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SneakyAnarchistVanCamper
03-25-2017, 03:43 AM
Does anyone know normal values for fuel temp at 50F? I plug in the scanner, turn the key to on, and 20 seconds later when I get to the screen the fuel temp is already at 70F and climbing 1F/sec, up past 110F. I started it up and the fuel temp started to drop. While engine is running it's 90-95F.

Do these values seem normal? My ambient temp sensor is missing.

"Fuel temperature sensor: If the engine is cold, the actual value sent will read
ambient temperature. The value rises after the
engine has been started."

"If the fuel
is too warm, the rail pressure in the system is lowered.
The controller quantity of the pressure regulating
valve is reduced and the fuel temperature is
lowered."

autostaretx
03-25-2017, 04:15 AM
From the bible:

84265

84266

The high pressure pump is doing a factor of 200 to 1600 compression over atmospheric pressure, so there will be quite a bit of heat resulting from that
(if it was a gas, it would be T=PV/KR, but i'm not sure how oil compression follows that relationship (off to google...))
... i'm back (mid-way) ... fascinating... the heat added to the fuel is apparently almost entirely due to the mechanical inefficiencies of the pump. If the pump is 80% efficient and consuming 1 horsepower, then 20% of a horsepower is spent heating the fuel. Oil is almost completely incompressible (it doesn't become less volume under pressure), so the gas law (in its liquid form) barely applies.

The fact that the sensor stops trying at 120 C hints that they're expecting up to about 100 C (212F), but not much more.
140 F is probably more like it in terms of "normal maximum" on a 70F day.

None of the session-captures i've done with my DAD show a "fuel temperature" readout.
--dick

SneakyAnarchistVanCamper
03-25-2017, 04:50 AM
I appreciate it, but I still have questions. It says the temp will rise *after* the engine is started, but my temp rises before the engine is started. Is this normal? Is there a fuel heater or is the lp pump warming it?

I suppose it is going off of the ambient temp, like the manual says, but the ambient temp sensor is missing so it's just using default values? I'm asking because I'm wondering if my random shutoffs and high/low rail pressure codes have something to do with fuel temp not being right. I replaced the fuel rail and it happened once more, shut off, a couple minutes into my drive after I replaced the rail. I'm hoping it was just from air in the system but I think the intermittent fault remains. I read some threads about no-starts and shut downs caused by the fuel temperature sensor, wondering if my situation might be related.

autostaretx
03-25-2017, 05:11 AM
I appreciate it, but I still have questions. It says the temp will rise *after* the engine is started, but my temp rises before the engine is started. Is this normal? Is there a fuel heater or is the lp pump warming it?.
Don't forget that the fuel passing to (and from) the engine is warmed (cooled) by passing through those dual-tubed coils (the "fuel cooler") that are mounted next to the fuel tank.

If you're running your tests after the engine has been running, those coils are filled with hot "extra" fuel being returned to the tank... and that will warm up the fresh fuel coming from the tank (just due to the low pressure pump pushing fuel through the coils) .

Crawl underneath and feel those coils to see if they're doing the heating you're seeing.

The real question is: do you see that pre-running temperature rise as the *first thing* (i.e. before running the engine at all) in the morning?

--dick

SneakyAnarchistVanCamper
03-25-2017, 11:18 AM
The real question is: do you see that pre-running temperature rise as the *first thing* (i.e. before running the engine at all) in the morning?
--dick

Yes, it does.
I repeated my test. The engine had sat for 4 hours in 45F weather. Should be plenty cold by then. With engine off, key on, fuel temp went from from 70F to 80F. I suppose this may be a made up default value because it goes off the ambient temp sensor which in my case is missing. I will have to repeat this test with my new ambient sensor plugged in.

Oilburner
03-25-2017, 06:19 PM
What is heating fuel with key on?

Cheyenne
03-25-2017, 07:02 PM
What is heating fuel with key on?

Nothing is heating the fuel with only the key on!

As you said in your first post, if the engine is cold then the fuel temperature reading defaults to read ambient temperature. And that is from the sensor which you then said you do not have!!!

What temperature is your scanner or dash display showing for ambient? I bet with the sensor missing it is defaulting to something like 255 or maybe higher, yes? If so this is the value your fuel temperature is defaulting to.

You MUST have a functioning ambient temperature sensor for these engine to function correctly.

Fix your ambient sensor then see if you have a problem with fuel temperatures, I'll bet the problem magically goes away.

Keith.

SneakyAnarchistVanCamper
03-25-2017, 11:17 PM
The dash displays "--", scanner displays "N/A". I have the new ambient sensor, but I want to see if my problem comes back before installing it. So far 100 miles after replacing the rail and it's been perfect.

