Jump to content

mechanical newbie (85 720)


ratboi3000

Recommended Posts

Howdy Ratsun,

I recently purchased a 1985 720 5 speed  and slowly but surely am getting acquainted with the beast. I unfortunately do not have records of previous service but i do know that the engine, clutch, and transmission are the original, we are pushing about 215,000 miles. For the most part it runs great. However there are a few things that have caught my eye. Im in the beginning of my path to becoming "car literate" and want to start dipping my toes into simple maintenance and fixes that are newbie friendly. I also just bid on an original nissan manual for the same year and model to make things easier down the road. 

SO!

It appears that its currently running a little rich, sometimes the car just turn offs (im not stalling it) it smells like gas sometimes and recently, when i turn it off in neutral the engine tries to stay one. Ive read that this can be remedied by turning the car off in gear but obviously id like to fix the bigger issue. additionally the other day after i filled up the tank it didnt want to stay on which has not happened to me yet.

Ive also noticed the shifter is rather stiff. It full engages and disengages, and it doesnt spit back out at me i just really have to slam it in there , and 5th gear can be really difficult to find ( however i had a performance shifter on my last car so i might just be used to shorter movements)

seeking newbie friendly projects also just down to get yall input before i take it to my guy to get looked at, hes going to be teaching me along the way and would like to have a good start point.

Just want to go down the check list and try to do some things myself if they are too difficult! thanks in advance. will upload photos when im off work!

 

Link to comment
  • Replies 25
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Posted Images

First off I will recommend that you purchase an '85 factory service manual (FSM) usually found on line. I think they are around $85 new so $20 is good but $50 is also fine as they pay for themselves the first time you use it. They are an exclusive source BIBLE for your year truck and published by Nissan. Other 'manuals' like Haynes cover the entire 6 year run of the 720 and include stuff you don't need and they just copy the FSMs anyway. Haynes are 1/2" thick, FSMs are about 2" thick so....

 

Running rich...

Next time the engine is warmed up take the top off the air filter and look at the choke plate. It should be vertical and open like this...

Qml955T.jpg

 

It should not be partly open or closed like this...

L043Tu4.jpg

 

There are other causes but eliminate this first as the cause.

 

Dieseling... (AKA run on after shut off)...

Can be caused by over rich mixture but there is a system for closing off the fuel supply to the idle circuit called the 'idle cut solenoid.' With engine off have someone turn the ignition ON OFF, ON OFF, ON OFF while you listen near the carburetor. What you should hear is a light clicking sound. Does it???

 

Stiff gear shifting...

While idling depress the clutch and slowly shift into reverse. Do you hear any gear teeth clicking or grinding as the mesh????? 

Check the fluid level in the clutch master, it's on the left side of the brake booster. It dry refill and try... you may have to bleed the hydraulic system.

Link to comment
35 minutes ago, datzenmike said:

First off I will recommend that you purchase an '85 factory service manual (FSM) usually found on line. I think they are around $85 new so $20 is good but $50 is also fine as they pay for themselves the first time you use it. They are an exclusive source BIBLE for your year truck and published by Nissan. Other 'manuals' like Haynes cover the entire 6 year run of the 720 and include stuff you don't need and they just copy the FSMs anyway. Haynes are 1/2" thick, FSMs are about 2" thick so....

 

Running rich...

Next time the engine is warmed up take the top off the air filter and look at the choke plate. It should be vertical and open like this...

Qml955T.jpg

 

It should not be partly open or closed like this...

L043Tu4.jpg

 

There are other causes but eliminate this first as the cause.

 

Dieseling... (AKA run on after shut off)...

Can be caused by over rich mixture but there is a system for closing off the fuel supply to the idle circuit called the 'idle cut solenoid.' With engine off have someone turn the ignition ON OFF, ON OFF, ON OFF while you listen near the carburetor. What you should hear is a light clicking sound. Does it???

 

Stiff gear shifting...

While idling depress the clutch and slowly shift into reverse. Do you hear any gear teeth clicking or grinding as the mesh????? 

Check the fluid level in the clutch master, it's on the left side of the brake booster. It dry refill and try... you may have to bleed the hydraulic system.

curious where you are finding these FSM so cheap, the 1985 720 manuals by nissan that im finding online are like 100-200, currently scouring forums for pdf versions

thanks for the starting points, im apartment living down here in socal so im gonna attempt to borrow a friends driveway this weekend. will update with pics

Link to comment

Bought mine years ago from the dealer here,it was 75 bucks...I also have the Haynes Nissan Manual. It's the Datsun/Nissan pickups and path finder.The Nissan Service manual does not go into details very good.The Haynes is more detailed on some things.Check this out. My Nissan book says oil capacity for my 2.4 4x4 with filter change is 4 1/4 quarts.My Haynes says 4 1/2 quarts. My owners manual says 4 1/2 quarts.So why is the Nissan book different.The Haynes manual will show you pictures of parts on a vehicle,which is better to see.I have looked up parts in my Nissan Manual and at times ended up seeing it better in my Haynes manual.Pictures are better than just explaining.Also when I change my transmission fluid.It will barely hold 2 quarts,both manuals say 4 1/4  pints.I change it every year..Ebay has a Nissan 85 service manual for 159 bucks.

