Cooling fans on fuel rails

[alanburton]

I drove my 83 280zx until the engine was hot enough to cause a vapor lock on start up after being parked about ten minutes in 90 degree heat. The fan that cools the fuel rails never kicked on. I knew the fan worked properly because after turning the engine off I pulled the lead from the thermostat switch located on the thermostat housing and ground it, and immediately the Fan started working. I knew then that my problem was the fan switch the screws into the thermostat housing so I ordered a new one and replaced it and I still got the same result. I don’t think the Fan would’ve kicked on if the engine was on fire. After that I searched on eBay and found the small thermostat switch that is normally open but closest when the temperature reaches 122°F. I simply grounded One side of the switch to a bolt on the valve cover and then plug the other end into the wire that I took off of the thermostat sensor. Now it works great, take my car out on a hot day and I Park it and my cooling fans come on every time. I’ve attached a picture of the small sensor Showing the way I attached it. You can find these on eBay for a couple of bucks, just make sure that you get one that’s normally open, and is the correct temperature that you’re seeking. The 122°F as work great for me.

 

 

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[EuroDat]

Hi alanburton,

Welcome to the club. Good to hear you fix your starting problem. This is a common problem on hot days or after a long run where the engine (exhaust) generates a lot of heat. Im not sure what temperature the fan cuts in. I know some 280Z guys use a timer on the fans to control how long they work. The fan wasn't available on the 280Z. It was an improvement added to the 280ZX.

Btw: The system shouldn't suffer from vapour lock, unless the system is looses pressure. One theory is the injectors stick when they overheat. Cooling does help clear the problem, though.

I had a similar problem and found the check vavle in the fuel pump was leaking. The system was loosing pressure and required long cranking to build up pressure and then start. On hot days it was worse. I tried a fanfor a while, but it didn't seem to make any difference. Replacing the check valve did. Now it holds pressure for a week or so.

 

[Zed Head]

18 hours ago, alanburton said:

searched on eBay and found the small thermostat switch that is normally open but closest when the temperature reaches 122°F. I simply grounded One side of the switch to a bolt on the valve cover and then plug the other end into the wire that I took off of the thermostat sensor.

Do you have a link to the switch?  It's not really clear where you put it or what kind it is.

[alanburton]

Do you have a link to the switch?  It's not really clear where you put it or what kind it is.

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[alanburton]

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You can see the temperature switch it’s the little shiny silver thing. There are two leads, attach one to the bolt on the valve cover to get ground. I put a female bullet connector on the other wire and then simply unplugged the single wire that’s attached to the temperature switch on the thermostat housing. Just disconnect that wire plug it into the other wire on the new switch and you’re done. I found the switch on eBay for less than two dollars from China


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[alanburton]

Hi alanburton,
Welcome to the club. Good to hear you fix your starting problem. This is a common problem on hot days or after a long run where the engine (exhaust) generates a lot of heat. Im not sure what temperature the fan cuts in. I know some 280Z guys use a timer on the fans to control how long they work. The fan wasn't available on the 280Z. It was an improvement added to the 280ZX.
Btw: The system shouldn't suffer from vapour lock, unless the system is looses pressure. One theory is the injectors stick when they overheat. Cooling does help clear the problem, though.
I had a similar problem and found the check vavle in the fuel pump was leaking. The system was loosing pressure and required long cranking to build up pressure and then start. On hot days it was worse. I tried a fanfor a while, but it didn't seem to make any difference. Replacing the check valve did. Now it holds pressure for a week or so.
 

Yea I had driven the fire out of my car for about two hours and then parked it for about 10 minutes and those fuel rails must’ve been boiling because I really had to put that throttle to the floor to get her started. That was the first only time I ever had that starting problem but that’s when I decided I was going to do something to lower the threshold for when my cooling fans came on. Prior to adding this new switch I couldn’t drive it hard enough in hot enough weather to get it to come on.


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[Dave WM]

280z no fan trick, if safe to, pop the hood, even just to the secondary latch, lets heat out. I always do this a gas stations when filling up good time to check the oil while at it.

[alanburton]

You can see the temperature switch it’s the little shiny silver thing. There are two leads, attach one to the bolt on the valve cover to get ground. I put a female bullet connector on the other wire and then simply unplugged the single wire that’s attached to the temperature switch on the thermostat housing. Just disconnect that wire plug it into the other wire on the new switch and you’re done. I found the switch on eBay for less than two dollars from China

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F401445968168

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https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F401445968168


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[alanburton]

Hi alanburton,
Welcome to the club. Good to hear you fix your starting problem. This is a common problem on hot days or after a long run where the engine (exhaust) generates a lot of heat. Im not sure what temperature the fan cuts in. I know some 280Z guys use a timer on the fans to control how long they work. The fan wasn't available on the 280Z. It was an improvement added to the 280ZX.
Btw: The system shouldn't suffer from vapour lock, unless the system is looses pressure. One theory is the injectors stick when they overheat. Cooling does help clear the problem, though.
I had a similar problem and found the check vavle in the fuel pump was leaking. The system was loosing pressure and required long cranking to build up pressure and then start. On hot days it was worse. I tried a fanfor a while, but it didn't seem to make any difference. Replacing the check valve did. Now it holds pressure for a week or so.
 

When the factory temp switch sees a temperature of around 190 degrees or somewhere there about the switch opens the connection to ground. When the ignition is turned (off) and this ground connection is present the fan timer kicks in and runs the fan for several minutes and then turns the fan off. As earlier stated I could never get the factory switch to work even on the hottest days but this new switch works very well for me.


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[Zed Head]

I like it, it's a good idea.  When I was looking for a switch like that I was focused on finding one for the thermostat to use coolant temperature for a cooling fan I had rigged up.  But, using air temperature seems just as good, maybe better.  When air is flowing because the engine is running the switch is off.  If heat builds up with the engine off it kicks on.  My other concern was always about it staying on and running the battery down.

Have you watched it while the engine cooled off?  Seems like it would turn on and off as the fan turned on and cooled the switch.

The other "fix" that many of us have found is an aluminum fuel rail.  It seems to act like a heat sink for the injectors.

[alanburton]

I like it, it's a good idea.  When I was looking for a switch like that I was focused on finding one for the thermostat to use coolant temperature for a cooling fan I had rigged up.  But, using air temperature seems just as good, maybe better.  When air is flowing because the engine is running the switch is off.  If heat builds up with the engine off it kicks on.  My other concern was always about it staying on and running the battery down.
Have you watched it while the engine cooled off?  Seems like it would turn on and off as the fan turned on and cooled the switch.
The other "fix" that many of us have found is an aluminum fuel rail.  It seems to act like a heat sink for the injectors.

There is a timed relay that is triggered by a grounded connection to the sensor wire connected to the thermostat. Once the ignition is shut off the fan timer is in a ready state. If it sees ground on that connection it will start the fan and allow it to run for a programmed period of time (10 - 15) minutes and then it shuts the fan off. If you were to turn the ignition back on and then off again and the temperature was still hot enough to open the switch to ground it would replete the process. If however you left the ignition off it could not be triggered again.


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[alanburton]

There is a timed relay that is triggered by a grounded connection to the sensor wire connected to the thermostat. Once the ignition is shut off the fan timer is in a ready state. If it sees ground on that connection it will start the fan and allow it to run for a programmed period of time (10 - 15) minutes and then it shuts the fan off. If you were to turn the ignition back on and then off again and the temperature was still hot enough to open the switch to ground it would replete the process. If however you left the ignition off it could not be triggered again.


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Also if you want to try this make sure to order the switch that is N/O or Normally Open. I’m using one set for 50°C or 122°F


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