Fuel restriction problems on diesel AND WVO

My fear: there’s some debris that got into the high pressure pump or some other component in there (see below, especially where I discuss “polymerization”). But maybe that’s way off target.

My simple question #1: Can a failing or debris-clogged high pressure pump lead to fuel restriction light and fuel pressure codes?

My simple question #2: assuming fuel filters and hoses are all new, which components from the low pressure pump up to the injectors could possibly cause fuel restriction light and fuel pressure codes such as P2007-1?

My complicated question: Which components might be failing and thus lead to the same fuel restriction conditions while running diesel AND running a second, separate WVO fuel system(see below), with the problem getting worse and worse over time (worse on WVO and only recently showing up on diesel)?

The van: 430k miles, 2002 om612 with two tank WVO conversion (pretty good custom kit with 2 mi filter, fuel temps between 180-250 F), also runs Diesel HPR (https://propelfuels.com/our_fuels?a...-xXS_g0nx9T5_XnN_p_hENVWZPbAYk4MaAqv8EALw_wcB) and used to run commercial biodiesel (https://choosesq.com/) in the stock tank.

The problem: there are likely two separate problems but maybe related for all I know.
  1. apparent fuel restriction problems
  2. uneven idle (air bubbles are present in diesel side but not in WVO)
The fuel restriction light comes on sometimes—always while running WVO now and a few times recently in the morning running diesel. The diesel side only cleared up when I changed a filter (but it happened again) or disconnected some hoses, etc...). Codes include:
  • p2007-2, P2007-1 monitoring of predelivery pressure is too small
  • Also once recently got P1187-8 rail pressure monitoring - pressure control valve jams in the closed position and P2006-2 predelivery pressure sensor - the signal voltage is too high. This was likely after I disconnected the fuel pressure sensor while running.

Things I’ve done to address this problem or apparently related problems in the past year:

The big story you may not have time to read: In May 2019 while on a cross country trip, the van developed a stalling issue at highway speeds. The problem started out mostly while running WVO, but it also occurred while running diesel. I changed all filters, but basically it didn’t go away. I have an online fuel filter just before the low pressure pump to catch any crud (polymers) that might come off the WVO components, and it did seem to be catching a lot of stuff, so I cleaned it over and over again. Basically, I just had to drive carefully for the last 3000+ miles to get home. I made it home to San Diego and put in remanned injectors after marginal results on leakoff tests. I broke two hold down bolts (it was the torque wrench’s fault, I swear!) and kind of struggled with the time serts. None of this helped. I then installed a new fuel pressure solenoid which seemed to solve the problem, though the WVO system continued to have similar concerns. I replaced some suspect WVO components and found major issues with polymerization on brass fittings (the system now only has stainless steel and aluminum fittings, so no more polymerization). A few months later I had uneven idle problems that may not be related, but may be. I installed a new fuel pressure sensor which cleared it up for a few weeks. Then both the rough idle and the stalling on WVO got more irksome (maybe I just noticed them more). Finally, I started the van one morning last week and couldn’t get above, say, 20MPH running on diesel. I always suspected debris made it past that inline filter, so I took off the fuel lines to the low pressure pump and blew air (with a bicycle pump) to see if I could get anything to come out. Nothing did, but when I hooked it up again, there were no fuel restriction problems on diesel. Still problems when I switched over to WVO. A couple days later, it happened again. I took things apart again and put them back together, and it runs fine now on diesel, but for how long?
 

Nautamaran

2004 140” HRC 2500 (Crewed)
I have opinions on running WVO systems on common rail diesels that I’ll keep mostly to myself, but suffice to say that it’s hard to achieve the fuel quality required.

So... it does sound like you’re dealing with a contaminated fuel system, and depending on your return-line plumbing this could have made it into your diesel tank too? (safest practice is to maintain return flow to a waste tank for several minutes after switching to diesel to prevent contamination of the diesel)

If you had polymerized clumps forming some may have been formed and built up downstream of your filter. This gum is likely what took out your fuel rail components? Did you flush or otherwise clean the system during that r&r? If not the only path out is through the rail solenoid or the injectors... and unless you made substantive changes to the WVO system the risk of gum formation remained.

I suggest you pull your wvo filter and inline filter and collect samples of the polymer contamination, then experiment with a couple of diesel fuel additives until you find one that does a very good job of breaking down the deposits. Then dose you diesel tank and hope for the best.

The elephant in the room is, of course, that your wvo fuel may not have been supplying the required lubricity to protect your HP Fuel Pump, and you may be staring at another expensive purchase... let’s hope not.

