No power to coil & backfiring through carb ??'s

09-28-2001, 11:22 AM

Checked the pos side of the coil, no power and still backfires through carb under heavy acceleration... found a vacuum leak at the carb base, replaced the gasket...

and to eliminate questions I replaced the ignition module (or whatever it is on the fender), replaced the distributer and the coil, new cap, new plugs, and the plug wires only have 200 miles on them... Timing is dead on @ factory recommended 12 deg.

ran a temp power wire to the pos side of the coil (i'll have to find the prob), and it starts, idles fine, and if you slowly take it to 4000 rpm's it runs mint.... BUT, from an idle, if you jump on it hard, it backfires huge through the carb (flames about a foot high)...

temp last nite was about 60 deg,,, any ideas?

I'm gonna call Holley and talk to their tech support, but thought i'd ask here too...

thx in advance..

------------------
84 GT,shorty headers, open dual's, bored .060, 10.5" clutch, T5, 89 heads, edelbrock Performer manifold, matched cam, 600 Holley..

PKRWUD · 09-28-2001, 11:43 AM

Trace the coil back to the ignition switch. The problem is in that circuit.

Sounds like you have a blown power valve in your carb.

Take care
~Chris

------------------
Retired Moderator
MustangNet

My site: JimPorterRacing

RACECAR spelled backwards is RACECAR

HEY !!! Are you ASE Certified ??? If you are, ask me about iATN. The best tool you'll ever have, and it's free !!!

09-28-2001, 12:07 PM

PK is that hard to replace, I am certainly not a carb person...

thx for the response, I was thinking it was in the carb tooo..

PKRWUD · 09-28-2001, 12:25 PM

4 bowl screws (either flathead or 5/16"), a 1" open end and a 5/8" open end for the fuel line going to the primary bowl, and the same 1" open end wrench to remove the power valve from the metering plate. You will need a new bowl gasket and a new metering plate gasket. Both have to be removed to get to the power valve. Make sure your replacement gaskets are BLUE, NON-STICK gaskets, and make absolutely sure that you clean off every single piece of old gasket material from the bowl, both sides of the metering plate, and the body. After you remove the power valve, look along the edge of the hex pattern, or on it's surface, for a number. Probably 65. Replace it with a power valve of the same value, and don't forget the power valve gasket.

email me.

Take care
~Chris

------------------
Retired Moderator
MustangNet

My site: JimPorterRacing

RACECAR spelled backwards is RACECAR

HEY !!! Are you ASE Certified ??? If you are, ask me about iATN. The best tool you'll ever have, and it's free !!!

09-28-2001, 07:39 PM

Chris, how do i know which one (primary or secondary??? or just replace both???

PKRWUD · 09-29-2001, 12:15 AM

Check your email. I need numbers. You may only have one. What's your list #?

Take care
~Chris

------------------
Retired Moderator
MustangNet

My site: JimPorterRacing

RACECAR spelled backwards is RACECAR

HEY !!! Are you ASE Certified ??? If you are, ask me about iATN. The best tool you'll ever have, and it's free !!!

demon357 · 09-29-2001, 03:58 AM

is it a fairly new holley? If so it should have power valve blow out protection. Do you have a mechanical advance or vacuum advance distributor?

09-29-2001, 09:05 AM

vacuum advance dist...

the carb is an 1850, i pulled it apart, it only has 1, double pumpers, i guess have 2..

PKRWUD · 09-29-2001, 10:26 AM

I sent you an email with the optimum changes to make to your carb. You will need a vacuum gauge to dial in the carb and the ignition timing. Let me know when you have one, and we'll set things up.

Take care
~Chris

------------------
Retired Moderator
MustangNet

My site: JimPorterRacing

RACECAR spelled backwards is RACECAR

HEY !!! Are you ASE Certified ??? If you are, ask me about iATN. The best tool you'll ever have, and it's free !!!

