FUEL pressure issue 540i

[MD540iT]

Im just starting a new thread on this, since it seems now THIS is the issue.

Can anyone clarify where fuel pressure is held? at the regulator/filter or at the Pump??
With the old filter the car would start immediately when the new (used) pumps were put in, but as my previous thread, the pumps were dying within a few days.

So now I have a NEW pump and NEW filter/regulator (both changed at the same time, and NOW fuel system is not holding pressure.

[Chedley]

….

So now I have a NEW pump and NEW filter/regulator (both changed at the same time, and NOW fuel system is not holding pressure.

Did you install new OEM brand fuel pump and filter ? Did you inspect or replace the fuel lines connected to the filter ??

[Bmwe39528i1998]

Fuel pressure is held between the fuel pump and the fuel rail. Fuel pump has a valve to prevent fuel from draining back to the fuel tank and thus holding the pressure.
How did you determine that there is no pressure after installing the new pump?
What happens if you prime the pump either by jumpering relay or cycling the key to "on" a few times?
Fuel has to go somewhere. If the pump is pumping, there has be to a leak somewhere.
Like Chedley asked, is this a brand new oem pump? Would be very unlikely for it to fail.

[JimLev]

The spec is the fuel system has to hold pressure with a 7PSI drop or less over a 20 min period after you shut the engine off.
Your injectors could be leaking.

[MD540iT]

The Saga continues!
Well... so here what our hero has been up to over the last few days. (think "bat-man" theme)

So to get the car running, with the NEW Pump and NEW filter, I had to jumper the relay and let it run... First for a couple minutes, last couple days had to let it run for 4-5 minutes, (I just left the jumper in there while driving. Killed my battery and needed a jump a few times from cranking too long (while having the relay jumper in).

In an attempt to narrow down the problem I decided to try something (play mission impossible theme now). I guess Im a glutton for punishment. I go to the salvage yard, I get another used pump! (oh no he di'int!!) Yep. But wait, may have lucked out, this car had a new pierburg/Ti automotive (who makes whalboro pumps), so this must be of some quality right?

Well after doing the relay-jump/let it prime for 5 min, then crank, I decided to throw in the Ti automotive pump.
BUT, heres a clue, so im going to take the NEW pump out, takes a few minutes to get to it. I pull off the fuel line on the tank cover, and only get a dribble of fuel.
(Now with ALL the other pumps, the fuel would have pressure and spray when I would pull the line off HMMMMM..)
Now heres another interesting thing, while getting the Ti-auto pump ready; the fuel line after sitting there, empty for about 5-8min all of a sudden started pouring fuel out for a few seconds.

So I put the Ti-auto pump in, had to prime the system for several minutes, then a bit of cranking, killed battery, got a jump, and it started, drove to the auto parts store (didn't shut the car off) picked up ANOTHER Mann fuel filter/regulator, and got home. haven't tried to start it since.

(oh aaaaand I got fired this morning )

- - - Updated - - -

Oh also, so here is why I don't think its leaking injectors (I'm not ruling anything out at this point)
Now, I didn't have this issue at all before with all the used pumps, Original Filter. they all started right up. Why they died is another issue.
The 2 things that changed were the filter and the NEW pump (yes it wasn't an OE pump, got it off amazon, had good reviews, what are the chances I'd get a faulty one?? (with my luck, apparently... If I have to ask....; that's why I got 4 from the salvage yard in the first place!!! LOL!)

[edjack]

I've never changed a -TU filter, but I have read that it's possible to install it backwards. Just sayin'.

[MD540iT]

is this correct?DSC03715.jpg

[MD540iT]

Ahhhhh,
Just went out to try to start it with this new(used) pump...... same thing just cranks.
Damn it, thought the 8th try would be the charm!

[MD540iT]

Well it eventually startted had to put it on the jump starter, after the pump running for 10 minutes, and several cranking tries
Went to my friends house, shut it off for 10sec amd tried again (this time I put the relay in)
Crank.... no start, 3rd try it started.

This may or maynot be interesting : while running with the relay in i pulled the relay (car kept running ) and put the jumper in the rpms rose a few hundred for a few seconds)

[JimLev]

is this correct?DSC03715.jpg

You'll have to figure it out. You didn't mark the 2 lines on the back side so we don't know which one is fuel in and fuel return.

Gas_Filter3.JPG

[MD540iT]

Im pretty sure its right
DIY on this forum States curved line goes to the center which is how I have it set up.
So what would happen if this filter / regulator was bad.
I found out AutoZone does rent fuel pressure tester however at this point it's pretty obvious fuel pressure is not being held after the pump is shutoff it seems to be all dumping back into the tank

[Bmwe39528i1998]

Wow you've been through a lot...
I don't think all 7-8 pumps were bad. They shouldn't be dying in a week.
I can't imagine how you would need to make the fuel pump run 2, 3, 5, 10! minutes to make the car start. It normally takes seconds.
Something else must be wrong.
Did you inspect all your fuel lines thoroughly? Maybe they got bent somehow.
This shouldn't be causing you so much grief.
Get the tool, get your pump running and measure how fast you get to 50-60 PSI at the fuel rail. Then measure how fast the pressure drops.
It will give us clues where to look next.
Also add some fuel to the tank just in case!

