[DefactoM6]

So I've been wondering, and maybe this is ignorant logic, but hear me out...

So the latest software "fix" from BMW to try and put the HPFP thing to rest focuses heavily on fuel delivery from the low pressure part of the system. Namely, the newest software turns the LPFP on for about 3 seconds when the ECU wakes up and the car hasn't been started recently. Although I personally think that this fix is bogus (got my first long crank literally the first time I cold started the car after I left the dealer for the 15k oil change and new software), both BMW and independent sources seem to suspect the LPFP, low press. sensor, or something else electrical in the fuel system are causing these failures. Given that the HPFP failures seem to plague certain cars, even with different HPFP revisions while other cars remain unaffected, an electrical issue, or some other flaw in the system would certainly seem to be a more likely culprit.

Given that BMW seems to think that priming the fuel system will help matters, what do we think the effects of a higher-flow LPFP would have? I would imagine that a LPFP that delivers more flow/higher pressure would make for less work from the HPFP, would eliminate any theories about lack of lubrication due to fuel starvation, etc. Not to mention that the extra pressure might even be able to yield a bit more pressure/volume on the high pressure side of the system, meaning that there's a little bit more headroom in there for cars running nitrous, upgraded turbos, etc. Please weigh in...


Side note...anyone notice how many different LPFP controllers BMW has released? I wonder why...and wonder if there is more to this...http://www.realoem.com/bmw/showparts...98&hg=16&fg=15

[hun77777]

interesting...

[vasillalov]

I am intrigued as well!

I have to tell you that if the HPFP failures are result of a faulty BOSCH electronic component, I will not be surprised a single bit!

BOSCH manufactures THE WORST electronic components. Their designs are good on CAD, but the manufacturing portion is worse than anything I've seen.

Example: Those idiots had 6 or 7 revisions of the ignition coils for the 1.8T VW engine and they still can't get it right. I know of several people who would drive around with spare ignition coils in their trunk. VW door lock problems -> crappy BOSCH micros witches. Faulty MAF sensors across the entire VW/AUDI line of engines -> made by BOSCH.

[themyst]

Based on the fact I don't see 10 "My HPFP is dead!" threads any longer, the new software and redesigned 943/933 pumps are doing their job for the most part.

FYI, I am on my 2nd pump (881), still old 31.2 software run the tank bone dry all the time, run 10% ethanol fuel, and my HPFP hasn't failed and it's been over 20k miles since the first replacement. *knock on wood of course*

[FlyingHorse]

I was hoping AMS finishing up the HPFP project,...

anyway i guess we have to wait for M1's one now.

[DefactoM6]

Originally Posted by vasillalov

I am intrigued as well!

I have to tell you that if the HPFP failures are result of a faulty BOSCH electronic component, I will not be surprised a single bit!

BOSCH manufactures THE WORST electronic components. Their designs are good on CAD, but the manufacturing portion is worse than anything I've seen.

Example: Those idiots had 6 or 7 revisions of the ignition coils for the 1.8T VW engine and they still can't get it right. I know of several people who would drive around with spare ignition coils in their trunk. VW door lock problems -> crappy BOSCH micros witches. Faulty MAF sensors across the entire VW/AUDI line of engines -> made by BOSCH.

Yeah...the E46 M3 coils were also complete shit. Thanks Bosch for that one too. I will say this though...I love the 044 pumps in the various projects I've had in the past. After having numerous walbros go, the 044s always held up.

Originally Posted by TrackRat

The LPFP flows more fuel than the engine can consume so increasing the pump capacity doesn't fix anything. The reason the LPFP is cycled longer on start-up with the new software is to compensate for a drop in the system fuel pressure when the engine is shut-off -- due to a failing HPFP that does not hold the system pressure with the engine shut-off.

If the HPFP is not failing it will hold the proper system fuel pressure for start-up even when the engine is shut-off. Cycling the LPFP longer builds the system pressure on start-up quicker after the HPFP has failed to hold the proper fuel system pressure when the engine is shut-off. It's a bandaid. A higher volume LPFP won't improve anything as excess fuel is just bypassed. IMO BMW needs to identify the root cause of the HPFP failures and correct the problem.

If the HPFP is failing to hold system pressure, what side is it failing on? High pressure or low pressure? Where is it dumping the pressure? And then why do we have the issues of people going into limp mode on the highway, restart the car and it's okay? If we have a mechanical failure, a restart shouldn't be able to make the problem temporarily go away. And in those cases, it's an issue of system pressure being inadequate, not just cause the HPFP is leaking around it. And just because the fuel pump isn't 0'd out on pressure doesn't mean that it flows more than the engine can take. And again, given that there are cars which have had 3,4+ HPFPs of different P/Ns, where each successive HPFP fails more quickly than the previous, versus other cars with the better part of 100k on the original HPFP, it still seems like there has to be an electrical culprit here.

Do you know exactly how much the stock LPFP flows?

