Puzzled? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**68350** · 09-05-2011, 01:26 PM

I have a 1970 402 in my shortbox. It has a stock quadrajet that was rebuilt, 65-67 396 heads, basically stock. It will start up fine if I don't start it for a few hours, but as soon as it runs for 20 minutes, it'll die and will not restart unless it sits for a while. Anybody have any ideas? thanks

BMERDOC · 09-05-2011, 01:29 PM

There seems to be a run on vapor lock and fuel starvation on the forum for a coupla days.

68gmsee · 09-05-2011, 01:33 PM

When you shut it down take the breather off and look down the throat of the carb with a flashlight to see if it's leaking fuel into the manifold. It usually takes a while for the fuel to evaporate off after you shut it down and that may be the reason it won't start right away.

Some quadrajets have leaking plugs and if they weren't sealed or sealed properly they may be leaking.

**Warrens69GMC** · 09-05-2011, 02:06 PM

Try using starting fluid and see if it starts with it. If it does, you have a fuel delivery problem. If not, its electrical - like ignition module, coil, etc...

OJ1988 · 09-05-2011, 02:15 PM

When you try and restart it, what does it do? Does it crank?

71swb4x4 · 09-05-2011, 02:16 PM

Just to clarify it is dieing after running for 20 minutes correct?

68gmsee · 09-05-2011, 02:50 PM

hmmm, I missed that part. If it dies on it's own, something else could be causing it. As mentioned above it could be ignition related.

It's still possible that flooding could cause it to die, but it wouldn't necessarily be at 20 minute intervals and you would notice that by blackish smoke coming out of the exhaust.

The 20 minutes may be about the time the engine reaches maximum temperature even though mine does it in about 10 minutes or so.

Maybe the coil???

**68350** · 09-05-2011, 05:27 PM

it has hei, it dies on its own after 10-20 minutes. It will crank all day after it dies, just wont restart. I did check to see fuel is still getting to the carb after it died, and fuel is still getting there.

71swb4x4 · 09-05-2011, 05:31 PM

Have you checked the HEI module? Maybe the module is going out and the heat of the engine is affecting it.

68gmsee · 09-05-2011, 05:45 PM

Quote:

Originally Posted by 68350

it has hei, it dies on its own after 10-20 minutes. It will crank all day after it dies, just wont restart. I did check to see fuel is still getting to the carb after it died, and fuel is still getting there.

Take a plug cable off, place close to block and see if it shoots a spark. Sometimes it's hard to see so if you have a bolt or similar insert it in the boot first then have someone crank it.

If it doesn't spark, then it's something in the distributor. Cap, rotor, module, coil.

hjewell2 · 09-05-2011, 09:25 PM

Quote:

Originally Posted by 71swb4x4

Have you checked the HEI module? Maybe the module is going out and the heat of the engine is affecting it.

Yes siree I had that happen to me once back in 1992 out in the middle of nothing. damm thing just stopped then got it started about hour later then stopped ten mins later. Got a ride home dropped in a HEI I had setting in a box started right up and made trip home. The ducks were safe that day never made it to hunting ground.

**68350** · 09-06-2011, 12:33 AM

Ok, i will check the hei out, because it was in the motor when I bought it.

**special-K** · 09-06-2011, 04:56 AM

It does sound like the module. A characteristic of a failing module is it cuts off when it gets warm,then works once cooled back down...for a while.

09-05-2011, 01:26 PM	#1
68350 Senior Member Join Date: Jan 2002 Location: Williston, ND Posts: 2,999	Puzzled? I have a 1970 402 in my shortbox. It has a stock quadrajet that was rebuilt, 65-67 396 heads, basically stock. It will start up fine if I don't start it for a few hours, but as soon as it runs for 20 minutes, it'll die and will not restart unless it sits for a while. Anybody have any ideas? thanks __________________ 68 Chevy CST/10, 50th Anniversary, 327/th400, 373 posi, buckets 68 GMC Shortbox Stepside, 402/th400, Tilt, Tach, Bucket Seats, 3.08 Positraction 69 Chevy Camaro SS, 383, 4 speed, positraction 70 Chevy El Camino SS396, Triple Black, 454/th400, Tach 70 Chevy Shortbox Stepside 4x4, 350/th350, Tilt, Tach, Cab Lights, Bumper Guards, Tow Hooks 70 Chevy 3/4 Longbox, 350/auto, 70k, SURVIVOR 71 Chevy Blazer, CST, 350/auto 71 GMC Sierra K2500, 454, 4 speed, 4.10 posi, 37s 71 Custom/30, Open Road, 350/th400, tilt 72 Chevy Shortbox Fleetside, 496 Stroker/th400, Tilt, Tach, Bucket Seats, 3.42 Posi 72 GMC Sierra Grande 2500. 427/th400, tilt, a/c, tool and stowage, buckets/console, 3.54 posi

09-05-2011, 01:29 PM	#2
BMERDOC Registered User Join Date: Jun 2011 Location: Richmond,Va Posts: 2,934	Re: Puzzled? There seems to be a run on vapor lock and fuel starvation on the forum for a coupla days. __________________ Nick Carter 1967 C10 Short bed Fleetside Project Cheap Thrills! 2WD C10 Modern/Performance Alignments Easiest Alignment Ever!

