I have a 2003 Dodge Ram 2500 (High pressure Common Rail HO diesel with CP3 injection pump, NOT VP44) which I recently had a Rover Hybrids kit installed into by Conscious Conversions of Austin, TX. I've been getting erratic lift pump pressures on the diesel side that I need a solution for, so let me first preface this by describing my setup:

If youre not familiar with the Rover Hybrids system, its a non-looped return system that relies on electric timers attached to the solenoids to time when the VO has passed through the system in order to switch the return path, there is no manual purge cycle. Theres a FASS on the VO side that provides lift pressure for the VO and is switched directly into the CP3 pump via solenoid switch (bypassing the stock filter housing). The diesel side relies on the stock lift pump to pull from the stock diesel tank through the stock filter housing and then through a solenoid switch into the CP3. I have an ISSPRO direct fluid fuel pressure gauge (not electric/isolated) plumbed in just before the CP3 to record fuel pressure at the injection pump.

After installation everything was generally working fine but the fuel pressure readings on diesel startup from the stock Carter fuel filter housing mounted lift pump were much lower than expected, maybe 5-8psi at idle and sometimes 3-4psi under acceleration. Within a couple weeks lift pressure was near zero all the time. When the truck reached temperature and I switch to VO, the FASS takes over lift pressure and it stays at a constant 15-20psi as expected without any degradation at all. I changed the fuel filter and cleaned out the filter housing with no effect. I was told this likely means a failing stock lift pump which seemed plausible since its having to push the fuel through more length of fuel line after the filter housing than before. I then bought a salvage pump with only 43,000 miles on it and installed that myself. The same thing happened to it... started out about 6-7psi and then began showing erratic swings in pressure while driving degraded to nearly nothing. This time it eventually made the truck unstartable as even bump starting it would not bring pressure over 3psi. Once again, while on the salvaged diesel side lift pump if the truck got to full temp and I switched over to VO, the FASS pressure would stay steady and reliable at 15-20psi.

Since I already had plenty of money invested in a FASS for the VO side I didnt see the point of getting ANOTHER FASS or Raptor or some other fancy (read: expensive) performance aftermarket lift pump for just the diesel side, however it was clear to me at the time that the stock lift pump just couldn't handle it anymore, for whatever reason. I then found a local diesel performance shop who said they could install an Airtex fuel pump to replace the busted stock lift pump for a relatively reasonable price relative to installing a performance pump like the Raptor, Airdog or FASS. The Airtex is installed on the engine end of the frame rail using the stock fuel line coupler and pumps into the stock fuel filter housing.

Unfortunately, this one had the same story. On the drive home it worked great, 10-15psi the whole way. Then after starting it up the next morning I started it up and it began having erratic pressure readings. When I bump start the Airtex it always shoots right up to 15psi, but when I start up the engine fully it may hover around 10psi at idle, then slowly drop to 5psi then shoot back up to 15psi for awhile then drop to 0 for 10-15 minutes at a time, then randomly shoot back up to 10-15psi again. There doesn't seem to be any patterns or consistency about the conditions under which it will read, other than it seems to be more stable after it warms up and has been running for at least 20 mins or so, but even when its at full temp, the stock diesel side supplied by the Airtex pump will often just lose pressure then come right back. I am still able to start the truck up and the engine does not stumble, though i notice that if the pressure reads 0 and I try to accelerate hard it does hesitate more before accelerating. Once again, when I switch to VO and the FASS, my pressure readings are clean and consistent.

I talked to the guys at the diesel performance shop who installed the Airtex and they essentially refuse to help diagnose this as they are convinced that i am dooming my truck by burning anything other than stock diesel in it. The best they will offer is to give me my money back on the Airtex pump and install another aftermarket pump that I provide and that they will not have to support. This essentially means something like a FASS, Airdog or Raptor, which I think are too damned expensive and too much pump for the job. They also claimed that my diesel fuel looked "too thick" and that I MUST be getting VO into my stock diesel tank and thats whats killing my pumps. Both times I changed the stock fuel filter myself and both times the fuel in there was most definitely dinodiesel and did not feel any "thicker" than fuel right out of the gas station pumps. If any VO was getting by into the diesel return due to poorly configured timers, it would have to be an insignificant amount since the stock diesel tank was essentially full the whole time. I think they just don't want to deal with anyone like myself.

