Editing Forums/Z31P/z31-performance-upgrade-forums engine-management/FYI: Fuel Temperature Sensor

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|op_user=Careless
|op_date=2011-05-05 07:06:31
|post_count=30
|archive_url=/Z31performance_archive/forum/z31-performance-upgrade-forums/engine-management/14291-fyi-fuel-temperature-sensor.html
}}

'''Careless:''' <small>(2011-05-05 07:06:31)</small>

'''FUEL TEMPERATURE SENSOR BASICS

The "Fuel temperature Sensor" located on the "Fuel Pressure Regulator" attached to the fuel rails sends the current temperature of the fuel in the rails to the ECU to command certain operations depending on which model year you have. All model years have the "Fuel temperature Sensor", but the function changes between years.

'''1984 & 1985 (EARLY) MODEL YEARS

For the 1984 model year (and possibly early 1985 model years that might share the same ECU), as the fuel in the fuel rails gets warmer the "Fuel temperature Sensor" relays the temperature increase to the ECU, and the ECU adjusts the fuel map to "enrich" the currently referenced fuel cell to add more fuel.

'''Below is page EF & EC-20 from the 1984 FSM.

As stated, it shows that the "Fuel Temperature Sensor" increases the amount of fuel injected based on the resistance of the sensor (Refer to page EF & EC-53, which is not shown, for the temperature/resistance scale that the ECU sees based on "Fuel Temperature Sensor").

Note: The last point on the left side of this diagram is "When fuel temperature is high".

[attachment=2:2vfsi7uh]EF & EC-20 - 1984.jpg[/attachment:2vfsi7uh]

'''1985 (LATE) & LATER MODEL YEAR

For the 1985 and later model years, the FSM does not indicate an enrichment in fuel maps based on the resistance of the "Fuel Temperature Sensor".

Below is page EF & EC-22 from the 1985 FSM (every year after shows the same diagram/data).'''

It DOES NOT make any indication as to the Fuel Temperature Sensor contributing to the fuel map by adding an enrichment modifier to the current fuel map cell.

Note: Comparing this diagram to the one from 1984 model years, you will see "When fuel temperature is high" is missing. It is fair to assume that this feature was removed/revamped from later model years perhaps due to issues with the early model years, being the first of their kind.

[attachment=1:2vfsi7uh]EF & EC-22 - 1985.jpg[/attachment:2vfsi7uh]

SURGE-TANK INFORMATION'''

Below is page EF & EC-31 from the 1985 FSM (every year after shows the same diagram/data).'''

[attachment=0:2vfsi7uh]EF & EC-31 - 1985.jpg[/attachment:2vfsi7uh]

The surge tank is only equipped on 09/86 and later Z31's equipped with Turbos.''' (Needs verification).

It is located in the DRIVER SIDE wheel well, infront of the wheel itself-near the frame rail… By looking at where your MAF is, you will see two rounded vacuum hard-lines that come down from the strut tower area near your ignition coil and transistor, and ultimately make their way through the sheet metal just above the frame rail- and lead into the surge tank.

The purpose of the surge tank is to store "above atmospheric" manifold pressure via a one way check-valve connected to a vacuum line that goes to the intake manifold. When the pressure in the intake manifold is above atmospheric pressure, some of that boost pressure is stored in the surge tank for later use. The check valve prevents pressure from coming back out of the vacuum line. The tank may have some sort of relief valve to vent off excess pressure above a limit set from factory.

This pressure stored in the surge-tank is not released until the car is shut off and re-started. If the "Fuel Temperature Sensor" tells the ECU that the current temperature in the fuel rails is above 40*C or 104*F, the "Pressure Regulator Control Solenoid Valve" that the outlet vacuum line from the surge-tank is hooked up to is activated. This causes the pressure that is in the surge-tank to be routed through the "Pressure Regulator Control Solenoid Valve", and to the "Fuel Pressure Regulator" for a certain amount of time based on the current fuel temperature- thus increasing fuel pressure during hot starts.

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'''Dman:''' <small>(2011-05-05 14:09:37)</small>

Nice work!

