In-tank Fuel Pump Modification

[wkohler]

Thanks Chris.
Does this unit screw out?
There are no bolts/screws visible when I remove the metal cover on the trunk floor.
RealOEM lists the same sender for the normal US and the euro 100l tank (with the conventional pump/sender setup tha tbolts in), Guess that means its just wider.
Mine is crenelated on the top rip too.
thanks

It twists counter-clockwise. Just an 1/8 turn or so. Remove the sender, then use a screwdriver between the studs to rotate it.

[mooseheadm5]

Will the 255 pump supply sufficient flow for the S38 variants under continued load?

If you derate the pump by 1/3 of its flow (suggested for road racing conditions) it will support over 350 bhp.

[Bav Ace]

If you can get the parts together, I can supply the cores and pumps, for two units.
I'll eventually need three, but two will work for now.

I have some parts coming in the mail which should arrive this week or early next, including a used fp carrier (I've been calling it a carrier, is that correct). Once those are in, we can find a good weekend and get them put together. Also, I might actually get to drive my car down since its up and running. More importantly, I need to get some trunk and hood emblems so it doesn't feel so naked.

[tig]

I'm bumping this thread because at some point I want to do this and am hoping it's been made easier with time and others doing it...

[1st 5er]

Define "easier".

The housing mod hasn't changed, but again, I can verify it's functionality as reliable.
I'm running this set-up in 4 vehicles and have had only one issue,
and that was a failure to completely tighten a hose clamp on one of the connections.
Thank God that error was in-tank. Tightening the clamp solved the problem and I was right back on the road.

[tig]

All the above seems so much more complicated than it needs to be. Either that, or I'm missing something.

Here's my original setup. Total depth is 22.5cm.


Here's my OE hanger and my new Walbro 340 pump at about the length it needs to be. Note the outlet from the Walbro fits inside the OE outlet pipe.


The stock rubber reducer is too long by about 1cm. I don't see why I can't just cut it and use hose clamps like this and call it a day?


I realize I'll need to secure the pump to the carrier, but why did the OP need to do all the fabrication when this appears it will work fine?

[Bav Ace]

I don't doubt that you can make that setup work. I approached the problem the way I did primarily because I enjoy tinkering. It's definitely not the easiest solution.

[1st 5er]

That looks simple enough Charlie.
I'll have to give that a try next time with the TRE-340's we are using.

There's still a hose reduction that has to be dealt with when you remove the outside pump.
That can be handled by some kind of reducer, which I've used in one of my applications, whereas OP's setup takes care of it at the housing and now only one size fuel hose is required throughout the system.

[tig]

I think that'll do it.

Now need to run to Ace to get something to reduce the line into the filter.

[tig]

For reducing from tank line to filter: How hackey/awful would it be if I just wrapped the inlet nipple of the filter with f4 or electrical tape to make its diameter larger?

Or, are nylon couplings ok with fuel?

[tig]

Best I could find at Ace was this Nylon 1/2x3/8" ID reducer with barbs. Seems like it will work fine.



The hose it's connected to will go to the inlet on the filter. Then the big side will go to the big line that comes out of the tank. This way I can leave the filter in place exactly as it is and simply remove the old pump.

[craigb93]

I think that'll do it.

Now need to run to Ace to get something to reduce the line into the filter.

I do not recommend you leave the plastic zip ties in there as a long term fix. Either metal hose clamps or metal lace wire would be the way to go.

-Dick

[tig]

I do not recommend you leave the plastic zip ties in there as a long term fix. Either metal hose clamps or metal lace wire would be the way to go.

Trying to find some hose clamps that are smaller; most people indicate hose clams won't let it fit through the opening.

Thanks.

[waynet1]

I do not recommend you leave the plastic zip ties in there as a long term fix. Either metal hose clamps or metal lace wire would be the way to go.

Trying to find some hose clamps that are smaller; most people indicate hose clams won't let it fit through the opening.

Thanks.

Try these.

[tig]

Try these.

I guess I have a date at Lowes tomorrow. Thanks!

[tig]

No time to go to Lowes today and no time to wrench. So I just ordered these on Amazon. I figure that over time I'll figure out good uses for the other 98 that will come in the package.

[maybeillbuyit]

CEK, I like the look of your walbro set up. I wish I hadn't just received my new bosch inline pump from amazon. Just wondering, the "stock" rubber reducer you cut down to hook up your walbro, was that the original rubber that came out of the tank or did you get it from the dealer? Also I wonder if nylon is ok with gas? Just wondering. Looks great

[tig]

The rubber reducer was on the original OE pump.

