secondary diaphrams

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Apr 24, 2006 | 10:40 PM

4x4bigblock

Thread Starter

Mountain Pass

Joined: Feb 2006

Posts: 174

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secondary diaphrams

i bought a barely used nissan sentra to save on gas. the carb was gummed up got that working. but it does not want to idle, it will run with full throttle. there is a thing called a secondary diapram. that runs off the vacuum and pulls a rod that adjust one of the barrels in the carb. if i move it by hand it works. at idle, i can see the gas spray doen the barrel. not sure if the diaphram is and or somehting along the vacuume end witch seems to control it. all the hoses are nice. there is two things witch look like 02 sensors on the manifold wich hit the vacuum line. and in the manual i think there is another vacuum control. i also was wondering if this hadf a tps throttle position sensor. the sensor light is on on the dash also.

thanks for your input
mike

Last edited by 4x4bigblock; Apr 24, 2006 at 10:43 PM.

Apr 25, 2006 | 10:04 AM

jimandmandy

Post Fiend

Joined: Jun 2001

Posts: 5,228

Likes: 5

From: Running Springs CA

Lots o' luck. Japanese carbs from the 1980's are insanely complicated. You had better get a shop manual.

Jim

Apr 25, 2006 | 10:57 PM

Tstorms

Junior User

Joined: Feb 2006

Posts: 63

Likes: 0

From: Albuquerque, NM.

You have a 1 bbl carb with a vaccume secondary. The secondary only opens at 3/4 to full throttle under load. You propbaly are not getting any fuel from the idle circuits.
They could be cloged or the idle fuel cut solenoid could be bad or lost power. You may need to find a mechanic that remembers carbs to check it out. If you can get it to Albuquerque I know I could fix it.

Apr 26, 2006 | 06:38 AM

4x4bigblock

Thread Starter

Mountain Pass

Joined: Feb 2006

Posts: 174

Likes: 1

if i use my finger to move the rod that comes out of the diaphram the gas flow and it idles. i can move the diaphram by vacuum and it works. i am just not getting the vacuum to it, or maybe its suppussed to be in a different position. if it had an adjustment i could have it running normal. like an idle adjustment. i will try the circuts and diaphrams. there seems to be a sensor on the intake that controls the vacuum. i thinks its bad cause the sensor light is on in the dash.

Apr 26, 2006 | 10:44 PM

Tstorms

Junior User

Joined: Feb 2006

Posts: 63

Likes: 0

From: Albuquerque, NM.

The sensor light is conected to a mileage counter and comes on at a predetermined mileage to indicate the recomended time to have the emission control systems opreation checked and recomended replacement of O2 sensor.
The sensor light has nothing to do with your problem.
By opening the secondary you are pulling fuel from the secondary fuel circuits giving it fuel to idle. You should see no fuel coming from the venturies at idle. At idle the fuel should come from the idle circuit below the throttle plates. Their is a idle mixture screw but it may be covered by a plug that needs to be removed to get to the adjustment. I would guess your problem is in the idle fuel cut solenoid.
No disrespect but it sounds like you know little about the operation of a carb. and this is not a good carb to learn on. I recomend you find a import mechanic and have it diagnosed and fixed. May save a lot of agervation and be cheaper in the long run.

Good Luck

Apr 28, 2006 | 07:20 PM

4x4bigblock

Thread Starter

Mountain Pass

Joined: Feb 2006

Posts: 174

Likes: 1

kinda fixed it

its not the diaphram i think. i found a bad wire so i changed them and the plugs which were real worn, cap , and rotor. i was thinking the o2 sensor is not right. it starts now. and seems to run the when it gets hot it loses power and and wont run. the radiator is broke so the cars heats fast. also the fan does not seems to be coming on but it did before? no i dont know a lot about carbs either. the exhaust has a hole right in front of the cat. i hope the cat is good. i will change that front pipe and i did the muffler wenty with a universal it was way cheaper $21 instead of $90. i am getting a radiator. i will price the soleniod you mentioned i was thinking that might be foul too. what about the relays can i check them? well thanks again...

Last edited by 4x4bigblock; Apr 28, 2006 at 07:23 PM.

Apr 29, 2006 | 01:38 AM

Ford_Six

Hotshot

Joined: Oct 2002

Posts: 18,488

Likes: 22

From: The Big, Oregon

I know from first-hand experience that Nissan engines do not like overheating. All adjustments to the carb and timing need to be made with the engine at operating temperature, if the thing is gushing out water and overheating, then you need to hold off testing and adjusting until the cooling system is fixed.