Fuel temp too high.

cbhansen

Well-known member
Joined
Oct 19, 2000
Location
Denmark, Europe
TDI
94 Passat 1.9TDI 1Z engine, 84 Golf II modified with 1Z engine
Hi,
i wanted to check the TDI timing with my VAG-COM.
I got the engine warm (coolant>80 degC) went into the TDI graph.
The message was: "Fuel temp is out of range (too hot)", and measured 239 degC.

Any ideas why? The only 'mod' is have made is to increase the injected amount of fuel to avoid schudder...

Please help

Thanks
 

MOGolf

Top Post Dawg
Joined
Jun 27, 2001
Location
underneath something
TDI
2001 Golf GLS TDI Reflex silver, rough road suspension and steel skid plate, 2004 Passat Variant, Candy White, rough road suspension and geared balanced shaft module, and much, much more. 2016 LR RR HSE TD6, 2019 Jaguar I-PACE
That 239 was just a raw number, not degrees C.

Your fuel temperature sensor in the pump might be defective. Let the car sit overnight. Before starting it up in morning, hook up VAG-COM and go to the ECM measuring blocks that shows the fuel temp, air temp, and coolant temp readings. They should be all reasonably close to each other. If the fuel temp reading way off, this would confirm the bad sensor.
 

cbhansen

Well-known member
Joined
Oct 19, 2000
Location
Denmark, Europe
TDI
94 Passat 1.9TDI 1Z engine, 84 Golf II modified with 1Z engine
Thanks, I'll do that.

So, in case the temp sensor is ok, then how do I do the TDI timing check from VAG-COM? The graph is based on fuel temp, and mine is way out of the scheme...

What is actually determining the fuel temp?
 

MOGolf

Top Post Dawg
Joined
Jun 27, 2001
Location
underneath something
TDI
2001 Golf GLS TDI Reflex silver, rough road suspension and steel skid plate, 2004 Passat Variant, Candy White, rough road suspension and geared balanced shaft module, and much, much more. 2016 LR RR HSE TD6, 2019 Jaguar I-PACE
[ QUOTE ]
So, in case the temp sensor is ok, then how do I do the TDI timing check from VAG-COM? The graph is based on fuel temp, and mine is way out of the scheme...

[/ QUOTE ]One other thought: Did you select the correct graph for your engine? I suspect you'll find the sensor is bad. If you go to the measuring blocks you'll find a group that displays the fuel temperature in degrees C. If it is showing a really odd number, it's a sure thing that the sensor is bad.
[ QUOTE ]
What is actually determining the fuel temp?

[/ QUOTE ]The fuel temperature sensor. It is located under the top cover of the injection pump and requires a special socket to remove one of the bolts (or creative use of something else), a small torx screwdriver, and a new sensor to replace it.
 

gbangs

Veteran Member
Joined
Jul 1, 2003
Location
United States
TDI
None currently
If you look here,

http://www.tdiclub.com/TDIFAQ/TDiFAQ-7.html#k

This is a second method of setting timing. It involves checking hot, idle timing from Measuring Blocks(non-basic) to be between 0.4 and 2*, but less than 3.

I've heard of another... 12* at 3000rpm, but I can't remember where I have seen it.

If your fuel sender element is indeed out, many people have simply replaced it with a fixed value resister. Search this site for the thread, as I don't recall where it is.

Good Luck,
 

bowlerman

Veteran Member
Joined
Jul 31, 2001
Location
medford, NJ
TDI
2001 jetta tdi black
fuel temp sensor in top of pump def bad. my dads car does same thing, just do timing when car is warm and dont worry about fuel temp.
 

cbhansen

Well-known member
Joined
Oct 19, 2000
Location
Denmark, Europe
TDI
94 Passat 1.9TDI 1Z engine, 84 Golf II modified with 1Z engine
Did some checking this morning when going to work. In meas blok-8, group 7, the fuel temp reports 103 degC. I guess that's OK?

I'll do more checking later today.
 