[MD540iT]

Oy vey, will try again tomorrow
this vid was informative:

[MD540iT]

W.
T.
F.
??

started the car today, did the usual turn the pump on, let it run for a few minutes, then start. Didn't take much cranking to start it this time.
drive down to autozone, stop the engine and unplug the jumper. Go in, rent the pressure tester, hook it up, turn the pump on, shows about 48psi.
Ok...
Turn off pump...pressure is holding, wait a few minutes, and pressure drops to 45.
Turn on pump... pressure jumps back up immediately. try and start the car, and it starts right up with in a couple turns.
Hmmmm.....
Turn off car, go put the relay in, wait a couple minutes, and monitor the gauge, turn key on, pressure jumps back up, Crank, and it starts!

WHAT? seems to be working. WTF?????
turn off car, go back in return the FP gauge.
come back a few minutes later, try and start (left the relay in)
starts right up.

I don't know whether to laugh or cry.

[mattmar1]

with a quick glance over this thread, i see no mention of the relay having been replaced. did i miss it? had intermittent funky problems with my e39 and a friends e60, in both cases it was the relay.

[Bmwe39528i1998]

Haha glad you got it working buddy!
Now go get your job back, tell them the car is running properly and you'll make it on time.
And yes, changing relays is way easier than replacing 8 pumps.
But if the relay was the problem, it still wouldn't explain running the pump for 5 minutes to build enough pressure to start the car.
You bypasses the relay to make the pump run but it still wouldn't start, that's why I thought it wouldn't be the relay.
If you can, keep the gauge tester handy for a few days in case it acts up again.
So far we don't know what wrong, why it wasn't working and why it started working.

[MD540iT]

yes I got another relay, that was the very first thing I did, when the first pump died.

Im now afraid to go out and start it again.

[Santaclaus4]

Can you just leave it running all the time? Lol...
Ok, not very funny. I loathe intermittent problems like that. Especially if you don't know if it's actually fixed.

[Chedley]

I've never changed a -TU filter, but I have read that it's possible to install it backwards. Just sayin'.

Yes...and it fits..!!

So, it seems that the OP's problems can be traced back to AFTER installing the "new" fuel filter.
I think you either have installed a bad filter -unlikely- or you installed it wrong (mixed lines, or fuel flow directions).
Could you check again the installation of the fuel filter, or even replace it. ? I mean 8 pumps and a couple relays can't all be bad …

[MD540iT]

well, I went to start it today for the first time about 5pm.... First try: No start, of course :-(
second try, it starts!! Ok well that's better than before, engine sounds a little rough, what is that? sounding NOT GOOD, open the hood, and here this:

[JimLev]

That doesn't sound good.
Did you ever check what the fuel pressure was at the rail?

[MD540iT]

Yes, post #14, , that may be irrelevant now.....

[Discosaur]

I know this is a few years ago now, but @MD540iT, wondering if you resolved the issue? I've been through the ringer on my 2001 540iT with this. It's been a couple months of trying this and that, sure that I got it, then a few days later, same thing. Starting takes several tries, or won't start at all.

Here's what I did so far:
fuel pump (no change)
cleaned MAF sensor
spark plugs (not sure why...)
in-line check valve (no change)
swapped fuel pump relay with another known good relay (no change)
Fuel filter and pressure regulator (new, germany. changed because there was fuel in the vacuum line to regulator, but overall issue still present)
I even swapped out a good battery thinking it might have been that.

Been taking pressure readings. around 40 when I turn ignition on with cold engine. 51 when running, 46 when shut engine off. Wait 15 minutes, 40. Wait an hour, 20 psi. stops dropping around 20. NO check engine lights through all of this yet.

I did a top-end job a year ago where I swapped out injectors with a rebuilt set, flow matched, etc. all bosch. they have been fine. But I feel like I have things pretty much narrowed down to injectors, PLUS I have these two noted symptoms now: 1) slightly rough idle. tach doesn't show it, but can hear some very faint irregularity in idle, like a misfire, back near muffler. and 2) whenever I throw the pressure gauge on to check again, I can hit the purge button to dump fuel and I usually get some air bubbles at first, and usually every time I put it on. Is that normal?? I also seem to notice that it might start up easier after I purge some fuel (and the minor air bubbles) through.

I am ready to take it in and have a leak-down or compression test done, or whatever they do to check for injector leaks (how do we diagnose that besides ruling out everything else, anyway?)

Pulling hair out at this point, and wife upset at this roller coaster of "I think I got it this time!" then next day "well, there is still something wrong".

What am I missing?? I've found several e39 threads on this topic, but not often is the resolution posted. Thanks guys..

[843dylan]

Just trying to revive this thread. Having a very similar issue.