EFI fuel accumulator mounting

[ntsqd]

Reputation and availability is why I've purchased the three Walbro's that I have (2X 60 psi for different projects & 1X 15 psi for the DD).

It probably does work to run them in series, but I'm really, really gun-shy about any restriction on the suction side. I'd run them in parallel with either check valves or a ball valve.

 

[garberz]

....It probably does work to run them in series, but I'm really, really gun-shy about any restriction on the suction side. I'd run them in parallel with either check valves or a ball valve.

I basically have them in parallel, I just need to switch them over manually, instead of those fancy check valves.

Mark

 

[ntsqd]

Yeah, those Aeromotive check valves aren't just given away. The Carter parts aren't too bad though. I'd put them on the outlet side of the pump so their restriction isn't as big of an issue.

I recall some time ago that there was a rash of lift pumps failing when used with an accumulator. The theory at the time was that the low pressure side didn't have enough flow resistance and the pumps were basically running wide open all of the time. I know some tried using a needle valve on the tank return to add some adjustable resistance to flow. Anyone recall more details?

 

[chuck]

Quote; "They're more expensive, but I prefer these pumps because of no exposed plastic and can plumb directly with AN adapter fittings."

Me too-

Chuck- you've "real-life" tested it so it works. My thought was theory only since every fitting or pump you have to draw thru or pump thru is a restriction...I get a bit hung up with stuff like that. I'm putting out over 500HP

We only run 420 hp so I don't know about more. The 255 liter pumps handle the 40 PSI at WOT and still have return flow so it should handle more HP, my guess. The pressure regulator is after the injectors so if the pump has to put out 50 PSI to end up with 40 at the injectors that is no big deal. The way we plumb the series pump is from tank to filter to first pump to 2ed pump to fuel rail. The two pumps are near the EFI tank with a switch so only one pump is on at a time. All the pumps I know of have built in check valves so if it doesn't work out change to parallel.
PS we have a new quite intank pump coming out soon.

 

[bsquared]

Okay guys,
Now I'm confused at what to go with. I've got the 255 inline HP fuel pump from FITech coming for the TB and am currently running a Carter P4070 LP pump with a filter after. Carter has done great mounted about halfway forward.

Leave the P4070 in the line to feed the HP pump and mount the HP in the engine bay or.......just put the HP pump near the tank and mount the filter somewhere in between?

Just trying to figure if I should keep the P4070 in the loop. Thanks, B2

 

[ntsqd]

Personal preference, seems to work either way. Some need the lift pump and others don't.

If you want to keep that Fram filter it should be between the tank and the EFI pump as I wouldn't trust it to EFI pressures (wasn't designed for it), which means that you'll want to keep the P4070 pump to feed it. You do not want the EFI pump to have to draw thru it. It might work, but it's bad practice.

I am doing something like this. I have a Sierra marine water separating fuel filter upstream of the soon to be installed EFI pump with a P4070 drawing from the tank & feeding the filter. Then comes the EFI filter after the EFI pump. I need to make a 'draw-straw' for the Sierra filter as then it will act as a small accumulator in the event that the pick-up in the tank is uncovered & sucks air.

 

[chuzie]

Correct, EFI return mixed with lift pump supply into the accumulator.
I have always felt the BC accumulator was done wrong. Leads to the "accumulators are bad and it runs better without them" badgering.

Plumbed wrong, with the right flow rates, it is possible the accumulator will do a better job of capturing air instead of removing it. The whole idea of an accumulator is for a supply of bubble free fuel to be available to the EFI pump. You want everything to go into the accumulator (fuel, air bubbles, vapor bubbles) and the bubbles to rise to the top and return to the main tank. If you merge the EFI return with the return to the tank you have lost the loop of fuel on the high pressure side. You could find yourself pumping good fuel back into the tank and not back into the accumulator. And the accumulator filling with air since it can't get out because the return line has a flow of fuel going back to the tank. Accumulator runs dry, you curse it as a failure. Plumbed correctly any air in the accumulator has priority to return to the tank before any fuel is returned.

I experienced this issue first hand immediately after installing a 3 port tee'd accumulator. It was a nightmare trying to figure out why I was always starving for fuel on the trails. Thankfully Broncobowsher helped me figure it out.

Tank / fuel filter / P4070 on rail by tank / accumulator on driver's firewall above wheel well / HP pump on driver's wheel well. Works like a charm especially on the trails.

I tried running only a HP pump and had too many issues so it may be my tank design, who knows.

I carry spare LP and HP pumps on excursions, but until I can afford a new tank with in-tank pump, this is my solution.

I also highly recommend a fuel pressure gauge. I firmly believe it is an invaluable tool in troubleshooting the EFI system. Mine is mounted on the hood but a lot of folks opt to have a little one inline on the fuel rail.

 

[bsquared]

Fuel Accumulators

Personal preference, seems to work either way. Some need the lift pump and others don't.

If you want to keep that Fram filter it should be between the tank and the EFI pump as I wouldn't trust it to EFI pressures (wasn't designed for it), which means that you'll want to keep the P4070 pump to feed it. You do not want the EFI pump to have to draw thru it. It might work, but it's bad practice.

I am doing something like this. I have a Sierra marine water separating fuel filter upstream of the soon to be installed EFI pump with a P4070 drawing from the tank & feeding the filter. Then comes the EFI filter after the EFI pump. I need to make a 'draw-straw' for the Sierra filter as then it will act as a small accumulator in the event that the pick-up in the tank is uncovered & sucks air.

