WVO fuel pump - PeachParts Mercedes-Benz Forum

bbjornson · #1 08-03-2009, 05:29 PM

My car was converted to run on both veggie oil and diesel utilizing a two tank system. The original fuel tank now uses the WVO, while an secondary fuel tank (5 gallon gas can) houses the diesel. The original fuel lines now go to the secondary fuel tank, so that is where I run out of most of the time.

My primary fuel tank (WVO) no longer supplies enough fuel to the engine. Whenever I switch it over, the car starts to lose idle and eventually won't start. This happened on the highway and luckily I was smart enough to switch it over to the diesel tank.

The problem is that I am about to drive back to NC from Maine and I want to use my original gas tank so I have to figure out what the problem is.

So far I have changed the fuel filter that is specific to the WVO and it was real dirty. This new tank utilizes electric pumps to send the fuel back and forth so I think that there lies a problem in either these pumps or in the fuel pickup that is located in the tank. Is there a way for me to check which part of the fuel system is giving me problems?

EDIT: Essentially, I am asking if there is a way for me to test the fuel pumps or do I have just have to replace them? Also, if this is the case where should I buy new ones?

1lowdiesel · #2 08-03-2009, 05:44 PM

imo just based off of fuel delivery, i would check the fuel pressure. see if you can have someone hook up a gauge, when you change over you shouldn't see more than a 1-2 psi drop.

if you need a new pump do a performance pump. we sell PureFlow Technologies pumps and they work great. little pricey but well worth it imo. they are just an inline pump.

http://www.xtremediesel.com/search.aspx?find=raptor

pselaphid · #3 08-03-2009, 05:49 PM

Unfortunately it sounds like your original diesel tank is probably all gunked up due to having WVO in it, which is non-compatible with the metal in the tank. The stuff polymerizes and eventually clogs the tank outlet. Switching the supply to the return line may clear it out enough to run it for a while, but I think you have to keep it pretty full. Cleaning out the tank screen under the tank will likewise buy you some time and would be the better option. Ultimately, you need to pull the tank, clean it, put it back, and stop putting WVO in it. Utilize a heavy plastic or aluminum WVO tank and rework it so the systems are completely isolated from each other. I'm not sure about the pumps you mentioned, so maybe they are involved in the problem or not, but if I understand your description, I'd bet on a clogged fuel outlet.

#4 08-03-2009, 07:12 PM

If you need a pump beyond the stock lift pump, you've got a clog, you aren't getting the oil hot enough, the oil is contaminated or the "conversion" is poorly designed.

Clean the strainer and check the temperature first.

bbjornson · #5 08-03-2009, 07:15 PM

Well I think the guy who put together this system used a new plastic tank when he installed it, but it probably just needs to be cleaned out.

What are the flow rate requirements that I should use if I have to end up looking for a new fuel pump?

#6 08-03-2009, 07:22 PM

Quote:

Originally Posted by bbjornson

What are the flow rate requirements that I should use if I have to end up looking for a new fuel pump?

Reversion back to diesel or redesign of the "conversion".

bbjornson · #7 08-03-2009, 07:25 PM

That doesn't help much. This system has 3 electric fuel pumps for the primary tank and if they are the culprit then I'll have to replace them. I just need to know what specs they need to be.

#8 08-03-2009, 07:30 PM

Quote:

Originally Posted by bbjornson

This system has 3 electric fuel pumps for the primary tank

There's yer sign.

pselaphid · #9 08-03-2009, 07:59 PM

Most dual tank systems are converted so that the stock lift pump sucks fuel through the filters instead of pushing it through. The lift pump works better in its original configuration as a pusher pump. BUT, it is a robust enough pump that it does fine unless the WVO is too thick/cool, or, as mentions, a clog is involved. I installed a boost pump at the WVO end to send it under pressure to the heated filter and heat exchanger, since I did not install a heated fuel intake. It is is Facet pump that runs 5-8 psi. I've never heard of more than one boost pump on a WVO system, though as many as four switching valves can be involved. Two or three valves is normal. Are you absolutely sure those are pumps and not electric solenoid valves?

bbjornson · #10 08-03-2009, 09:09 PM

You're right, they are the switching valves. Didn't think about that. Anyway, ya I have the same pump in the trunk that helps push the WVO towards the front of the car. I have a heat exchange pickup and I also have an insulated filter but those are not currently being utilized because there was a leak in that system.

pselaphid · #11 08-03-2009, 09:29 PM

Okay, its starting to make sense. Possibly, if the boost pump has failed, its the sort that will not allow fuel through when its off, or maybe clogged. You can bypass it and see if the lift pump will then pull, but put diesel in it to test it. Those valves are easy to test. Just jump them with 12v and see if they click. Probably they will. Check the grounds from the valves and confirm you have them properly grounded. However, you've defeated the most important part of the system, the WVO heaters. Get it running on diesel and drive someplace where you can rework the system properly. You still need to clean that tank strainer. Diesel will not dissolve the gunk. If you can get it running, drive happily on diesel, then do a properly configured and sealed installation when you get to where you are going. Take about 10 filters of each kind with you.

bbjornson · #12 08-03-2009, 09:35 PM

Okay cool. I have been running diesel in it ever since I got it but I'm sure it still got clogged up. I hear clicking, so something must be working.

What type of solution should I used to clean the tank pickup and screen?

TchTchr · #13 08-03-2009, 09:44 PM

Put on old throw away clothes and some safety glasses and use compressed air on the screen. Make sure to point the air nozzle away from anything you don't want to get all filthy!

X2 on the steel tank and wvo don't get along very well.

pselaphid · #14 08-03-2009, 10:11 PM

When you get it out, you can just scrub it with a soft brush and some degreaser, hose it off and blow dry it (a post rinse with rubbing alcohol will make it dry faster). But yes, use goggles and expect to get fuel all over everything getting it out. A gallon or so so will still be in the tank after draining, and you're attire will absorb that. Stick some probes into the tank and scrape around to gauge how much gunk it built up.

RichC · #15 08-03-2009, 11:45 PM

Check the tank vent.

I have found this to be a common problem.

I have noticed that many veggie users fill the fuel tank completely full.

We usually dont have a fancy fill nozzle that clicks off like on the gas station pumps.

We fill the tank with a hose, and fill it untill we can see the veggie at the filler.

When the tank gets over filled the fuel gets into the tank vent and cloggs it.

When the the tank cannot get air thu the vent it causes a vacuum inside the tank.

And eventually the fuel pump cannot compete aginst the vaccum,
and does not provide enough fuel for the engine to run.

This is a common problem, with strange symptoms.
I am sure it has fueld the " veggie destroyed my car idea "

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And before we get into a " veggie destroys " rant.

This also happens to people that overfill the tank with diesel.