Why won't my engine keep running? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

LandonL · 04-25-2010, 07:02 PM

I'm not the most brilliant guy when it comes to engines and I have a problem. I have a 1967 GMC Stepside, with the original Inline-6 250 in it, with the original Rochester Carb.

The Problem:
I can get the truck to start, and I can give it gas and it will rev up but after about 10-20 seconds a plume of gas will shoot out of the carburetor and the engine shuts off. It won't ever stay going. Does anyone know what could be causing this?

LandonL · 04-25-2010, 07:31 PM

Just tried it again, ran longer and idled but when I gave it some gas it did the same thing.

Shaky · 04-25-2010, 08:07 PM

Before I did anything else, I'd try to check the timing. Any idea how many miles are on it?

Also - I usually update to the '68-72 Monojet when I get one of these. I've just had better luck with the later model carb and it bolts on.

LandonL · 04-25-2010, 08:39 PM

It has 87k original miles on it.

LandonL · 04-25-2010, 08:42 PM

Also, how exactly would the timing cause this to happen. (Not joking, I barely know anything). Thanks!

Legolas894 · 04-25-2010, 09:50 PM

Don't get frustrated. Search around on the forum. There's lots of older posts and I'm sure you'll find some help. I have a quadrajet carb on mine and I know that if the PCV hose isn't hooked up, it will start but won't idle. Not sure what carb you have. Does it have any hoses or outlets that are wide open? You can buy little rubber caps that fit over any open outlets.

**Boog** · 04-25-2010, 10:28 PM

Is this a newly purchased truck? Or has it been sitting a while and now is doing this?

LandonL · 04-26-2010, 04:32 PM

No, hasn't been sitting. All started happening when I unbolted the exhaust manifold to clean and paint it. I reconnected everything, replaced all the gaskets. It's like the carb is coughing, I have no clue what could be causing it..

Shaky · 04-26-2010, 04:58 PM

Quote:

Originally Posted by LandonL

Also, how exactly would the timing cause this to happen. (Not joking, I barely know anything). Thanks!

If the valves are opening at the wrong time, the piston could be pushing back through the carb. It might not be the problem, but I like to make sure the basics (like timing) are right before I spend too much time looking for other issues.

Shaky · 04-26-2010, 05:02 PM

I'd also look under the distributor cap and make sure the centrifugal weights aren't sticking. If they are, it could mean that your timing is good at low rpm but off at higher rpm.

If you have a vacuum source (Mighty Vac) it would be good to check the vacuum advance also.

There's nothing plugging the exhaust (big mouse nest)?

Shaky · 04-26-2010, 05:04 PM

Quote:

Originally Posted by LandonL

No, hasn't been sitting. All started happening when I unbolted the exhaust manifold to clean and paint it. I reconnected everything, replaced all the gaskets. It's like the carb is coughing, I have no clue what could be causing it..

I just read this. Is the exhaust flapper valve still there? Does it move?

LandonL · 04-26-2010, 05:15 PM

The flap is still there and works fine, checked it already. I need a gasket for the connection point of the exhaust manifold and intake manifold, if just a tiny bit of air is leaking could that cause it?

Shaky · 04-26-2010, 05:50 PM

Quote:

Originally Posted by LandonL

The flap is still there and works fine, checked it already. I need a gasket for the connection point of the exhaust manifold and intake manifold, if just a tiny bit of air is leaking could that cause it?

No - there's no air movement there. That's just a heat transfer point from the exhaust manifold to keep the carburetor warm. The underside of the intake manifold is blind.

Are you sure you have a good seal where the exhaust (and intake) manifold meets the block?

LandonL · 04-26-2010, 05:56 PM

Yeah, nothing leaks out of the block's ports.

292farmer · 04-26-2010, 07:57 PM

is your choke working? when i was fiddling with my new to me (used) carb while it was running 1200-1400rpms i closed the choke for curiosities sake and the carb made a hiss and gas shot out the top and coated my hand, and the motor died, i'd see if the choke is sticking? sorry this was so long just seeing if u can relate this to your situation good luck!
btw mines a 292 inline 6 so a 1bbl carb too.

