Pump issues

[Mr Ute Member Find all posts View Profile Close Mr Ute]

My Nissan SD33 WVO conversion is currently using an electric fuel pump and struggling to get enough pressure. I've tried a facet, carter & holley and all have been poor. (as others have stated - vane pumps are no good for WVO). I want to keep the WVO & diesel fuel & filtering systems as separate as possible for reliability. I've considered using the stock lift pump for WVO and the electric pump for diesel, but have concerns with the stock LP trying to push unheated oil through a cold filter - this will appear as a dead end until the filter heater kicks in to heat the HMP oils in the filter. Will this excess strain cause me grief with the lift pump? the stock diesel filter has a return to tank so that the LP is still passing diesel when running on WVO.
I also considered using the LP for both diesel & WVO but steered away from this option due to excess contamination on the diesel filter.
My preference is to leave the stock LP for diesel & use some form of electric pump for WVO, but does such pump exist and can it be purchased at a reasonable cost (something in 24V would be a great help )

[Tony From West Oz Vice Chairperson of WARFA Find all posts View Profile Close Tony From West Oz]

Re: Pump issues

My Nissan SD33 WVO conversion is currently using an electric fuel pump and struggling to get enough pressure. I've tried a facet, carter & holley and all have been poor. (as others have stated - vane pumps are no good for WVO). I want to keep the WVO & diesel fuel & filtering systems as separate as possible for reliability. I've considered using the stock lift pump for WVO and the electric pump for diesel, but have concerns with the stock LP trying to push unheated oil through a cold filter - this will appear as a dead end until the filter heater kicks in to heat the HMP oils in the filter. Will this excess strain cause me grief with the lift pump? the stock diesel filter has a return to tank so that the LP is still passing diesel when running on WVO.
I also considered using the LP for both diesel & WVO but steered away from this option due to excess contamination on the diesel filter.
My preference is to leave the stock LP for diesel & use some form of electric pump for WVO, but does such pump exist and can it be purchased at a reasonable cost (something in 24V would be a great help )

I also have discounted using vane pumps and Mallory do not recommend even using diesel with their Georotor pumps. I have swapped the stock fuel pump to pump used cooking oil and using the Holley Blue for the biodiesel starting fuel.
In my most recent conversion, I am using a second fuel selection valve to use the fuel pump on that 300D for either of the fuels, separately from the other fuel.

I have examined many (non EFI) fuel pumps in the last 50 years since my interest in the ICE was awakened when I inherited my mum's damaged Morris Minor and repaired it, and drive it into the ground over 3 years (another story, another time) and all of them have been a 'constant pressure' operation. The electric pumps either were of a solenoid type which pushed the diaphragm against a spring, the electronig ones which cause a metal plunger to oscillate back and forth, pumping the fuel thru the valves or vane pumps which are fitted with a pressure relief valve to release pressure if flow is low. The cam driven ones relied on the cam pushing the diaphragm against a spring. The spring supplies pressure to the fuel.

If in doubt, get a pressure gauge and monitor the pressure from the fuel pump with it connected to pump veggie.
You could also provide another return line (to the veggie tank) to allow some flow while the starting fuel is in use.

[bruceT Senior Member Find all posts View Profile Close bruceT]

Re: Pump issues

Personally, I see no reason for two lift pumps. Either way, the pump has to pump fuel, whichever circuit it's drawing on, so why not design your system that way? I have now run 10,000km on my system, which uses the stock lift pump for both circuits, and it works just great. So far, I've not yet had a clogged filter. In fact, apart from a couple of cartridges that I pulled out just to cut them open to see what the elements were looking like, and to check they were not disintegrating (they were not), I'm only on my third cartridge!

If you are filtering your wvo to at least 5 micron before refueling, I don't think you need to be concerned about pulling cold wvo though your filter until the heater kicks in. If your filter is heated by coolant from the car's heater circuit, this heat will arrive quite quickly. Any waxes or tallows that may initially bind to the filter elements, will melt as soon as the heat arrives and passright through. The same would be possibly true for electrically heater fuel filters, althought these might not get as hot as they are usually regulated to about 40degC, or thereabouts. For this reason, I personally would not consider electrically heated fuel filters.

