROTOR PLATE..[[[iE RELUCTOR ]] AND SENSOR ..IT WILL NOT RUN . THE GAP MUST CLOSE SOME AS YOU ROTATE IT IN THE MIDDLE ...EGG SHAPE ........WHY I KEEP ON ABOUT THAT DISTRIBUTOR ...JUST HAVE A HUGH FEELING .....MATCH THAT DISTRIBUTOR .WITH A NEW ONE .YOU WILL SEE THE DIFFERENT'S IF THE OLD IS BAD .HANG IN THERE ...DONT LET THAT TRUCK BEAT YOU . Link to comment Share on other sites More sharing options...
Double D racing Posted February 5, 2012 Author Report Share Posted February 5, 2012 ok...i have been told by a few that it could be the dist.when i took it out we looked it over and put the rotor cap back on it and did not notice anything wrong.bottom gear had a little wear but not as bad as ive seen...now once again my buddy swares up and down its the fuelpump.he says this type system has to have up to 100 psi fuel pressure to the injectors which tells the motor to fire ??? help me on that one... Link to comment Share on other sites More sharing options...
JamesHigdon Posted February 5, 2012 Report Share Posted February 5, 2012 That motor has to have between 48 and 60 PSI to run, about 55 running and 60 while priming. I'm confused, are you still getting spark at the coil but not at the wires? If so thats the issue you have to solve first. Link to comment Share on other sites More sharing options...
HiTech Posted February 5, 2012 Report Share Posted February 5, 2012 ok...i have been told by a few that it could be the dist.when i took it out we looked it over and put the rotor cap back on it and did not notice anything wrong.bottom gear had a little wear but not as bad as ive seen...now once again my buddy swares up and down its the fuelpump.he says this type system has to have up to 100 psi fuel pressure to the injectors which tells the motor to fire ??? help me on that one... no fuel pump nore fuel pressure control firing ..a bad ground on the left rear frame rail can be a source of fuel pump problem.s ...but you have already poured gas down it .and it did not start .... now unless you have an injector stuck open and dumping fuel it should have started .or tried to ...you can check fuel pressure .or pull the plugs and see which one.ones are black or smell heavy of fuel ...........i know you said you pulled dist ..but i did not see where you checked the clearance between the cam sensor and the reluctor plate .wished i could draw a pic for you and put it on here .but i aint that good with computor.....it is not the gear thats a concern ..........seeing you changed the cam sensor ..that slot you had to line up in order to pull the sensor out ..is the area we are concerned about ..the dist rotates clock wise ..just counter of the slot .is the plate aiming down and slides through the cam sensor ....it is probably three inches long .....notice one side of the rotor plate has nothing hanging down .the other has the plate we are talking about ..if that iis not egg shaped as you turn it and the gap opens up in the middle ..the gap will close alittle .it will not run ........ Link to comment Share on other sites More sharing options...
Double D racing Posted February 5, 2012 Author Report Share Posted February 5, 2012 uggg.well its a whole lot easier to pull distributor than the fuelpump....i will pull it tomorrow if it warms up a little.i remember the rotor sittin on the baseplate we where lookin at it like it was warped or funky or somethin....to be continued....... Link to comment Share on other sites More sharing options...
JamesHigdon Posted February 6, 2012 Report Share Posted February 6, 2012 If you are getting fire at the coil then it's not the cam sensor or the crank sensor. Before spending anymore money do yourself a favor and check for spark at all 8 of the spark plugs. If the coil is sparking but the plugs aren't its a very simple deal. If the coils firing and the plugs are firing then it's most likely fuel, you can get a cheap fuel pressure tester at most parts stores for $30. Link to comment Share on other sites More sharing options...
brettsb16a2 Posted February 6, 2012 Report Share Posted February 6, 2012 Use a professional scan tool to diagnose this, probably would have seen the problem right away. You can't diagnose a computer controlled car like a race car. Link to comment Share on other sites More sharing options...
4cylfordz Posted February 6, 2012 Report Share Posted February 6, 2012 a bum dist still sounds like the culprit but just for grins did you see if the rotor turns when your cranking? ive seen many a roll pin bust before and no rotation= no run (also no oil press) Link to comment Share on other sites More sharing options...
KISS_Racing Posted February 6, 2012 Report Share Posted February 6, 2012 Use a professional scan tool to diagnose this, probably would have seen the problem right away. You can't diagnose a computer controlled car like a race car. Can we stop for a sec? Get a can of starter fluid and spray a little at a time in air inlet hose past air cleaner. Have someone else crank it give it a spirt about every 20 - 30 seconds. If it fires up then back track fuel system. Also keep in mind that fuel pumps require constant voltage at crank. I have seen weak batteries cause start issues. (Just sayin') And yes, he isn't a sponsor on here but is a fellow racer and a good friend. The shop on the Eastside of SA is a good one and WILL NOT rip you off! Link to comment Share on other sites More sharing options...
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