LandonL · 04-26-2010, 09:05 PM

Fixed the problem. The bolt keeping the distributor in place was almost fully worked out, twisted it back into place and the engine purred like a kitten. Now I just need to get it 100% timed properly. But as for now I'm happy.

04-25-2010, 07:02 PM	#1
LandonL Registered User Join Date: Nov 2009 Location: Georgia Posts: 440	Why won't my engine keep running? I'm not the most brilliant guy when it comes to engines and I have a problem. I have a 1967 GMC Stepside, with the original Inline-6 250 in it, with the original Rochester Carb. The Problem: I can get the truck to start, and I can give it gas and it will rev up but after about 10-20 seconds a plume of gas will shoot out of the carburetor and the engine shuts off. It won't ever stay going. Does anyone know what could be causing this? __________________ ---\| 1967 GMC Stepside \|-- 250 L6 .030 over ---\| 1985 Porsche 944/1 \|--- Build Thread: '67 GMC http://67-72chevytrucks.com/vboard/s...d.php?t=378640

04-25-2010, 07:31 PM	#2
LandonL Registered User Join Date: Nov 2009 Location: Georgia Posts: 440	Re: Why won't my engine keep running? Just tried it again, ran longer and idled but when I gave it some gas it did the same thing. __________________ ---\| 1967 GMC Stepside \|-- 250 L6 .030 over ---\| 1985 Porsche 944/1 \|--- Build Thread: '67 GMC http://67-72chevytrucks.com/vboard/s...d.php?t=378640

04-25-2010, 08:07 PM	#3
Shaky Six in a row makes it go... Join Date: Mar 2009 Location: Vacationland: Maine Posts: 1,346	Re: Why won't my engine keep running? Before I did anything else, I'd try to check the timing. Any idea how many miles are on it? Also - I usually update to the '68-72 Monojet when I get one of these. I've just had better luck with the later model carb and it bolts on. __________________ 67 C20 long step resto: http://67-72chevytrucks.com/vboard/s...d.php?t=342086 66 C10 long step build: http://67-72chevytrucks.com/vboard/s...=1#post3814790 CT to Alaska in a 67 C10: http://67-72chevytrucks.com/vboard/s...d.php?t=399224 “The height of sophistication is simplicity." - Clare Boothe Luce Last edited by Shaky; 04-25-2010 at 08:08 PM. Reason: Add info.

04-25-2010, 08:39 PM	#4
LandonL Registered User Join Date: Nov 2009 Location: Georgia Posts: 440	Re: Why won't my engine keep running? It has 87k original miles on it. __________________ ---\| 1967 GMC Stepside \|-- 250 L6 .030 over ---\| 1985 Porsche 944/1 \|--- Build Thread: '67 GMC http://67-72chevytrucks.com/vboard/s...d.php?t=378640

04-25-2010, 08:42 PM	#5
LandonL Registered User Join Date: Nov 2009 Location: Georgia Posts: 440	Re: Why won't my engine keep running? Also, how exactly would the timing cause this to happen. (Not joking, I barely know anything). Thanks! __________________ ---\| 1967 GMC Stepside \|-- 250 L6 .030 over ---\| 1985 Porsche 944/1 \|--- Build Thread: '67 GMC http://67-72chevytrucks.com/vboard/s...d.php?t=378640

04-25-2010, 09:50 PM	#6
Legolas894 Chemist under the hood... Join Date: Apr 2009 Location: Fort Erie,ON, Canada Posts: 617	Re: Why won't my engine keep running? Don't get frustrated. Search around on the forum. There's lots of older posts and I'm sure you'll find some help. I have a quadrajet carb on mine and I know that if the PCV hose isn't hooked up, it will start but won't idle. Not sure what carb you have. Does it have any hoses or outlets that are wide open? You can buy little rubber caps that fit over any open outlets. __________________ Current fleet: 2013 GMC Sierra, 5.3L, 4x4 1988 GMC Sierra, 305, Auto 1984 Jeep Grand Wagoneer, 360 V8 1997 VW Cabrio, 2.0L 2017 Toyota Rav4, 2.5L Stuff I wish I still had: 2013 Toyota Matrix [RIP] 1967 GMC 910 Fleetside, 283 V8 [1st Love-SOLD] 1987 Jeep Cherokee Laredo 4X4, 4.0 I-6 [SOLD} 1994 Chevrolet Caprice Classic, 5.7LV8 [SOLD] 1995 Chevrolet Astro AWD, 4.3L V6 (RIP) 1998 Chevrolet Suburban 4x4, 5.7L V8 [SOLD]

