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No Spark


Rosie
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Have a problem with my '97 Chevy half ton. Was driving it the other day, and it sputtered and Quit. Got no spark. Changed coil, cap, rotor, plugs and wires (was planning on this anyway. Just bought the truck). Tried to start it last night and still no spark. Any Ideas? Thanks... Oh, yeah. Got the 4.3L engine if that matters...

Edited by Rosie
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well .. could be ignition module if its spider injector system which it should be it is mounted on the bracket next to the coil .that can be checked at autozone ...or if it is throttle body injected which it should not be that one is under the rotor and can be checked too ..late night so foggy minded here ...common problem with the sound of sputter then died could be one of two possible things here as well .cam sensor and or crank sensor . that will take a bit more work checking out then you may want to miss with ..if you have a friend with a scanner or pay the deposit at autozone which isn't all that cheap but will get all your money back borrow a scanner I will bet it had a code in the system warning you about one or the other ..I could go on with other possible's but that will take a lifetime to explain and would still miss something lol..

Edited by HiTech
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the scanner at autozone is hand held and easy enough to use .its a loaner tool so it wont cost you other than a deposit to borrow it .and yes you can check the truck at home just plug it into the ob2 plug right under the stearing wheel turn on the key and follow the directions that come with the scanner ..if the scanner wont light up with key on check for blown fuse on the truck ..

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well heck happened to fast to catch it ...have any junk yards around I would get all three parts .module .crank sensor .cam sensor ...... but you can take the ign module to autozone and test it first or check with your local autopart store see if they have the tester ........has this truck given you any issues .like hard to start after running it .does this truck seem to try and start as you release off the start position . maybe just a tad back fire or shimmer ..if so it will be one of two things .cam or crank sensor and both are related .. as old as this truck is it could be one of em ..the cam sensor in the distributor controls spark timing and injector timing ..hate to throw this at you but the pass key could have gone bad .that's another story ..and have you check the fuses ..

Edited by HiTech
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10 to 12 volts is all you need ... I would clean and check all grounds . the one bolted to your thermostat housing is real important . I have even seen the fuel pump ground being a problem on this system .it is located on most old chevy on the upper frame rail at bout 11 oclock on your left rear tire just sorta have to look for it .. so many things can be the problem on this truck ..sure was glad when chevy got rid of this crappy system for the most part ..it will drive you insane ...

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  • 3 weeks later...

sometimes it wont catch a code when a problem of certain sensors just gives up like this has ...I found in the distributor when the tang I call it that goes through the cam sensor will warp out of shape over time instead of being a perfect curve .the middle will warp towards the outside of the cam sensor causing it to lose the proper gap between the pick ups ...he can check the gap from the start of the tang as one turns the motor by hand if it is warped in the middle it can keep it from firing .found two distributors having that problem ..

Edited by HiTech
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  • 5 years later...

I know this is an old post, but I thought I would add my 2 cents.  This same ignition/PCM/ fuel system is found on the 4.3L W engine, 5.0L M engine, 5.7L R engine and works similar on the big block 7.4L J  with the exception of different fuel injectors. The 4.3 and 5.0 are found almost exclusively in 1/2 ton trucks with a few exceptional odd special ordered combinations. The 5.7L is found in all classes up to 1 ton. The 7.4L big block only comes in the 3/4 and 1 ton. These engines were installed in trucks from 1996 to 2000 (in Classic 3/4 & 1 tons). I think the best way to tackle this would be using a scan tool; owned or rented. While cranking, look for an RPM signal. If there is a RPM reading, this most likely eliminates the crank sensor. This would leave either the ignition module or ignition coil. A  bad module or connection at the module would most likely set fault codes. Seeing that there are no codes set, I would then proceed to the coil. Before condemning the coil, I would inspect the coil connector. The connector has two leads,  a pink circuit which is battery voltage and a driver circuit which goes to the module. The wires are notorious for breaking inside the insulation. A tug on each circuit would break the plastic insulation revealing the open circuit.  Fixed!