-dave
 

Nautamaran

2004 140” HRC 2500 (Crewed)
Also: P2007-2 indicates the lift pump isn’t doing its job effectively, for whatever reason. I’ve never opened one, but the 612’s LP lift pump probably has a diaphragm and valves. If the valves are gummed up they’ll leak back and give you low feed pressure. A clogged supply filter can also cause this. The LP fuel pressure sensor (B132, down near the oil cooler?) is a dead-end low point so could trap deposits.

-dave
 

Midwestdrifter

Engineer In Residence
Your say your filter is 2 micron, have you confirmed there is no chance of bypass or other contamination? Some filters will plug up and pass contaminants. Have you confirmed fuel delivery pressure to the HP pump is at least 50psi at all times?

Your uneven idle is on diesel only? Or on WVO or both?

Polymer film can build up on injectors and the rail solenoid. Have you run the engine on 100% diesel purge? Thats a common fix for WVO systems that have buildup.

Are you seeing air bubbles in the clear lines?

You may need a 5 psi lift pump before your filters to feed the mechanical LP pump.
 
Your say your filter is 2 micron, have you confirmed there is no chance of bypass or other contamination? Some filters will plug up and pass contaminants. Have you confirmed fuel delivery pressure to the HP pump is at least 50psi at all times?

Your uneven idle is on diesel only? Or on WVO or both?

Polymer film can build up on injectors and the rail solenoid. Have you run the engine on 100% diesel purge? Thats a common fix for WVO systems that have buildup.

Are you seeing air bubbles in the clear lines?

You may need a 5 psi lift pump before your filters to feed the mechanical LP pump.
The rough running is on diesel and WVO.
I burned through two cans of diesel purge with a hose directly in the can last summer but they didn’t help.
I can’t say for sure that the filter doesn’t let in contaminants when plugged, but I se the same filter for prefiltration and have seen it stop completely when plugged. So I don’t think so.
I see tiny bubbles on diesel. Can’t see them on WVO
I have not confirmed the fuel pressure. Just to be clear, this is a 2002 with the low pressure pump on the engine, not in the tank (MidwestDrifter I believe you gathered that, but just to be clear). I don’t know how I’d check the pressure. Perhaps my autel 802 can tell me the pressure.
I’d be surprised if there as polymerization up stream from the fuel switchover valve. I always purge properly, so I don’t think the oil would have the necessary combination of time and oxygen to polymerize on those parts, like the rail.
As for a pump feeding the pump, the WVO system features a good pump pushing fuel from the WVO tank in the rear of the van (the filters, btw, are not under the hood by mounted to the tank). I don’t have a tool for measuring the pressure output of that pump, but I did pump some through an open hose to see if it was moving well, and it seemed to be working as expected.
 
I have opinions on running WVO systems on common rail diesels that I’ll keep mostly to myself, but suffice to say that it’s hard to achieve the fuel quality required.

So... it does sound like you’re dealing with a contaminated fuel system, and depending on your return-line plumbing this could have made it into your diesel tank too? (safest practice is to maintain return flow to a waste tank for several minutes after switching to diesel to prevent contamination of the diesel)

If you had polymerized clumps forming some may have been formed and built up downstream of your filter. This gum is likely what took out your fuel rail components? Did you flush or otherwise clean the system during that r&r? If not the only path out is through the rail solenoid or the injectors... and unless you made substantive changes to the WVO system the risk of gum formation remained.

I suggest you pull your wvo filter and inline filter and collect samples of the polymer contamination, then experiment with a couple of diesel fuel additives until you find one that does a very good job of breaking down the deposits. Then dose you diesel tank and hope for the best.

The elephant in the room is, of course, that your wvo fuel may not have been supplying the required lubricity to protect your HP Fuel Pump, and you may be staring at another expensive purchase... let’s hope not.

-dave
Dave,
Thanks for your replies. Conventional wisdom (which could be wrong) is that WVO lubricates pumps better than diesel. Do you hav different info?
Your point about additives seems to be in line with MidwestDrifter’s question about Diesel Purge, which WVO folks use for just that purpose. I did try that last summer without success.
I did make substantial changes to the WVO system, removing all brass fittings Except those leading to the filters (on my to do list), but I did not flush the rail, HPP, or LPP (the low I blew out with air). Diesel purge is meant to clean components, so hopefully that was effective.
If the low pressure pump isn’t doing its job, that’s usually because of a restriction prior to the pump. I think I’ve eliminated that. How do I test the Low pressure pump to see if it is having the problems You describe?
Thanks.
mike
 

Zundfolge

1-2-4-5-3
Re wvo as a better pump lubricator. There are more factors than just lubricity at play, the wvo is also heated (assuming you're targeting something in the 160°-180°F range) and so you are introducing changes in both lubricity and temperature which can swell and contract seals, over time, well that's not great for seals. As you're probably aware the vans have fuel cooling coils at the tank so fuel temps don't get too high during sustained operation.