MOGolf

Top Post Dawg
Joined
Jun 27, 2001
Location
underneath something
TDI
2001 Golf GLS TDI Reflex silver, rough road suspension and steel skid plate, 2004 Passat Variant, Candy White, rough road suspension and geared balanced shaft module, and much, much more. 2016 LR RR HSE TD6, 2019 Jaguar I-PACE
Check the temps in the morning (assume you park the car all night), by turning the key to on but do not start the car. Let us know what it reads.

It is way too high. On a hot summer day, driving at 105kmh, mine was only 63C.
 

cbhansen

Well-known member
Joined
Oct 19, 2000
Location
Denmark, Europe
TDI
94 Passat 1.9TDI 1Z engine, 84 Golf II modified with 1Z engine
Will do tomorrow morning. I can part the car outside, then it is definitively cold, apprx -5 decC outside.

Does the "measured" fuel temperature have effect on other measurements?
 

dieseldorf

Top Post Dawg
Joined
Oct 11, 2000
Location
MA
TDI
ex- 1996 wagon, ex-2000 Jetta
[ QUOTE ]


Does the "measured" fuel temperature have effect on other measurements?

[/ QUOTE ]

Yes
 

cbhansen

Well-known member
Joined
Oct 19, 2000
Location
Denmark, Europe
TDI
94 Passat 1.9TDI 1Z engine, 84 Golf II modified with 1Z engine
Checked this morning.
It turned out to be rather "warm" outside.
Before the engine was started measblok 8 group 7 reported
air intake temp: 8 degC
coolant: 9 degC
fuel temperature 103 degC

So the fuel temp sensor is def bad!!
 

Korte

New member
Joined
May 22, 2017
Location
Hungary
TDI
2.0 CFFB
What is the normal fuel temp range for CR TDI?

Hi All, I just wondering what is the normal range of the fuel temp in my CR TDI engine. Based on the VCDS measures, the fuel temp is more or less same as the intake air temperature. In spring time starting from cold start:
-outside temp: 14
-coolant temp goes from 14 to 90
-intake air temp goes from 14 to 22
-fuel temp goes from 14 to 22 too.
Is it Ok? Thanks,
 

Korte

New member
Joined
May 22, 2017
Location
Hungary
TDI
2.0 CFFB
I find a document named "VCDS AND PD TDI ENGINE HEALTH CHECK - PASSAT". There is a sentence in it:
"The Fuel and coolant temperatures are far more important than you might think. The engine ECU may be relying on 6 Duration maps and 10 Beginning of Injection maps for Injection Quantity. The over riding factor for adjusting these maps is Fuel temperature. (Coolant temperature if fuel temperature sensor fails) Adjustment temperatures are approximately: -20, -10, 0, 11, 20, 25, 40, 55, 70, 89 Degrees Celsius. So if the ecu thinks the temperature is below 89 degrees C, it will not run on it's optimum economical settings."
 

Matt-98AHU

Loose Nut Behind the Wheel Vendor
Joined
Apr 23, 2006
Location
Gresham, OR
TDI
2001 Golf TDI, 2005 Passat wagon, 2004 Touareg V10.
Hi All, I just wondering what is the normal range of the fuel temp in my CR TDI engine. Based on the VCDS measures, the fuel temp is more or less same as the intake air temperature. In spring time starting from cold start:
-outside temp: 14
-coolant temp goes from 14 to 90
-intake air temp goes from 14 to 22
-fuel temp goes from 14 to 22 too.
Is it Ok? Thanks,
Not the right forum for a commonrail question, but yes, after a cold soak, those temps look just fine.

I have had an issue with a customer's commonrail when after driving for about exactly 30 minutes, the fuel temp would climb above 80 C and suddenly the car would lose power with no codes stored, I could also see the duty cycle of the fuel metering valve on the HPFP would trend higher than normal at that point.

Turns out, the feed and return fuel lines at the firewall were crossed and it wasn't allowing the thermostatic element in the fuel filter housing to send return side fuel straight back to the tank after it had gotten up to the appropriate temperature to do so. Sorted out the fuel line routing and the fuel temp would stay in the 50-55 C range and no longer had a performance issue due to extreme fuel temp.
 
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