Long cranking after car sitting for 3+ days - fueling issue

[kodachrome]

Im pretty sure this is a fuel pump related issue... :

- M54B30 engine swap
- Early E28 without the intank pump, just external (and new, tried several different types) Bosch Pump


Runs great, starts great within 36hrs of the last start. However after that and its maybe 7 cycles of the ignition to even begin to get it to fire up. Ive replaced Fuel Injectors and CPS sensors already. I had a whopper 1000hp AEM capable pump on it for a while and eventually it started getting noisy which make me think the fuel is draining back to tank or away from the suction hose or something.

The M54 engine setup is slightly different from M30's in that its a "returnless" fuel system, the excess fuel goes to the fuel filter and then straight back to the tank (on the stock return line), not all the way to the injectors and back.

I don't think that has any bearing on the problem... BUT shouldnt there be a fuel check (one way) valve somewhere in my setup? I tried one just before the fuel pump (really hard to fit as the filter is beside it and huge) and it didnt help.

[1st 5er]

Why no in-tank pump?

The problem with a failed in-tank pump and good external pump, OE setup, normally has poor to no delivery ~ 1/4 tank.

How much fuel is in the tank?

[Aldo525]

Newer BMW like e53 X5 m54b30 use a "Fuel filter with pressure regulator", also used on e39´s; OE 16126754016.... That filter is the "new" version of "filter + fuel accumulator" used in the early e28 518i K Jet injection system (also e21 and maybe others) that is a mechanical way to maintain the fuel pressure over the injection system if the engine is not working for several days....

Perhaps you need that type of filter (I mean e53 filter) to have a secure fuel pressure after 36 hours.....

Just an idea....

[Mike W.]

Why no in-tank pump?

Most euro E28s less than 535s didn't have one, just the external.

[1st 5er]

Why no in-tank pump?

Most euro E28s less than 535s didn't have one, just the external.

Ouch!!!

[kodachrome]

Newer BMW like e53 X5 m54b30 use a "Fuel filter with pressure regulator", also used on e39´s; OE 16126754016.... That filter is the "new" version of "filter + fuel accumulator" used in the early e28 518i K Jet injection system (also e21 and maybe others) that is a mechanical way to maintain the fuel pressure over the injection system if the engine is not working for several days....

Perhaps you need that type of filter (I mean e53 filter) to have a secure fuel pressure after 36 hours.....

Just an idea....

Ah, so that is the fuel filter I have that I mentioned, its a big unit sitting beside the external fuel pump. Well actually this is the correct Part with the FPR on it is per my setup:
https://www.turnermotorsport.com/p-340646-fuel-filter/
13327512019
Unfortunately, for whatever reason thats not sufficient or I have some other issue!

EDIT:
Lol... ok so I just found this by chance:
https://www.youtube.com/watch?v=6ezt4M1NZDk
The M54B30 stock fuel pump has a check valve in it. And this is the Bosch unit I have installed, which is for the E28 (and similar era):
https://www.bosch-motorsport-shop.com.a ... -fuel-pump

Which does not have a check valve in it. Lol, damn, maybe its that simple. Not sure what went wrong with my previous testing with a check valve, though video linked above shows installation of a check valve on an M54B30 e39/e46 afterthe fuel pump (which is in-tank on those models of course).
I installed my check valve before the fuel pump (between the filter and pump) as I thought that made the most sense. I guess I might be able to install it post the pump, but I thought the fuel was draining back to tank from the pump, which would only be stopped by installing the check valve before the pump, not after. Perhaps its just draining back from the injectors and thats all Im trying to stop.

[kodachrome]

Most euro E28s less than 535s didn't have one, just the external.

Ouch!!!

Yeah its pretty lame!