Temperature measurements on a Mk 4 PD Golf

[Julian]

Further to a recent thread, I made some measurements on our Golf fuel system today.  Some of the readings taken on plastic tubes may be a bit suspect, especially the black supply from the tank, but these are what I came up with using an IR thermometer.

I'd estimate the ambient air to be circa 10°C, temperature of the concrete drive 8.7°C and the car was at normal running temperature ... 90°C according to the gauge.









So looks quite promising for running bio during the winter.  Does anyone know whats in the tank ... pump filter etc?

[rbdazza]

There are loads that run PD engines on B100 year round with no issues, why do you think you will hit problems?

My Passat when through last winter on B100 with no winteriser, I think one batch got a splash of petrol but only a few % and it sailed through winter. admittedly, starting on very cold mornings wasn't the usual instant start but was hardly worryingly long.

[Julian]

HMPEs ... if you've had them form in a car, you wouldn't be asking the question!

[rbdazza]

doesn't that apply to any car though, not just a PD Vag?

[1958steveflying]

In the tank you have a fuel pump built into the fuel gauge sender unit this has a gauze under its intake, the return goes back into this chamber always keeping it full of fuel, it only pumps to prime the system when you first turn on the ignition. This is handy when you change filters but other than that the car will run fine without it so long as all other fuel system components are up to spec.

[1958steveflying]

If you get hooked up to Vagcom you can accurately see the fuel temperatures coming out of the engine, not unusual to see around the actual engine temperature of 90c.

[Julian]

doesn't that apply to any car though, not just a PD Vag?

Yes, that's why I've made a heated filter for the Disco .... http://www.biopowered.co.uk/wiki/Heated_fuel_filter

Cleaning out tank on the Disco, although a relatively easy job, is extremely unpleasant in sub zero temperatures, and I don't want to go through the same procedure on the Golf.  Not least of all for the ear bashing I'll get when she can't get to work one winters morning.

In the tank you have a fuel pump built into the fuel gauge sender unit this has a gauze under its intake, the return goes back into this chamber always keeping it full of fuel, it only pumps to prime the system when you first turn on the ignition. This is handy when you change filters but other than that the car will run fine without it so long as all other fuel system components are up to spec.

Useful info, thanks Steve. 

The gauze may be an issue, but if the return is very close and I have problems, insulating the fuel cooler to reduce it's effectiveness could help increase the tank temperature and alleviate any problems if I have them.

If you get hooked up to Vagcom you can accurately see the fuel temperatures coming out of the engine, not unusual to see around the actual engine temperature of 90c.

Would that I could!  The alarm keeps going off and I've taken a fuse out to temporarily cure it ... problem is it disables the interior lights and electric windows too ... she's not overly happy about that.  I've got a Chinese blue tooth reader on it's way, but from past experience with cheap Chinese kit and Vagcom, I'm not holding my breath.  If this one doesn't work I'll have to bite the bullet and splash out on the real thing.

Good to know that fuel temperature is monitored, it'll be interesting (and far more accurate that my efforts above) to see how quickly the return reaches an HMPE safe temperature from cold.

[greasemonkey]

Interesting. Can you actually get to the tank, to put your hand on it? At those temps, it should feel pretty warm. Just to confirm your readings, sort of thing.
I have heard in the past that the fuel in teh tank gets pretty warm.
The question is, does one run less fuel in the tank, so it gets warm quicker, or run more fuel, so it stays warm longer.
Depends on what sort of trips it's doing, I suppose.

[Julian]

Interesting. Can you actually get to the tank, to put your hand on it? At those temps, it should feel pretty warm. Just to confirm your readings, sort of thing.
I have heard in the past that the fuel in the tank gets pretty warm.
The question is, does one run less fuel in the tank, so it gets warm quicker, or run more fuel, so it stays warm longer.
Depends on what sort of trips it's doing, I suppose.

Yes, in most places, and they seemed about right.  What I couldn't work out was the incoming fuel temperature.  I'm 99% sure I've got the flow and return the right way round because they are colour coded ... black for flow and blue for return.  The flow from the tank seemed to be consistently in the 40 - 45°C range at various points, when the flow back to the tank, (after the cooler) appeared to be only 27°C.  I might try and rig up a thermocouple which I can stick down the fuel filler.

I wonder if there's some sort of thermally controlled bypass for the fuel cooler ... that might explain it.

[Julian]

I wonder if there's some sort of thermally controlled bypass for the fuel cooler ... that might explain it.

Just had a Google and there doesn't seem to be.

[greasemonkey]

Something sounds slightly amiss.

I bought some of these, if your short of a temp gauge. They are well worth the money.
http://www.ebay.co.uk/itm/Home-Digital-Probe-LCD-Screen-Fridge-Freezer-Thermometer-Temperature-Gauge-/231359762517?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item35de1dd055

[Julian]

I've got three of those on the processor ... all with flat batteries!

I've still got that little lash-up circuit I started playing with for a veg controller using an Arduino.  That will measure and display three temperatures, but I'd quite like to finish that as a veg controller must get round to doing that ... looks like it could be done for less than 20 quid.

I think I've gleaned enough information to be fairly confident of combating HMPEs ... but it's nice to know how it all works and what might go wrong.