BMW 320d E46: Won't Start After Head Gasket Replacement

I replaced the head gasket on a 320d M47 model from 1999 with 306,000 km. When I removed the oil return lines, there was some gurgling. The fuel injection pump was probably running dry. I then closed the oil return line.

Today, I reassembled it. In the process, I adjusted the ignition, and on the fuel line that wasn't yet connected, diesel leaked out after a short time. So, the ESP must have been completely full of diesel. When I tried to start it, it didn't fire up. I opened the fuel injection lines again until diesel started spraying out, then tightened them, but the engine still wouldn't start. Then, I disconnected the hose from the intake manifold, sprayed in some brake cleaner, and tried to start it. As long as I give it brake cleaner, the engine runs (although not as rough as with starting fluid). So, I hitched a tractor to it and had it towed through half the town, but the engine still wouldn't start. Then, I removed the intake manifold again, unscrewed one injector, bent the fuel line so I could screw the injector back in. I tried to start it again, but no diesel was spraying out of the injector. If I loosen the coupling nut, the diesel comes out, apparently with too little pressure.
What do you think about this? The engine started normally before the fuel injector replacement, but after the replacement, the fuel injection pump is defective!


The needle lift sensor is stored in the error memory, but as far as I know, it only limits the fuel injection amount. Of course, I didn't read the error memory before the repair. However, I had to remove the injectors using a hammer impact tool.


"Someone else experienced a similar problem with another E46 with the same engine. The engine started normally, was driven out of the garage, then stalled and wouldn't restart, with a mileage of 80,000 km. A new fuel pump was installed, and the engine immediately started."

Could the pump be internally blocked, or is the pump control unit faulty?

"Is there anything else I can check before I install the replacement fuel pump? I'm going to connect the oscilloscope to the injector control valve to measure the injection quantity/timing. What should the waveform look like?"

When I connect the tester and start it, the bar indicating the fuel injection amount increases.

chli1976 wrote:

I sprayed it with brake cleaner and started it... ...The pipe was bent so that I could screw on the injector nozzle.

It's not meant to be rude, but I'm not surprised the car isn't working anymore, given these kinds of "measures."

If I'm not mistaken, that's a VP44 injection pump, right? It definitely doesn't like being bled by "priming" it repeatedly. If there's nothing else stored in the memory except for the NHG (presumably an error code), you can assume the pump is faulty. With over 300,000 kilometers (or miles) and actions like that, it's more or less normal.

Yes, you are right, it is a VP 44.

So, I tried using brake cleaner and the fuel line after it wouldn't start with the normal starting procedure.

In your opinion, how should I have checked whether the problem was caused by a fuel injector issue or by incorrect valve timing? When I spray brake cleaner into the injectors, I barely notice any difference in the engine's sound.

What exactly do you think I broke by implementing those measures you're questioning? If you can explain it to me, then I can accept your statement.

I didn't bleed them by "burping" the system, but instead turned the ignition on until fuel started leaking out near the oil return lines. I already mentioned that above.

chli1976 wrote:

but the ignition was turned on all the way until fuel started leaking out of the oil drain pipes.

How can diesel fuel leak out of the oil lines when the engine is not running?

I don't know how familiar you are with BMWs. But this one has a pre-lift pump that runs for 60 seconds when the ignition is turned on.

chli1976 wrote:

I don't know how familiar you are with BMWs. But this one has a pre-lift pump, which runs for 60 seconds when the ignition is turned on.

Okay, even if that's the case, nothing is leaking from the oil return lines. Please consider what function these lines have.

Then I expressed myself poorly, or you misunderstood me. The oil return line that runs from the injectors to the ESP return line is connected to the ESP, but not to the injectors. And that's where the diesel came from.

But that doesn't help me solve my problem!!

chli1976 wrote:

But that doesn't help me solve my problem!!

However, that's actually the key point. You haven't bled the pump. While I don't have extensive knowledge of BMW diesel engines, I do know about the VP44. And the principle behind the VP44 is almost the same for every manufacturer. What I'm about to list applies to brands like VW/Audi, Opel, etc. I'm not 100% sure if it's the same for BMW, but I'm quite certain because, as I said, the principle is the same.

