Vacuum leak or carb problem?

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1978J10REDWHITE
Posts: 263
Joined: Fri Nov 20, 2020 7:25 pm

Re: Vacuum leak or carb problem?

Post by 1978J10REDWHITE »

Purchased rolls of the rubber tubing. 3/32, 5/32, 7/32, then the other sizes you can do those piece at a time as those are not all that long, just get enough to do the job.
And do everything inside the cab too.
I had the vacuum switch on the Emergency switch was faulty leaking .. So beware that,
Typical most part houses do not have exact OEM material sizes, so a tight fit or use clamps on the ends might be needed.
I had three rigs and all them went this way and needed it!!
Don't overlook your three metal tubes set, on passenger side, behind manifold, that go down to trans side, those can be clogged or have holes in them possibly.
Remember, It's a good idea to "suspect" all the manifold vacuum porting switches, EGW vlv, The round vacuum accumulator on firewall, and every part which may have cracked plastic port tubes etc.
So to TS it might be a bit entailed yet once you locate things you though might be OK but are NOT you will learn what almost ALL Jeep owners have REALIZED the same..
Eliminate Every possibility of vacuum leaks, as then in the future or your ownership, this is already addressed and should not haunt you..
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devildog80
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Joined: Wed Apr 13, 2022 2:41 pm
Location: Apache Junction AZ

Re: Vacuum leak or carb problem?

Post by devildog80 »

Nice......worthwhile project for sure.

Keep up the good work :)
'81 CJ5 Base, 258 I6, MC2100, T176 4 spd, 300 TC, D30 Front NT, 3.31, 2-Piece AMC 20 rear NT, 3.31, 4" high arc spring lift
'84 Grand Wagoneer, 401 V8 (.030 over), MC2150 HA Comp, 727 auto, Selec-trac NP229, AMC 20 REAR - D44 FRONT - WT 3.31, 4" high arc spring lift
Rather be driving, than waiting to be modified
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1978J10REDWHITE
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Re: Vacuum leak or carb problem?

Post by 1978J10REDWHITE »

Yes, like tgreesa said go to stop and buy spools of material. I I recall it was 3/32, 5/32, 7/32 then there are other sizes which those you want to measure up and get correct lengths.
One of th smaller hoses maybe 3/32 a full spool was too mush so verify how much each size before getting a full spool of them.
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Stoney
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Joined: Thu Nov 12, 2020 7:54 am
Location: North Carolina

Re: Vacuum leak or carb problem?

Post by Stoney »

Just wanted to let everyone know that I got the problem solved!
Upon further inspection i saw that the hose that goes from the PCV valve to the intake was swollen and leaking so I replaced that, and I also had an open valve on the carburetor itself that I plugged, then I took the carburetor to get tuned and thr truck runs alot better now I don't have to constantly keep a foot on the gas to jeep it alive anymore. I also replaced the transmission modulator so it shifts better and does t lag when accelerating.

Though the shop I took it to sold me I had some "blowback" I think they called it, which indicates low compression? Am I doomed?
The more you yell at the Jeep, the better it'll behave :fsj:
'91 YJ - '97 XJ - '01 XJ - '79 J-10
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tgreese
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Location: Medford MA USA

Re: Vacuum leak or carb problem?

Post by tgreese »

Blow-by? Pressure in the crankcase caused by worn rings. PCV system deals with that, in principle.
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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letank
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Re: Vacuum leak or carb problem?

Post by letank »

Stoney wrote: Tue Aug 30, 2022 4:03 am Though the shop I took it to sold me I had some "blowback" I think they called it, which indicates low compression? Am I doomed?
Not doomed , but at some point the air filter housing starts to fill with some oil, check and clean as needed.... or you can add an oil catch can between the oil filler and the air filter housing.

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74 wag (349 Kmiles... parked, next step is a rust free body)
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Srdayflyer
Posts: 398
Joined: Mon Mar 18, 2019 2:08 pm

Re: Vacuum leak or carb problem?

Post by Srdayflyer »

you said this truck was not running when you got it, the question is how long was it not running, a month 6 months a year?, the idle circuit ports are real small and may have gummed up and this would definitely be and idle issue, in arizona due to the heat no op cars and trucks fuel can go bad in as little as 3-4 weeks, i would disconnect and plug all vacuum line as mentioned earlier, and start trouble shooting. my bet is plugged carb idle circuit, i got rid of all the factory emissions equip, installed the holly sniper efi and distributor and run only a cat in the exhaust, my last emissions test came in under the factory original specs and it runs so much better plus i got a 3mpg increase, not huge but it helps
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