Do you have any pictures of this said surge tank. Never seen one on either of my turbo cars that I scrapped.

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'''NissanEgg:''' <small>(2011-05-05 21:05:45)</small>

Don't remember anything in the driver side fender well of my 86T. Pix of said part?

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'''shromy:''' <small>(2011-05-05 21:33:37)</small>

It is in in the D/S fender of 88t and up cars, I would imagine anything from 4/87t and up has it as well. I have never seen one in an NA, but that is because I have never worked on the 4/87 and up NA.

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'''shromy:''' <small>(2011-05-05 21:47:13)</small>

[quote]'''michaelp wrote:''' 

{{Quote|user=shromy|It is in in the D/S fender of 88t and up cars, I would imagine anything from 4/87t and up has it as well. I have never seen one in an NA, but that is because I have never worked on the 4/87 and up NA.

Well then idk wtf the "surge tank" is then, because no 84-89 NA has it, my friends 88T doesn't have it, and no 84-86 has it. They all have a charcoal canister/evap tank on the passenger side…}}

Strange. Try looking behind the inner fender inside the wheel well, in the area of the side marker plug. Every 88 and up turbo car I have worked on has it, thats around 6 of them. FYI I couldnt find it in the FSM with a brief look.

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'''Careless:''' <small>(2011-05-05 22:40:59)</small>

edited first post.

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'''Careless:''' <small>(2011-05-06 00:45:08)</small>

K, allow me to set something straight in this thread (and any future FYI's I write form here on in).

People ask "what does this thing do" constantly. And I explained/outlined what it does "for your information".

I can't answer all the questions because both cars I have are equipped with it, and missing information is a matter of searching for it on my end if I decide it's vital, and on your end if you really need to know.

Basically, if your car doesn't have a surge tank, and it does not seem as though a surge tank ever came on your car, and the pressure regulator solenoid is no where to be found- then this thread is negligible.

There are so many split-year configurations for these cars and trim levels that to list them all is something I'm not prepared to do because in reality- it doesn't make a difference to anyone with a set of eyeballs. If you car has these apparatuses, then read along. If you don't know where these things are located or can't find them using the mentioned locations- assume your car doesn't have them, and add that to your mental list of surge-tank non-equipped vehicles (which will surely change when someone mentions that they in fact did have a surge-tank on their car of the same month/year/trim for some stupid nissan reason, and you guys go and mix up your information and bitch at each other about who's right or left).

Cool?

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'''shromy:''' <small>(2011-05-06 01:26:11)</small>

No one seems to be bitching, Betty. Just trying to find the cars that do and do not have the unit installed. Fairly sure I told you its use and lack there of a year ago. I for one am trying to see if the NA cars had them or not. I have never worked on a 4/87 and up NA. I know non of the pre 4/87 cars had them.

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'''Careless:''' <small>(2011-05-06 01:31:43)</small>

A certain someone was questioning its existence because he's never seen one before.

All i'm doing is posting what the Fuel Temp Sensor does. If you don't have a surge tank- then you don't need to worry about it, I guess? I don't recall if you explained this to me before. If you did, thanks- but other people have asked about it since then and the answer was never really explained in the same or more depth as the FSM (which people fail to check FIRST).

Whatev. If I'm going to post anymore FYI's I'm not going to reply within unless I see fit.

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'''DeleriousZ:''' <small>(2011-05-06 01:32:48)</small>

keep 1st post, delete everything else, lock thread.

well done careless!

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'''shromy:''' <small>(2011-05-06 01:44:21)</small>

viewtopic.php?f=1&t=24090

No, no full write up. Same info you posted about it. Which is not in the fsm so far. No mention what so ever of the part that is on the cars. It is there, it exists, Mikep found it when he looked. Willing to bet they all have them, after certain build date. Good work Buddy [archived image: smile.png].

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'''JeffSly:''' <small>(2011-05-06 01:47:57)</small>

When I read this I knew I recalled reading that the fuel temp sensor could trigger enrichment. As here in the '84 FSM

[archived image: 84EFEC20.jpg]

So, independent of the possible surge tank/pressure regulator it may still do something year and split-year dependent.

