idling problem

1980-1986 Datsun 720 forums. All 720-specific topics and discussion can be found here.
sawyer's720
Posts: 87
Joined: Mon Aug 02, 2010 2:17 pm
Car: 1984 Datsun 720

Post

i recently rebuilt the carb and once i got it started up it idled irratically, backfired, and now it's idling around 2000 rpm and i can't retard the timing enough to slow it down. the idle screw is also completely turned down. vacuum lines maybe?


User avatar
captainzeros
Posts: 209
Joined: Sun Jan 24, 2010 8:00 pm
Car:  
1981 Datsun 720 Longbed
1973 Datsun 240Z
Location: Independence, OR

Post

Sounds like vacuum lines.

sawyer's720
Posts: 87
Joined: Mon Aug 02, 2010 2:17 pm
Car: 1984 Datsun 720

Post

thats wht i was thinkin, alright thanks man.

sawyer's720
Posts: 87
Joined: Mon Aug 02, 2010 2:17 pm
Car: 1984 Datsun 720

Post

can anyone post pictures of their vacuum lines?

User avatar
fastboatman29212
Posts: 493
Joined: Sun Jul 25, 2010 6:45 pm
Car: left this forum. Sold my truck.
Location: South Carolina

Post

My 86 is completely stock so my lines are all like factory, but I have replaced the rotted lines with new lines, but it's still stock. It might take a dozen or more pics to show all the lines, so may I suggest that you cap off all the lines except the vacuum advance and see if that fixes the problem. Take good notes as to what goes where when you disconnect the lines.

If capping the lines off fixes the problem, you can keep it that way or run new vacuum lines like I did. It takes about 30 feet of vacuum line, so you can count on spending $30 or more. See my earlier post.

Link: vacuum-lines-completely-replaced-wow-t506342.html

sawyer's720
Posts: 87
Joined: Mon Aug 02, 2010 2:17 pm
Car: 1984 Datsun 720

Post

thanks man, i already replaced every one of the vacuum lines but i did notice that you had a couple different sizes on the table. everyone that i've replaced was a smaller type and that took me a little over ten feet. i didn't replace the bigger ones that run to the distributor, canistor or where ever the other big line goes. but i only saw those three. is there more that the PO might has changed to a smaller size?
thanks for all the help guys, i really appreciate it.

sawyer's720
Posts: 87
Joined: Mon Aug 02, 2010 2:17 pm
Car: 1984 Datsun 720

Post

all vacuum lines are in the correct places and are new. now it will idle down but it won't stay idling. i've replaced the plug wire, cap and rotor. it helped with throttle responce but i have absolutely no power. i think the power part is a timing issue but where it's at right now is where it idles at spec. is there an adjuster for the idle other than the idle screw?

User avatar
breadbox
Posts: 8549
Joined: Tue Oct 17, 2006 4:09 pm
Car: Red 89 240sx,Black 89 Koop, White 84 720 4x4KC
Location: Va Bch

Post

the gas pedal kinda controls it with throttle position.

sawyer's720
Posts: 87
Joined: Mon Aug 02, 2010 2:17 pm
Car: 1984 Datsun 720

Post

i don't think that would be it because it was never adjusted after tkaing off the carb. i guess i could check to see if the vac lines are in the right spot again.

kongen867
Posts: 16
Joined: Sun Dec 19, 2010 8:15 am
Car: Datsun 720 Pickup

Post

im curious... :P
My 720 is a 1.8 ... And it has 2 vacuum lines, one for distributor cap and one for the air filter? You guys talk like its rotary engine with 100s of them, wich engine is in? :)

User avatar
PEZi
Posts: 21113
Joined: Thu Dec 11, 2008 8:21 am
Car: Mitsubishi Lancer Evolution IX Mitsubishi Racing Edition
Location: Pikes Peak, CO
Contact:

Post

pics?

sawyer's720
Posts: 87
Joined: Mon Aug 02, 2010 2:17 pm
Car: 1984 Datsun 720

Post

kongen867 wrote:im curious... :P
My 720 is a 1.8 ... And it has 2 vacuum lines, one for distributor cap and one for the air filter? You guys talk like its rotary engine with 100s of them, wich engine is in? :)
it's a Z24 2.4 gas engine.

Pezi: i'll have pics up tomorrow morning probably.

User avatar
PEZi
Posts: 21113
Joined: Thu Dec 11, 2008 8:21 am
Car: Mitsubishi Lancer Evolution IX Mitsubishi Racing Edition
Location: Pikes Peak, CO
Contact:

Post

kongen867 wrote:im curious... :P
My 720 is a 1.8 ... And it has 2 vacuum lines, one for distributor cap and one for the air filter? You guys talk like its rotary engine with 100s of them, wich engine is in? :)
the z24 has a f*** of vac lines... this is what mine looked like back when i still had all that crap

Image

User avatar
captainzeros
Posts: 209
Joined: Sun Jan 24, 2010 8:00 pm
Car:  
1981 Datsun 720 Longbed
1973 Datsun 240Z
Location: Independence, OR

Post

kongen867 wrote:im curious... :P
My 720 is a 1.8 ... And it has 2 vacuum lines, one for distributor cap and one for the air filter? You guys talk like its rotary engine with 100s of them, wich engine is in? :)
The USDM 720s with the Z22 and the Z24 engine have a good number of vac lines in them. All you really need for them to run well is one to the vac advance on the distributor and the rest can be chopped off and capped and the truck will run well (just never pass emissions testing if you have to). Unless your truck is from some market without hardly any emissions controls, a previous owner probably did a major vacuum line delete before you got it.

kongen867
Posts: 16
Joined: Sun Dec 19, 2010 8:15 am
Car: Datsun 720 Pickup

Post

captainzeros wrote:The USDM 720s with the Z22 and the Z24 engine have a good number of vac lines in them. All you really need for them to run well is one to the vac advance on the distributor and the rest can be chopped off and capped and the truck will run well (just never pass emissions testing if you have to). Unless your truck is from some market without hardly any emissions controls, a previous owner probably did a major vacuum line delete before you got it.
Hmmm maybe that will explain why i does 20l/100km or 13 miles/gallon.... But i dont think so, like i wrote my engine is a 1.8l and the car is from europe so i dont think it is the same as yours...

