Fuel starvation while running on veg?
September 18, 2012 - 11:15am
Hi folks. I’ve been having an issue for some months now and have failed to track it down, I’m turning to you for help. Here’s the info:
1992 300D, 297K, 81K on veggie.
Greasecar kit installed by previous owner
I get what sure feels like fuel starvation under load, and more oddly, while turning or after a hard-ish stop. If I switch back to diesel for a second and back to veg it’s fine for the most part. I changed the fuel filter, no change. I thought maybe I had chicken skin in the tank so I pulled the sending unit out and found a very clean tank. But we’ll get to that in a second.
So, I’m suspecting maybe my valves have a partial blockage in one of them? Has anyone else experienced that? Can I/should I take the valves apart and clean them? Since the car runs great on diesel I know it has to be the valves or something on the veg side. Should I put a vacuum gauge on the fuel line somewhere? If so, where and what am I looking for? Now on to the tank. There was no poly inside, very clean except the obvious fitting you see.
[IMG]http://i303.photobucket.com/albums/nn144/tpospeshil/Grease/unionsTILTED.jpg[/IMG]
That fitting will spend some time exposed to air when the fuel level gets below ¼ tank so I’m not surprised. I’ll be replacing the coolant loop with aluminum when I tackle that nasty gasket material you see floating around in there. Does anyone know where I can get a small sheet of viton rubber to make new gaskets?
Does anyone have any advice for me? Am I missing anything here?
September 18, 2012 - 3:47pm
#2
A few questions: What is the VO fuel pump? Is the MB lift pump being used for D2 AND VO? Might want to check the output of the VO fuel pump - under load it might not be supplying enough fuel. I'd disconnect the output hose of the supply valve and power up the valve and the VO fuel pump; place a glass jar to capture the VO as it is pumped out. There should be a good amount of VO flowing. Or use a pressure gauge to measure the pressure. I might be wrong, but the pressure from the MB lift pump should be around 5 - 7 lbs.
September 18, 2012 - 6:43pm
#3
Agreed with what Mr. Rene de Lathauwer said.
You can compare the volume of diesel delivered to the volume of veggie delivered.
Or use a pressure gauge to measure the pressure.
Suggest to install a fuel pressure/vacuum gauge on dashboard to monitor the pressure/vacuum
right before the injection pump.
If diesel and veggie share the same lift pump (and injection pump can be lift pump if there is no another lift pump),
the reading on diesel mode would be the same as the reading in veggie mode with new veggie filter and HOT veggie.
Compare the readings between diesel mode and veggie mode while driving under load.
A significant difference (between diesel and veggie) in pressure drop or vacuum increase under load would
means flow restriction and the fuel delivery system failed to deliver enough volume of fuel to the IP.
September 19, 2012 - 8:10am
#4
Thanks folks. I think I have a press/vacuum gauge I can install. You say right before the IP, right? I"m using the stock MB IP for both fuels.
I guess I have my work cut out for me this weekend. I'll tell you, owning a W124 sure takes away any free time you used to have on the weekends haha.
September 19, 2012 - 12:54pm
#5
You say right before the IP, right?
Yes.
using the stock MB IP for both fuels.
So the IP is also the lift pump. Expect to see vacuum (negative presure) on the gauge.
owning a W124 sure takes away any free time you used to have on the weekends haha.
But you will have fun!!!
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Assuming there is no air leak (sucked in) problem and since you have over 80K miles on veggie,
I suggest to take the valves apart and clean them. Also suspect flow restriction on pex line.
There was a post here mentioned that the pex line collapsed and problem was solved after replacing the pex line.
__________________
'05 Cummins CTD 24V HPCR RAM 2500 QC SLT SB Black 4X4 48RE 325 hp 610 ft.lbs
GC Kit + 3rd Tank WVO(80%)/RUG(20%) + Co-Pilot
3-Tank Operation managed by Co-Pilot: Blending(warm up) / Veggie(hot run) / Diesel(purge for next start)
Smarty Jr 40/70/100 hp (Timing Map Modification)