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Dodgeman
Re: What kind of things would keep fuel out of my carb?
#11
No life (a.k.a. DattoMaster)
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From Southern Tablelands N.S.W. Australia
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Quote:

A14force wrote:
You aren't using a carb with an anti deiseling soleniod are you? That will stop fuel getting into you carb if it's not getting any power.
The anti dieseling solenoid will prevent fuel from flowing in the idle circuit only. Nothing else.
If it has failed, then the engine will not idle, but will run at all throttle settings above idle speed & it has no effect on fuel flow to the carb.

What will prevent fuel flowing to the carb?
1. No fuel in tank. [refill]
2. Blocked pickup in tank. [blow clear with air, then drain sediment from tank]
3. Damaged pickup in tank that works only when fuel is above a certain level. [replace pickup line]
4. Floating obstruction in fuel line to stock primary filter in engine bay. [disconect fuel line at both ends & blow clear with air]
5. Faulty or blocked primary filter. [replace]
6. Faulty rubber fuel line sections at filter & elsewhere on the suction side of the fuel pump that allow fuel pump to suck air periodically. [replace]
7. Faulty fuel pump. [Repair or replace]
8. Floating obstruction on pressure side fuel line from pump to carb. [Disconect at both ends & blow clear with air]
9. Obstruction in final filter. [small gauze strainer under needle & seat. Remove it to access this strainer.] [Strip & clean, or replace as necessary]
10. Faulty needle & seat. [replace]
[I have never personally encountered this problem, nor have ever heard of it happening to anybody I know in a 43 year career in & out of the motor trade.]

That should cover most possibilities.


Posted on: 2008/10/19 2:05
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Datsunitus
Re: What kind of things would keep fuel out of my carb?
#12
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****UPDATE****

Thanks dodgeman for all your info, I went out and worked on the car for about 4 hours.

Here is what I did, took apart every line from carb to rear of car blew air through both ways.

Tried starting no go.

Tried blowing from the rear and carb filled up with gas then quickly died.

Unhooked main gas line from behind rear wheel. My car has a full tank of gas and it only filled 1/4 gallon container in about 5 minutes. Seems slow.

On top of the tank I checked the breather line and it seemed fine.

After numerous times trying to start went to remove gas cap and it was under alot of negative pressure.

****Question****

other then what I did what else could it be? When blowing from the front of the car into the fuel line I was able to blow gas out of the gas cap.

The flow rate definitely seems low.... what are your thoughts? thanks





Quote:

Dodgeman wrote:
Quote:

A14force wrote:
You aren't using a carb with an anti deiseling soleniod are you? That will stop fuel getting into you carb if it's not getting any power.
The anti dieseling solenoid will prevent fuel from flowing in the idle circuit only. Nothing else.
If it has failed, then the engine will not idle, but will run at all throttle settings above idle speed & it has no effect on fuel flow to the carb.

What will prevent fuel flowing to the carb?
1. No fuel in tank. [refill]
2. Blocked pickup in tank. [blow clear with air, then drain sediment from tank]
3. Damaged pickup in tank that works only when fuel is above a certain level. [replace pickup line]
4. Floating obstruction in fuel line to stock primary filter in engine bay. [disconect fuel line at both ends & blow clear with air]
5. Faulty or blocked primary filter. [replace]
6. Faulty rubber fuel line sections at filter & elsewhere on the suction side of the fuel pump that allow fuel pump to suck air periodically. [replace]
7. Faulty fuel pump. [Repair or replace]
8. Floating obstruction on pressure side fuel line from pump to carb. [Disconect at both ends & blow clear with air]
9. Obstruction in final filter. [small gauze strainer under needle & seat. Remove it to access this strainer.] [Strip & clean, or replace as necessary]
10. Faulty needle & seat. [replace]
[I have never personally encountered this problem, nor have ever heard of it happening to anybody I know in a 43 year career in & out of the motor trade.]

That should cover most possibilities.


Posted on: 2008/10/19 19:54
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LittleFireyOne
Re: What kind of things would keep fuel out of my carb?
#13
No life (a.k.a. DattoMaster)
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I was inclined to agree with Dodgeman on this. I reakon it's no.7 but now that you mentioned the pressure in the tank? hmmm

Posted on: 2008/10/20 5:37
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cheater_5
Re: What kind of things would keep fuel out of my carb?
#14
No life (a.k.a. DattoMaster)
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possibly try blowing out the breathing hole in the filler cap. The tank has to draw in air when petrol is removed from somewhere, hense the low pressure if its blocked...

Posted on: 2008/10/20 9:29
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dazza1200
Re: What kind of things would keep fuel out of my carb?
#15
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i had a car once that would die at the same spot every day
fuel cap wasnt breathing and once the vaccum got high enough the car would stop
run car without cap to test
most cars around mid 70's on have a breather in the cap to let air in for charcoal cannister system before then most had none just breather pipes that vent to atmosphere
dazza

Posted on: 2008/10/21 11:53
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Dodgeman
Re: What kind of things would keep fuel out of my carb?
#16
No life (a.k.a. DattoMaster)
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The boys have hit on the one thing that I completely overlooked. As the fuel is drawn from the tank it must be replaced by air, at atmospheric pressure. I bet the problem is worse when you have a full thank of fuel [small airspace above the fuel] & not quite so frequent when the tank is very low. [large air volume]
When the pressure in the tank is low enough, the atmospheric pressure pushing back down the line from the carb is enough to prevent the fuel pump diaphragm from rising & pushing fuel into the carb.
Think of it as suction from the tank pulling the fuel back.

