72 blazer ign problem - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**too much stuff** · 11-21-2005, 10:11 PM

I just picked up a 72 blazer and just got it running. The problem is the engine starts good when cold, but won't even fire when hot. Runs good, shut it off, no start. It has a 307 all stock, with point dist. and an auto tranny. Any ideas? I'm thinking coil, But would like some input. Thanks, Eric

Longhorn Man · 11-21-2005, 11:26 PM

Does it crank over at all... or just click?

GMC AMI · 11-22-2005, 08:20 AM

Sounds like the coil and they are cheap to replace. A good starting point to start with. You may want to check the point wire connection. I had one that when warmed up was just loose enough to lose the fire to the points. The screw did not look loose but was my problem.

bouncytruck · 11-22-2005, 12:21 PM

I had a problem with my '69 shutting off when it was hot. I would have to wait for it to cool a bit to get anything when I turned the key. It ended up being the plug into the back of the ignition melted. The ignition switch died and that killed the plug. I swapped out the plug and the switch and it was solved.

The switch in my '72 also died and it melted the plug into the back of it. I seems like it could be a weak point in the ignition system.

Look under the dash and see what shape the plug into the back of the switch is in. It might be a simple fix.

**too much stuff** · 11-22-2005, 06:54 PM

Longhorn, cranks over fine except for a "hard" spot when cranking.
Bouncytruck, my 69 did the exact same thing this summer till i did the new ign switch.
mike, i will check the connections.
The truck is not dying on me, you can shut it off when it is running fine and then it won't start until its cold again.

cdowns · 11-22-2005, 07:58 PM

a good way is to start out with a tune up// new plugs gapped correctly,new points gapped correctly,new condensor and rotor,new fuel air and oilfilters, new oil do all that then you're ready to set the timing// while you're under the hood is a good time to check for dryrotted vaccume hoses and brittle cracked dryrotted sparkplug wires and cracks in the dizzy cap also if vehicle has set for a spell you could put a quart of marvel mystery oil into 5gallons of new current gasoling/// most engines respond well to this type treatment alot of times it's cheaper in the long run to just do this basic stuff first

**truckdude239** · 11-22-2005, 08:04 PM

sounds like an coil put i'd go ahead and do an tune up while iwas at it

**too much stuff** · 11-23-2005, 12:04 AM

I started it up tonight with no problems, let it run about 2 minutes and shut it off. No start. Put my spark tester on the coil and have no spark. I am going to start with a coil tomorrow. I have done the oil change and the previous owner did points, plugs condensor and cap. It also has ALL new gas in it. If its not too cold i will update you guys tomorrow. Thanks.

**VetteVet** · 11-23-2005, 01:34 AM

Well thinking about this one I have an idea that the trouble may be in the wiring from the starter to the coil that delivers 12 volts to the coil during starting. It is connected to the outside terminal on the solenoid and is a yellow wire. I would try using a jumper from the battery positive to the coil positive the next time it won't start and have someone crank the engine to see if it will fire up.

**kwmech** · 11-23-2005, 01:56 AM

Could also be the condensor. Just do a good old fashioned tune-up. OR now would be a good time for an HEI

**too much stuff** · 11-24-2005, 01:08 AM

Well, i put a coil in and seems good so far. It is -10 degrees With wind chill right now so i didn't spend alot of time on it.
Hei will be the way to go, but i don't want to stick alot of time and $$$ into it until i can see how it will run.
Thanks for all the input. Eric

cableguy0 · 11-24-2005, 01:14 AM

you can pick up a used hei for about 35 bucks. and it wont take more than an hour to do the swap. if you have replaced a distributor before. much more reliable easier starts and better mileage to boot

11-21-2005, 10:11 PM	#1
too much stuff Roadtrip! Join Date: Feb 2003 Location: Grand Rapids MN Posts: 13,718	72 blazer ign problem I just picked up a 72 blazer and just got it running. The problem is the engine starts good when cold, but won't even fire when hot. Runs good, shut it off, no start. It has a 307 all stock, with point dist. and an auto tranny. Any ideas? I'm thinking coil, But would like some input. Thanks, Eric __________________ 67 gmc custom lwb dakota truck. Sold...And bought back 69 swb 4x4 project (in progress) 70 c-10 lwb texas truck 70 4x4/BB/bkts/posi/tach(retired) 70 swb (wifes) 70 jimmy camper 71 K-5 factory 2wd 71 cheyenne 4x4/tach/posi/ plow rig 71 Cheyenne20 BB, buckets, tach, tilt, 4 speed 72 jimmy CST wyoming rig 72 jimmy Colorado rig 72 lifted texas 4x4 3/4 ton burb 65 fury conv. 383/auto 65 chrysler 300 "L" 413 auto

11-21-2005, 11:26 PM	#2
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: 72 blazer ign problem Does it crank over at all... or just click?

