Carburetor troubleshooting?

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Stoney
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Carburetor troubleshooting?

Post by Stoney »

Howdy,

I'm trying to troubleshoot my fuel system as to why my 79 J-10 with 360 V8 isn't starting. Bought in September 2020.

So far I've replaced the fuel filter and fuel pump. I've then removed the fuel line from the Carb and cranked the engine to see if I had fuel flow and I did, so I don't think there is anything clogging up the tank line. It has 4barrell Holley carb that the previous owner said was rebuilt in March of 2019 and the truck was running at that point. I don't know much about carburetors so I'm not sure how to trouble shoot it so I can eliminate it from the possible issues that's keeping the truck from starting.
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tgreese
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Re: Carburetor troubleshooting?

Post by tgreese »

Any sudden no-start is gas or spark.

Does it start if you put gas down the carb throat?

It's a 4150, 4V aftermarket carb with vacuum secondaries. I suggest you get a book and learn about Holley carbs. They are very tunable and comparatively easy to tune. Lots of different tuning parts are available. https://www.amazon.com/s?k=holley+carbu ... graa90oz_e
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
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Stuka
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Re: Carburetor troubleshooting?

Post by Stuka »

Its worth checking for spark. You should get a nice blue spark. A weak yellow spark could result in hard start situations. And no spark would of course result in no starting at all.

And like tgreese mentions, put some fuel or starting fluid down the carb to see if that will get it to start.
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Stoney
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Re: Carburetor troubleshooting?

Post by Stoney »

tgreese wrote: Sat Jan 23, 2021 9:34 am Any sudden no-start is gas or spark.

Does it start if you put gas down the carb throat?

It's a 4150, 4V aftermarket carb with vacuum secondaries. I suggest you get a book and learn about Holley carbs. They are very tunable and comparatively easy to tune. Lots of different tuning parts are available. https://www.amazon.com/s?k=holley+carbu ... graa90oz_e
I'm sorry, completely forget to mention, when I first bought the truck me and the previous owner got it started and it ran for about 5 seconds before it died by pouring gas down the carburetor.
thanks a lot for IDing that Carb for me.
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chevelleguy
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Re: Carburetor troubleshooting?

Post by chevelleguy »

It’s actually a 4160 series. If you post a pic of the list numbers that are on the choke air horn we can tell you exactly what model you have, but I would bet it’s a 600 cfm.


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rocklaurence
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Re: Carburetor troubleshooting?

Post by rocklaurence »

Look for fuel delivery. A stuck float, fuel through the Squirter/Accelerator pump. If you have fuel, then check spark.
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Stoney
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Re: Carburetor troubleshooting?

Post by Stoney »

chevelleguy wrote: Mon Jan 25, 2021 8:40 am It’s actually a 4160 series. If you post a pic of the list numbers that are on the choke air horn we can tell you exactly what model you have, but I would bet it’s a 600 cfm.
now if only I knew what the heck the choke air horn is haha. I'll go look it up and get back to you on that
The more you yell at the Jeep, the better it'll behave :fsj:
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Re: Carburetor troubleshooting?

Post by Stoney »

So I was looking down into the carburetor as my wife tried turning it over and pumped the gas. I could see the valvws opening and gas going into them, so I'm figuring that it's not fuel that's the problem right now.

I bought an inline spark plug tester to see if I was getting spark and I'm not. I thought that was a bit strange because I was able to get the truck started a few months ago, though it died after about 5 seconds. I already have a new dizzy ready to go, but I'd like to get it started before I replace that and the coil. Could they be the issue?
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'91 YJ - '97 XJ - '01 XJ - '79 J-10

chevelleguy
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Re: Carburetor troubleshooting?

Post by chevelleguy »

I think you have the Duraspark system. Distributor contains the pickup coil, they do go bad sometimes (I’ve had a couple fail over the years), ignition module is on the fender, those can fail too, and yes the coil it’s self can go bad.


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'83 Wag Limited, 360/727/pinned 229/D44 front/AMC20,lockrite,rear/6" BJ lift w/ 35/12.50/15 M/T Baja MTZ/ Pro-Jection EFI.

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tgreese
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Re: Carburetor troubleshooting?

Post by tgreese »

Unplug the module from the harness and clean thoroughly with electronics contact cleaner and a softish bristle brush. Same with the pickup coil plug between the harness and the distributor. These are well known to corrode and go open. Look for green corrosion and crumbly plastic. If the connectors crumble, replace the module or pickup coil.

Easiest way to test a coil is to put it in another car and see if you get spark. Or try a new coil in this car, either from another car or from the parts store. You can also ground and lift the primary wire from the coil to the module, and see if it makes spark. If you have a good coil, then the next most likely is a bad module. You can test the pickup coil with a multimeter - see the TSM.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.
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HowardT64
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Re: Carburetor troubleshooting?

Post by HowardT64 »

tgreese wrote: Sat Jan 23, 2021 9:34 am Any sudden no-start is gas or spark.

Does it start if you put gas down the carb throat?

It's a 4150, 4V aftermarket carb with vacuum secondaries. I suggest you get a book and learn about Holley carbs. They are very tunable and comparatively easy to tune. Lots of different tuning parts are available. https://www.amazon.com/s?k=holley+carbu ... graa90oz_e
It will...
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HowardT64
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Re: Carburetor troubleshooting?

Post by HowardT64 »

The coil is new. This is the same issue I was having before I had the mechanic put on the power steering unit and check the carb. He said the choke was not functioning properly....now it is doing it again....
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HowardT64
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Re: Carburetor troubleshooting?

Post by HowardT64 »

Got good news...we found that our finances would allow me to...get this, get a new carb!!! and with no core :) So, when I get the new one...i should be back up and running :)

WOO HOO!!!
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Stoney
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Re: Carburetor troubleshooting?

Post by Stoney »

What is going on HowardT?
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quakerrd39
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Re: Carburetor troubleshooting?

Post by quakerrd39 »

Tzke the carb off clean in up. Make sure allthe jets are open. You have a flot jet that may be the prob. Blow it out. Clean clean. Lay all the parts out as you take a part so you can clean and put back. Take your time.
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HowardT64
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Re: Carburetor troubleshooting?

Post by HowardT64 »

Stoney wrote: Fri Feb 12, 2021 5:55 pm What is going on HowardT?
Howdy!! Whats up? :)
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HowardT64
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Re: Carburetor troubleshooting?

Post by HowardT64 »

quakerrd39 wrote: Sun Feb 14, 2021 12:01 pm Tzke the carb off clean in up. Make sure allthe jets are open. You have a flot jet that may be the prob. Blow it out. Clean clean. Lay all the parts out as you take a part so you can clean and put back. Take your time.
When I get the carbs switched...ill get the paint can style of carb cleaner...pull the old carb apart, soak it for a while and just rebuild it. Once that is done, stick it back as a back up carb should I need another in the future :)

And yes, I will take my time :)
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