Wow, moving to intank pump on early euro e28 looks kinda impossible

[kodachrome]

Early euro e28 has no lift pump in the fuel tank, only external pump. I have an m54 engine swap and it's great bit I'm plagued with terrible cold starts. Moving to intank pump is my next step in combating this. However, wtf am I to do with this dinky opening!?

And without drilling fuel tank how would run power to new pump even if I just dropped it in there beside the level sender?

https://imgur.com/a/WNvYiU6

[Mike W.]

First step is throw a new fuel pump at it, and or an additional check valve. Factory fuel pumps in good shape hold pressure for very long periods of time, nearly indefinitely. Only reason a M52 swap should be hard starting from a fuel pump is lack of residual pressure. I've cut into fuel lines in junkyards on cars that have clearly been sitting for a very long time, to have fuel spraying everywhere. And at least some, if not all M52s have a prime function build into the engine management which alone should eliminate the pump as a problem.

Next. Now I don't know how hard to find or expensive, but a later fuel tank with the bolt in sender/pickup. Not knowing NZ that might be easy or stupid expensive.

Next. For a really odd long shot, or maybe not quite that long, for a time at least US spec E21s used that camlock style pickup, but with the later oval sending unit and a prepump. Additionally, and I'm not positive, but pretty sure, it was the same length. Think 1980, I think that was the one I had like that.

Next. Find a rusty donor tank, cut out the bolt in area which will likely still be in good shape, cut a larger hole in yours and weld/braze it in place.

But really, a good pump should hold pressure and not be a factor in hard starts, but there are other options. IMO the prepump mostly allows you to run the tank closer to empty before you run out by a gallon or more, eliminates (with some marginal pumps) fuel starvation at low tank levels and high RPM/load and minimizes vapor lock under hyperextreme heat conditions.

[kodachrome]

Thnaks Mike, though frustratingly Ive this is the 4th fuel pump (general aftermarket retail unit, a whopper 1000lph mega inline pump which started to whine, then back to a new OEM Bosch pump (OEM to the E28) and now this attempt at a smaller intank pump (AEM 340lph).

This isnt an M52, its an M54 and the M54 has tons of people with this compliant, its a nightmare to troubleshoot. The M54 is a returnless fuel system, ie the unused fuel doesnt return from the fuel rail, it has a 3 output fuel filter (with integrated FPR) that shunts excess back to the fuel tank (filter is of course mounted beside the pump under tank).

I've already changed the plugs, coils, CPS sensors and of course multiple pumps. I also put a fuel check value after the filter, so it goes:
"Suction" from tank -> new Bosch pump -> M54 Bosch 3 Filter with integrated FPR -> Fuel Check Valve -> line to fuel rails/injectors.

Incidentally Ive just changed my Fuel Filter FPR combo as I checked the pressure and it was reading 60PSI despite having a new 3.5bar (50psi) FPR in there. Its now reading 50psi and I havent tested it properly since.

On the old tank idea, I considered it too.. but then if I was going to the hassle of dropping tanks, I'd probably just drain then drill my existing mint tank to fit the pump in somehow. Its really just powerlines I cant figure out how to get in there without an explosion from drilling!


PS: Your E21 suggestion lead me to this: https://www.bmw2002faq.com/forums/topic ... fuel-pump/
Which sure looks like the Late E30 318is has the same small opening for the fuel sender but has an intank pump offset in there too!

[Federico]

https://www.mye28.com/viewtopic.php?t=147207

[vinceg101]

This isnt an M52, its an M54 and the M54 has tons of people with this compliant, its a nightmare to troubleshoot. The M54 is a returnless fuel system, ie the unused fuel doesnt return from the fuel rail, it has a 3 output fuel filter (with integrated FPR) that shunts excess back to the fuel tank (filter is of course mounted beside the pump under tank).

