In-tank Fuel Pump Modification

[dam5h]

Agreed on oring, I got one at dealer when I put in my walbro, much easier than trying to find a match.

[davintosh]

Yeah, the dealer... Every time I go there for anything it's at least a two business day wait (usually longer for an e28-specific part.) I was at Menards for something else last night and found a decent match with a #97 o-ring from the plumbing department. It'll get me by until I can get the real McCoy.

I ended up extending the discharge pipe down; I didn't like how the pump felt a little loose with just the hose in there. I used some brass pipe I had in my stash from another project, and a shaved-down brass 3/8" barbed hose mender fitting. No photos yet; I'll grab some before I put it all back together this afternoon.

[davintosh]

Here it is, in all its glory. I ended up having to move the hose clamp a bit to get it to fit through the access hole in the tank (test fitted it with the rubber gasket) and turned the ground screw around so the head is on the outside instead of the end of the screw.

I got the pump -- an HFP-340H from Amazon for $50 (but now it looks like the price is $90... not sure what the story is on that, but...) Probably overkill for my wheezy eta, but it'll do.

I got it installed in the tank over the weekend but didn't have time to get underneath and finish connecting the hoses. May not have time for that until Wednesday either.





I wasn't comfortable with braising, and figured the connection was less critical on the return line, so I used some Permatex Instant Gas Tank Repair epoxy to seal things up. I'm more in the Jeremy camp of fuel pump aesthetics, and less concerned with how it looks than getting it working. I would love to have used an adapter like what Paul made for Chris, but I haven't seen any mention of that item since it came up in the other thread. I also considered briefly what ScottinVA did with his, but again the whole braising thing skeered me oft. I'll be watching this puppy closely to make sure nothing leaks, but I'm pretty sure it'll work fine. (knocks on wood.)

[1st 5er]

Turbo next?

[davintosh]

I was forced into wrapping up this conversion today by the unexpected death of my e32's alternator; it died on me this morning, leaving enough juice in the battery to start it at noon and drive it home.

It took about a half hour to pull new hose through and hook up the new pump to the filter, and it started with just the slightest bump to the starter. Ran like a champ, and it felt like the slight hesitation on heavy acceleration was less, if not gone. The car likes new parts.

[slofut]

Davintosh,
I'd like to know if your fuel pump mod has been working well? Did you have to use a different fuel filter, I think the orig has a 3/8 inlet and a 1/4 outlet? And did the hose clamp on the pump fit through the hole ok?
Thanks,
Bill

[tbrints]

I installed same setup on my M5 but with the Walbro hp pump, which came with a different style bottom filter.
It has worked great so far since the summer with a good trek to South Texas for TexFest.

[1st 5er]

... fuel filter, I think the orig has a 3/8 inlet and a 1/4 outlet? ...
Thanks,
Bill

It's the external pump that has the differing size inlet/outlet,
thus the pump housing modification.

As far as reliability, since my first install, our E28 ///M5 in May 2012,
I've since installed the same setup in 4 other cars.
The only failure was a blown off in-tank hose, shortly after the first install,
and that due to a failure to completely tighten one of the clamps.
Not sure who put that unit together, but due to my hands on approach,
and learning by doing temperament, I've got feeling it was yours truly.

I most recently replaced the stock failed in-tank pump in my wife's E32 735i with the same TRE-340.

Enjoy...

[davintosh]

Davintosh,
I'd like to know if your fuel pump mod has been working well? Did you have to use a different fuel filter, I think the orig has a 3/8 inlet and a 1/4 outlet? And did the hose clamp on the pump fit through the hole ok?
Thanks,
Bill

Still working great, although I no longer own the car. My oldest son bought it from me when I moved in July, and has been daily-driving it since then. I think I had to reposition the hose clamp slightly to get it through the hole, and I needed to turn the bolt around that held the ground wire connector. I probably could've cut the end of the bolt off, but...

[slofut]

Hey guys,
Thanks much for the replies. I got a HighFlow HFP340 and swapped the in-outs on the pump hanger, so I have 5/16 ports on both now. Will run a new 5/16 hose down to the filter. One thing for sure, it'll be easier to troubleshoot!

[tig]

Someone, in one of these Walbro threads, posted a comment about an alternative to the Walbro that's noticeably quieter. I thought I made a note of that, but can't find it. I've tried searching through all the threads, but can't find the post that way either.

Does anyone remember?