Diagnosis.
The tank is not breathing, possibly due to either a faulty, or incorrect fuel cap.

It's such an obvious cause & I missed it completely, i'll just go sit in this corner & put my dunce cap on. Durrr.

Posted on: 2008/10/21 18:05
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kelmo
Re: What kind of things would keep fuel out of my carb?
#17
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And a gas cap is still available from your Nissan dealer
17251-U7402 $29.17
or an after market one just make sure it si vented.
If they don't have a listing for a 1200, have them check for a 280Z, 1977 and up but not a ZX as they were threaded.

my 2 cents worth.

Hey Dodgeman, no worries. We all know your still one of the smartest eggs in this basket

Posted on: 2008/10/21 18:30
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Dodgeman
Re: What kind of things would keep fuel out of my carb?
#18
No life (a.k.a. DattoMaster)
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Quote:

Datsunitus wrote:
****UPDATE****
Tried blowing from the rear and carb filled up with gas then quickly died.

On top of the tank I checked the breather line and it seemed fine.

After numerous times trying to start went to remove gas cap and it was under alot of negative pressure.

****Question****
other then what I did what else could it be? When blowing from the front of the car into the fuel line I was able to blow gas out of the gas cap.
OK, I've sat in the corner for a while & had a think. Now I have a couple of questions.

Lets see.
1. You dismantled most of the fuel system & blew it clear. So that's all good.
2. You blew from the rear & the carb filled. Where did you blow FROM? Did you blow into the fuel tank filler?
3. You unhooked the fuel line from behind the rear wheel, ... then what? Did you simply let it drain into a container? I can't look while writing this so I will check later to see if you have a coupe [low fuel tank, under rear floor] or a sedan [high fuel tank, behind back seat.]
4. After trying to start the car with a full tank, you found a LOT of negative pressure in the tank. It didn't even start & it had a lot of negative pressure?
5. You blew from the engine end & fuel was ejected from the fuel cap? So the fuel cap will let fuel escape, but won't let air in? [negative pressure remember]

Just to amuse an old man, try starting it with the fuel cap off. If it starts, then screw the idle up to about 1000 or so & let it run for a few minutes. If it's still running, then refit the cap.
If it dies after another few minutes, [give it a chance] see if you can get the cap off before it dies completely.
If it suddenly picks up again then spend $29.17 & buy your car an early Xmas present from your Nissan dealers parts counter.

Posted on: 2008/10/21 19:59
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Datsunitus
Re: What kind of things would keep fuel out of my carb?
#19
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Here is the update thanks again for your post giving me ideas.

When I blew from the input to the fuel filter in the engine bay with the gas cap off gas came out the cap when I was not paying attention.

So from here back it seems ok. From the filter forward I was able to push fuel to the carb that was in the filter.

I bought an electric fuel pump and hooked that up to give it a whirl. It sucks gas to the fuel filter but then wont send it any futher. Maybe a vaccum problem positive pressure in the carb? Or closed down jet? I dont know.


When testing the fuel tank for flow, I drained it into a container. There was no noticeable difference with the cap on or off. I only got about 1 quart (about a liter) in about 5 minutes. And this was off the main line.

There is absolutely no gas in the carb.

What are the two panels for on top of my tank? Anything there I should check? My manual does not really tell me what these are. Thanks

Also one note the fuel vapor thing on my firewall looks like it was bypassed. Do any of these components lead to my problem?


For the record I have a coupe 1971.






Quote:

Dodgeman wrote:
Quote:

Datsunitus wrote:
****UPDATE****
Tried blowing from the rear and carb filled up with gas then quickly died.

On top of the tank I checked the breather line and it seemed fine.

After numerous times trying to start went to remove gas cap and it was under alot of negative pressure.

****Question****
other then what I did what else could it be? When blowing from the front of the car into the fuel line I was able to blow gas out of the gas cap.
OK, I've sat in the corner for a while & had a think. Now I have a couple of questions.

Lets see.
1. You dismantled most of the fuel system & blew it clear. So that's all good.
2. You blew from the rear & the carb filled. Where did you blow FROM? Did you blow into the fuel tank filler?
3. You unhooked the fuel line from behind the rear wheel, ... then what? Did you simply let it drain into a container? I can't look while writing this so I will check later to see if you have a coupe [low fuel tank, under rear floor] or a sedan [high fuel tank, behind back seat.]
4. After trying to start the car with a full tank, you found a LOT of negative pressure in the tank. It didn't even start & it had a lot of negative pressure?
5. You blew from the engine end & fuel was ejected from the fuel cap? So the fuel cap will let fuel escape, but won't let air in? [negative pressure remember]

Just to amuse an old man, try starting it with the fuel cap off. If it starts, then screw the idle up to about 1000 or so & let it run for a few minutes. If it's still running, then refit the cap.
If it dies after another few minutes, [give it a chance] see if you can get the cap off before it dies completely.
If it suddenly picks up again then spend $29.17 & buy your car an early Xmas present from your Nissan dealers parts counter.

Posted on: 2008/10/21 23:27
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converted
Re: What kind of things would keep gas out of my carb?
#20
No life (a.k.a. DattoMaster)
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for me it used to be a 2G corner entry at Eastern creek turn 1...hehehehehe

I still got it

Posted on: 2008/10/22 0:37
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