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PeterAC
14th September 2011, 10:13 AM
I have a new 1980 300D that goes like a rocket on diesel. I have just started using a blend of approx 20% ulp and wvo. It runs great on the mix but is rough on startup on a cold morning. It is now just starting to stumble on some warm startups when sitting for 10 mins or more. On startup after a few revs it is purring.

Will the rough start cause long term issues. Is the rough sometimes startup indicating what?

tbird650
14th September 2011, 12:15 PM
This is the subject of some quite spirited debate on this forum with opinions and experiences varying considerably.
I believe the issue stems from the ulp overheating and creating bubbles, vapourizing, frothiness, airlock or whatever term one wants to give it.
One solution is reduce (or eliminate) the ulp content in favour of other blending substitutes.
ULP has the bonus of being very "viscocity reducing" but has the downside of being volatile. In monitoring of injector line temps in my Hiace, I can report that the issue starts around 40'C and upward. The effects are relevant to ambient temps, blend ratio and journey duration.

Short glow plug life is another issue that a number of vege vehicles suffer from.
It would be worth checking them as starting will be poor if some have burnt out. Blending has reduced the incidence of burn out of the G.P.'s for me as has the fitting of a momentary push button switch to interrupt the trigger circuit of the G.P. timer.

Tony From West Oz
14th September 2011, 11:10 PM
It may be that you have too much petrol in your blend.
Try adding more veggie oil to the tank and see what difference it makes after more driving to mix the oil into the blend.

I start my 300D easily when warm at any time of year on straight veggie oil.
Cold starts on veggie oil are possible any time of year (with good GPs) by leaving the GPs on until the indicator lights on the dash brighten up again (indicating the end of the glow time).
If using a blend, I would suggest no more than 10% ULP when daytime temperatures are above 20C.

Regards,
Tony

PeterAC
15th September 2011, 01:05 AM
Yes I did what you have said and dropped the % down to 10%. I'll see how this goes tomorrow and get back to you both.

Cheers

Jeffrey S. Brooks
15th September 2011, 01:27 AM
I have a new 1980 300D that goes like a rocket on diesel. I have just started using a blend of approx 20% ulp and wvo. It runs great on the mix but is rough on startup on a cold morning. It is now just starting to stumble on some warm startups when sitting for 10 mins or more. On startup after a few revs it is purring.

Will the rough start cause long term issues. Is the rough sometimes startup indicating what?I do not believe that the 1980 300D has a fuel line heater, unless an after market one was added. If there is no fuel line heater, then your problem is not too much ULP, but not enough.

If your engine stops stumbling after warm startups from dropping your ULP percentage down to 10%, then you have solved your problem, but I doubt it will.

PeterAC
16th September 2011, 02:39 AM
Problem solved, addressed two ways.

1. Reduced the ulp to 10%
2. Waited till the full glow plug cycle had finished by observing the dash lights.

Thankyou all three for your input. Much appreciated.

Peter<><

Jeffrey S. Brooks
17th September 2011, 01:09 AM
You weren't waiting for the glow plug cycle to finish before cranking your engine?!!!

Tony From West Oz
17th September 2011, 03:06 AM
JSB,
My comments are vehicle specific. Both PeterAC and I drive Mercedes 300Ds.
For these cars, the GP light extinguishes long before the GP power is turned off by the GP relay.
With diesel fuel, the GP light time is normally adequate glow to start the engine reliably.
When using straight veggie or veggie blends, for the first cold start of the day, it is advisable to wait for a full glow period (ie the GP relay times out) before cranking to ensure reliable starting of the engine. After that, the engine retains enough heat that the GP Light time is sufficient glowing for reliable starting.
Usually, if my 300D engine is warm - hot, it is not necessary to wait for the glow at all. I just crank and go.

Too much petrol in the blend will cause problems with hot starting as the engine "heat soaks" the fuel system, causing the petrol to boil from the veggie and causes vapour lock. Once the engine starts, the airflow cools the fuel pipes and the blend is at a low enough temperature that the petrol does not boil.

I believe that the most likely location of the vapour lock is in the injector lines themselves, as the slow pressure rise caused by the boiling petrol pushes the fuel into the injector return lines. It then takes much more cranking to push the petrol vapours out of the injector lines, before fuel hits the injectors. The fuel being pumped into the injector lines will still boil the petrol off, as the temperature is still too high.

If this is your problem, try putting a damp cloth on the injector lines before cranking. You will still need to crank more, but the fuel pumped into the injector lines will be cooler and the petrol will not be boiling off, so the starting should be more reliable.
When running, remove the cloth to avoid other issues.

