In-tank Fuel Pump Modification

[Mike W.]

Insulate them individually. If you tie them together you'll short the fuel pump circuit and blow the fuse, hopefully. If you don't blow the fuse you'll start a fire, so to avoid all of that, just insulate them with heat shrink tubing, fold one back on itself, then tape the two insulated wires together, then secure somewhere up there so they don't rub out and short to ground.

You can do it simpler, but the above requires multiple things to go wrong before they can short.

[harrypalmer]

It seems very obvious but I'm still confused so please bear with me: Am I interpreting correctly there's no need for a coupler between the 12X18 hose and fuel filter as originally posted?

Is the nylon coupling you got rated for fuel?

Probably not.

but simply do as explained and shown below?

First, take the original rubber connector that goes from the original transfer pump and cut it in half, where the smaller diameter section meets the larger diameter section.You'll use the smaller diameter piece INSIDE your 12x13 tubing to step the size down.

Under the car Use the other piece of tubing you salvaged from the old in-tank pump to size-reduce the 12x18 line coming from your tank to the filter.

So in essence the same rubber connector piece can be utilized for both, the in-tank pump mod AND also the 12X18 hose to fuel filter. Is that the case here? Thanks in advance.

[davintosh]

It seems very obvious but I'm still confused so please bear with me: Am I interpreting correctly there's no need for a coupler between the 12X18 hose and fuel filter as originally posted?

In looking back on where that conversation came from, I'd recommend disregarding Charlie's (cek) reference to that nylon coupler. Pretty sure he gave up on that idea.

The coupler idea was primarily to deal with the different tubing sizes that go between the original in-tank pump and the primary pump that's under the car. If you use the original outlet on the in-tank assembly, you could do as Charlie did, and use one of the smaller pieces of hose inserted into the bigger hose as an adapter. I can see how that would work really well.

What I did was to swap the inlet and outlet pipes on the in-tank assembly so that the same size hose could be used between the pump and the filter. That way the only place you need to worry about different tubing sizes is on the return side. Here's the comment where I described what I did:
viewtopic.php?f=3&t=101410&p=1312469&#p1312469 (also viewtopic.php?p=1443787#p1443787 )





The barbed adapter that I used at the top of the assembly could easily be replaced with Charlie's method of stepping down from the larger tubing size to the smaller. Or you could come up with a better idea.

Does that help?

[harrypalmer]

Yes it does. Thank you very much!

[tig]

@davintosh did it right (as usual). Do as he said.

(I did it right on Minerva).

[harrypalmer]

It seems very obvious but I'm still confused so please bear with me: Am I interpreting correctly there's no need for a coupler between the 12X18 hose and fuel filter as originally posted?

In looking back on where that conversation came from, I'd recommend disregarding Charlie's (cek) reference to that nylon coupler. Pretty sure he gave up on that idea.

The coupler idea was primarily to deal with the different tubing sizes that go between the original in-tank pump and the primary pump that's under the car. If you use the original outlet on the in-tank assembly, you could do as Charlie did, and use one of the smaller pieces of hose inserted into the bigger hose as an adapter. I can see how that would work really well.

What I did was to swap the inlet and outlet pipes on the in-tank assembly so that the same size hose could be used between the pump and the filter. That way the only place you need to worry about different tubing sizes is on the return side. Here's the comment where I described what I did:
viewtopic.php?f=3&t=101410&p=1312469&#p1312469 (also viewtopic.php?p=1443787#p1443787 )





The barbed adapter that I used at the top of the assembly could easily be replaced with Charlie's method of stepping down from the larger tubing size to the smaller. Or you could come up with a better idea.

Does that help?

Wow I'm and totally missed the barbed adapter in your pictures. Guess was distracted by the painted top of the in-tank pump. Will do as you suggest. I appreciate your help and thank you for taking the time in your reply. The same goes for Charlie's posts. All invaluable.

[harrypalmer]

@davintosh did it right (as usual). Do as he said.