I know this isn't meant to be a wvo suitability question, but it introduces such a great field of unknowns into troubleshooting fuel issues that it's worth noting all potential problems.

I remember back in my wvo-days hearing of certain years of vw tdi's who's ip's were not very tolerant of extensive switching between wvo/bio/diesel due to pump seal swelling/shrinking...
 

Nautamaran

2004 140” HRC 2500 (Crewed)
VW tdi’s had seal issues with the switch to ULS diesel too... and marine gasoline engines and fuel systems are having big issues with mandated ethanol content. Back to topic...
 
Re wvo as a better pump lubricator. There are more factors than just lubricity at play, the wvo is also heated (assuming you're targeting something in the 160°-180°F range) and so you are introducing changes in both lubricity and temperature which can swell and contract seals, over time, well that's not great for seals. As you're probably aware the vans have fuel cooling coils at the tank so fuel temps don't get too high during sustained operation.

I know this isn't meant to be a wvo suitability question, but it introduces such a great field of unknowns into troubleshooting fuel issues that it's worth noting all potential problems.

I remember back in my wvo-days hearing of certain years of vw tdi's who's ip's were not very tolerant of extensive switching between wvo/bio/diesel due to pump seal swelling/shrinking...
I’ve always wondered about those cooling coils. My oil has been as hot as 250 degrees, and I’ve always worried that the coils were telling me the van doesn’t like hot fuel.
So, help me understand what we’re asking about. We’ve got lubricIty and temp stresses on “the seals.” What seals? Internal seals on the HPP and the LPP? Are these the replaceable seals? If so, WVO might be viable with a seal replacement every X years. know people say the LPP hardly ever has problems, so I assume there’s no rebuild for that.
And how does one test to see if the seals or if the pump are bad? I don’t see any fuel leaking from either pump, though it’s not so easy to see in there. Maybe the leak is too subtle.
Mike
 
I don’t know if this will be meaningful for anyone, but I’ve been asked a couple times if I’ve measured my fuel pressure. Here’s a video of live data from my MaxDiag:
If it means anything to you, let me know.
Thanks, friends.
Mike
 

veganxxx

Member
What is the Wvo system setup?
I see one hydra force valve in the video. What size are the supply and return valves? What kind of fuel line are you using from the valve to feed the low pressure pump? What kind of fuel lines for the Wvo side from tank to filter and filter to valve? What is the plumbing order? Do you have an electric feed pump on the Wvo side? If so, what pump and what pressure rating?

I’ve converted 2 612 Motors. One of them had a collapsed pex line in a hose in hose setup that would result in the vacuum sensor fuel filter error to occur and create limp mode. Once replaced with standard hose it fixed the issue. The idle In the video sounds like starving for fuel. It also sounds like a fuel quantity valve going bad on a 04-06 Sprinter but the 02 doesn’t have one. The other conversions I’ve done have been 04-06 so everything is pressurized in the fuel systems.
 
VeganXXX,
What size are the supply and return valves? 3/8"
What kind of fuel line ... from the valve to feed the low pressure pump? Rubber to short segment of stock nylon
What kind of fuel lines for the Wvo side from tank to filter and filter to valve? Aluminum and rubber
What is the plumbing order? Tank-filters-pump-HIH-Hydraforce
Do you have an electric feed pump on the Wvo side? If so, what pump and what pressure rating? Raptor, adjustable (actual setting right now I don't know)
Are you running a loop return? Selectable loop or return

