FUEL and Coolant TEMPS .. HELP

[BOB_TDI]

am currently having injection pump issues (1268 code) While following through on Forum suggestions I have encoubtered an another anomoly

After my tdi is full up to operating temp (1hr of driving and dash temp about 180* F (aprox 82*C) my VCSD shows Coolant temp as 43* C and my FULE temp at 78*C. Could these sensors have been "crossed" some how? Where are they located??

BOB

 

[garciapiano]

Seems like a bad coolant sensor. Fuel gets pretty hot, that looks like a normal range for fuel temp.

 

[Vince Waldon]

Perhaps you already know this, but the coolant temp sensor has two sensors internally: one feeds the cluster, and one talks to the ECU.

Pretty common for one side to misbehave and the other be fine, and often it's the ECU side that goes south.

Sounds like what's happened to you.

To answer your other question, the fuel temp sensor is inside the injection pump, so that the ECU knows the temp of the fuel just before it burns (since fuel temp affects flame propagation time).

 

[BOB_TDI]

Vince,
THANK YOU!! It must be the one piece unit (4 pin) located on the coolent housing in front of engine between injectore 3 & 4. Does 78*c fuel temp seem high?

 

[Vince Waldon]

The coolant sensor is a 4 pin unit (been a while since I've had an early model but I think it's where you say it is), and 78C is sounds reasonable for fuel temp...the fuel is being compressed in the injection pump and things gets warm.

 

[BOB_TDI]

More help!

My Injection Pump is a 0460404970 10MM for 1z engin with 7 pin plug and a 3 (2?) pin plug (1996 Passat wagon TDI)

Can I use a 0460404977 IP with a 10 pin plug if I rewire the IP (for 1998 -2005 TDI)

Both IP's are for a manual trans and 10MM pumps

 

[turbodieseldyke]

IIRC, when the fuel temp sensor fails, it reads too cold, and results in worse fuel economy.

There's a thread pinned at the top of this forum, for using Mk4 pumps in our Mk3's.

 

[BOB_TDI]

Turbodieseldyke,
THANK YOU FOR THE insight!!!! I read the article and thread and it makes perfect sense. I hope to fix my n146 moduls and not replace_(rebuild) ny IP. 1268 fault may be because of "low voltage" on key on callibration (groop 019 reas .6 v and 3.3v) along with my bad coolant temp sensor (max 45*C). I have access to a machine shop but I really dont want (unless necessary) to refit the Mk4 IP. Perhaps the Mk4 n146 module will fit on my Mk3 pump and solve my problem ANY IDEAS???

BOB

 

[BOB_TDI]

FINAL FOLLOWUP! THANKS for ALL the help and insight!!

FIXED my 1268 fault code; "flashing yellow /engine light" Here is how. I disassembled the top portion of the N146 module and cleaned everything inside. I repositioned the electromagnetic field yoke so it did not rub the armature and reassembled. There is only one video on youtube that showes the entire process. Here it is: ALH VE Pump Quantity Adjuster Disassembly - YouTube If you decide to do this to your VW feel free to email me for some aditional things I learned ..... I learned a LOT!

 

[ToddA1]

Not that I’m experiencing this code, but why wait for someone to email you? Just post your notes…

-Todd