Better still, reduce the % petrol in the blend as PeterAC has.

Regards,
Tony

froggo
17th September 2011, 09:25 PM
Hi PeterAC,

I found in my HJ45 Troopy at 60deg C fuel temp, with 20% ULP 80% WVO my fully rebuilt inline I.P suffered from vapor lock. Same temp 15% ULP runs beautiful.

Experimentation is good! Glad you found what your engine likes.

God bless, froggo.

Jeffrey S. Brooks
18th September 2011, 02:06 AM
...I believe that the most likely location of the vapour lock is in the injector lines themselves, as the slow pressure rise caused by the boiling petrol pushes the fuel into the injector return lines. It then takes much more cranking to push the petrol vapours out of the injector lines, before fuel hits the injectors. The fuel being pumped into the injector lines will still boil the petrol off, as the temperature is still too high...Regards,
TonyInteresting hypothesis, Tony, but evaporation is a function of vapor pressure, thus vapor-lock is only likely to occur on the vacuum side of the lift pump, because the pressures in the injector pipes should be sufficient to keep petrol liquid at 100s of degrees C.

I live in southern AZ where the summer time temperatures can rise over 120F (50c), however, very few petrol powered engines here experience vapor-lock, that means petrol can remain liquid at 120F (50c) with the reduced pressure of the lift pump.

Tony From West Oz
19th September 2011, 12:19 AM
JSB,
My comments above were in relation to an engine which is not running. In this case, there is no high pressure in the injector lines and fuel would be pushed into the injector return lines by the vaporised petrol.

As more fuel is pumped into the injector lines (before the engine starts) the petrol in that fuel also starts to boil off.

If you can get enough fuel into the injector lines to allow injection pressure to build up and start the engine, the vapour lock will not be an issue for 2 reasons:
1. The heart soak caused by the hot engine will not be an issue - the fan will draw air across the injector lines, removing this heat.
2. The fuel pressure will be hitting 300+ Bar around 5 times per second at an idle of 600RPM (Just a mental calculation, the actual frequency is not important in this context), so any petrol which starts to boil off will be rapidly forced back into solution by the injection pressure.

I agree that "while the engine is running" the most likely location in the fuel system for vapour lock to occur is in the suction side of the fuel pump, especially if there is a fuel filter before the fuel pump. Even a clean fuel filter provides some restriction to fuel flow.

Regards,
Tony

Jeffrey S. Brooks
19th September 2011, 03:14 AM
I have an IDI 1983 6.2L Detroit diesel. I have noticed that the injector pipes remain pressurized for more than 24 hours after the engine has been shut down, so the gasoline in my blend never has a chance to vaporize on the positive side of the IP.

silver_fox_aus1
19th September 2011, 10:39 AM
Hi All,

If I remember my high school science we learnt about STP (Standard Tempure and Pressure) how liquids will change there boiling points in accordance with the STP rules. In this case due to the pressure as all other things are equal comparatively. We can boil water at zero degrees if we decrease the pressure to zero conversely if the fuel pressure gos up to 1,000s of psi then shouldn't the boiling point be massive increased due to the pressure rise to obtain Boiling point.

I have found with my infrared temp gauge that even though the oil may be very hot coming out of the heat exchanger by the time it reaches the injectors it has dropped down to very low temperature and it is just that the injectors themselves have heated up so high that the fuel is again so hot .

If there is a problem with my reasoning please let me know.

Gene

Tony From West Oz
19th September 2011, 11:25 PM
I have an IDI 1983 6.2L Detroit diesel. I have noticed that the injector pipes remain pressurized for more than 24 hours after the engine has been shut down, so the gasoline in my blend never has a chance to vaporize on the positive side of the IP.

JSB,
Exactly how did you "notice" that the Injector lines were pressurised?

From what I have read on the operation of both rotary and inline Injector Pumps (and electrically modified IPs) the injector lines SHOULD only be under pressure at the injection point, otherwise injector dribble would be a major issue.
At all other times, the injector pump REMOVES pressure from the injector lines and allows the injector return (bleed) lines to carry away any slight build up of pressure.

If you have a rotary or inline Injector Pump, there should be NO pressure in the injector lines if the engine is not running. If you have, get your IP and injectors checked because there is something wrong.

Regards,
Tony

Jeffrey S. Brooks
20th September 2011, 01:38 AM
JSB,
Exactly how did you "notice" that the Injector lines were pressurised?When I pulled my injectors to clean them I found the hard injector pipes were still pressurized. The manual also had a caution regarding getting your fingers cut off if they were too close to the nut when cracking it. My engine uses a mechanical rotary IP.