Fuel pump runs but not injecting?

[jmile46]

Hey guys, so the past few weeks my e32 has been throwing a slew of issues at me. First off a bad main relay which caused me to install a new(used) fuel pump as well. Then a bad crank position sensor.

So I was finally able to enjoy the car this past sunday. She drove good all day. Then I took it out later in the night. Outside temps at about 5 degrees farenheit. All of a sudden the car started to bog on me when accelerating. I was able to go into neutral and it would idle. I was able to make it home although it would be hiccuping. Let it sit overnight and then next morning I cranked her and it started, idled for maybe 30 seconds then died. I tried again and it fired up and died instantly. Now no start. So I underwent my usual troubleshooting that ive been doing for the past couple weeks. I jumped the fuel pump relay and while the pump did come on it sounded quieter and kind of odd. Given its still very cold here. But the main thing I noticed is that there was no injectors firing. Normally when I jump fuel pump relay I hear pump and I hear gas shooting out the injectors. This time that did not happen. With jumper in place car was able to start but died instantly.

So now im pretty sure its fuel related. Car has a quarter tank, which ive driven with less before. I think I’ll fill it up a little before I do anything else. But to me it seems almost like this pump has enough life to start but not pump sufficient amounts of fuel. I don’t know what else would not allow fuel to injectors. Fuel filter is brand new, and car has been running since so its not backwards. And I wouldn’t imagine injectors clogged overnight. I don’t have a fuel pressure tester. Any opinions? 1988 735i m30b35

[unity]

Need vehicles details please as your profile only says 2003 BMW, this is the E32 section.

[jmile46]

Need vehicles details please as your profile only says 2003 BMW, this is the E32 section.

Oops! Darn I always forget. This is my 1988 735i. M30b35

[shogun]

you have to test the fuel pump. Nominal data: The M30 fuel pump is originally Bosch, operating pressure is 3 bar, conveying capcity at 12 V 1.9 liter/minute, conveying capacity against counterpressure 875 ccm/30 seconds, Power consumption is 5A.
Easiest way to test the 2 fuel pumps on my 750 without much work and disassembling: Open the hood, remove the cover from B+ post, use a piece of cable/wire and jumper from B+ for a brief time directly onto fuse 23 and then to 24. Ignition off when you do this. Before doing that squeeze the 2 fuel hoses coming up left hand side and do the same after you gave power to the fuses. The fuel pumps will prime for a moment then. As engine is off, one can easily hear each fuel pump when they start pumping, also the fuel hoses should then under pressure afterwards. I can also hear the gas travel thru the fuel pressure regulator back into the return line.
Normally the good fuel pump actually has a much higher fuel pressure than the nominal 3 bar, that is why it can push the fuel thru the FPR.
Fuel injectors also need the signal from the crankshaft position sensor in order to know where the crankshaft is turning.

simple testing of volune: http://bmwe32.masscom.net/sean750/fu...Regulators.htm

Fuel injection
The Motronic ECU contains a fuel map with an injector opening time for basic conditions of speed and load. Information is then gathered from engine sensors such as the AFS, CAS, CTS, and TS. As a result of this information, the ECU will look-up the correct injector pulse duration right across the engine rpm, load and temperature range. The injectors are arranged in two banks with injectors 1 and 3 (4 cylinder) or 1, 3 and 5 (6 cylinder comprising one bank, and injectors 2 and 4 (4 cylinder) or 2, 4 and 6 (6 cylinder) making up the other bank. Each bank is connected to the ECU via an independent ECU pin. The Motronic 1.1 & 1.3 multi-point injection system pulses the injectors semi-sequentially and once every two engine revolutions. During engine start-up below 600 rpm the ECU pulses all injectors simultaneously. Once 600 rpm has been attained and if the ECU has received a signal from the CID sensor, each injector bank will be pulsed alternatively according to which pair of cylinders are approaching TDC. If a signal is not received from the CID sensor the injectors will remain on simultaneous operation. However, if the CID sensor subsequently sends a signal to the ECU after the engine has commenced running, the ECU will pulse the injectors semi-sequentially after the next deceleration phase - even if the CID sensor then ceases to send a
signal.
During start-up from cold, injector pulse duration is increased to provide a richer air/fuel mixture and pulse frequency is also increased. In addition, the ignition timing is also retarded. Injector frequency & pulse duration and degree of timing retard depend upon the engine temperature both during start-up and immediately afterwards. If the engine is restarted within one minute of the first start occurance, less overall fuel is injected to reduce the risk of fuel flooding into the engine.

Fuel injectors
The fuel injector is a magnetically operated solenoid valve that is actuated by the ECU. Voltage to the injectors is applied from the main relay and the earth path is completed by the ECU for a period of time (called pulse duration) of between 1.5 and 10 milliseconds. The pulse duration is very much dependant upon engine temperature, load, speed and operating conditions. When the magnetic solenoid closes, a back EMF voltage of up to 60 volts is initiated. The fuel injectors are mounted in the inlet stubs to the engine inlet valves so that a finely atomised fuel spray is directed onto the back of each valve. Since the injectors are pulsed in two banks, fuel will briefly rest upon the back of a valve before being drawn into a cylinder.
https://www.bimmerforums.com/forum/s...ic-1-1-1-3-BMW

[jmile46]

Well, I wish i tested before creating a thread. So I noticed that somehow this car had its gas tank dented in its life. Who knows how, but it kind of slipped my mind when doing fuel pump that it sits cockeyed. Car was at a quarter tank and I guess I now know that anything lower than a quarter is too low. I filled it with gas and started right away.
Im sorry for wasting time, especially yours Shogun, that was fantastic information.