(I did it right on Minerva).

I will, your work on Minerva's fantastic. Thank you Charlie.

[harrypalmer]

It seems very obvious but I'm still confused so please bear with me: Am I interpreting correctly there's no need for a coupler between the 12X18 hose and fuel filter as originally posted?

In looking back on where that conversation came from, I'd recommend disregarding Charlie's (cek) reference to that nylon coupler. Pretty sure he gave up on that idea.

The coupler idea was primarily to deal with the different tubing sizes that go between the original in-tank pump and the primary pump that's under the car. If you use the original outlet on the in-tank assembly, you could do as Charlie did, and use one of the smaller pieces of hose inserted into the bigger hose as an adapter. I can see how that would work really well.

What I did was to swap the inlet and outlet pipes on the in-tank assembly so that the same size hose could be used between the pump and the filter. That way the only place you need to worry about different tubing sizes is on the return side. Here's the comment where I described what I did:
viewtopic.php?f=3&t=101410&p=1312469&#p1312469 (also viewtopic.php?p=1443787#p1443787 )





The barbed adapter that I used at the top of the assembly could easily be replaced with Charlie's method of stepping down from the larger tubing size to the smaller. Or you could come up with a better idea.

Does that help?

Before I proceed I need your opinion on this please.

My goal is to keep a one size hose (8X13mm) for both intake and return the way you accomplished it, but with a twist.

To do this:

1. I'd step down the larger tubing size to the smaller, using Charlie's (rubber insert) method to utilize it as the intake tube.

2. Then, I would proceed with Davintosh barbed step down method but only at the top of the assembly so I can fit the 8X13mm hose. This would mean I would not switch the return for the intake lines. Mainly because I don't understand why the slim (return) tube is epoxy-welded.

However, in doing what I am proposing, I can see that the larger intake tubing would somehow be reduced twice: 1 at the pump intake with the rubber insert. And 2 at the top of the assembly with the barbed fitting.

Would this cause any pressure problem, or do you think it may work?

-Jack

[davintosh]

Sorry to be late in responding; it's been a crazy week!

Before I proceed I need your opinion on this please.

My goal is to keep a one size hose (8X13mm) for both intake and return the way you accomplished it, but with a twist.

To do this:

1. I'd step down the larger tubing size to the smaller, using Charlie's (rubber insert) method to utilize it as the intake tube.

2. Then, I would proceed with Davintosh barbed step down method but only at the top of the assembly so I can fit the 8X13mm hose. This would mean I would not switch the return for the intake lines. Mainly because I don't understand why the slim (return) tube is epoxy-welded.

However, in doing what I am proposing, I can see that the larger intake tubing would somehow be reduced twice: 1 at the pump intake with the rubber insert. And 2 at the top of the assembly with the barbed fitting.

Would this cause any pressure problem, or do you think it may work?

-Jack

I'm not quite following you here. Are you keeping the original pump setup or converting to a single high-pressure pump in the tank? It's not clear to me where you'd be using the larger fuel hose.

When I made this conversion the larger tubing was eliminated entirely, and I used only the smaller 8mm hose throughout. On the original setup, the larger 12mm hose was only used from the lift pump assembly to the high pressure fuel pump intake; 8mm attached to the output of that pump. By switching the output of the pump to the smaller tube, that meant I could use 8mm to the inlet on the fuel filter. The step-down fitting on the larger pipe on the assembly allowed 8mm to be used for the return line as well.

[harrypalmer]

Davintosh, no worries.

Bottom line, will attempt a partial combination of both Charlie's method, and your method as well, by installing one TRE pump. Eliminate the external pump, and only utilize 13X8mm hoses everywhere.

Allow me to re-visit:

I'd replicate Charlie's how-to-cut and measure the rubber connector reducer inside the assembly. This would allow me to keep the intake's larger tube as originally intended.

Now, to utilize 8mm hoses everywhere, I'd reduce the same larger assembly tubing (but only) at the top, or exterior of the assembly, using your method; of barbed metal coupler and epoxy/weld it in the same fashion as you described.

