j.agee

Hi,
My old 85 nissan p.u. (about 250,00 miles) suddenly started cutting out at idle speed and won't stay running unless I crank up the idle screw too high. It had been missing for a while, but suddenly got way worse and wouldn't stay running. I know there's a lot of possible reasons for this (electrical and fuel problems), but does anybody know the most common, or any specific things to check first for a nissan 85 pickup? Thank alot.

jerryp58

This seems to be a really common question lately (so I'd suggest doing a Search), but with all those years a miles, there's a pretty long list of things it could be:

tune-up (plugs, wires, cap, rotor)
fuel filter
air filter
O2 sensor
EGR
bad vacuum hose(s)
coil
fuel pump
injector(s)

Depending on what above has been changed recently, you may also want to do a fuel pressure check and a compression check.

Any computer codes showing up?

__________________

Jerry
2004 Frontier, King Cab, XE, 4x1, 4-cyl, 5-spd

j.agee

Thanks Jerry,

And what do you mean by 'any computer codes showing up?'

Thank you.

jerryp58

Well, I'm assuming your '85 has fuel injection (even if it's just throttle body injection) and therefore a computer controlling it.

The computer (ECU or whatever they'll call it) monitors the engine by various sensors (O2 sensor, throttle position sensor -TPS, manifold temp, manifold pressure, etc.). If one of those sensors or an injector goes bad, the computer will show a code saying so.

Now, if you don't have an ECU code reader (maybe as little as $30, as high as hundreds of $$), there's usually a way to read the code's through the dash's Check Engine light. A Haynes manual, or hopefully someone on this forum besides me, will be able to tell you the procedure for doing that.

I hope this helps a bit.

__________________

Jerry
2004 Frontier, King Cab, XE, 4x1, 4-cyl, 5-spd

j.agee

Jerry,
Thanks again. Your information helps a lot. I'm going to go through those things you suggested, several of which I wouldn't have been able to think of on my own.

If you happen to run through this thread again, is there one thing I should check first, if my truck is also backfiring when I downshift to slow down, and coast, with my foot off the gas?

Thanks.

HandMeDown

If it's the same 85 pickup as I have, the 720, then it's carburated, but electronically controlled, so there is still and ECU.

You'll find some troubleshooting info here:
http://groups.msn.com/NissanDatsun720PickupOwners

jerryp58

Wow, an '85 with a carburetor! Is there a rebuild kit available for it? Does it have a fuel bowl with a float? I can't remember what happens when there's a hole in the float. It seems that would cause it to flood, yes/no? Would increasing the idle speed help a flooding situation? Does it still use jets that can wear out or get clogged?

__________________

Jerry
2004 Frontier, King Cab, XE, 4x1, 4-cyl, 5-spd

j.agee

Yes, mine's a carbureted model also. I'm still going to do general tune-up first, then check into the carburetor. I don't totally know the answers to those '85 nissan carburetor questions', Jerry. Maybe HandMeDown does. But after I'm done, if general tune-up doesn't help, I very well may learn the answers to those questions.

Thanks for your input guys.

no1see2me

You have the exact same symptoms that I had at one time and the problem ended up being the EGR Valve, at least I think that is what it is called. The diaphragm was rotted out. The one I am talking about is the one that the tube goes to that comes from the exhaust manifold and the valve itself is bolted to the intake manifold.

HandMeDown

Yep, up till 86 most models were carb. 86.5 was the first model with FI.
I believe so, but if you don't have to worry about emissions just get a converstion kit for a weber 32/36, you can find the whole kit for around 400 online. Plus it gives you about 10-15 extra HP!
Yes on all accounts.
Might temporarily postpone a rebuild, but like I said, if that is the case then why not just pick up a weber? (well assuming you don't have to pass emissions that is..)

I currently have a carb that is flooding on me, I was given this advice on the site I pointed you to in my earlier post:


Some of the most common possibilities for the problem that you describe are all in the INLET NEEDLE VALVE ASSEMBLY. You will have to open the front of the carb. and also remove the fuel inlet valve assembly to be able to do a good job of inspecting the valve assembly and the float settings. If you are VERY careful, you can do this with the carb still on the truck, but be warned, if you lose a small part it will cause a big problem, so at least cover the top of the engine with a towel having one edge tucked as far under the carburetor as you can get it, to help catch and hold any parts that you take off, to keep from losing them. The front cover gasket/"o" ring and/or the inlet valve may not seal well after they have been opened/removed, so if you notice a new leak after reassembling the front cover and the inlet valve, one of them is a likely culprit for the new leak.

these are common problems:
a. groove worn in tip of needle, causing continuous fuel flow into carb between tip and seat (depending on the severity of the groove, this can cause an intermittant or continuous problem)
b. small piece of crud caught between needle and seat causing valve to remain partially open all the time (continuous problem until blockage gets dislodged)
c. Needle or valve body or both are worn, causing needle to hang up when it should be closed. (this can be a hrd one to to track down, because it may be something that only happens occasionally)
d. float has lost it's proper height setting and is now set much too high, allowing fuel to continually flow into carb (this will cause a continuous problem, but when the engine is started cold, it MAY act reasonably normally, then continue to accelerate as it warms up )
e. float has taken on fuel and will not float above fuel, as a result it never raises high enough to shut the flow of fuel off completely (continuous problem, possibly with the same scenario as above)

j.agee

Here's what the problem was:

The carburetor idler sylenoid sensor (whatever it's called, it's on the top left back of the carburetor as you face the engine) was not getting any juice-- the positive wire going from it to the battery had a short in it (in a bundle of wires). It idles like new again--even though there's over 250,000 miles on it (maybe more, the odometer is broke).

Thanks Jerry, HandMeDown, no1see2me for helping me troubleshoot. Your suggestions helped me get the darn thing repaired. Thank you.

HandMeDown

No problem.. I hear that that's a common problem with these things, the engineers just didn't put enough slack in that little wiring harness. Glad it was an easy fix.