04-25-2010, 10:28 PM	#7
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,452	Re: Why won't my engine keep running? Is this a newly purchased truck? Or has it been sitting a while and now is doing this? __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

04-26-2010, 04:32 PM	#8
LandonL Registered User Join Date: Nov 2009 Location: Georgia Posts: 440	Re: Why won't my engine keep running? No, hasn't been sitting. All started happening when I unbolted the exhaust manifold to clean and paint it. I reconnected everything, replaced all the gaskets. It's like the carb is coughing, I have no clue what could be causing it.. __________________ ---\| 1967 GMC Stepside \|-- 250 L6 .030 over ---\| 1985 Porsche 944/1 \|--- Build Thread: '67 GMC http://67-72chevytrucks.com/vboard/s...d.php?t=378640

04-26-2010, 05:02 PM	#10
Shaky Six in a row makes it go... Join Date: Mar 2009 Location: Vacationland: Maine Posts: 1,346	Re: Why won't my engine keep running? I'd also look under the distributor cap and make sure the centrifugal weights aren't sticking. If they are, it could mean that your timing is good at low rpm but off at higher rpm. If you have a vacuum source (Mighty Vac) it would be good to check the vacuum advance also. There's nothing plugging the exhaust (big mouse nest)? __________________ 67 C20 long step resto: http://67-72chevytrucks.com/vboard/s...d.php?t=342086 66 C10 long step build: http://67-72chevytrucks.com/vboard/s...=1#post3814790 CT to Alaska in a 67 C10: http://67-72chevytrucks.com/vboard/s...d.php?t=399224 “The height of sophistication is simplicity." - Clare Boothe Luce

04-26-2010, 05:15 PM	#12
LandonL Registered User Join Date: Nov 2009 Location: Georgia Posts: 440	Re: Why won't my engine keep running? The flap is still there and works fine, checked it already. I need a gasket for the connection point of the exhaust manifold and intake manifold, if just a tiny bit of air is leaking could that cause it? __________________ ---\| 1967 GMC Stepside \|-- 250 L6 .030 over ---\| 1985 Porsche 944/1 \|--- Build Thread: '67 GMC http://67-72chevytrucks.com/vboard/s...d.php?t=378640 Last edited by LandonL; 04-26-2010 at 05:16 PM.

04-26-2010, 05:56 PM	#14
LandonL Registered User Join Date: Nov 2009 Location: Georgia Posts: 440	Re: Why won't my engine keep running? Yeah, nothing leaks out of the block's ports. __________________ ---\| 1967 GMC Stepside \|-- 250 L6 .030 over ---\| 1985 Porsche 944/1 \|--- Build Thread: '67 GMC http://67-72chevytrucks.com/vboard/s...d.php?t=378640

04-26-2010, 07:57 PM	#15
292farmer Registered User Join Date: Nov 2009 Location: stoddard nh Posts: 693	Re: Why won't my engine keep running? is your choke working? when i was fiddling with my new to me (used) carb while it was running 1200-1400rpms i closed the choke for curiosities sake and the carb made a hiss and gas shot out the top and coated my hand, and the motor died, i'd see if the choke is sticking? sorry this was so long just seeing if u can relate this to your situation good luck! btw mines a 292 inline 6 so a 1bbl carb too. Last edited by 292farmer; 04-26-2010 at 07:58 PM.

04-26-2010, 09:05 PM	#16
LandonL Registered User Join Date: Nov 2009 Location: Georgia Posts: 440	Re: Why won't my engine keep running? Fixed the problem. The bolt keeping the distributor in place was almost fully worked out, twisted it back into place and the engine purred like a kitten. Now I just need to get it 100% timed properly. But as for now I'm happy. __________________ ---\| 1967 GMC Stepside \|-- 250 L6 .030 over ---\| 1985 Porsche 944/1 \|--- Build Thread: '67 GMC http://67-72chevytrucks.com/vboard/s...d.php?t=378640

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