Since I have not removed the original assembly from my car yet, I need to figure out unsure how you measured the rubber connector in the smaller tube, and also how you epoxy/welded the larger tube in the inside of the assembly, so I thought I'd better keep the original functionality of both intake and return lines and not switch them just yet, the way you did.

Really hope I'd made sense this time around. English as a second language can be challenging some times. Either way, I'd still appreciate your opinion whenever you have a moment please. Thank you once more. It will give me a valid reason to ship a six pack of your fav brew your way!

-Jack

[tig]

Davintosh, no worries.

Bottom line, will attempt a partial combination of both Charlie's method, and your method as well, by installing one TRE pump. Eliminate the external pump, and only utilize 13X8mm hoses everywhere.

Allow me to re-visit:

I'd replicate Charlie's how-to-cut and measure the rubber connector reducer inside the assembly. This would allow me to keep the intake's larger tube as originally intended.

Now, to utilize 8mm hoses everywhere, I'd reduce the same larger assembly tubing (but only) at the top, or exterior of the assembly, using your method; of barbed metal coupler and epoxy/weld it in the same fashion as you described.

Since I have not removed the original assembly from my car yet, I need to figure out unsure how you measured the rubber connector in the smaller tube, and also how you epoxy/welded the larger tube in the inside of the assembly, so I thought I'd better keep the original functionality of both intake and return lines and not switch them just yet, the way you did.

Really hope I'd made sense this time around. English as a second language can be challenging some times. Either way, I'd still appreciate your opinion whenever you have a moment please. Thank you once more. It will give me a valid reason to ship a six pack of your fav brew your way!

-Jack

My suggestion is to get your hands on a hanger so you can "just do it". Either source a used one, or just pull the sucker from your car.

BTW, "English as a FIRST language can be challenging some times."

[harrypalmer]

Davintosh, no worries.

Bottom line, will attempt a partial combination of both Charlie's method, and your method as well, by installing one TRE pump. Eliminate the external pump, and only utilize 13X8mm hoses everywhere.

Allow me to re-visit:

I'd replicate Charlie's how-to-cut and measure the rubber connector reducer inside the assembly. This would allow me to keep the intake's larger tube as originally intended.

Now, to utilize 8mm hoses everywhere, I'd reduce the same larger assembly tubing (but only) at the top, or exterior of the assembly, using your method; of barbed metal coupler and epoxy/weld it in the same fashion as you described.

Since I have not removed the original assembly from my car yet, I need to figure out unsure how you measured the rubber connector in the smaller tube, and also how you epoxy/welded the larger tube in the inside of the assembly, so I thought I'd better keep the original functionality of both intake and return lines and not switch them just yet, the way you did.

Really hope I'd made sense this time around. English as a second language can be challenging some times. Either way, I'd still appreciate your opinion whenever you have a moment please. Thank you once more. It will give me a valid reason to ship a six pack of your fav brew your way!

-Jack

My suggestion is to get your hands on a hanger so you can "just do it". Either source a used one, or just pull the sucker from your car.

True! Correct 8mm hoses arrived just now, thus ending my procrastinating.

BTW, "English as a FIRST language can be challenging some times."

LOL. Double that ^ ^ ^
So when you said, "(I did it right on Minerva)." how did you do it then? Just curious. Thanks.

[harrypalmer]

Oops! I did it too

Inspired and encouraged by Davintosh and Charlie, (thank you boys) made the pump modification this weekend by copying Charlie's rubber reducer step method from the OEM in-tank to the new TRE pump pickup. And then sort of adopting Davintosh method of reducing the large tubing with a barbed connector at the top (exterior of the assembly) to hook up with a 8mm hose and here's were I diverted from Davintosh, is that I kept the original intake and return lines to and from the in-tank pump assembly as BMW intended. I was very hesitant of doing it (my way) until I read that Davisntosh also had some doubts too when reversing the lines. So I'm happy to report my car's engine starts right away with no hesitation and have driven her in multiple occasions and scenarios and she feels steady with no pressure loss that I can perceive.

