Engine Help on dead cylinder

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jrichker

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I have a LOT of unkind and unpleasant things to say about people who convert an EFI car to carb. However, I will skip them and simply tell you that you made a terrible error in judgement when you converted an EFI car to carb.

The EFI system has diagnostics built into it that with just a simple jumper wire you can find almost all the things that aren't working properly. When the codes dump out, you post the codes here on Stangnet I have 5.0 Foxbody code definitions that tell you where to look and what you need to do to fix the problems.

Since it is a carb car, it is time to beg, borrow or buy a vacuum gauge to troubleshoot the problem. Most auto parts stores will rent or load one if you have a credit card.

Vacuum Gauge readings
attachments\606429
 
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General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
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Those plugs are toast. They don't cost that much and unless you have some tulane (I doubt you have) they are hard to clean, you can try but really just get some copper plugs, no need for those plutonium coated gold plated wizbang fancy sparkers unless you have a Mr. Fusion adapted to it.
Give us a pick of the engine compartment aka 'doghouse' please
Do you know what your fuel pressure is?
New carb, new distributor?
 

BigFatRoss

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Oct 18, 2020
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I have a LOT of unkind and unpleasant things to say about people who convert an EFI car to carb. However, I will skip them and simply tell you that you made a terrible error in judgement when you converted an EFI car to carb.

The EFI system has diagnostics built into it that with just a simple jumper wire you can find almost all the things that aren't working properly. When the codes dump out, you post the codes here on Stangnet I have 5.0 Foxbody code definitions that tell you where to look and what you need to do to fix the problems.

Since it is a carb car, it is time to beg, borrow or buy a vacuum gauge to troubleshoot the problem. Most auto parts stores will rent or load one if you have a credit card.

Vacuum Gauge readings
attachments\606429
Hello

jrichker, Thanks for posting chart, VERY HELPFULL!​

I have a question. Now that his car is running a carb, should the vacuum gauge be connected to manifold vacuum, OR ported vacuum, I’m assuming (ported vacuum). In addition if you could clear the “FOG FACTOR” for me, ……

Depending on the carb, I’m assuming you know when you are on PORTED vacuum when the gage reads 0 (at idle) and will see gauge move when the idle is increased?

And when you are connected to MANIFOLD vacuum, the gauge will be giving you a constant reading (at idle and or increased idle)?
Thank you in advance for your help.
 

92mustang74

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Apr 26, 2020
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Just a thought that is easy to do, turn the carb around, if you can, then if 3 4 5 & 7 are not firing, it is your carb for sure.
 
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luisjluis1

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Dec 4, 2020
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1 side of your carb is clogged up.
Pulling the carb right now. if I find nothing wrong I'm going to flip it like 92mustang74 said to see if the problem flips to the other cylinders. What should I be looking for if a side is clogged? I'll also go get some nicer plugs today. Thanks.
 

Monkeybutt2000

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Aug 11, 2019
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Pulling the carb right now. if I find nothing wrong I'm going to flip it like 92mustang74 said to see if the problem flips to the other cylinders. What should I be looking for if a side is clogged? I'll also go get some nicer plugs today. Thanks.
Is this a new carb? Can you not see fuel squirt when you work the throttle linkage?
 

KRUISR

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Apr 16, 2015
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When you have your carb off, check to see what cylinders are feed from what side of the carb. If all 4 you are having issue with are same side of carb. That to me is screaming as the problem.
 

luisjluis1

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Dec 4, 2020
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Its a brand new carb and intake from summit. Ive seen fuel squirt into both primaries when I goose it. Could it not be getting enough air?
Just pulled the carb. one side of the intake is dry while the other is wet. the dry side feeds all the bad cylinders. this is the problem. Thanks to all for your help! I will definitely find the problem with the carb here soon.
 

2Blue2

will be trying this sex one when I can find it
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Mar 5, 2019
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How could it be the intake? If you've verified that each spark plug has spark, and your distributor is installed correctly,it's your carb.
This is logical but,

Just spitballing
Could the intake have shipping material plugging it ?
I remember seeing a blower with plastic wrap still on bottom get installed.


maybe time for a compression test?
 

luisjluis1

Member
Dec 4, 2020
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Columbia, Mo
This is logical but,

Just spitballing
Could the intake have shipping material plugging it ?
I remember seeing a blower with plastic wrap still on bottom get installed.


maybe time for a compression test?
We just got the good cylinders to fire with the carb off by spraying starting fluid straight into the intake. Bad ones still didn't fire. Carb is out of the question now. It has good compression (10:1) but still could be valves. The problem is definitely down to spark or valves not working correctly.