Here's a video giving a quick tour of the WVO system:
But it's basically like this: Heated poly tank w/aluminum coolant heater coil, 3/8" hose into water separator, then 2 mi filter, then to the adjustable Raptor pump, then to the HIH (3/8" aluminum inside 5/8" coolant) up to the front of the van. It comes out of the HIH and goes into a 26 plate nickel braised FPHE, then out via 3/8" hose to a fuel temp sensor, then to the supply hydraforce valve, then to a DIY electric in-line heater (3/8" aluminum tube with injector line heater wire wrapped around it--doesn't do much), then to a fitting stepping down from 3/8" to 1/4" barb with the 1/4" barb stuck into a short piece of nylon fuel line that connects to the LPP. On the return side, there's another hydraforce valve that also has a manual valve hooked up to the veggie side so that I can either loop the return or send it back to the tank.
It's worth noting that when the fuel restrictions problems started, the system was significantly different. I replaced a Vegtherm with the FPHE--I previously had a larger FPHE under the van because it was too big to fit under the hood) and added the Hydraforce to replace some brass 3-way valves that were jammed with polymerized oil. I also replaced all other brass fittings except for the ones on the tank side of the fuel filters, installed new hose throughout the system (with the exception of a few spots), tried different nylon fuel lines at that last stage before entering the LPP, etc... I've changed fuel filters, tried running with a looped return and with an unlooped return.
It is completely possible that there is a problem with the veggie system and a coincidental problem with the diesel side that cropped up at the same time--for example, I know there is some source of air bubbles in the diesel side--but in my mind, it's more likely that something between the fuel selector valve and the injectors is the problem. And air bubbles don't trip P2007 errors or clogged filter lights.
Unless someone offers compelling advice or guidance on how to accurately troubleshoot, I think I will get a LPP from a junkyard next week and try to guess and check replacing pumps until I get it right (presumably, they may also have a HPP that I can try after the LPP). A member has sent me some PM's and suggested that I should rebuild my HPP, and that's a no-brainer except that I don't have the time or energy to do such a meticulous job right now.
So, I welcome any thoughts people have.
Thanks.
Mike
 

veganxxx

Member
What size valves- not just the fitting sizes, the valve sizes- svo8 or svo10? Sprinters need more flow than svo8.

have you taken the valves apart and cleaned them? The cartridges can polymerize even though the housings are aluminum. The Orifices inside are tiny. Easy test you could crab diesel supply and engine supply off the valve and barb them together to eliminate valve restriction as a possibility.

Did your raptor come with a metal screen on the inlet? If so have you checked that for blockage?

could be that the Veg therm created carbon deposits that got into the fuel pumps and are now causing residual issues.
 

veganxxx

Member
Also I know why you have that small filter before the valve on the veggie side, but that will never flow enough to supply the motor. I would eliminate it.

in general, sprinters in particular don’t do well with a loop return. This is more the case in a pressurized system 04-06 but I would Also just do only a full return in an 02-06 or any conversion for that matter. If your manual loop valve has a leak that could be drawing in air on the supply side even when set to full return.
 

Midwestdrifter

Engineer In Residence
Previous experience with aerospace fuels has shown that polymerization can occur even in a line with minimal air present. Prior microbial growth, production byproducts, or other contamination can cause the production of unstable species. Either by cracking the fatty acids, or by stripping some of the hydrogen bonds, creating poly unsaturated chains. These can then be catalyzed by contact with zinc, or even steel parts.

Another cause can be sub micron globules of these molecules/species. Changes in pressure/temperature can cause them to clump together (not always straight polymerization). The resulting hard lacquers are not soluble in most non-polar solvents, but surprisingly are soluble in water.

I cannot say one way or another, but brief alcohol dosing can sometimes provide relief in some cases.

In your case there are a number of unknowns, but you should focus on flow rate, as the HP system needs significant fuel volume to cool itself, and even modest restriction to the LP pump can cause issues. Hence my suggestion of a lift pump. The LP pump can likely only tolerate a few psi of pressure drop on the vacuum side, this is at flow rate of 2+ liters per minute.

As far as your rough idle goes, air infiltration is a common cause, but you have so many possible causes, that you are in uncharted territory.
 
What size valves- not just the fitting sizes, the valve sizes- svo8 or svo10? Sprinters need more flow than svo8.
I’ve never heard that and it makes me very sad. I got the valve from Plantdrive, Where the description says, “Works for most cars, pickups, tractors, generators, boats, etc. . ... Some (highway tractor size) trucks might require larger valves.” They also have a write-up on flow rate: “Free-Flow rate using gravity fed 250 ml funnel of Canola oil @ approx. 50 degrees Celsius: 375ml per minute (approx 6 US Gallons per Hour).”
However, they also sell a replacement cartridge, SV-08. So I guess that implies the valves I bought were SV-08 and that’s a problem.

have you taken the valves apart and cleaned them?
No. They’re brand new.

QUOTE="veganxxx, post: 882182, member: 9676"]
The cartridges can polymerize even though the housings are aluminum.[/QUOTE]
Wow. That’s bad news.

