Can the HPFP cause fuel to leak into my oil? Have fuel in oil issues... Any help/advice would be much appreciated!

Bmurata90

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Nov 28, 2019
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This is a repost to the "correct" forums section.

I've replaced coils, plugs, and index 12 injectors. How can I narrow this down? I'm tired of changing my oil ever 1000k miles or even less because of this to try and prevent damage to my internals. The motor only has 37k miles on it. When I bought it, the injectors were leaking and I replaced them immediately. Solved all misfire codes, but oil still smells of fuel. I make sure to not take as many short trips as possible, I let the engine run for 5-10 mins before driving it, and I also WOT from time to time to heat up and dissipate the fuel from the oil. I have no idea what to do from here. Can the fuel pressure regulator cause this too? I could really use some help. Also, can black oil after an oil change smell like fuel from carbon deposits and I'm just overthinking this? I'm not trying to blow this engine up because of stupid fuel in oil.
Thanks for your time,
Brandon

A person named "ShocknAwe" replied: Are you running super rich for some reason? Or maybe a bad burble tune?

My reply: I'm definitely running rich and I'm not sure why. I'm FBO with MHD stage 2+. No corn. Is it possible that the O2 sensors were damaged during DP install? I did most of the installs myself, but had them do the catless downpipes. This is a really good shop apparently and knowledgeable. I've dealt with them ever since I got the car 5 years ago. I didn't go to MHD stage 2+ until I got everything I needed to ensure no failure points besides this. I honestly thought replacing the injectors would solve the issue. Who knows how long those injectors were leaking before I bought the car and how many times fuel slipped by the piston rings. I'm really hoping that my piston rings aren't toast. Can a faulty HPFP cause this? It's an 09 Z4 so I wouldn't be surprised that the HPFP isn't doing well. I tried to get it recalled but stupid stealership wouldn't replace it as they saw no issues with it during testing. Drove my car for 500 miles and cost me $200 to have them not recall a known failure point. Never again. Also, when I bought the car I noticed that the exhaust tips were black as hell with less than 20k miles on the car. Again, thought it was the injectors since it solved the misfires. I also brought this up to the shop and they said "they took a lighter to the fuel cap and nothing happened". They also claimed to smell no fuel in my oil when I clearly can smell it every time I change it. Just in case I was tripping, I asked numerous people what my oil smelled like. Immediate response was "fuel". I'm in the process of yet another oil change with a blackstone report to see exactly how much fuel is in my oil. Also, my car has never burned oil. Ever. Which concerns me as I feel like it's being replaced with fuel. From what I've read, an MHD Stage 2+ tune automatically turns off the CEL for the O2 sensors. I have 2 O2 sensor faults right after I clear the codes. Also, I did a cold start and revved up my engine to 1.5k RPM and the RPM was bouncing about 300 to 400 RPM per second for a couple minutes. Did I get a faulty set of index 12s from FCP? Car idles and starts up just fine though. A few days ago there was one time I started up my car while swapping tires and the ignition was jumpy, sluggish, or whatever you wanna call it. There was only 1 time that the CEL didn't come on for about an hour after clearing them.

Also, I have had burble issues, so I switched back to stock burbles and this was an issue prior to MHD.

I'm no expert on this matter and could really use some advice. I need to figure this out to move forward on my build.

Again, I appreciate your time to read this and I look forward to a reply/solution,
Brandon
 

swellengear

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Sep 3, 2023
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Highly unlikely that the hpfp is leaking fuel into the oil system. The hpfp is a sealed unit, with no oil feed. On some hpfps, when the bellows fail, they leak fuel into the hpfp, but if this were the case, you would have mega fuel pressure issues, but no fuel in your engine oil.

If you do have fuel in your oil, my guess would be a leaky injector. A basic test you could try, is to take the car for a bit of a drive, let it sit overnight, and then pull your sparkplugs. If you find a visibly wet plug, that stinks of fuel, you've found your dodgy injector.
 
