AEL pump timing

Posted: Sun Nov 28, 2010 9:47 am

Hallo

Can someone help with an idea why the fuel temperature is so high in vag-com TDI timing graph?

It gives 216 for fuel temp. At the same time at ch.7 fuel temp is 84oC.

Bandwidth Buster Joined: Aug 12, 2006 Posts: 803

218'c ouch,there is a fuel temp sensor built into the fuel pump on these,i believe they are around £10 to buy.I should think that would be likely to be the problem,i take it vagcom hasnt showed you any codes relating to this?

Posted: Sun Nov 28, 2010 5:28 pm

I seriously doubt the problem is this sensor. As I wrote, at the same time ch.7 says the fuel temp is 84oC.

Bandwidth Buster Joined: Aug 12, 2006 Posts: 803

well you obviously couldnt get engine to the 'normal' temp of 85'c as you have ticked the 80'c box so how can it be 84'c?i thought it delicked when it went above 80'c?

Posted: Wed Dec 01, 2010 8:55 am

Something weird going on but you could try adjusting the timing to the first screen shot, and ignore the tdi timing graph for the moment. At 3.8° btdc it appears to be far too advanced at the moment.

Also if you fully read the link I sent you in the pm you'll see why you should be using the 1200 rpm option when setting the timing, however that wont make any difference until you solve the fuel temp weirdness...

Posted: Wed Dec 01, 2010 10:55 am

Thank you for the advice!

I do not agree with you about using 1200 far AEL, which makes 1000rpm during timing.

Yesterday I made timing on AAT. When I started the basic setting it made 1200rpm.

So I think some engines(maybe AAT) make 1200rpm for timng and you are supposed to use 1200 graph, the rest do 1000rpm and you use 1000rpm graph.

I fact my timing varies 3,8-5,2. At the picture I have screenshoted when it was 3,8 not intentionally.
Is it bad for the engine to work so advanced?
Why this value varies so much(on the graph it moves with 10 degrees, 60-70 degrees)?

Posted: Wed Dec 01, 2010 11:35 am

As mentioned in the linked topic (which I've added a link to below for anyone following this thread), from what I understand about these cars and engines the 1200 rpm setting correlates correctly to the specified / actual when viewed in measuring blocks 004, it doesn't run the engine at 1200rpm, which is confusing to say the least, but at 1000rpm just as if using the 1000rpm graph ... If you set A6 AAT or AEL using the 1000rpm setting then compared to measuring blocks 004 it will be too advanced. This can trick you into thinking it is better because over advance can really help cold starting....however I'm happy to be proved wrong if some can prove me wrong, and explain in detail why

AAT in Audi 100 which uses a different ECU and supply voltages is what you would use the 1000rpm setting for, at least that is what I understand form what I have learnt, but I have no hands on experience of the 100 version of the C4 TDI

http://www.audifans.net/ftopict-30042-.html

It does seem odd you are getting two different readings from one senor but I've noticed in the past that the fuel temp figure in the timing graph doesn't always correlate with the reading in measuring blocks even allowing for Celsius / Fahrenheit.. obviously yours seems way out and you are really going to have to rule out the temp sensor in the pump before delving further into the problem. It's quite easy to change but ideally you need a special tool for the tamper proof bolt.

I think there's also some confusion with coolant temp and fuel temp here, if your coolant temp is under 80c then unless you are somewhere very hot, or it's been sitting hot for a while (heat soak) then fuel temp should always be lower than coolant temp, not 84c & above.. it's hard to be sure as your not in the UK (it's about -4°C here at the moment)...but looking at current temps in Sofia Bulgaria it's about 10°C to 15°C so fuel temp of 83°C (183.2°F) is highly unlikley. I think about 140°F (60°C) is the highest fuel temp I've ever seen in TDI graph in the height of UK summer with some heat soak as well...

my advice swap out fuel temp sensor with known good or new one as first step..

http://www.myturbodiesel.com/1000q/multi/fueltempsensor.htm

Posted: Wed Dec 01, 2010 12:44 pm

Thanks for the explanation!

This 84oC for fuel in ch.7 I saw after test driving with high load and rpm to make logs, the engine was very hot, the coolant was 89oC, but everything uder the hood, was very warm. The ambient temp was 17-20oC.

In most of the cases I see 40-50oC for the fuel on ch.7.

I am not sure I explained very well. On this A6-1994 AAT, when I started TDI timing graph, it really made 1200rpm - on rpm meter(i dont know what is the word), not 1000rpm like mine AEL. Obviously some engines are designed to do timing at 1200 rpm. I suppose that is the reason for this 2 positions in the menu.
I agree with your observations about correlation of the values in the graph and at the ch.4. But on the other hand the graph depends very much on temp of the fuel. In my graph, if the fuel is 120, advance is no so huge.

Posted: Fri May 18, 2012 9:07 am

DId you ever get tot the bottom of this? Mine is the same, I've replaced the fuel temperature sender but I'm still getting 200+ when in the TDI timing graph, yet chanel 7 is saying 75°C.

Posted: Fri May 18, 2012 7:00 pm

The 200 metioned in the VCDS screen is not calibrated in degrees Celcius. The ECU uses a different scale of temperature units for certain sensors in different windows of VCDS.
Once you put in your correct engine code the software will raise your RPM to the desired level for timing checking.

Posted: Fri May 18, 2012 9:39 pm

Mine goes off the edge of the graph, it also gives a warning at the bottom of the page saying that fuel temp is too high.

I'll try and get a screen shot tomorrow.

Posted: Sun Jan 27, 2013 12:16 pm

Andy any further foward with this? Mine is also over 200.C