Last week I found out just how powerful the stock Bosch lift pump on a w123 Benz 300D is. I use 25 litre plastic marine outboard tanks for my WVO. Unfortunately, when I changed tanks, I forgot to release the breather valve on the filler cap. I drove around for two days without checking in the boot, but when I did, to load some shopping, I got a shock. The tank had completely collapsed! It must have taken some incredible suction to do that! Anyway, I thought I had destroyed it for good, but filling it with hot water, has almost restored it's shape. Then some time in the sun, with the valve closed, has allowed some pressure to build in the tank and it's almost as good as new. One thing is for sure, it tested my system for leaks!

By all means, use the the same lift pump for both diesel and wvo circuits, but keep the filters separate, or you will get very slow change-overs.

[Captain Echidna Senior Member Find all posts View Profile Close Captain Echidna]

Re: Pump issues

I can verify by "slow" we are talking grater than 1000 k's. (dont ask how I know this, but I did find it out about 5 years ago)

[Mr Ute Member Find all posts View Profile Close Mr Ute]

Re: Pump issues

Thanks all for you input.

In my most recent conversion, I am using a second fuel selection valve to use the fuel pump on that 300D for either of the fuels, separately from the other fuel.

My problem with using the stock lift pump for both fuels is that the Nissan SD engine returns the fuel to tank from the filter, not the IP. This creates a real headache trying to prevent oil contamination of the diesel filter during change over. WVO can easily turn solid in the unheated diesel filter, due to the regions that I operate the vehicle in, I'll stick with two pumps for ease of plumbing & peace of mind.

I have swapped the stock fuel pump to pump used cooking oil and using the Holley Blue for the biodiesel starting fuel.

I am now intending to go down this path, I assume that there is no problem using the Holley Blue for Diesel?

[bruceT Senior Member Find all posts View Profile Close bruceT]

Re: Pump issues

Thanks all for you input.

My problem with using the stock lift pump for both fuels is that the Nissan SD engine returns the fuel to tank from the filter, not the IP. This creates a real headache trying to prevent oil contamination of the diesel filter during change over. WVO can easily turn solid in the unheated diesel filter, due to the regions that I operate the vehicle in, I'll stick with two pumps for ease of plumbing & peace of mind.

Why not re-route the return straight to the tank, by-passing the filter?

[Mr Ute Member Find all posts View Profile Close Mr Ute]

Re: Pump issues

Hi Bruce, my config has no fuel return from the IP - it only has a fuel line in. The lift pump draws from the tank and then to the filter & IP. Injector bleeds are returned to the filter and all excess fuel is returned from there.

[Tony From West Oz Vice Chairperson of WARFA Find all posts View Profile Close Tony From West Oz]

Re: Pump issues

Mr Ute,
open the connection between the injectors return line andthe filter. Block the connection to the filter and measure the amount of fuel coming from the injectors return. In my MB 300D, I found that it took 4000km to deliver 1 litre of fuel to the measuring container. I felt that this amount of fuel would not affect operation much so I left it going to the diesel tank (I could just have easily looped it or returned it to the veggie tank - if I had a return to that tank)
By having separate filters, your purge time will be reduced significantly, over using a shared filter. By providing separate return lines, one to each tank, you can choose how to deal with the injectors return line.

The Holley Blue should be fine for pumping diesel or biodiesel. It does not like Used Cooking Oil or UCO blends with other fuels.

[Mr Ute Member Find all posts View Profile Close Mr Ute]

Re: Pump issues

Hi Tony,
Yes I did this injector return test early on before I commenced the WVO conversion. As you said next to nothing is returned from here so I have left this return going to the diesel filter. This filter is replaced at regular service intervals and it has not suffered any by leaving this connection in place.
I measured up the new fuel lines to swap over the Holley & stock LP, should complete in the next week or so (I had my 'other' car crunched last week so have spent a bit of time sorting that mess out ) I'll keep you posted.
Cheers.