[1st 5er]

Someone, in one of these Walbro threads, posted a comment about an alternative to the Walbro that's noticeably quieter. I thought I made a note of that, but can't find it. I've tried searching through all the threads, but can't find the post that way either.

Does anyone remember?

I don't hear any of mine.
http://treperformance.com/i-656-bmw-255 ... odels.html

[tig]

Someone, in one of these Walbro threads, posted a comment about an alternative to the Walbro that's noticeably quieter. I thought I made a note of that, but can't find it. I've tried searching through all the threads, but can't find the post that way either.

Does anyone remember?

I don't hear any of mine.
http://treperformance.com/i-656-bmw-255 ... odels.html

Gracias.

[davintosh]

Mine was plenty quiet too.

[tig]

Someone, in one of these Walbro threads, posted a comment about an alternative to the Walbro that's noticeably quieter. I thought I made a note of that, but can't find it. I've tried searching through all the threads, but can't find the post that way either.

Does anyone remember?

I don't hear any of mine.
http://treperformance.com/i-656-bmw-255 ... odels.html

Update:

Today, I replaced the Walbro that I showed above with the TRE unit. Much, much, quieter.

Video showing different is noise levels between Walbro and TRE:

https://youtu.be/N44ZNsCyVIc

Glam shot of the TRE with the included condom thingy that it comes with. Note with this cover on it BARELY fits and the rubber will likely tear upon removal.

[BDKawey]

my one complaint with my 255, it is loud as hell. given i have no interior in my trunk... but still

[1st 5er]

Glam shot of the TRE with the included condom thingy...

Almost NSFW.

[Dvs]

Hey guys,

Thanks for info, i got some inspiration from this thread and i attached a picture of my primitive assembly.

As it seemes the top part of my gas tank is pretty rusty and it kept braking my fuelpumps...so i got fuel tank restoration kit from the Eastwood company (can't link the product atm because their website down) but will post followup on how that kit is working, meanwhile i just grabed a new pump from pepboys ( Spectra SP1067 that pushes fuel with around 2,5 - 5 psi to the inline pump, attached to this is the Carter strainer STS-9).

And now to the actual point why i am writing this: first of all i read about some people here saying that the in tank pump might be usless and that a stronger pump in the tank or under the vehicle would suffice, well the thing is that those german engieers did know what they are doing and let me tell you why, there is aso called drag coefficient that applies to liquid too, not just to aerodynamics, in other words, hypothetically speaking your pump is pushing with 10psi 10 gallons per hour on a straight pipe, which is just fine, as longer the pipe as more the pressure drops at the destination, and then here starts our problem, the fuel delivery sistem on the cars is not straight, there is formula in fizics that determins the coefficient of drag for each and evey curving that is in the fuel delivery line, this drag makes your pressure drop a lot. Don't ask me about thay formula, try googling it lol.

This is where my issue was, after my in tank pump broke (who knows when that happened...) my vehicle was just working fine until the in line broke too, which is a strong one, 90-125psi. This in line pump broke exactly because of this drag coefficient: in order for that pump to be able to deliver an avrage of 100psi to your injectors it has have that fuel delivered to its door step, because if not the pump has to do sucking and the pushing, this also lowers its performance and the psi with which the fuel gets delivered....plus all the

This is why they made the system with two pumps...

[1st 5er]

Hey guys,

Thanks for info, i got some inspiration from this thread and i attached a picture of my primitive assembly.

You forgot something.

And the rest...

As it seemes the top part of my gas tank is pretty rusty and it kept braking my fuelpumps...so i got fuel tank restoration kit from the Eastwood company (can't link the product atm because their website down) but will post followup on how that kit is working, meanwhile i just grabed a new pump from pepboys ( Spectra SP1067 that pushes fuel with around 2,5 - 5 psi to the inline pump, attached to this is the Carter strainer STS-9).

And now to the actual point why i am writing this: first of all i read about some people here saying that the in tank pump might be usless and that a stronger pump in the tank or under the vehicle would suffice, well the thing is that those german engieers did know what they are doing and let me tell you why, there is aso called drag coefficient that applies to liquid too, not just to aerodynamics, in other words, hypothetically speaking your pump is pushing with 10psi 10 gallons per hour on a straight pipe, which is just fine, as longer the pipe as more the pressure drops at the destination, and then here starts our problem, the fuel delivery sistem on the cars is not straight, there is formula in fizics that determins the coefficient of drag for each and evey curving that is in the fuel delivery line, this drag makes your pressure drop a lot. Don't ask me about thay formula, try googling it lol.

