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Vacuum Secondary not kicking in on carb?

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dorkpunch

Vacuum Secondary not kicking in on carb?
« on: April 24, 2007, 06:54:28 PM »
'87 sammy, just got it a week ago (see my other post).  so far it has trouble holding 55 on the flat and the first tank was averaging 17mpg.  all four cylinders had 175 psi of compression, but it would appear that the secondary barrel in the carb is not opening.  its got the vacuum spageti mess but from what i can tell, where the main line comes out of the carb there is no vacuum.  it comes out of the side of the carb, T-s, goes to the vacuum pot and to some type of electrical switch, then out of the switch to the pot.  any ideas anyone?  i think this is my low power problem- while it was running i poked a screwdriver down there to open the butter fly and it had a lot better throttle response.
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Offline Vagabond

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Re: Vacuum Secondary not kicking in on carb?
« Reply #1 on: April 24, 2007, 07:44:58 PM »
Welcome! Do you have stock gears?  What size are your tires?
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dorkpunch

Re: Vacuum Secondary not kicking in on carb?
« Reply #2 on: April 24, 2007, 07:52:09 PM »
stock everything.  more info in my other post:  http://www.zukiworld.com/forum/index.php?topic=16991.0
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Offline Rhinoman

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Re: Vacuum Secondary not kicking in on carb?
« Reply #3 on: April 25, 2007, 09:44:39 AM »
You won't get enough vacuum to open the secondary unless the engine is under load. How are you testing this? The only easy way to test this that I can think of is to disconnect the pipe and plug it. Go for a drive and if theres no difference then it isn't opening.
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2000 Vitara 1.6, 3+3 Lift, 33"MTs, 5:83s, LWB brakes, Winch, Snorkel, Safari Rack
1986 SJ413K PickUp, 1.6L conversion.

OBD1 - Full diagnostics on a PC/Laptop: http://www.rhinopower.org
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dorkpunch

Re: Vacuum Secondary not kicking in on carb?
« Reply #4 on: April 25, 2007, 10:17:28 AM »
Just by looking at it as i rev the engine.  I think it should at least flutter a bit under acceleration.  looking down the barrels the primary is wet and you can tell its working, but looking down the secondary it just looked dry and unused, like the butterfly hasnt opened in a very long time. 

I'll try disconnecting it and see if it makes any difference.  what is the blue electrical switch/sensor just above the pot for?
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copperfever

Re: Vacuum Secondary not kicking in on carb?
« Reply #5 on: April 29, 2007, 08:09:35 PM »
Hey there,
I don't mean to assert that you lack carb know-how, but are you sure that it is the secondary and not the choke butterfly? I've had 2 Samurais, and both of their chokes failed, staying closed all of the time. One of them stopped working on the interstate, I instantly dropped from 65mph to 45mph, and went from getting 23mpg to less than 15! I just wired them open, problem solved. The only difference is I have to pump the accelerator once before starting, and hold it open a little during warm up.
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Offline tipover

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Re: Vacuum Secondary not kicking in on carb?
« Reply #6 on: April 29, 2007, 11:30:40 PM »
it is near impossible to get it to open with out a load.  THere is a way that you can modify the vacuum hoses on the valve cover side of the carb.  I forgot which ones you switch and you will get a little more a little faster.  IIRC the stock configuration has a vacuum restricter and vacuum switch on the secondary that you can by-pass.
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Wheeler-87 Samurai JX. 7" lift, 1.6 TBI, lockers hybrid rear, 33" Swampers, 6 to 1s in a billet housing.
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Offline mrfuelish

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Re: Vacuum Secondary not kicking in on carb?
« Reply #7 on: April 30, 2007, 11:41:30 AM »
I'm not real sure about this but when i was messing with mine I bypassed the vac. dampener and the solinoid that I think hooks to the fith gear switch on the trans,it is one of the two round white plugs on the fire wall by the master cylinder, the other plug is for your reverse light so that would be easy to find by putting it in reverse with the key on then unplugging it to see if the lights go out.
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1987,1988,1988,1990 samurai's,  1953 m38a1,  1996 x-90,blue.1996 x-90 red.1994 2 door tracker.   only Dead Fish go with the flow.                No Hairy Nosed Wombats were ran over on the trail today.       My ZUK is Xenophobic.
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Offline tipover

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Re: Vacuum Secondary not kicking in on carb?
« Reply #8 on: April 30, 2007, 06:58:03 PM »
Quote from: mrfuelish on April 30, 2007, 11:41:30 AM
I'm not real sure about this but when i was messing with mine I bypassed the vac. dampener and the solinoid that I think hooks to the fith gear switch on the trans,it is one of the two round white plugs on the fire wall by the master cylinder, the other plug is for your reverse light so that would be easy to find by putting it in reverse with the key on then unplugging it to see if the lights go out.