That said thanks to OP for posting this, I now understand a difference between my '84 future project and '86 current project that I wasn't aware of.

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'''shromy:''' <small>(2011-05-06 01:51:54)</small>

{{Quote|user=|}}

What? A bunch of things to throw in the nearest garbage can? Engineers??????????????????wtf??????????????

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'''JeffSly:''' <small>(2011-05-06 02:01:20)</small>

{{Quote|user=|}}

 Are you kidding me? This post is an FYI of what the fuel temp sensor does or doesn't do. Since it didn't just say, "It senses fuel temp" I'd consider it relevent that the '84 ECCS uses the number…

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'''Careless:''' <small>(2011-05-06 06:15:41)</small>

Well I'm only adding to this because JeffSly uncovered an important issue.

see first post.

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'''zracer:''' <small>(2011-05-18 19:45:35)</small>

pics or it doesnt exist lol jk

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'''Careless:''' <small>(2011-05-18 20:28:43)</small>

{{Quote|user=|}}

could say the same for your attempted joke. :nanan?re

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'''Z31'85MT':''' <small>(2011-05-18 23:07:55)</small>

Sticky this?

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'''utjon:''' <small>(2012-02-09 17:38:45)</small>

Thanks for this information, is this something that can be junked? I saw that you plumbed the fpr into the manifold back in late 2010 and bypassed this surge canister, has that affected anything?

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'''Careless:''' <small>(2012-02-09 19:18:09)</small>

not that i can tell. most FPR's use a manifold vacuum signal that is direct to manifold. it shouldnt hurt a thing.

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'''utjon:''' <small>(2012-02-10 00:56:04)</small>

I saw Rick mentioning that he needed one based on having A/C but isn't that just for the vacuum pump and not the surge canister?

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'''METSI:''' <small>(2013-08-28 16:54:36)</small>

Hi guys. I know this is an old thread so I apologize for adding a post. My question is, can the fuel temp sensor be removed? I have seen a few Z31's with an adjustable fpr installed in the OEM fpr's location. The sensor was not re-installed anywhere else, just taped to the harness. I was going to try and insert the fuel temp sensor in a fuel line using a "t" fitting or just tape it back. Any thoughts?

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'''jaqattack02:''' <small>(2013-08-28 19:52:22)</small>

If you're installing an aftermarket FPR I think you're safe to just remove it. By the time you get to that point I'm assuming you have some kind of tuning software as well, so you're going to be tweaking the fuel maps yourself at this point. Not having it hooked up just means the ECU is always going to see the same reading from it, so it's not going to be messing with the enrichment based on the temperature.

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'''300zxturboftw:''' <small>(2013-08-28 20:16:13)</small>

Mine broke off, got another from a member here. It lasted a week before breaking off again. I gave up.

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'''METSI:''' <small>(2013-08-29 12:42:54)</small>

Thanks for the replies. I think I've figured out how to have the adjustable fpr and sensor. I'll let you know how it turns out. I won't be able to adjust fuel maps with my setup. I'm waiting for my JWT ECU to come back from being reprogrammed. I would assume the fuel temp sensor needs to be functional, in my set up anyways.

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'''michaelp:''' <small>(2013-08-29 15:35:21)</small>

I havent run a FTS in ages, even with stock tunes. meh.

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'''85NA2T:''' <small>(2013-08-29 16:23:17)</small>

{{Quote|user=|}}

^ This

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'''METSI:''' <small>(2013-09-03 19:52:51)</small>

In that case, it'll be gone [archived image: smile.png] Thanks guys.

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'''les_joey_paul:''' <small>(2013-09-03 23:43:47)</small>

My car reacts to a bad FTS connection. Very rough idle. Some hard starts. With the connection repaired, it works like a dream.

85 na running 87 ecu.

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'''michaelp:''' <small>(2013-09-04 00:52:08)</small>

{{Quote|user=|}}

It reacts to a bad FTS connection or sensor…but if its unplugged/removed, it won't react negatively at all.