1. The VP44 does not require a pre-injection pump; it is self-priming, like the VP37.
2. However, it always has one. But this isn't actually a pre-lift pump; it mainly has a protective function. It simply fills an auxiliary tank, which has a sensor. The engine can only be started when the sensor indicates that there is enough diesel in the tank.
3. The VP44 fuel injection pump doesn't like to spin without diesel fuel. That's why point 2 is important to prevent that from happening.

I hope this helps you understand the VP44 better. But as I said, I don't know for sure if it applies to your BMW.

And you've already answered why diesel fuel can't come out of the oil drain lines when the engine isn't running. It's because the line connects to the return system.

So, once again.

When the pre-lift pump is running, it pushes fuel through the filter into the common rail system (ESP). If the return line on the ESP is open (as it is in my case because the oil leak line is not yet connected), then fuel will flow through this line while the ignition is on (but the engine is off), as long as the pre-lift pump is running and the ESP is filling. Therefore, the pump cannot be faulty. I hope you understand now. In fact, diesel fuel has even leaked out of the pressure connections on the injector lines that are not yet connected.
I recently replaced the ESP (Electronic Stability Program) on an Audi A6 Quattro. This model also has a pre-lift pump in the tank that pushes the diesel up to the ESP. I followed the same procedure there, and it worked.
The A6 without Quattro also has a pre-lift pump in the tank, but this only fills the swirl pot in the tank and does not push the diesel to the ESP.

However, this remains the same problem. Even if the pre-pump is powered by the inverter, there may still be air bubbles in the pump, and even tiny amounts of air can prevent the required pressure from being generated.

Unfortunately, your description sounds like the problem. I'm afraid I have to agree with the previous commenter that the risk of damage after using the brake cleaner and tractor method is not insignificant.

We always write here that with a diesel engine, if everything is properly bled (and completely bled), it should start immediately after a repair; otherwise, something is still wrong. Never resort to brute force methods when dealing with it.

Perhaps you accidentally kinked a connecting hose during the installation, and now the pump is drawing air at that point.

"If anyone has a repair manual for an A6 AKE, model year 2005, with a V6 engine and VP44 fuel injection pump, please note that the procedure for bleeding the fuel system describes short-circuiting the pre-lift pump until fuel flows out of the leak-off line."

And how is the ESP supposed to take damage if it's full of diesel and I'm starting the engine with starting fluid/brake cleaner?

If everything had been okay, the car would probably be running smoothly right now, wouldn't it?

It's certainly not okay, and it's probably due to the ESP, but I couldn't have damaged it by starting the engine with the starter fluid. If the ESP wasn't properly bled, I can imagine that it could have been damaged by that. But there's nothing more I can do than fill the ESP with diesel.

Right now, I'm trying to figure out if there's anything else I can check to be absolutely sure it's the ESP (Electronic Stability Program) that's the problem. It's not easy and it's a lot of work to replace it. I replaced a similar unit in a car about a year ago, with the same problem, but that one just died on its own and wouldn't start, and it had 80,000 km on it, not 300,000 km. In that case, I also used a starter fluid to see if the engine was even running, to help narrow down the problem.

I don't know how you figure out whether it's the pump itself or if something else is the problem. Of course, I don't just have a pump lying around.

The bleeding process was almost perfect, as the BMW obviously has a real pre-lift pump.
I would prefer to have the hose disconnected and then play the organ.

Otherwise, it's likely the engine control unit (ECU). If there's software available for BMW, similar to VAG-Com, you can use it to check if the ECU is communicating with the fuel pump. If not, you'll need to take it to an authorized BMW service center.

I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.
In Lanz's latest post, it states that there is no actual pre-lift pump in the BMW.

christians wrote:

Otherwise, it will be the control unit. If there's software like VAG-Com available for BMW, you can use it to check if the engine control unit is communicating with the pump; if not, you'll need to take it to an authorized service center.

I have the diagnostic software, and besides the needle injector, there are no other errors present. And with this error, only the injection amount is reduced to 25 mg/H.