This is where my issue was, after my in tank pump broke (who knows when that happened...) my vehicle was just working fine until the in line broke too, which is a strong one, 90-125psi. This in line pump broke exactly because of this drag coefficient: in order for that pump to be able to deliver an avrage of 100psi to your injectors it has have that fuel delivered to its door step, because if not the pump has to do sucking and the pushing, this also lowers its performance and the psi with which the fuel gets delivered....plus all the

This is why they made the system with two pumps...

[tn535i]

I'm not sure I understand the logic of the rest above... The main higher pressure pump has NO Problem with a few extra turns and length of tube if it is moved to the tank. The FPR means it runs at a lower pressure than it is capable of. And it doesn't work harder if the in tank pump is out... it might actually use less current... but it is more prone to cavitation then get hot from lack of fuel cooling and that is more likely the problem along with vapor in the fuel being delivered to the rail.

My guess is that at the time of development the main pressure pump wasn't certified or considered 'safe' for inside the fuel tank. So it was an external pump with a wimpy little 'safe' in tank lift pump. Now that there are perfectly good in tank main pump solutions it's a better system choice.

[BDKawey]

while the science above is true that by no means doesnt mean that the 255 cant handle an m30 or even a turbo m30 on their own. subarus only have one pump and the walbo 255 is the go to fuel pump upgrade for bigger turbos pushing 350+hp

[BDKawey]

does anyone consider it being a potential problem of the walbo trying to pump fluid but being restricted by having to pump through the weaker stock in line pump? anyone have a walbro with their in line still installed?

[tn535i]

I think it would be a mistake to try that, you may have little to no flow and not maintain pressure and heat the fuel excessively. Generally bad idea.

[BDKawey]

thats currently what is on my 302 car, it hasnt really been driven far at all on the setup. im having issues with pressure at the rail, like not really any at all haha. enough to start up but then it cant keep running.

the car sat for a year while doing the swap with a full tank of gas. im thinking it spoiled the filter, ill delete the inline while im at it. other than that an the regulator I shouldn't have any problems at all.

[davintosh]

thats currently what is on my 302 car, it hasnt really been driven far at all on the setup. im having issues with pressure at the rail, like not really any at all haha. enough to start up but then it cant keep running.

the car sat for a year while doing the swap with a full tank of gas. im thinking it spoiled the filter, ill delete the inline while im at it. other than that an the regulator I shouldn't have any problems at all.

Yeah, just delete the inline; it only makes sense to yank it out when you've got a good in-tank pump. And while you're deleting that and replacing the filter, you might as well replace all of the soft fuel lines at the back of the car while you're at it.

[1st 5er]

You can leave the in-line in place, just bypass it.
I can't see how enough fuel can be passed through it to accommodate runability.

That probably contribites to the cause of main pump failure
after the stock in-tank pump fails,
overworking itself pulling fuel through the failed pump.

[tn535i]

The in tank pump is a centrifugal impeller and fuel can pass pretty easily while the main pump is probably a roller and fuel will not pass easily.

If you leave the inline in place and plumb around it be SURE to remove the lead wires or it will still run, but run dry, probably burn up and maybe blow the fuse.

[1st 5er]

[BDKawey]

Yeah itll get ditched next week. Did everyone solder the walbo wire to the little tab at the top of the housing?

I bought a housing off someone because mine was trashed but the ground tab on the connector on the housing was snapped off and rusted and still in the pigtail he sent me too.

I was thinking wiring the positive though the connector and then i might have to drill a tiny tiny hole in the top of the housing and feed the ground right through it and silicone around the hole to make sure it sealed and not leaking.

Anyone else maybe have a better idea?

[davintosh]

Yeah itll get ditched next week. Did everyone solder the walbo wire to the little tab at the top of the housing?

I bought a housing off someone because mine was trashed but the ground tab on the connector on the housing was snapped off and rusted and still in the pigtail he sent me too.

I was thinking wiring the positive though the connector and then i might have to drill a tiny tiny hole in the top of the housing and feed the ground right through it and silicone around the hole to make sure it sealed and not leaking.

Anyone else maybe have a better idea?

I soldered the positive to the connector at the top, but then used the eyelet on the ground wire to connect to something on one of the tubes using a screw. Works fine. I think I had to turn the machine screw around so the nuts were on the inside because the end of it was interfering with the assembly going into the tank.

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