[philgli]

Hello all,

I am sure this has been covered a dozen times but searching shows 1000 n54 threads and hardly any n55 threads...

Getting long starts and occasional tumbling idle, especially when its cold. Car is at 70k miles.

Got the battery checked and its strong. Before i drop $400 on HPFP, any chance its starter or alternator?

If its HPFP, any n55 specific DIYs? I see about 7 for n54 but i thought there were a few differences...

[HawkeyeGeoff]

Originally Posted by philgli

Hello all,

I am sure this has been covered a dozen times but searching shows 1000 n54 threads and hardly any n55 threads...

Getting long starts and occasional tumbling idle, especially when its cold. Car is at 70k miles.

Got the battery checked and its strong. Before i drop $400 on HPFP, any chance its starter or alternator?

If its HPFP, any n55 specific DIYs? I see about 7 for n54 but i thought there were a few differences...

Check if you have a code/ghost code for HPFP. That will confirm it....but long cranks generally mean it's kind of getting close to on it's way out. Though the N55 does have updated software that kind of prolongs them from what I've read/seen even with this condition.

[philgli]

ok, best way to look for these types of codes is using something like the MHD built in code reader or something?

[Bob_Loblaw]

I just replaced the HPFP on my N55 335i last weekend. Fairly straightforward. I used this diy for an N54 135i: https://www.e90post.com/forums/showthread.php?t=654820

The pump part of it was basically the same, only differences were disassembly to get to the pump. As with anything under to hood, just take your time, take photos and label connectors as you disassemble.

[MartinWake]

My car when its cold sometimes does take some time to crank up but then after that starts right up

[Pladi]

Originally Posted by philgli

Hello all,

I am sure this has been covered a dozen times but searching shows 1000 n54 threads and hardly any n55 threads...

Getting long starts and occasional tumbling idle, especially when its cold. Car is at 70k miles.

Got the battery checked and its strong. Before i drop $400 on HPFP, any chance its starter or alternator?

If its HPFP, any n55 specific DIYs? I see about 7 for n54 but i thought there were a few differences...

Mine failed close to this period. N55. Very easy DIY.

To make sure its ur HPFP u need to log the rail pressure. Most of us here use mhd logging. U have to pay for it but ita very useful for future troubleshooting. If u dont want to pay that PID paramteter is available for free with apps such as Torque PRO ABD OBD adapter.

Log to make sure but long cranks def the pump. They go bad on n55 too esp when tuning.

When replacing u can reach out to me. Have no time making how to but i can answer any questions.

[philgli]

Thanks for the responses everyone!

Think I should get MHD and just flash map 0, run some logs and post them up? Anything besides rail pressure to look for?

[Zygote55]

Originally Posted by philgli

Hello all,

If its HPFP, any n55 specific DIYs? I see about 7 for n54 but i thought there were a few differences...

Here's the step-by-step guide from newtis.info

https://www.newtis.info/tisv2/a/en/e...nit/1VnYWFl0U5

[philgli]

Originally Posted by Pladi

Mine failed close to this period. N55. Very easy DIY.

To make sure its ur HPFP u need to log the rail pressure. Most of us here use mhd logging. U have to pay for it but ita very useful for future troubleshooting. If u dont want to pay that PID paramteter is available for free with apps such as Torque PRO ABD OBD adapter.

Log to make sure but long cranks def the pump. They go bad on n55 too esp when tuning.

When replacing u can reach out to me. Have no time making how to but i can answer any questions.

Ok i now have MHD with monitoring. Any idea what rail pressure should be at startup and then at WOT? I can shoot you logs if that helps...

[Pladi]

Originally Posted by philgli

Ok i now have MHD with monitoring. Any idea what rail pressure should be at startup and then at WOT? I can shoot you logs if that helps...

Post the logs ill tell u. Hpfp differ in pressures in general but under wot 2000 psi. Average up to 2200. Anything under 1700 probably not ideal.

At idle sometimes when colder over 1000 is common then drops to 700 which is average. Warm idle.

Any dips in a graph is not good. The rail is constant usually at idle. As well as wot. If it dips then not good.