100_6427.jpg

Edited by Thomas Perkins
Link to comment
27 minutes ago, Thomas Perkins said:

Bought mine years ago from the dealer here,it was 75 bucks...I also have the Haynes Nissan Manual. It's the Datsun/Nissan pickups and path finder.The Nissan Service manual does not go into details very good.The Haynes is more detailed on some things.Check this out. My Nissan book says oil capacity for my 2.4 4x4 with filter change is 4 1/4 quarts.My Haynes says 4 1/2 quarts. My owners manual says 4 1/2 quarts.So why is the Nissan book different.The Haynes manual will show you pictures of parts on a vehicle,which is better to see.I have looked up parts in my Nissan Manual and at times ended up seeing it better in my Haynes manual.Pictures are better than just explaining.Also when I change my transmission fluid.It will barely hold 2 quarts,both manuals say 4 1/4  pints.I change it every year..

100_6427.jpg

so that exact one is what i found on ebay for at least $130 i sent an offer for $95 hoping i can snag it i found a different one that still seems to be from nissan

heres the link to the other one. Is it gonna be the same thing pretty much?

https://www.bonanza.com/items/add_item_to_cart_complete/619822215?offer_item_id=95388162

 

Link to comment

That is the owners manual.I have one,what comes with the truck,their are different kinds of Nissan Manuals.Also their are different kinds of Haynes manuals for our trucks,The one I have,has a Nissan 4x4 truck on the front cover.It is real good and detailed.The Nissan manual I have has the diesel and Canada section in it.Some stuff in it is not very detailed.

Link to comment
6 minutes ago, Thomas Perkins said:

 

 

That covers 16 years and two totally different truck models squeezing even more information you can't use into 1/2" book.

 

An '85 FSM will detail all engines... Z24, Z20 and SD25 diesel, two and 4 wheel drive, single and dual tire axles, H-190 and C200 rear differentials, long and short wheelbase and King Cab frame specifications and bodies. Only thing I don't like is the over all electrical diagram of the truck. I like the '83 or '82 and older showing the runs and the wire colors.

Link to comment
27 minutes ago, datzenmike said:

 

 

That covers 16 years and two totally different truck models squeezing even more information you can't use into 1/2" book.

 

An '85 FSM will detail all engines... Z24, Z20 and SD25 diesel, two and 4 wheel drive, single and dual tire axles, H-190 and C200 rear differentials, long and short wheelbase and King Cab frame specifications and bodies. Only thing I don't like is the over all electrical diagram of the truck. I like the '83 or '82 and older showing the runs and the wire colors.

is it more of a convenience thing? like not having to sift through a bunch of info that doesnt apply to me? cause its a $100 difference haha

Link to comment

Did the truck pass smog when you transferred title? It's possible that there is a vacuum leak causing the low idle. A smog check would probably catch this, but who knows.

 

Re- the shifter, the bushings in the stick are easily replaced, which will take up some slack. Other causes of stiff shifting can come from a buildup of gunk around the shift mechanism inside the tailhousing. If the truck sat for many years or suffered from lack of oil changes, maybe time and heat cycles will loosen it up. And then there are other causes that are not easily fixed.

Edited by Stoffregen Motorsports
Link to comment

 

I haven't seen an '80 FSM. I have an '84 and it's all white and almost 2" thick with a blue drawing of the 720.

 

 

 

These are for the '80 but looks like 2 and the 4wd is a supplement.

 

https://www.ebay.ca/itm/164900053923?hash=item2664cf23a3:g:jmcAAOSweptgvBZs

 

 

Image 1 - 1980 Datsun Pickup Service Shop Repair Manual W/ 4 Four Wheel Drive Model 720

 

Here's another...

 

https://www.ebay.ca/itm/283094833513?hash=item41e9c45969:g:oAoAAOSw15VbbEjj

 

 

Link to comment

Nothing wrong with a 4x4 supplement or having coverage of the SD22 diesel engine. One day you may buy another 720 for a parts truck... would be handy to know about them.

Link to comment

The running after ignition is off is called 'dieseling.'  Do you think that there is any indication of burning oil, as a slightly blue out of the tailpipe, particularly at startup, or when you let go of the throttle?  On a related note, you might just need to clean or replace your spark plugs, check the spark plug wires for electrical resistance, and check under the distributor cap and on the rotor for electrical erosion and corrosion.  Definitely check the choke, as Mike already mentioned.  I resize cellphone photos using an app called GIMP for ease of upload; pics of the equipment that you are working with would help.  Like, is the EGR valve still hooked up?  Mine was rusted internally, which made it kind of idle on exhaust, not a good scenario for tuning, and it could result in unburnt fuel, akin to running rich.

Link to comment
On 1/15/2022 at 11:16 AM, datzenmike said:

 

Dieseling... (AKA run on after shut off)...

Can be caused by over rich mixture but there is a system for closing off the fuel supply to the idle circuit called the 'idle cut solenoid.' With engine off have someone turn the ignition ON OFF, ON OFF, ON OFF while you listen near the carburetor. What you should hear is a light clicking sound. Does it???

 

 

 

You have to have gas and air for run on to occur. Idle cut solenoid not working, choke on or idle set too high can do this

 

As to the EGR.... it is not activated when engine cold, full throttle or idling. Combustion products can build up on the valve and prevent it closing properly at idle. This leak of inert gasses dilutes the mixture and result in a rough to very rough idle. The cure is to just wire brush the valve clean.

Link to comment

My EGR had a rusted seat, so exhaust would theoretically leak thru, regardless of the vacuum signal on the diaphragm that controls the valve plunger?  I'm no expert.  Then the PO had the idle up too high to make it just idle, and I would wing thru the dieseling by stopping the motor with the clutch, in gear, with the brake on.

 

Maybe the truck in question is a Weber without the solenoid, but, it is California, so maybe not.

Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.