Thanks NTSQD,
Does that Sierra separator need to have a return line back to the tank to remove air? I'm thinking I might do something like that as well if it will help insure better fuel delivery to the HP pump. Thanks for the advice, B2

 

[ntsqd]

The Sierra part is only a filter, not an accumulator. It is only by my adding a 'draw-straw' i.e. a tube extending the output port to near the bottom of the filter that it will act a bit as an accumulator. Doing this will not purge air from the fuel supply ala the BCB accumulator, it will only act as a reservoir for the EFI pump to draw from during those times when the tank pick-up is exposed to air.

IMHO if you really want to remove any entrained air from the fuel you need a swirl pot similar to what is used on some high end endurance racing vehicles. Simply dumping the fuel into a holding tank isn't going to do it. Dry sump oil tanks also have certain features in them specifically designed to remove air bubbles from the oil (much more difficult than getting it out of fuel). All of this is likely taking things way too far for the need or use.

 

[bsquared]

I am doing something like this. I have a Sierra marine water separating fuel filter upstream of the soon to be installed EFI pump with a P4070 drawing from the tank & feeding the filter. Then comes the EFI filter after the EFI pump. I need to make a 'draw-straw' for the Sierra filter as then it will act as a small accumulator in the event that the pick-up in the tank is uncovered & sucks air.

Read up on the accumulators and just ordered this Sierra one online. I was even able to use my 5 buck rebate check from West Marine!

Thanks for the tip, NTSQD! Cheers, B2

 

[ntsqd]

I have the filter in place & functioning with the carb, but I have not yet looked into what it will take to make the tube and attach it. At best this filter's fuel volume is less than 1/2 of the BCB part.

Sounds like you will beat me to it, so post up what you find and do.

 

[bsquared]

I will post my progress and am planning on digging in this weekend! Found this post here on CB.com where someone tapped a regular external oil filter for an accumulator and return to the tank. I'm a little worried about the LP pump running full on and only restriction to keep pressure on that part of the system will be the 5/16" restriction on the return line. I do have a LP pressure reg I could put on the return to the tank for backpressure, if needed.

http://classicbroncos.com/fuel_accumulator.shtml

Thoughts?

 

[ntsqd]

I have no plans of a 'T' in mine with the return line running thru it. It will simply be a reservoir of fuel that the HP pump draws from and refilled only by the lift pump.

Were I going to make it into a accumulator ala that article I still would not use a 'T'. There would be 4 fittings on it as first mentioned by Bowsher. LP supply from the tank, and a return to the tank. Supply to the EFI pump via a tube that sucks from near the bottom of the filter, and a return from the engine's fuel rail.

I would consider putting one of the Carter check valves linked above on the supply fitting so that the pump has to work against it, i.e has to make at least 6 psi before the valve opens. That way the lift pump isn't running wide open. Some might be tempted to put it on the tank return fitting, but that will pressurize the whole filter which means that the fuel rail return will also have to be at least 6 psi which means that the fuel rail pressure would raise that same 6 psi. Not a good idea.

 

[Broncobowsher]

Carter 4070 running open flow for years, not a problem. Takes it just fine.

The cheap knocker fuel pumps (the ones that go klunk, klunk, klunk, klunk, klunk) until they build fuel pressure. Usually the cheap ones from the local parts store. They are a diaphgram pump like a mechanical carb pump but have a set of points to trigger a coil to pull back the diaphgram. Those you don't want to run wide open.

 

[ntsqd]

Nether did Dusty's Holley red (blue?) pump like running wide open. At least that's how I recall that long ago failure.

 

[bsquared]

Carter 4070 running open flow for years, not a problem. Takes it just fine.

The cheap knocker fuel pumps (the ones that go klunk, klunk, klunk, klunk, klunk) until they build fuel pressure. Usually the cheap ones from the local parts store. They are a diaphgram pump like a mechanical carb pump but have a set of points to trigger a coil to pull back the diaphgram. Those you don't want to run wide open.

BroncoBowsher,
Appreciate your help. Okay, do regular fuel accumulators have a back pressure valve built in to keep the 5lbs or so on the line to the HP pump? Does the BCB accumulator have back pressure valve? In the article I referenced he just tapped it 1/8" NPT and ran 5/16 hose back to the tank.

If I need back pressure to keep it at 5 lbs I can use my current one to the Q-jet and just put it between the accumulator and the tank, Si? Don't want to put it back there, but seems to me I shouldn't be open ended into the tank with no / little restriction.

I've got two 5/16" ports into the tank so I'm going to run a separate line from the throttle body. (aka fuel rail)

Thanks for the help! Stuff starts arriving tomorrow. Accumulator first, and my new radiator back on and get it running / driving. FI Tech will probably be over the Holidaze. Cheers, B2

 

[ntsqd]

I've only ever seen them run wide open. It wasn't until pumps started failing that some sort of restriction for the pump to work against was theorized as perhaps necessary. Doesn't sound like the P4070 pump needs such a thing. I know that I've used one for fuel transfer duties that has worked fine running with no restriction, but it's hard to put much time on something like that - even over many years.

 

[Broncobowsher]

No restriction on the accumulator. If the pump needs backpressure, it is a crap pump to start with.

 

[bsquared]

Cool!!! Easy Peasy then. Thanks guys....I'll post my progress here. Cheers, B2

 

[bsquared]

I am doing something like this. I have a Sierra marine water separating fuel filter upstream of the soon to be installed EFI pump with a P4070 drawing from the tank & feeding the filter. Then comes the EFI filter after the EFI pump. I need to make a 'draw-straw' for the Sierra filter as then it will act as a small accumulator in the event that the pick-up in the tank is uncovered & sucks air.

Update and question on this install. Got the short filter to fit where my current one is and the element has a solid baffle 2" below the seal and less than halfway down the filter. Means my pickup tube will only be 1 3/4" down into the element.

Question: Can this water separator canister be changed out with a regular canister filter, like an oil filter, and get more depth for the sump?

Thanks for the help! B2