# Z24i starts cold, shuts down just as it's warmed up, won't start warm



## wahilde (Nov 9, 2009)

I have a 1986 (bought new in 1985) 720 4x4 Sport Truck with throttle-body injection, so I'm calling the motor a Z24i because it is TBI. This truck always starts when it's cold, but just before the temp gauge hits normal operating temperature (just south of dead center) it shuts down just as if I turned off the ignition key. No sputter, no slowly winding down to 0 rpm, no funny noises -- it just quits like I had turned it off. THEN it won't start at all because it's warmed up and won't start again until it's stone cold (hours later). The starter motor can turn the motor over easily for as long as you want to crank it over, but it won't start once it's warm. I DO get a code 24 (throttle valve switch) on the ECS, so I guess I need to replace the throttle position sensor, but I'm not sure that a bad throttle position sensor would cause such behavior, plus I don't know how to check a throttle position sensor to see if it's really bad. Can anyone tell me how to test my throttle position sensor? I have the Chilton manual, but I'm about ready to burn it -- can't find anything about the throttle position sensor in there. And can someone tell me what happens once the motor warms up?


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## brookwood61 (Aug 18, 2005)

It is a Z24I engine. Check to see if you can hear the fuel pump running, when it shuts down. It should come one for a few seconds when the key is in the on position.
Good Luck


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## brookwood61 (Aug 18, 2005)

There is a post somewhere in this forum, where someone posted the 86 Nissan 720 Factory Supplement Manual,that covers the throttle body in these. I'll see if I can find it.
Here it is..post 25
http://www.nissanforums.com/hb-truck/150512-idle-stumbles-when-coming-stop-2.html


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## wahilde (Nov 9, 2009)

brookwood61 said:


> It is a Z24I engine. Check to see if you can hear the fuel pump running, when it shuts down. It should come one for a few seconds when the key is in the on position.
> Good Luck


When I turn the key to the ON position, the fuel pump runs for about 5 seconds and then shuts off, then I start the truck. The truck will run fine until it warms up (takes maybe 3 to 5 minutes depending on outside temps). It'll rev up just fine (over 3K rpm) and back -- I only mention this because a lot of folks have issues with rpm changes around the 2800 rpm mark -- I don't have that problem. I've never noticed if the fuel pump was running when the engine quit -- I'll listen for it next time.


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## wahilde (Nov 9, 2009)

brookwood61 said:


> There is a post somewhere in this forum, where someone posted the 86 Nissan 720 Factory Supplement Manual,that covers the throttle body in these. I'll see if I can find it.
> Here it is..post 25
> http://www.nissanforums.com/hb-truck/150512-idle-stumbles-when-coming-stop-2.html


Thanks very much. I've been looking all over the place for TPS install/test instructions. That thread really helps.


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## brookwood61 (Aug 18, 2005)

That is the Holy Grail of 720 manuals.


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## 87z24shortbed (Feb 18, 2009)

i had a mitsubishi montero that had the same problem i changed the little electo dudad in the dizzy and it fixed i think it was expensive but you can check out other stuff first


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## jblakeslee (Nov 30, 2005)

My Ka24E did the same thing....it was the Temp sensor located on the intake manifold, it would tell the computer the engine was overheated, when it was not, and it would not start when warm.....let it cool down, no problem....

On mine there are two sensors, one is just for the temp light, the other is for the ECU.....replaced the ECU sensor and all has been fine since......

They are less than $20 bucks at Autozone


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