My kit installers have been suggesting that I might have some kind of obstruction in the diesel fuel tank like an algae bloom, but I think if my tank screen or fuel lines were obstructed, then I would be getting *consistently* lower lift pump pressure, not erratic pressure. Plus, I don't have the facilities or tools to drop the tank and look into the darn thing, and having someone else do this for me would be an expensive proposition on just a hunch (Ive heard about the bottle test where you pull the vacuum side of the fuel supply line off and you suspend it in a bottle of diesel to compare pressure readings determine whether the restriction is in the tank or fuel lines, but thusfar Im not willing to get diesel all over my driveway again just to test another wild theory). Many have suggested clogged diesel fuel filters, but I have checked and changed the filters multiple times with no effect. One fellow mentioned I might have a faulty Cascade Overflow Valve on the CP3, but once again, wouldn't that cause similar problems with pressure while running on VO from the FASS? I had yet another that said something about ECM/PCM might be cycling the pump off and on due to a bad sensor, but diagnosing that requires an astoundingly expensive scanning machine to do that, and anyone who would do that isnt going to work cheap.

have I overlooked any other potential causes or solutions? What else could be the culprit here? I REALLY REALLY dont want to blow another $400+ on a Raptor for the diesel side of a truck that already has a FASS installed on the VO side. That just seems like so much overkill on one truck just to make it run reliably. I'm seriously considering ditching the Rover Hybrids system design and using the components I have to convert it to a system with a looped return and a purge cycle so that the FASS can be used for BOTH diesel and VO, but im not totally sure thats feasible or even affordable labor-wise. My installers relied heavily on Shane of Rover Hybrids for tech help and I don't really feel comfortable bothering him any more about this, but Im really getting near the end of my rope here. I just want a truck that gets >10psi lift pressure AT ALL TIMES whether its on diesel or VO... whats the best and most affordable way to do that?

I only know my 12V setup with any specificity, but I'd almost put money on a gunked-up intake screen in the tank. Why the erratic (but always low) pressure? Your pump is getting a choked flow, and it has to suck what it's getting up from the tank. The pump's prime depends on being filled for each pump-stroke, and I suspect it will fill only occasionally (giving a brief increase in pressure) and then spit that slug out...and then starve again (showing lower pressure) until it gets another slug, repeating that ad nauseum. The spikes in pressure even out somewhat before they reach the gauge point.

What's the construction of the in-tank screen and uptake like on the '03? Is your lift-pump on the block, or in the tank? On my '97, the intake is within a large plastic canister with fine nylon screen windows on it - stock lift pump is mechanical. As part of my mods I put an electric pump within that canister - fit like it was intended to go there. And yes, I soon had a problem with it, but not from the canister screen. The pump has a tiny and even finer-meshed screen over its intake that I'd made the mistake of leaving in place. Some biodiesel-related goo that had happily passed right through the nylon canister-screen quickly occluded the little pump intake-screen. The pump rep reminded me that he had mentioned this could be a problem in non-gasoline use (it had been a month or so, and I'd forgotten that detail...) and once I took that screen out, pressure and performance were right back.

Not to gloat, but in my case, it's easy to get into the tank - I put a dump-bed kit on it, so it's a five-minute job to get the whole canister out of the tank. In your case, though, to convince yourself without the creeper-work, how about backflushing the fuel supply line with low-pressure air (5-15 psi, maybe, with fuel tank cap off) to see if you detect any unexpected dynamics within the tank? A quick pressure increase and equalization would of course indicate a really thick clog...keeping your ear to the open tank might clue you in as well as to what's going on, based on how quickly bubbling from within takes place. I'd put a little regulator and pressure-gauge right on your working-end of the air-hose so you know what you're putting in and how the pressure is changing.