yea I remeber something about that too.  IIRC  the 5th gear switch lets the secondary open sooner and I think it goes to open loop.  I forget for sure now.
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Wheeler-87 Samurai JX. 7" lift, 1.6 TBI, lockers hybrid rear, 33" Swampers, 6 to 1s in a billet housing.
RV Dingy-2003 2 door tracker
Tow-97 PSD F250 Crew SB Dana 60 conversion
87 samurai-spoa ZookEV electric conversion.
RV- 31' Monaco Mckenzie
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Offline daddyizzle

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Re: Vacuum Secondary not kicking in on carb?
« Reply #9 on: May 01, 2007, 06:51:59 PM »
Quote from: mrfuelish on April 30, 2007, 11:41:30 AM
I'm not real sure about this but when i was messing with mine I bypassed the vac. dampener and the solinoid that I think hooks to the fith gear switch on the trans,it is one of the two round white plugs on the fire wall by the master cylinder, the other plug is for your reverse light so that would be easy to find by putting it in reverse with the key on then unplugging it to see if the lights go out.
  What would this do? If there is a way to bypass a bunch of the emission hoses and switches and run with more power and still get good gas mileage and easy starts, I'm sure a few of us would like to know. Not trying to hijack the thread, I just found some interesting suggestions in it.

-Adam
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If all criminals were behind bars, there would be no one left to patrol the streets.

86 Samurai Tin-Top stock with a Harley 44 sidedraft carb
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dorkpunch

Re: Vacuum Secondary not kicking in on carb?
« Reply #10 on: May 01, 2007, 10:00:18 PM »
yes, i'm sure its not the choke.  i'm not to experienced on auto carbs, but i know my way around many a motorcycle.  I'm kinda tempted to take a set of 4 Kiehns i've got and adapt them on there...   ;) 

I did unplug the vacum line and go for a drive.  It was more spluttery and a little worse on accelleration, but not much worse.  So apparently the secondary is working, at least a little. 

What else should i be looking for in a sammy that tops out at 55, gets 17mpg, has 175 psi of compression on all four cylinders, and was supposedly ( i say supposedly cause i'm pretty sure the guy i bought it from had NO clue what he was talking about) rebuilt 25k miles ago? I'll try the 5th gear vacuum switch thingy...
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Offline mrfuelish

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Re: Vacuum Secondary not kicking in on carb?
« Reply #11 on: May 01, 2007, 10:07:19 PM »
The vac bypass let the secondaries open in all five gears, the mpg went down because I have 31'' tires and need to use all of the hp that it has, it makes a big diffrence with that mod, taking the bolt out from under the gas pedal,and a larger exhaust pipe from the cast iron manifold to the muffler, and the 11.00 carb fix or tube in the float bowl trick that gets rid of the flat spot, my mileage went from 47 mpg with stock tires to about 27 mpg with the 31's and not flooring it all the time and running fourth gear, no fifth gear, but the mods will let it go the speed limit and more down hill, LOL
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1987,1988,1988,1990 samurai's,  1953 m38a1,  1996 x-90,blue.1996 x-90 red.1994 2 door tracker.   only Dead Fish go with the flow.                No Hairy Nosed Wombats were ran over on the trail today.       My ZUK is Xenophobic.
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Offline mrfuelish

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Re: Vacuum Secondary not kicking in on carb?
« Reply #12 on: May 01, 2007, 10:11:48 PM »
if it has the stock exhaust pipe it is collapsing on the inside and will do what yours is doing also, change out the first three feet or so of the exhaust pipe. (it is a double wall pipe)
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1987,1988,1988,1990 samurai's,  1953 m38a1,  1996 x-90,blue.1996 x-90 red.1994 2 door tracker.   only Dead Fish go with the flow.                No Hairy Nosed Wombats were ran over on the trail today.       My ZUK is Xenophobic.
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Offline thefirstzukman

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Re: Vacuum Secondary not kicking in on carb?
« Reply #13 on: May 01, 2007, 10:35:16 PM »
Gut the shit out of the carb....  I don't even run a choke on mine and hook the secondary valve to a ported vacuume sorce.  You still cant go very fast but you will get there alot faster.  I am in the middle of building a manifold running a set of 1200cc crotch rocket carbs do it if you can it will be better but the stock carb is great off road and you can help it out a bit and make it run alot better.
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Offline Rhinoman

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Re: Vacuum Secondary not kicking in on carb?
« Reply #14 on: May 02, 2007, 04:44:01 AM »
Quote from: dorkpunch on May 01, 2007, 10:00:18 PM
What else should i be looking for in a sammy that tops out at 55, gets 17mpg, has 175 psi of compression on all four cylinders, and was supposedly ( i say supposedly cause i'm pretty sure the guy i bought it from had NO clue what he was talking about) rebuilt 25k miles ago? I'll try the 5th gear vacuum switch thingy...

Camshaft and ignition timing. Valve lash, carb float level, fuel pressure all the usual stuff really.
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2000 Vitara 1.6, 3+3 Lift, 33"MTs, 5:83s, LWB brakes, Winch, Snorkel, Safari Rack
1986 SJ413K PickUp, 1.6L conversion.

OBD1 - Full diagnostics on a PC/Laptop: http://www.rhinopower.org
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