11-22-2005, 08:20 AM	#3
GMC AMI Registered User Join Date: Apr 2004 Location: The Other Maine! Posts: 2,236	Re: 72 blazer ign problem Sounds like the coil and they are cheap to replace. A good starting point to start with. You may want to check the point wire connection. I had one that when warmed up was just loose enough to lose the fire to the points. The screw did not look loose but was my problem. __________________ 1968 Chevy 4x4 307 4 speed

11-22-2005, 12:21 PM	#4
bouncytruck SKINNY TIRES RULE! Join Date: Sep 2001 Location: Bothell, WA Posts: 11,049	Re: 72 blazer ign problem I had a problem with my '69 shutting off when it was hot. I would have to wait for it to cool a bit to get anything when I turned the key. It ended up being the plug into the back of the ignition melted. The ignition switch died and that killed the plug. I swapped out the plug and the switch and it was solved. The switch in my '72 also died and it melted the plug into the back of it. I seems like it could be a weak point in the ignition system. Look under the dash and see what shape the plug into the back of the switch is in. It might be a simple fix. __________________ bouncytruck 1972 K5 The Hauler 1994 K1500 Suburban The Daily2010 Kia Soul Wife's Ride2014 Fiat 500L

11-22-2005, 06:54 PM	#5
too much stuff Roadtrip! Join Date: Feb 2003 Location: Grand Rapids MN Posts: 13,718	Re: 72 blazer ign problem Longhorn, cranks over fine except for a "hard" spot when cranking. Bouncytruck, my 69 did the exact same thing this summer till i did the new ign switch. mike, i will check the connections. The truck is not dying on me, you can shut it off when it is running fine and then it won't start until its cold again. __________________ 67 gmc custom lwb dakota truck. Sold...And bought back 69 swb 4x4 project (in progress) 70 c-10 lwb texas truck 70 4x4/BB/bkts/posi/tach(retired) 70 swb (wifes) 70 jimmy camper 71 K-5 factory 2wd 71 cheyenne 4x4/tach/posi/ plow rig 71 Cheyenne20 BB, buckets, tach, tilt, 4 speed 72 jimmy CST wyoming rig 72 jimmy Colorado rig 72 lifted texas 4x4 3/4 ton burb 65 fury conv. 383/auto 65 chrysler 300 "L" 413 auto

11-22-2005, 07:58 PM	#6
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: 72 blazer ign problem a good way is to start out with a tune up// new plugs gapped correctly,new points gapped correctly,new condensor and rotor,new fuel air and oilfilters, new oil do all that then you're ready to set the timing// while you're under the hood is a good time to check for dryrotted vaccume hoses and brittle cracked dryrotted sparkplug wires and cracks in the dizzy cap also if vehicle has set for a spell you could put a quart of marvel mystery oil into 5gallons of new current gasoling/// most engines respond well to this type treatment alot of times it's cheaper in the long run to just do this basic stuff first __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

11-22-2005, 08:04 PM	#7
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,233	Re: 72 blazer ign problem sounds like an coil put i'd go ahead and do an tune up while iwas at it __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube

11-23-2005, 12:04 AM	#8
too much stuff Roadtrip! Join Date: Feb 2003 Location: Grand Rapids MN Posts: 13,718	Re: 72 blazer ign problem I started it up tonight with no problems, let it run about 2 minutes and shut it off. No start. Put my spark tester on the coil and have no spark. I am going to start with a coil tomorrow. I have done the oil change and the previous owner did points, plugs condensor and cap. It also has ALL new gas in it. If its not too cold i will update you guys tomorrow. Thanks. __________________ 67 gmc custom lwb dakota truck. Sold...And bought back 69 swb 4x4 project (in progress) 70 c-10 lwb texas truck 70 4x4/BB/bkts/posi/tach(retired) 70 swb (wifes) 70 jimmy camper 71 K-5 factory 2wd 71 cheyenne 4x4/tach/posi/ plow rig 71 Cheyenne20 BB, buckets, tach, tilt, 4 speed 72 jimmy CST wyoming rig 72 jimmy Colorado rig 72 lifted texas 4x4 3/4 ton burb 65 fury conv. 383/auto 65 chrysler 300 "L" 413 auto

11-23-2005, 01:34 AM	#9
VetteVet Msgt USAF Ret Join Date: Jan 2005 Location: Kalamazoo, Michigan Posts: 8,709	Re: 72 blazer ign problem Well thinking about this one I have an idea that the trouble may be in the wiring from the starter to the coil that delivers 12 volts to the coil during starting. It is connected to the outside terminal on the solenoid and is a yellow wire. I would try using a jumper from the battery positive to the coil positive the next time it won't start and have someone crank the engine to see if it will fire up. __________________ VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative.

11-23-2005, 01:56 AM	#10
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,503	Re: 72 blazer ign problem Could also be the condensor. Just do a good old fashioned tune-up. OR now would be a good time for an HEI

11-24-2005, 01:08 AM	#11
too much stuff Roadtrip! Join Date: Feb 2003 Location: Grand Rapids MN Posts: 13,718	Re: 72 blazer ign problem Well, i put a coil in and seems good so far. It is -10 degrees With wind chill right now so i didn't spend alot of time on it. Hei will be the way to go, but i don't want to stick alot of time and $$$ into it until i can see how it will run. Thanks for all the input. Eric __________________ 67 gmc custom lwb dakota truck. Sold...And bought back 69 swb 4x4 project (in progress) 70 c-10 lwb texas truck 70 4x4/BB/bkts/posi/tach(retired) 70 swb (wifes) 70 jimmy camper 71 K-5 factory 2wd 71 cheyenne 4x4/tach/posi/ plow rig 71 Cheyenne20 BB, buckets, tach, tilt, 4 speed 72 jimmy CST wyoming rig 72 jimmy Colorado rig 72 lifted texas 4x4 3/4 ton burb 65 fury conv. 383/auto 65 chrysler 300 "L" 413 auto

11-24-2005, 01:14 AM	#12
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,950	Re: 72 blazer ign problem you can pick up a used hei for about 35 bucks. and it wont take more than an hour to do the swap. if you have replaced a distributor before. much more reliable easier starts and better mileage to boot __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.