09-28-2001, 11:22 AM	#1
about-2-give-up Guest Posts: n/a	No power to coil & backfiring through carb ??'s Checked the pos side of the coil, no power and still backfires through carb under heavy acceleration... found a vacuum leak at the carb base, replaced the gasket... and to eliminate questions I replaced the ignition module (or whatever it is on the fender), replaced the distributer and the coil, new cap, new plugs, and the plug wires only have 200 miles on them... Timing is dead on @ factory recommended 12 deg. ran a temp power wire to the pos side of the coil (i'll have to find the prob), and it starts, idles fine, and if you slowly take it to 4000 rpm's it runs mint.... BUT, from an idle, if you jump on it hard, it backfires huge through the carb (flames about a foot high)... temp last nite was about 60 deg,,, any ideas? I'm gonna call Holley and talk to their tech support, but thought i'd ask here too... thx in advance.. ------------------ 84 GT,shorty headers, open dual's, bored .060, 10.5" clutch, T5, 89 heads, edelbrock Performer manifold, matched cam, 600 Holley..

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09-28-2001, 11:43 AM	#2
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	Trace the coil back to the ignition switch. The problem is in that circuit. Sounds like you have a blown power valve in your carb. Take care ~Chris ------------------ Retired Moderator MustangNet My site: JimPorterRacing RACECAR spelled backwards is RACECAR HEY !!! Are you ASE Certified ??? If you are, ask me about iATN. The best tool you'll ever have, and it's free !!!

09-28-2001, 12:07 PM	#3
about-2-give-up Guest Posts: n/a	PK is that hard to replace, I am certainly not a carb person... thx for the response, I was thinking it was in the carb tooo..

09-28-2001, 12:25 PM	#4
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	4 bowl screws (either flathead or 5/16"), a 1" open end and a 5/8" open end for the fuel line going to the primary bowl, and the same 1" open end wrench to remove the power valve from the metering plate. You will need a new bowl gasket and a new metering plate gasket. Both have to be removed to get to the power valve. Make sure your replacement gaskets are BLUE, NON-STICK gaskets, and make absolutely sure that you clean off every single piece of old gasket material from the bowl, both sides of the metering plate, and the body. After you remove the power valve, look along the edge of the hex pattern, or on it's surface, for a number. Probably 65. Replace it with a power valve of the same value, and don't forget the power valve gasket. email me. Take care ~Chris ------------------ Retired Moderator MustangNet My site: JimPorterRacing RACECAR spelled backwards is RACECAR HEY !!! Are you ASE Certified ??? If you are, ask me about iATN. The best tool you'll ever have, and it's free !!!

09-28-2001, 07:39 PM	#5
about-2-give-up Guest Posts: n/a	Chris, how do i know which one (primary or secondary??? or just replace both???

09-29-2001, 12:15 AM	#6
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	Check your email. I need numbers. You may only have one. What's your list #? Take care ~Chris ------------------ Retired Moderator MustangNet My site: JimPorterRacing RACECAR spelled backwards is RACECAR HEY !!! Are you ASE Certified ??? If you are, ask me about iATN. The best tool you'll ever have, and it's free !!!

09-29-2001, 03:58 AM	#7
demon357 Registered Member Join Date: Sep 2001 Posts: 13	is it a fairly new holley? If so it should have power valve blow out protection. Do you have a mechanical advance or vacuum advance distributor?

09-29-2001, 09:05 AM	#8
about-2-give-up Guest Posts: n/a	vacuum advance dist... the carb is an 1850, i pulled it apart, it only has 1, double pumpers, i guess have 2..

09-29-2001, 10:26 AM	#9
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	I sent you an email with the optimum changes to make to your carb. You will need a vacuum gauge to dial in the carb and the ignition timing. Let me know when you have one, and we'll set things up. Take care ~Chris ------------------ Retired Moderator MustangNet My site: JimPorterRacing RACECAR spelled backwards is RACECAR HEY !!! Are you ASE Certified ??? If you are, ask me about iATN. The best tool you'll ever have, and it's free !!!