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21 hours ago, mfmotorsports said:

I know this is an old post, but I thought I would add my 2 cents.  This same ignition/PCM/ fuel system is found on the 4.3L W engine, 5.0L M engine, 5.7L R engine and works similar on the big block 7.4L J  with the exception of different fuel injectors. The 4.3 and 5.0 are found almost exclusively in 1/2 ton trucks with a few exceptional odd special ordered combinations. The 5.7L is found in all classes up to 1 ton. The 7.4L big block only comes in the 3/4 and 1 ton. These engines were installed in trucks from 1996 to 2000 (in Classic 3/4 & 1 tons). I think the best way to tackle this would be using a scan tool; owned or rented. While cranking, look for an RPM signal. If there is a RPM reading, this most likely eliminates the crank sensor. This would leave either the ignition module or ignition coil. A  bad module or connection at the module would most likely set fault codes. Seeing that there are no codes set, I would then proceed to the coil. Before condemning the coil, I would inspect the coil connector. The connector has two leads,  a pink circuit which is battery voltage and a driver circuit which goes to the module. The wires are notorious for breaking inside the insulation. A tug on each circuit would break the plastic insulation revealing the open circuit.  Fixed!

 DANG  2016 when we spoke of this .. time sure as heck flys .. good info though ..

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Even though it's an old post, I would think there are quite a few of our members driving these trucks around as tow vehicles for our race cars. I know we spend hours in the garage or shop getting our cars ready for race day, sometimes neglecting the haulers that get us there. Hope it helps.

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many years ago well documented on here i had  i had a yukon or something eating my lunch .as time went by it was eating everyone else lunch right along with me i had hundreds of hour  and every ones attention  with all of us trying to figure out  this hell on wheels .. i am  fairly  good  on  chevys  .this one had an issue with cam and crank sensor going out of range after a few minutes of running .. not one stone was left unturned .the owner begged me to give up on it , HE  could not afford the effort ..well i didnt charge him outside of the job he hired me to do  .fuel pump replacement ..  almost 4 months on this truck  .. now everyone had the same answer i did  .but nothing worked , i tested every wire ground sending units  borrowed ecm and every other  thing i needed off a donor .. if it didnt fix  the issue donor parts came off .. . i talked to folks who built the trucks system .no answers they had ....   something made me do this on  a lucky strike   after telling the owner monster trucks were coming to corpus the next week if i have not found the issue we were going to let them crush it ..  he agreed .. i  went out side to move the truck  it wuld run fine for a few minutes  as it started acting up  .i touched the crank sensor  and the darn thing stayed running .i  took my finger off it would go to junk and die  .. HUMMMMMM..... SO I TOOK A SHOT AND REPLACED THE TIMING COVER  .fixed it ..that carbon  cover was swelling  and pushing the crank sensor out  a couple of thousands  from the reluctor ..  no one has seen that before and i havent seen or heard of it ever  happening again ..  most likely everyone would give up  and never noticed that .. sometimes it best to be lucky than good  .

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I believe it. Although it has never happened to me, I have heard of that. Those plastic covers tend to warp if removed repeatedly and overtightened. These engines are pretty old at this point so would probably advise to replace it if you have to remove it(cam or timing chain change). I have seen where the brass insert will pull out of the plastic when tightening the crank sensor retaining bolt. Finally, there is a service bulletin that addresses crank sensors  contacting the reluctor wheel. The bulletin advises you to shim out the crank sensor.

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On 4/1/2022 at 9:56 PM, mfmotorsports said:

I believe it. Although it has never happened to me, I have heard of that. Those plastic covers tend to warp if removed repeatedly and overtightened. These engines are pretty old at this point so would probably advise to replace it if you have to remove it(cam or timing chain change). I have seen where the brass insert will pull out of the plastic when tightening the crank sensor retaining bolt. Finally, there is a service bulletin that addresses crank sensors  contacting the reluctor wheel. The bulletin advises you to shim out the crank sensor.

FUNNY PART   that truck i had had never been worked on and back then no one had that answer . found it  by accident . the old saying  sometimes better to be lucky than good .. but that luck turned into months and hour sleepless nights i cant sleep much when i am  tried like that . i hate losing  when somethings you know could be just a small unusual problem .something simple . some times a nightmare  .

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