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Bmurata90

Specialist
Nov 28, 2019
58
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2010 BMW Z4 35i
Highly unlikely that the hpfp is leaking fuel into the oil system. The hpfp is a sealed unit, with no oil feed. On some hpfps, when the bellows fail, they leak fuel into the hpfp, but if this were the case, you would have mega fuel pressure issues, but no fuel in your engine oil.

If you do have fuel in your oil, my guess would be a leaky injector. A basic test you could try, is to take the car for a bit of a drive, let it sit overnight, and then pull your sparkplugs. If you find a visibly wet plug, that stinks of fuel, you've found your dodgy injector.
I literally had these replaced brand new from FCP Euro a little over 10k miles ago.. This is a hard one to swallow if this ends up being true, but about to find out. I'll keep you posted. I'm just worried about my piston rings. I can get the injectors for free.
 
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Bmurata90

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Nov 28, 2019
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2010 BMW Z4 35i
Highly unlikely that the hpfp is leaking fuel into the oil system. The hpfp is a sealed unit, with no oil feed. On some hpfps, when the bellows fail, they leak fuel into the hpfp, but if this were the case, you would have mega fuel pressure issues, but no fuel in your engine oil.

If you do have fuel in your oil, my guess would be a leaky injector. A basic test you could try, is to take the car for a bit of a drive, let it sit overnight, and then pull your sparkplugs. If you find a visibly wet plug, that stinks of fuel, you've found your dodgy injector.
All spark plugs are dry. They aren't leaking. What else can cause fuel to be in oil? I know a bad HPFP can because I've watched Vehicular DIY replace his for this exact reason.
 

fmorelli

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All spark plugs are dry. They aren't leaking. What else can cause fuel to be in oil? I know a bad HPFP can because I've watched Vehicular DIY replace his for this exact reason.
I suggest sending your oil out to Blackstone for analysis.
 

swellengear

Lurker
Sep 3, 2023
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Swellendam, South Africa
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'09 BMW 135i
For fuel to get into your oil via the hpfp, you would need at least 2 seals in the pump to fail simultaneously. It would then need to make its way through your vacuum pump, before it could even reach your oil. If this was the case, you would have no high fuel pressure, limp mode, and codes. As mentioned before, the hpfp is a sealed unit, with no direct connection to your engine oil.

images (192).jpeg
 
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Bmurata90

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Nov 28, 2019
58
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2010 BMW Z4 35i
For fuel to get into your oil via the hpfp, you would need at least 2 seals in the pump to fail simultaneously. It would then need to make its way through your vacuum pump, before it could even reach your oil. If this was the case, you would have no high fuel pressure, limp mode, and codes. As mentioned before, the hpfp is a sealed unit, with no direct connection to your engine oil.

View attachment 89778
I really appreciate the in depth reply on this. Looks like I'll be looking elsewhere and wait for my Blackstone report in the mean time.
 
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Bmurata90

Specialist
Nov 28, 2019
58
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2010 BMW Z4 35i
Any updates?
Been out of town for a bit so I haven't sent in my blackstone report yet. Will be doing so in the next few days. I'll keep you posted. Also, a couple weeks ago I started my car and one of the cylinders started shaking via slight misfire for about 1 - 2 seconds, so I guess it could be a bad injector. When I get home I'm going to check my codes via MHD to see if it picked up on that. CEL is always on because I think my O2 sensors are fried. Shouldn't MHD autocode them out from showing on CEL? Not the most knowledgeable on this platform, but I know a decent amount. Still learning.
 

Bmurata90

Specialist
Nov 28, 2019
58
10
0
F.L.
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2010 BMW Z4 35i
I suggest sending your oil out to Blackstone for analysis.

FINALLY got my Blackstone report back. Here it is:

Looks like the fuel is fine, but it's just weird to me that it smells of fuel with only .5% fuel in it. I guess fuel just has a strong smell to it regardless of the amount. Besides that, can you or anyone tell me if anything seems off? Looks like a few things are, but please let me know what you think. I use Liqui Moly. On my last oil change, I used Castrol Edge euro with Ceratec. My next will be Molygen which I've already ordered via FCP Euro for cheap oil changes with great oil.
 

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