I'll bet you're right the fuel temps will go back to normal when I replace the ambient sensor, but what I was really wondering is if the ambient sensor can affect fuel temp reading so drastically that it actually shuts down while driving.

Edit: Day 2 of test drives. Ambient sensor has nothing to do with my shutdowns, new fuel rail solved it. Now I will replace the ambient sensor and observe fuel temp.

autostaretx
03-26-2017, 05:55 PM
Everyone's been talking about the ambient temperature sensor, yet many members don't have one (lost due to the normal scrapes and vicissitudes of daily driving).

The ECU/ECM gets the (behind front license plate) "ambient" temperature indirectly via the Instrument Cluster (IC).
But the temperature it really cares about is the "air" temperature, which it gets via a direct wire to the Mass Air Flow (MAF) sensor (it needs it to calibrate the MAF's flow result).
It does cross-check the ambient against the air temp (codes P2013 and P229 for ambient issues).
If one of the two sensors is not reporting (MAF unplugged or Ambient lost), the ECU uses the remaining one. (i don't recall if simply losing the ambient sensor even turns on the Check Engine light).

Note final sentence on this page:

84290

Here's the page on the information the ECU gets "indirectly" ... things it needs/wants to know, but which are not part of the "tight-loop" control of the engine's fuel/emissions control.

84291

--dick
p.s. the other critical temperature sensor is the Intake Air Temp (IAT), which is measuring the "heated by turbo compression and cooled by intercooler" air that's going into the engine along with the fuel. It can run without that sensor, too .. but has no low-end power when doing so.

grumpy-old-van
03-27-2017, 09:11 AM
You can get aftermarket pre heaters
Is it possible that one may have fitted at some time?

Would normally only be fitted in severe cold climate..
or if someone ran it on veg oil?

edit:
just looked up averages for Oregon
its like my ideal range, may have to move there

grumpy-old-van
03-29-2017, 05:09 PM
My temp gauge doesnt work and no light on dash
in fact im gonna order one now I keep looking for the temperature when i get in
weird what you miss

SneakyAnarchistVanCamper
03-29-2017, 10:17 PM
Your coolant temp sensor doesn't work? That's pretty important. I recommend you ohm out coolant temp sensor wires, maybe replace coolant temp sensor.

What do you mean by no light on dash? No coolant temp error light? Or the orange display does not light up?

"No dash lights? Check license plate lights"
"
https://sprinter-source.com/forum/images/buttons/viewpost.gif (https://sprinter-source.com/forum/showthread.php?p=260991#post260991) I just had this EXACT SAME PROBLEM and I fixed it. Went to get the van inspected for tag renewal and Junior says that one of the tag lights doesn't work. Says he can fail it and I can fix and come back for additional charge or Junior has the bulb and he can fix. Chose door number 2 so I didn't have to come back.

Driving to SC early in the morning the next week and notice I don't have any instrument lights on the dash, ok who was the last idiot to work on van, Junior, and he replaced the license plate bulb. Experimenting, I find that if I turn key on without starting, lights work, but as soon as I start it, lights go out. Check license plate light and Junior has broken the bulb holder and tried to jam it in there. It is loose and could easily short out. License plate light is on the same circuit as the lights.

It did short out and the fuse is under the drivers seat. It is fuse number 8. I replaced mine and it shorted again and blew the fuse. Junior broke the license bulb bracket so bad it is shorting. Replaced the bracket and fuse and all is well."

IMAC
11-15-2019, 09:37 AM
Nothing is heating the fuel with only the key on!

As you said in your first post, if the engine is cold then the fuel temperature reading defaults to read ambient temperature. And that is from the sensor which you then said you do not have!!!

What temperature is your scanner or dash display showing for ambient? I bet with the sensor missing it is defaulting to something like 255 or maybe higher, yes? If so this is the value your fuel temperature is defaulting to.

You MUST have a functioning ambient temperature sensor for these engine to function correctly.

Fix your ambient sensor then see if you have a problem with fuel temperatures, I'll bet the problem magically goes away.

Keith.

You MUST have a functioning ambient temperature sensor for these engine to function correctly.

Hello Keith.
Is the ambient temp critical to ECM or just gives temp at the Instrument Cluster.
I have a situation in a 416 CDI Sprinter engine is 612.981 It is giving good boost and acceleration response in the morning or evening when ambient is around 16 to 18 deg C but in the middle of the day when temps reach 26 to 30 deg C the boost drops off remarkably and the Sprinter gets a bit sluggish and dark smoke.
I've checked all the wires from contact to contact and all good checked the fuel temp sensor and all good there as well as the fuel temp sensor and boost air temp are apparently linked in the ECM somehow.
Any clues.
Thanks
IMac