User avatar
captainzeros
Posts: 209
Joined: Sun Jan 24, 2010 8:00 pm
Car:  
1981 Datsun 720 Longbed
1973 Datsun 240Z
Location: Independence, OR

Post

Yep, being a european market model would explain why it's not the same as an american market model.

edit: What model of 1.8 is it, anyways? Z18? Or some other model?

kongen867
Posts: 16
Joined: Sun Dec 19, 2010 8:15 am
Car: Datsun 720 Pickup

Post

captainzeros wrote:Yep, being a european market model would explain why it's not the same as an american market model.

edit: What model of 1.8 is it, anyways? Z18? Or some other model?

I honestly dont know, havent checked or know where to check... :/
Maybe you can point me in the direction where to look?

flinterman2000
Posts: 1011
Joined: Mon May 04, 2009 5:32 pm
Car: 2000 Nissan Wingroad, 85 Datsun 720 Pick Up.

Post

Does it have 4 plug wires or 8? The 4 is usually the L18 and the 8 is usually the Z18. I don't think any 720 had the CA engine as stock.

User avatar
captainzeros
Posts: 209
Joined: Sun Jan 24, 2010 8:00 pm
Car:  
1981 Datsun 720 Longbed
1973 Datsun 240Z
Location: Independence, OR

Post

On the Z series engines, it's right here:
Image

User avatar
captainzeros
Posts: 209
Joined: Sun Jan 24, 2010 8:00 pm
Car:  
1981 Datsun 720 Longbed
1973 Datsun 240Z
Location: Independence, OR

Post

and on an L series, it's here at the back:
Image

kongen867
Posts: 16
Joined: Sun Dec 19, 2010 8:15 am
Car: Datsun 720 Pickup

Post

Looks nothing like your pics m8.. My carb is on the right side of the engine like the 2nd pic... But then i only have 4 plug wires from the cap... And theres 6 on the 2nd pic but i'll check for the engine number

User avatar
captainzeros
Posts: 209
Joined: Sun Jan 24, 2010 8:00 pm
Car:  
1981 Datsun 720 Longbed
1973 Datsun 240Z
Location: Independence, OR

Post

They made both six and four cylinder L series motors. That's a six cause it's in my 240Z and I don't have any 4 cylinder L series motors to take pictures of.

flinterman2000
Posts: 1011
Joined: Mon May 04, 2009 5:32 pm
Car: 2000 Nissan Wingroad, 85 Datsun 720 Pick Up.

Post

If its european it could be a J series engine.
Image

and this is where it would be.

Image

:yesnod

kongen867
Posts: 16
Joined: Sun Dec 19, 2010 8:15 am
Car: Datsun 720 Pickup

Post

its not that one either.... Havent looked yet, old truck wont start... But i think its an L18...

sawyer's720
Posts: 87
Joined: Mon Aug 02, 2010 2:17 pm
Car: 1984 Datsun 720

Post

For Cedar, this is where you find the part number on the carb. Image
All the Vacuum lines. if i need better pics just let me know. Image Image Image Image Image Image Image Image Image Image Image

cedar
Posts: 13
Joined: Mon Dec 27, 2010 9:18 pm
Car: 1984 720 4wd KC

Post

@sawyer's720 thanks for the pictures!
for some reason mine is blank right there. strange. is it like a metal tag or sticker? maybe someone removed it, looks like the carb has been worked on before for sure.
anyway your help is much appreciated.

sawyer's720
Posts: 87
Joined: Mon Aug 02, 2010 2:17 pm
Car: 1984 Datsun 720

Post

no it was lightly stamped in and inked. very lame. you have to hold a flashlight to it at an angle to see it. you might be able to press something plyable into it to try and get a mold. i held the flashlight. my service manual has some of the part numbers if you'd like them.

sawyer's720
Posts: 87
Joined: Mon Aug 02, 2010 2:17 pm
Car: 1984 Datsun 720

Post

also, now that im looking at the pictures i realized that i posted them in the wrong oder. i took the pictures in such an order that you could see where they all ran to. unfortunately i messed that up. sorry

cedar
Posts: 13
Joined: Mon Dec 27, 2010 9:18 pm
Car: 1984 720 4wd KC

Post

sawyer's720 wrote:no it was lightly stamped in and inked. very lame. you have to hold a flashlight to it at an angle to see it. you might be able to press something plyable into it to try and get a mold. i held the flashlight. my service manual has some of the part numbers if you'd like them.
hmm ok I'll have to really take a closer look tomorrow morning, I had a flash light on it and tried to clean it with a cloth but its quite possible i missed it. thanks for that info.
yeah i mean i'd be interested in what your model is, just trying to order a rebuild kit. does yours have ac?

thanks

sawyer's720
Posts: 87
Joined: Mon Aug 02, 2010 2:17 pm
Car: 1984 Datsun 720

Post

no it doesn't i have a ton of numbers.

info i need from you. year, federal or california, 2 or 4 wheel drive and if its z24 or z20


Return to “Datsun 720”