525i M50 does anyone knows how it primes?

[bfrqrv]

Hi,

Anyone knows if the E34 M50 primes the fuel rail a few seconds before start?

[bfrqrv]

I saw it once I am sure but never again and replaced the Motronic relay and the fuel relay

[bfrqrv]

I hope someone has still a E34 with m3.1.1 and hear or see if this car primes the fuel rail before start

[bfrqrv]

nobody ? Is there anyone that can turn over the key to the second position for me?

[danespann]

My m50 car does not prime until actually cranking.

[bfrqrv]

My m50 car does not prime until actually cranking.

Yes it looks like thats normal, but I am sure the pre-crank was there for a few times minimum. I even see the prime when I hooked up a gauge one time, that makes me searching for a ghost maybe.

[shogun]

we discussed that before , Can-t-hear-the-fuel-pump-priming-when-turning-the-key https://www.bimmerforums.com/forum/showthread.php?2348204-Can-t-hear-the-fuel-pump-priming-when-turning-the-key

[bfrqrv]

Yes i read that before. It's a good discussion but I think I don't see or understand the real issue. Can you maybe help me with this specific case? I am sure I heard and even saw the prime a few time when I hooked up my gauge to test the pressure so there must be a prime? It's a M3.1.1 M50TU from 1994. I replaced fuel pump (not original) fuse,both relays, fpr and DME.

[bfrqrv]

Is there anyone else maybe that can turn over the key to the second position and listen f the fuel pump runs for 1-2 seconds? It's a M3.1.1. in a E34 525I 1994

[bfrqrv]

Hi Shogun, do you know if your text here is also for the M3.3.1 1994?

"Relays
The Motronic electrical system is controlled by a main fuel injection relay and a fuel pump relay. A permanent voltage supply is made to the main relay terminals 30 and 86 from the battery positive terminal. When the ignition is switched on, the ECU earths terminal 85 through ECU terminal number 36 which energises the first relay winding (on the 1987 M1.1 system, this connection was made directly to earth). This causes the first relay contacts to close and terminal 30 is connected to the output circuit at terminal 87. A voltage supply is thus output at terminal 87. Terminal 87 supplies voltage to the injectors, ECU terminal 37, ISCV and the CFSV when fitted. In addition voltage is supplied to the fuel pump relay terminal 86. When the ignition is switched on. the ECU briefly earths fuel pump relay contact 85 at ECU terminal 3. This energises the relay winding, which closes the relay contact and connects voltage from terminal 30 to terminal 87, thereby providing voltage to the fuel pump circuit. After approximately one second, the ECU opens the circuit and the pump stops. This brief running of the fuel pump allows pressure to build within the fuel pressure lines, and provides for an easier start. The fuel pump relay circuit will then remain open until the engine is cranked or run. Once the ECU receives a speed signal from the CAS, the relay winding will again be energised by the ECU, and the fuel pump will run until 3 seconds after the engine is stopped. The 3 seconds delay in switching off the pump relay allows the fuel pump to maintain pressure on engine shut-off to avoid engine run-on. In addition, on some vehicles control of the OS heater is made through a separate OS relay. Once the ignition is switched on, a voltage supply is made to the OS heater relay terminals 30 and 86. When the engine is started, the ECU connects relay terminal 85 to earth through ECU pin 23. The relay actuates and the output voltage at terminal 87 provides voltage to the OS heater. The ECU switches off the relay under certain conditions of speed and load."

So as a summary I need to know 2 things by fact:

#1 Does this Bosch M50 M3.3.1 E34 1994 suppose to prime the fuel rail for a few seconds in key position #2?
#2 When thats a positive what is there more to replace then Motronic relay. fuel relay, fuel pressure regulator, fuel filter, fuel pump, DME and checked ignition.

[shogun]

My info was based on the older M1.1, M1.3, I have no detailed info about the newer M3.3.1 1994 M50 system. The info I posted there I once found in a description for the M1.1 1.3 for Bosch in general, not especially for BMW, this system was also used for other car brands. the file is from Opel scanner http://www.opel-scanner.com/files/DME_1.1_1.3.pdf
On a German forum someone posted for the E32 M30 engine DME, that this is not correct with the priming for M30:
Wenn das DME Relais anzieht liegt PLUS an der Spule vom Benzinpumpenrelais an. Die 86 wird aber von der DME selbst PIN 1 gegen Masse geschaltet. Erst wenn dies geschieht, zieht auch das Benzinpumpenrelais an. Beim M30 ist es zumindest so, das die Benzinpume erst zugeschaltet wird, wenn die DME vom OT-Geber ein Signal bekommt.

When the DME relay is engaged, PLUS is on the coil of the fuel pump relay. However, the pin 86 is switched to ground by the DME itself PIN 1. Only when this happens does the fuel pump relay also work. With the M30 it is at least the case that the fuel pump is only switched on when the DME gets a signal from the OT sensor.

as you are from the Netherlands, you might understand German, here is the technical BMW file Fehlersuche DME 1.1 E32 735i - fault search DME M1.1 (maybe that helps a bit, although it is not yr DME type) https://web.archive.org/web/20141031175728/http://wp1016621.server-he.de/fotost/f01970/FehlersucheDME11-735i.pdf

DME M3.3 M60 description https://www.bimmerforums.com/forum/showthread.php?2019306-Digital-Motor-Electronics-DME-M3-3-8-cylinder-M60-technical-details

[bfrqrv]

Very good info indeed.Still it's weird that we have so few experience responses on if the M50 E34 1995 525i must prime or not. Only Danespann has a negative but I am sure there mist be more users that can give any kind of input here

[shogun]

you can also ask on the German E34 forum https://forum.e34.de/index.php but registration takes some time, as it does not work automatically due to too many spam registrations, every new registration is now checked by moderators and manually approved or not