There are many step by step photos of the whole process here: https://www.flickr.com/photos/109547372@N04/? for anyone interested.

I decided to put to use a brand new Airtex assembly that I had stored for years but never used because the rubber reducer was and is unadulterated merd and garbage. Had to rip off some pieces and trim (cut) to fit the larger tube, the retaining electrical side screw, and slightly and gently bend it all enough to fit inside the tank even with the rubber condom thingy, and nothing broke or ripped of.

Much thanks to Charlie because he really made me look more than once at what I needed to pay attention to. Getting the right correct length, measuring multiple times, and also reminding me (through his post) to have the filter pointing to the correct opposite direction of the pickup. Maybe conventional stuff for some here but essential to me, for which I'm grateful.
Lastly, much thanks to Davintosh too, because without his "simple" yet "brilliant" (for me) epoxy weld reducing method I would have not done this. Now, as Charlie suggested, I will be selling both my deleted but still working external and in-tank pumps next. This forum is a great place and I owe my gratitude to many of you. Thanks.

[glowell222]

I have just completed this mod as well while I replaced my fuel tank. I no longer have the small hesitations during acceleration that I never really noticed until they were missing. A very large thank you to those who have contributed to this post.

[harrypalmer]

I have just completed this mod as well while I replaced my fuel tank. I no longer have the small hesitations during acceleration that I never really noticed until they were missing. A very large thank you to those who have contributed to this post.

Glad for you. My car now is exactly suffering from some small hesitations during hard acceleration when A/C is not engaged. Oh well.

Prior to this mod I tested two Fuel Pressure Regulators and both were fine. Does anyone have any insight on this please?

[jacobthegoat]

After completing this modification, I started to overthink my doings and pose this simple question:

The small connection between the pump and the lift assembly I used a small section of BMW fuel hose with a reducer as shown by cek.

Is the standard fuel hose used for this modification rated for in tank use? Is the fuel line “submersible” or will it deteriorate over time? It doesn’t specifically say submersible but cek seems to be using the same hose as I did.


I used the TRE 340 and stock BMW fuel lines
Part # here - 13-53-7-563-456

[glowell222]

I can't answer your question. I can state that I used typical BMW fuel line for that small section. After about a month, I was having problems making it up steep hills-almost like a fuel starvation issue. I pulled the assembly from the tank, thinking something had come loose. I found that small section had deteriorated and was loose. I replaced it with fuel line specifically rated for submersion. So far, no trouble, and we will have to see if it bears this out.

[Shawn D.]

It's expensive, but I have been sourcing and using specific "submersible" hose for in-tank use. Given the trouble and labor involved, it's worthwhile, IMO.

[davintosh]

I'd be hesitant to use standard fuel hose in the tank.

I didn't really think about that much beforehand, but on both of the cars I've done, the pumps came with a kit that included a section of fuel hose. Looking back at it the site I bought the most recent one from, it doesn't specifically say it's submersible, but since the vendor specializes in fuel pumps I think it's safe to assume it'll work.

https://www.highflowfuel.com/genuine-wa ... -gss340g3/

[funkycharms]

Thanks for bringing this up. I just completed the upgrade 2 weeks ago, and didn't even consider. Ended up stuffing some of the provided tre hose into a standard 13mm line. Guess it's something I'll keep an eye out for

[harrypalmer]

It would be most helpful if glowell222 could actually name the brand and or reference of said submersible hose for anyone's interest.

BTW and FWIW, had previously commented having some sort of hiccups with my own pump mod, but I was wrong as it is only susceptible when the fuel gets too warm (very particular to my car). Will be installing a fuel cooler next week and report.

[Shawn D.]

It would be most helpful if glowell222 could actually name the brand and or reference of said submersible hose for anyone's interest.

It's not hard to find, just search the interwebs for "submersible fuel hose." I recently got some from Summit Racing.