Interesting, on the US M54B30 E39 (2002) the fuel filter is under the passenger seat tucked up against the frame rail. Quite a distance from the pump and tank. Not sure what model you took the M54 from.
[Sorry, don't mean to jump in the middle of this; I have nothing else really to add. You're in good hands with Mike]

[Aldo525]

I'm not sure if Mike was referring to this system on the early euro e28s without pre pump and that serves to maintain the pressure of the fuel system. My 518i K Jet has it and I think the US e21 also used it. The photos are not very good, it was when I redid the entire system, new pump, filter and "pressure maintainer" but it could be a solution for those bad cold starts.

[Mike W.]

I'm not sure if Mike was referring to this system on the early euro e28s without pre pump and that serves to maintain the pressure of the fuel system. My 518i K Jet has it and I think the US e21 also used it. The photos are not very good, it was when I redid the entire system, new pump, filter and "pressure maintainer" but it could be a solution for those bad cold starts.

I am familiar with it, but that's not what I'm talking about. I've always called it an accumulator, perceived it to be a dampener, but wasn't really sure what it did. K jet is kind of run off of fuel pressure so pressure is super critical, L jet/Motronic or even more modern versions will tolerate much more variation in pressure and still run at least ok, if not like they should.

The late E30 solution looks ideal, I knew they went to an intank main pump at some time, but I've never had an E30 or even worked on one at all so I didn't know how it mounted, dimensions or even what it looked like.

What I was referring to is in the pic below, I'm fairly certain it is the same size camlock that they used since Bavaria and probably 2002 days. But the pump is just a prepump, not a main pump like late E30s have.

https://www.realoem.com/bmw/enUS/showpa ... Id=16_0007

[kodachrome]

I'm not sure if Mike was referring to this system on the early euro e28s without pre pump and that serves to maintain the pressure of the fuel system. My 518i K Jet has it and I think the US e21 also used it. The photos are not very good, it was when I redid the entire system, new pump, filter and "pressure maintainer" but it could be a solution for those bad starts

This is pretty interesting, I just checked it out. It's a Bosch Fuel Accumulator (aka fuel damper). It's used on lots of non BMWs, all non electric injection cars.

It has a check valve in it and a small capacity chamber for fuel to aid hot restarts apparently.
I don't have an issue with hotstarts, so not sure if it would help my situation, however there is another issue I suspect, taken from a Ferrari forum:
"fuel goes from the tank to the fuel pump, then to the accumulator, then to the fuel filter, and then forward to the engine"

In my case the M54 fuel filter has the return line in it, excess fuel pressure is bled back into the tank. That would defeat the purpose of the accumulator as the line is going to loose pressure post accumulator itself. Also the accumulator is a 3bar device, not sure it can be increased?

[Galahad]

Have you considered going to a filter and FPR in the engine bay?

[kodachrome]

Have you considered going to a filter and FPR in the engine bay?

Not really, what would that solve though?
It would mean finding space in engine bay (doable I imagine) and running a much shorter vacuum line (currently I just reuse the original fuel return line).

However it would also mean :
- pushing unfiltered fuel all the way through the stock fuel feed line under the car (which probably isnt a major concern).
- re-using the original return line as the "non-return" system that diverts unused fuel back to the tank. So it would be "returnless" as per OEM from the fuel rail (ie no return line) but still actually returns excess via the fuel filter, now in engine bay. Which feels odd as BMW presumably could have designed it that way on the E46 and E39 and X5 etc this engine was in but didnt.
- moving the non-return (check valve)

Not really sure of the pro and con of that? The check valve I guess would be after the pump and before the filter too.

[Galahad]

Not really, what would that solve though?
...

I only suggested because it seems like you're dealing with issues from the factory setup, so going aftermarket might improve things. Additionally, the shorter the amount of fuel line that is under pressure, the easier it is going to be to diagnose any sort of pressure drop while sitting.

[kodachrome]

Not really, what would that solve though?
...

I only suggested because it seems like you're dealing with issues from the factory setup, so going aftermarket might improve things. Additionally, the shorter the amount of fuel line that is under pressure, the easier it is going to be to diagnose any sort of pressure drop while sitting.

Thanks, Ive been pondering the suggestion since and think Ill try it! I presume you were thinking of moving the fuel check valve into the engine bay too?