Whatever those tests indicate or don't, if your stock-pump fuel-pressure is suddenly OK after that quick backflush, you'll know what task awaits...

I am curious to know how you like your Rover kit? I have a similar truck looking to convert.

At the time I bought, the Rover Hybrids kit was one of the few kits available specifically for the 2003+ Dodge Cumming common rail turbo diesel. Right now both Greasecar and DFA (Vegistroke) have kits available for the 3rd gen CTDs and if i were to do it all over again, i would go with the DFA "Vegiram" simply because its more straightforward and less complicated than the Rover hybrids kit (in fact, Shane at Rover is starting to carry these kits as well).

Dont get me wrong, the components and design of the RH kit is great, but its a very complicated system that relies on complicated wiring and a timer actuated system that does not have a manual purge cycle. Shane's modified FASS pump is actually quite good, but I think you can get away with a less expensive/more compact option as is bundled with the Vegiram system.

I like that the Vegiram has all of the major components integrated into a single block. it makes installation and troubleshooting much more straightforward. The RH system, while very robust and well thought out, is still nonetheless very complicated and I would not consider installing it unless you are VERY mechanically inclined, if not an experienced automotive professional. If you are having someone install it for you, they will need to be experienced gearheads, not just WVO/SVO experts.

I have a 2003 Ram that I have converted to run on WVO with a 2 tank system. The system though is one I fabbed together over 2 years in the making. I run a 2 pump system with the fuel pressure sensor mounted in the fuel y-block with Earls flow-check valves on each input fuel line. Again, to monitor the pressure prior to the CP3 and to detemine when filters are starting to reach full life use.

Like you stated the erratic pressure is on the disel side only! One person responded regarding the fuel tank, I hate to say that if you have replaced all filters as you stated you have one options and that is in the tank pickup. The dodge pickup system in the tank is a plastic basket with a one-way membrain mesh type screen. That screen is extremely fine and if you have any gunk (believe diesel is not as clean as you think coming from the pumps) in the tank it will restrict the amount of fuel passing through it. That is when the fuel level is around 1/4 full. If this is still occurring with a full tank (level of diesel is above the wall of the pickup housing) then diesel is flooding the syphon pickup (means the mesh is the problem) then it is likely your diesel pickup tube in the tank is gunked up, with what? One small problem could be some oil is getting to you diesel tank. I know that you stated the RH system is a no loop, but what about the stock fuel system there is a return line back to the tank. Was that completely removed? One other option could be one of the connectors is not torqued and cause a vaccum leak allowing fuel pressure to drop.

No, idea if any of this will help but your problem is very likely at the tank, not the pumps.

I run a 2 pump system, Airdog on the diesel and raptor on the diesel. They have been trouble free and keep a constant 18 psi under a hevy pedal load!

I was finally able to resolve this problem, but it actually turned out that I WAS getting VO in my diesel tank. It seems my kit installers were confused about which polarity of the solenoid was wired to which posts on the timer device provided in the Rover hybrids kit. The result was that the return valve was NOT firing to switch to VO return when I switched to VO supply, causing my diesel tank to quickly fill with VO. This resulted in very hard starts and erratic lift pump pressure when on diesel, though the CP3 still managed to work like a champ as long as it could be provided with SOME fuel.

After we resolved the wiring issue and I drained out the VO on the diesel tank, everything worked as expected and despite several very hard starts, there was no discernible damage to either the CP3 or my injectors (I had an injection specialist hook it up to a scanner and measure the pressure readings and flow rates, which were right at normal under both VO and diesel). The diesel side Airtex lift pump runs at around 15-18psi consistently and the FASS will run 17-20 depending on how much diesel I mix with the VO in the VO tank (I try to thin it out a little by runing a long purge time of 100sec).

The only problem I have now are a buzzing noise in my pressure gauge and erratic readings on my temp gauge once it gets over 180F... but I think all I need for the pressure gauge is one of those ISSPRO snubbers and I might have a loose connection back behind the temp gauge... I just have to find the time to tear out the console to get to my gauges and have a look.