QUOTE="veganxxx, post: 882182, member: 9676"]
Did your raptor come with a metal screen on the inlet? If so have you checked that for blockage?[/QUOTE]

screen. It’s placed immediately after the filter, though.

QUOTE="veganxxx, post: 882182, member: 9676"]
could be that the Veg therm created carbon deposits that got into the fuel pumps and are now causing residual issues.[/QUOTE]
Yes. That’s what I think.

To be clear, I ran veggie in this van for four years with cheaper, low quality valves. I used it to move from Portland to San Diego packed to the gills and towing my family’s EV. Fuel restriction is a new problem, or at least a recently escalating problem—I’m now thinking that my penchant for driving veeeeeery slow could have masked problems from the beginning. Things went from fine to troubled to bad, so the valve sizing issue is a big concern, but I think the source of escalating difficulties must be beyond that. I’ll next try to swap out the LPP and get the WVO system right.
Thanks for your insights, VeganXXX, MidwestDrifter, and everyone else.
 

veganxxx

Member
If you have the same exact issue with diesel and veg, I would start with a valve bypass and see if that helps the diesel side.

with a raptor feeding the mechanical pump, there should be no issues priming And thus stalling Only on Wvo seems like a fuel restriction not an air leak. Also note that if you have a high enough pressure electric pump pushing against a mechanical pump there could be damage done to the mechanical pump parts that aren’t designed to see pressure. Not sure if this applies to Sprinter But that is definitely the case with the idi ford and chevy mechanical fuel pumps. I would keep the raptor on the lowest pressure setting. also I would take off the Wvo supply line to the valve and do a flow and air bubble check into a clear container since you can activate the raptor without starting the vehicle.
 
If you have the same exact issue with diesel and veg, I would start with a valve bypass and see if that helps the diesel side.

with a raptor feeding the mechanical pump, there should be no issues priming And thus stalling Only on Wvo seems like a fuel restriction not an air leak. Also note that if you have a high enough pressure electric pump pushing against a mechanical pump there could be damage done to the mechanical pump parts that aren’t designed to see pressure. Not sure if this applies to Sprinter But that is definitely the case with the idi ford and chevy mechanical fuel pumps. I would keep the raptor on the lowest pressure setting. also I would take off the Wvo supply line to the valve and do a flow and air bubble check into a clear container since you can activate the raptor without starting the vehicle.
I don’t know if I would say there is an exact same problem on WVO and diesel. That’s a big question I’m trying to answer with these posts, trying to understand how the LPP and HPP might be related to those symptoms which usually suggest fuel starvation. Most days I can run on diesel fine, but some days I start it up (on diesel of course) and immediately get a clogged filter light and fuel restriction codes. The uneven idle, which might be a separate problem, has occurred even when I had no WVO valve installed. I don’t recall if I ever saw fuel restriction problems when there was no valve installed or it was bypassed for testing purposes.
I contacted the Plantdrive person (it’s just one person) to ask about SV-08 versus SV-10, and he said he is aware of the question of valve size (that’s why he did the flow rate tests) but believes and has found the SV-08s to be fine with Sprinters.
Because my problem is so inconsistent on the diesel side, testing it with a bypass may result in weeks of uncertainty about whether it has made any difference.
In order to be able to test the WVO side, I’m thinking maybe I could rig up a simple manual ball valve (the one from my loop return, which I think I will give up anyway) to replace the supply Hydraforce for testing purposes. This is not a bypass, of course, but that ball valve must be plenty big compared to an SV-08.
The local junkyard that lists a lift pump from a 2003 Sprinter says it‘s tank mounted, so I guess I can’t just throw a pump in this week to test it out.

“with a raptor feeding the mechanical pump, there should be no issues priming And thus stalling Only on Wvo seems like a fuel restriction not an air leak.”

Yes.

“Also note that if you have a high enough pressure electric pump pushing against a mechanical pump there could be damage done to the mechanical pump parts that aren’t designed to see pressure.”

I hadn’t thought of that. This is yet another reason to suspect the ultimate problem is that LPP. I did at some point dial up the pressure high enough to pop off the fuel line into the LPP once, at which point I dialed it down, but not all the way. Except I think that occurred after the problems started last summer. Idk.

“I would take off the Wvo supply line to the valve and do a flow and air bubble check into a clear container since you can activate the raptor without starting the vehicle.”

I did this a few days ago, but maybe I wasn’t looking for the right thing. What kind of flow would you expect? What should I be looking for? I just wanted to see if it was moving freely, but I didn’t take ay measurements or anything.
Thanks again.
mike
 

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