09-05-2011, 01:33 PM	#3
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Puzzled? When you shut it down take the breather off and look down the throat of the carb with a flashlight to see if it's leaking fuel into the manifold. It usually takes a while for the fuel to evaporate off after you shut it down and that may be the reason it won't start right away. Some quadrajets have leaking plugs and if they weren't sealed or sealed properly they may be leaking.

09-05-2011, 02:06 PM	#4
Warrens69GMC Registered User Join Date: Jan 2003 Location: Safford,AZ Posts: 3,625	Re: Puzzled? Try using starting fluid and see if it starts with it. If it does, you have a fuel delivery problem. If not, its electrical - like ignition module, coil, etc... __________________ 1969 307, t350 1950 Chevy Wagon 1978 Big 10 1967 C10, 250,3-OTT

09-05-2011, 02:15 PM	#5
OJ1988 Just a car guy Join Date: Feb 2006 Location: New Washington, IN Posts: 991	Re: Puzzled? When you try and restart it, what does it do? Does it crank? __________________ 1955 belair Blown Pro Street cruiser 1971 Camaro Pro Touring 1973 Vega Drag Car 1970 C20 tow rig

09-05-2011, 02:16 PM	#6
71swb4x4 Senior Member Join Date: Nov 2003 Location: Brookings, SD Posts: 10,497	Re: Puzzled? Just to clarify it is dieing after running for 20 minutes correct? __________________ Some people are like slinkies, they aren't good for anything, but you can't help but smile when you see one tumble down the stairs.

09-05-2011, 02:50 PM	#7
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Puzzled? hmmm, I missed that part. If it dies on it's own, something else could be causing it. As mentioned above it could be ignition related. It's still possible that flooding could cause it to die, but it wouldn't necessarily be at 20 minute intervals and you would notice that by blackish smoke coming out of the exhaust. The 20 minutes may be about the time the engine reaches maximum temperature even though mine does it in about 10 minutes or so. Maybe the coil???

09-05-2011, 05:27 PM	#8
68350 Senior Member Join Date: Jan 2002 Location: Williston, ND Posts: 2,999	Re: Puzzled? it has hei, it dies on its own after 10-20 minutes. It will crank all day after it dies, just wont restart. I did check to see fuel is still getting to the carb after it died, and fuel is still getting there. __________________ 68 Chevy CST/10, 50th Anniversary, 327/th400, 373 posi, buckets 68 GMC Shortbox Stepside, 402/th400, Tilt, Tach, Bucket Seats, 3.08 Positraction 69 Chevy Camaro SS, 383, 4 speed, positraction 70 Chevy El Camino SS396, Triple Black, 454/th400, Tach 70 Chevy Shortbox Stepside 4x4, 350/th350, Tilt, Tach, Cab Lights, Bumper Guards, Tow Hooks 70 Chevy 3/4 Longbox, 350/auto, 70k, SURVIVOR 71 Chevy Blazer, CST, 350/auto 71 GMC Sierra K2500, 454, 4 speed, 4.10 posi, 37s 71 Custom/30, Open Road, 350/th400, tilt 72 Chevy Shortbox Fleetside, 496 Stroker/th400, Tilt, Tach, Bucket Seats, 3.42 Posi 72 GMC Sierra Grande 2500. 427/th400, tilt, a/c, tool and stowage, buckets/console, 3.54 posi

09-05-2011, 05:31 PM	#9
71swb4x4 Senior Member Join Date: Nov 2003 Location: Brookings, SD Posts: 10,497	Re: Puzzled? Have you checked the HEI module? Maybe the module is going out and the heat of the engine is affecting it. __________________ Some people are like slinkies, they aren't good for anything, but you can't help but smile when you see one tumble down the stairs.

09-06-2011, 12:33 AM	#12
68350 Senior Member Join Date: Jan 2002 Location: Williston, ND Posts: 2,999	Re: Puzzled? Ok, i will check the hei out, because it was in the motor when I bought it. __________________ 68 Chevy CST/10, 50th Anniversary, 327/th400, 373 posi, buckets 68 GMC Shortbox Stepside, 402/th400, Tilt, Tach, Bucket Seats, 3.08 Positraction 69 Chevy Camaro SS, 383, 4 speed, positraction 70 Chevy El Camino SS396, Triple Black, 454/th400, Tach 70 Chevy Shortbox Stepside 4x4, 350/th350, Tilt, Tach, Cab Lights, Bumper Guards, Tow Hooks 70 Chevy 3/4 Longbox, 350/auto, 70k, SURVIVOR 71 Chevy Blazer, CST, 350/auto 71 GMC Sierra K2500, 454, 4 speed, 4.10 posi, 37s 71 Custom/30, Open Road, 350/th400, tilt 72 Chevy Shortbox Fleetside, 496 Stroker/th400, Tilt, Tach, Bucket Seats, 3.42 Posi 72 GMC Sierra Grande 2500. 427/th400, tilt, a/c, tool and stowage, buckets/console, 3.54 posi

09-06-2011, 04:56 AM	#13
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,851	Re: Puzzled? It does sound like the module. A characteristic of a failing module is it cuts off when it gets warm,then works once cooled back down...for a while. __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~



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