Air problems? Other?

For discussing the modifications needed for diesel vehicles to run with 2 tank veggie oil conversions.

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Air problems? Other?

Postby vwoodruff » Mon Mar 30, 2009 9:24 am

Hey all...

95 Dodge Ram 2500 12-valve, 2-tank, 3-valve conversion.

I used Sun Wizard's configuration with the exception of routing the coolant through a balanced, parallel loop for the FPHE (i.e. the coolant line tees to the FPHE and one loop through the filter and tank, rather than running in series through all three).

My tank is a customized marine tank with Dana Linscott's heated VO pickup and a HIH to the engine compartment and a vented diesel cap.

It appears that I'm having an issue with air for both fuels. On the diesel side, the air issue appears at startup, where the truck will have to push through air at ignition. The longer it sits, the worse the issue. After it has started there are no problems. It also feels as though the power is a bit lower than I noticed when I first had the truck.

On the VO side, it shows up as a "can't run on VO" issue. It CAN run on VO, but it tends to go to vacuum under a high load and eventually stalls out. The vehicle will start again (on VO) after struggling for fuel, but will eventually go into vacuum and stall and create a bigger fuel starvation.

I checked all of the fittings and tightened the ones that seemed to be possible problems. I don't see any fuel leaks. The sender for the pressure gauge is just before the IP. VO pressure starts at 5-10 psi following switch before declining into vacuum.

Temperature is good. VO is good. My brain is going a bit crazy. Besides the fact that I haven't put in a needle valve and the gauge ticking is like slow torture while driving, I have been chasing symptoms on this thing since the conversion. I have converted 8 or 9 MBs and never run into this type of issue.

Any thoughts? The only place I can think that I could address a possible leak is at the injector line plug at the top of the fuel filter. I used braided injector hose (a la the MB diesel ones) with a threaded bolt as a plug (no clamp). I'm thinking I should get an unthreaded plug, but it seems like the pressure is so low there that it shouldn't be causing this big an issue, nor that it would cause an issue on both fuels.
vwoodruff
 
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Postby SunWizard » Mon Mar 30, 2009 11:14 am

Move a clear inline filter around until you find the source of your air leak. It sounds like a large enough leak to be very visible.

What is your pressure on D2? Mine runs 20-35psi on both VO and D2, and if you never get to this you could have a worn lift pump or overflow valve, or a clogged filter. How hot is your VO where it enters the filter?
YVORMV - Your veg. oil results may vary.
95 Dodge Cummins 4x4 SVO WVO conversion.
81 Mercedes 300D- stock and happy on V80/D20 blend.
Low fossil net zero house- 100% solar power and heat.
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Postby vwoodruff » Mon Mar 30, 2009 12:38 pm

Hey...

The fuel pressure on RUG is anywhere from 20-30+ psi. I'm pretty sure the lift pump is in good shape. I am going after a needle valve soon to keep the tick-tick-tick from driving me batty, and I should be able to get a more accurate read there.

I don't have a temp. gauge near the filter (it's after the FPHE), but I'm pretty happy with the temp (I've shot it with an IR camera) there. I put the FPHE in parallel (with a ball valve to balance) with the rest of the loop to maximize temp at the filter and tank. I initially thought I was having a problem there.

I have an inline filter between the filter valve and the diesel filter that had air in it after sitting for a bit. I've checked all of the fittings on the engine side of the supply valve. With the exception of the plug I mentioned in the previous post, I'm at a bit of a loss.

I'm going to check the diesel filter today for a leak (the snow's melting a bit) and am going to open up the bleeder bolt to see where I stand there. Other than that... hmmmm.
vwoodruff
 
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Postby SunWizard » Mon Mar 30, 2009 1:52 pm

Have you tried changing the VO filter? Do you hot pan test each batch for water? Water can clog a filter very quickly once the paper absorbs it.
YVORMV - Your veg. oil results may vary.
95 Dodge Cummins 4x4 SVO WVO conversion.
81 Mercedes 300D- stock and happy on V80/D20 blend.
Low fossil net zero house- 100% solar power and heat.
SunWizard
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Postby vwoodruff » Mon Mar 30, 2009 2:08 pm

I'm trying to resolve the air issue first before I try the filter. I am pretty sure the filter is ok. Water-wise at least... the VO I get from a buddy of mine who has a pretty great system. I've had no problems with the fuel before, and I'm only 1/4 of a tank of VO in on this rig.
vwoodruff
 
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Update...

Postby vwoodruff » Tue Apr 21, 2009 7:37 am

Here's a bit of an update on my progress...

- The bolt (w/ hose clamp) as a plug experiment failed miserably... should have known better. The plugged return line atop the diesel filter does have enough pressure to cause an issue. I replaced the bolt with a properly sized plug and hose clamp and that resolved the air issue on the diesel side.

- I kept getting a diesel drip, drip, drip and thought it might be from the diesel filter. Nope. Lift pump... the lift pump is designed to weep diesel when the diaphragm ruptures. I spent part of the weekend swapping that out. I'm not sure why the diaphragm ruptured... may have something to do with air in the veggie side.

- I was trying to troubleshoot the veggie side... heat was great at tank, but the line was cold coming out of HIH? WHat? I figured there must be a constriction, which made little sense because the diesel was purging to the VO tank. SO I figured it must be air. I put a 12V electric pump on the engine side of my supply valve and pumped. Air. Air. Trickle. Trickle. Finally a bit of flow. Even after 10-15 minutes there were air bubbles in the pump discharge. After pulling about 4 gallons, I decided to close up the supply valve and give it a shot. The truck ran better on veg, though it still bogged down and went to vacuum under heavy load (i.e. it wouldn't go above 50-55). New filter already in. I tried to pull more air, and the performance was a bit better - bog down when flooring accelerator or adding load above 60-65.

Yesterday, after fixing the diesel level sender (which was $0.30 in parts, a couple hours of labor) and the ABS speed sensor, I decided to attack the VO again. I put the 12 V pump at the VO pickup to purge the line. Hardly anything came out... I figured there must be too much friction head for the pump and 70F VO. So I hooked everything back up, drove the truck, and when it was up to temp and I switched to VO, I also hooked up the 12V pump. It didn't help one iota. My VO pressure was around 15psi under low and medium load, but it still bogged down when I floored the accelerator.

This is driving me nuts. I'm going to check my temp at the VO filter today. If not there, I am at a loss.

Best,

V
vwoodruff
 
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Joined: Sun Feb 15, 2009 10:22 am


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