It's cek, not CEK. Sheesh. That's like people who call me Chuck. I tell them "you can call me Chuck. Once."

[maybeillbuyit]

Oh sorry about that Chu...... I mean cek

[tig]

Oh sorry about that Chu...... I mean cek

[PDX5]

Charlie, take a look mid-way through this thread (http://www.mye28.com/viewtopic.php?t=98095), for your answer to why we don't used the stock reducer.

[tig]

Ah, well shit. The money quote:

The stock rubber "hose" that connects the pump to the pickup WILL rupture when using a 255lph pump. AMHIK. The clamps will just speed the process along.

Never braised before. Guess I get to learn a new skill.

[dam5h]

I used silver solder and it holds fine.

[tig]

I got to thinking...

What if the smaller end of the original rubber reducer fit inside a 13mm fuel hose?


Like this:


I'd have the strength of real fuel hose, without having to resort to metal fabrication. Figured I'd give it a try. Used Oetiker clamps:


Feels super-stout. Thoughts?

[tig]

Got the old pump out and the reducer to the filter done.



Sealed up the pump wires with F4 tape and tucked them away.

Now gotta go ship stuff to dub-nub and do some Honey-Doos and then I'll drop the in-tank pump in and see how it works...

[tig]

Just like everyone else who's done this, I had to discover by myself that it's a REALLY tight fit and wrapping the pump with rubber just won't work. I'm not even sure why people try; I guessed the idea was to make the pump quieter.

Any-who, I slimmed it all up by using a single tie and one piece of rubber jammed in between the pump and the return tube to make it more straight and the metal zip tie even tighter.




Just got back from a test drive and it appears to be working great. I think my adjustable FPR dial shows a much more stable pressure when I blip the throttle.

Hope my trials & tribulations with this help others. If it falls apart or something you know I'll add to this thread...

[wkohler]

I like those ties. I need to get some. Is the nylon coupling you got rated for fuel? I used brass NPT fittings on the B7. Had to use the 5/16 harb to NPT, a coupler and an NPT to 3/8 barb. That was after discovering that having a Menards nearby would have been more useful than three different specialty hose and fitting stores.

[tig]

I like those ties. I need to get some.

Note they are hard to get tight. I had to get them as tight as I could by pulling with pliers and then use the rubber to expand the whole thing to make 'em really tight.

Is the nylon coupling you got rated for fuel?

Probably not.

[maybeillbuyit]

I found this post really interesting , looks like I will be going the walbro route as I just installed a new bosch inline pump and found the intank unit that I thought was working was not Very poor timing on my part, at least I THINK I know what I'll do next. I just came across this: http://www.jegs.com/i/JEGS/555/15946/10002/-1?CT=999 I'm sure there are other options out there.

[demetk]

Would a swagged copper tube that could be braised on work?

[davintosh]

Dumb question time: Is there a reason not to use the smaller diameter pipe for the pump output? That would eliminate having multiple size hoses & adapters in the pump's output path. Putting an adapter on the return line would cause fewer pressure-related issues.

The only downside I can think of is losing the longer discharge pipe as a mounting point for the pump itself, but considering the fact that later model cars (e32s & e34s anyway) use pumps that only attach to the tank by way of hoses, I wouldn't think it'd be a huge issue. If it is an issue, extending the larger tube to the same length as the smaller tube wouldn't be a difficult thing either.

Flame suit on.

[dam5h]

Genius!

[ElGuappo]

Earlier cars did it too.
My euro '84 735 came with the 100 liter fuel tank, and had the bayonet mount tank level sender without a helper pump, and ONLY used the main in line pump.

So the other option here, instead of doing the in tank pump, would be to modify the pickup with piping from the top to the strainer, and only use an in line external pump.

[davintosh]

I thought about the single external pump too, but I'm pressing ahead with the in-tank mod.

A couple more questions related to it:

1. The stock return pipe connects to the fuel strainer body, which just has an integrated diverter to direct fuel away from the bottom of the tank. I'm guessing that isn't a terribly important feature, but would it make any difference to have the return pipe a few inches above the bottom of the tank? I'm debating whether to bother extending the 10mm tube or not.
2. The Bentley says that the O-ring at the top of the sending unit ought to be replaced when the sender comes out; does anybody know what size it is? I may just take the thing over to the parts store and see if they can size one to it. The old one looks like it's been in there for the life of the car; all crusty and jammed in the little gap, and I doubt it'll come out in one piece.

[ElGuappo]

I wouldnt bother extendign the return pipe.
The oring when new is actually kinda square, at least the last one I bought was.
Total about 2", but its cheap so jus tbuy the BMW unit.

[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.