[glowell222]

It would be most helpful if glowell222 could actually name the brand and or reference of said submersible hose for anyone's interest.

It's not hard to find, just search the interwebs for "submersible fuel hose." I recently got some from Summit Racing.

This is exactly what I did (Summit Racing), and I had to buy several different diameters to work out which one was best. Of course, I don't recall which one I ended up using, so double-useless on my part-apologies for that.

[harrypalmer]

BTW and FWIW, had previously commented having some sort of hiccups with my own pump mod, but I was wrong as it is only susceptible when the fuel gets too warm (very particular to my car). Will be installing a fuel cooler next week and report.

A year later, have installed a E28 specific fuel cooler. It does greatly improve the engine's drive ability in traffic. However, the fuel starvation is present when pulling hard (4,500 to 6,500 rpm via a D'sylva chip) which is the way I mostly drive. Anyway, I am going to take the intank fuel pump out and get a dedicated submersible fuel hose like Davintosh suggested earlier. And report back again.

Does anyone out there, have experienced fuel starvation with this fuel mod?

[1st 5er]

BTW and FWIW, had previously commented having some sort of hiccups with my own pump mod, but I was wrong as it is only susceptible when the fuel gets too warm (very particular to my car). Will be installing a fuel cooler next week and report.

A year later, have installed a E28 specific fuel cooler. It does greatly improve the engine's drive ability in traffic. However, the fuel starvation is present when pulling hard (4,500 to 6,500 rpm via a D'sylva chip) which is the way I mostly drive. Anyway, I am going to take the intank fuel pump out and get a dedicated submersible fuel hose like Davintosh suggested earlier. And report back again.

Does anyone out there, have experienced fuel starvation with this fuel mod?

My only delivery issue has been when tank is extremely low on fuel, ~ 1/8 tank, and under hard cornering.
Submersible high pressure hose is a must.
Somebody out there knows the rating numbers,
or they may be listed earlier in this thread.

[gwb72tii]

Ask Charlie what he did with Vlad

[harrypalmer]

My only delivery issue has been when tank is extremely low on fuel, ~ 1/8 tank, and under hard cornering.
Submersible high pressure hose is a must.
Somebody out there knows the rating numbers,
or they may be listed earlier in this thread.

When you say 1/8 tank, how much fuel would you say is that in gallons?
In my case I feel fuel starvation occurs when there are roughly 4 gallons left in the tank (if I don't accelerate hard I won't notice it at all) but as mentioned earlier I usually drive hard, which makes the fuel range obsolete, or about 150 miles.

BTW my fuel pressure last time I measured (two different fuel regulators) read fine. Should I try larger fuel injectors at this point?
Any suggestions welcomed.

[harrypalmer]

Ask Charlie what he did with Vlad

I will. Thank you.

[tig]

Ask Charlie what he did with Vlad

I will. Thank you.

Like I remember. I'm regularly doing mye28.com searches on topics, finding threads with great writeups on how to do things, and then discovering that I'm reading something *I* wrote. ADHD FTW!

[1st 5er]

My only delivery issue has been when tank is extremely low on fuel, ~ 1/8 tank, and under hard cornering.
Submersible high pressure hose is a must.
Somebody out there knows the rating numbers,
or they may be listed earlier in this thread.

When you say 1/8 tank, how much fuel would you say is that in gallons?
In my case I feel fuel starvation occurs when there are roughly 4 gallons left in the tank (if I don't accelerate hard I won't notice it at all) but as mentioned earlier I usually drive hard, which makes the fuel range obsolete, or about 150 miles.

BTW my fuel pressure last time I measured (two different fuel regulators) read fine. Should I try larger fuel injectors at this point?
Any suggestions welcomed.

~ 2 gallons.
Typically would be just about the time the light would come one. It had only happened on a hand full of occasions, as I don't normally let the tank get that low. It's usually refilled around 1/4 tank or better.

I have no fuel pressure or injector recommendations.