Perhaps the some of the LPFP controllers suck at delivering the proper PWM to the pump, so they don't deliver the proper pressure at the right time, causing undue wear on the HPFP because they are starving for fuel. Therefore, even though the absolute flow of the pump might be enough for the motor, it is still too low when it is needed. And an upgraded pump might help solve that, even though it is kinda like solving the problem with a sledgehammer when a scalpel is prescribed. Or maybe something like a boost-a-pump in line with the signal to just keep the pump operating at a higher level in general. Either way, it would still be fixing the problem.

I just had to take my grandmother back home, and after loading her into the car, sitting down, getting a big, fat, ugly long crank and having her immediately say, "so what's wrong with your car?"...man, this is embarassing. And the knowledge that after getting another one that I will probably have yet another one go is really annoying. I still love the car enough that I will keep it, but man, this is definitely a drag.

[PKumarM3]

is there an hpfp problem in europe? or is it only in the states?

if only in the states, i think our emissions and gas is to be blamed - not bmw.

[DefactoM6]

They have them in Europe and Asia as well. People were suspecting ethanol for a while, but that one seems to have been debunked.

[Alpina_B3_Lux]

Originally Posted by PKumarM3

is there an hpfp problem in europe? or is it only in the states?

if only in the states, i think our emissions and gas is to be blamed - not bmw.

There are also quite a number of HPFP problems in Europe, too. They're not as numerous as in the US, but they definitely exist, and with a particular emphasis on the 135i/335i.

So even if part of it may be a lesser fuel quality, this can only be a part of the equation.

FWIW, I had to change my HPFP earlier this year, and I've always driven the best fuel available in Germany and Luxembourg.

Alpina_B3_Lux

[David1]

The low pressure fuel pump is an on demand pump and does not run all the time. The software runs the in tank pump more than before so changing the LPFP won't help.

[DefactoM6]

Originally Posted by David1

The low pressure fuel pump is an on demand pump and does not run all the time. The software runs the in tank pump more than before so changing the LPFP won't help.

Hmm...on RealOEM, I didn't see a 3rd pump. All I saw was the aforementioned in-tank, and I assumed that's what the LPFP was that everyone referred to, and is what I was talking about when wondering about the benefits of upgrading it. If there is a 3rd pump that is missed in diagrams, I agree that upgrading an on-demand pump is probably less than beneficial. So for all intents and purposes, let's say that the LPFP that I have been referring to is the in-tank pump.

[David1]

Originally Posted by DefactoM6

Hmm...on RealOEM, I didn't see a 3rd pump. All I saw was the aforementioned in-tank, and I assumed that's what the LPFP was that everyone referred to, and is what I was talking about when wondering about the benefits of upgrading it. If there is a 3rd pump that is missed in diagrams, I agree that upgrading an on-demand pump is probably less than beneficial. So for all intents and purposes, let's say that the LPFP that I have been referring to is the in-tank pump.

Correct, the LPFP is in the tank. One side is the pump and the other side is a regulator. There is only 1 LPFP.

[DefactoM6]

So you're saying that the in-tank pump is only working some of the time? If that's the case, then I think that there really might be something here. And I'm assuming the regulator functions differently than a FPR does in a normal EFI system. If the in tank pump/regulator aren't being properly or adequately triggered, the HPFP is basically starving for fuel, and is effectively having more stress put on it because of the vacuum.

I am still curious about the many different PNs that BMW had for the fuel pump controllers. According to RealOEM, my car could have one of four different controllers...ones ending in 339, 173, 028, and 046. FWIW, they relist the 173 and 028 controller for after 03/09, and the 046 controller for after 03/10 (N55 or N54is presumably). So one might draw the conclusion that there might have been something wrong or less desirable about the 339 controllers. IDK how easy it is to locate the controllers on these cars, but I would be curious to know who has what controller...if there is a link between HPFP failure and these controllers. Again, the fact that BMW has gone through more revisions of fuel pump controllers than they have for HPFPs seems to indicate something here...

[vasillalov]

...very interesting. The logic is sound. A crappy in-tank fuel pump controller could definitely cause fuel starvation. What I suspect is happening is that the in-tank pump controller is malfunctioning intermittently. This would explain why it is very hard for dealerships to diagnose the problem and see what's failing.

When my HPFP went out, the dealership went through a complete set of tests on the low pressure side of the fuel system. The work order states that they tested the fuel pressure sensor on the low side and they also tested the flow from the in-tank fuel pump. Both of these tests were within specs and they proceeded to replace my HPFP.

My guess, and it is just a guess, is that the in-tank pump produced "in-spec" results at that time but on the road, for whatever reason, it might malfunction and starve the HPFP...

[David1]

That is one of the issues addressed in the software update.

[exquisit]

so since it has been a few years since this was posted, has there been any updates as to whether upgrading the lpfp to say a walbro 460 help prolong the life of a hpfp?

[Chris@BoostConcepts]

Well, It certainly can't hurt to have a more stable fuel supply pressure to the HPFP as has been proven with E85 concentrations. But unless you are seeing an issue with pressure drop with the fuel you are using, there is really not much point in upgrading as the additional flow capabilities of the walbro would be overkill. Now if you are seeing pressure drop then by all means you should replace the pump with either a new stock unit if it previously met your demands or an upgraded Walbro unit if you have plans to further modify output of the car or use a more volume dependent fuel type such as ethanol.

Chris