Author Topic: Fuel leak (Read 12976 times)

Pierre · « **on:** March 07, 2009, 03:19:20 PM »

My E30 M42 developed an intermittent fuel leak from the soild fuel lines going to the fuel rails.
When it leaks, it's significant and it dumps onto the starter.
But then, sometimes it's dry as a bone.
And, of course, it leaks when I want to leave to go to work. Nd it it won't leak when I am trying to fix it.
I have heard that I may have a bad fuel pressure regulator. Is there a way to test a regulator? Can the regulator fail intermittently?

Thank you

ak96ss · « **Reply #1 on:** March 08, 2009, 08:39:35 AM »

There are two short pieces of rubber hose that connect the fuel rail to the fuel lines - they dry rot, and result in exactly the leak you are talking about. They need to be replaced, and while you are at it, consider the fact that ALL the rubber lines are the same age as those two lines.

carlos318is · « **Reply #2 on:** March 09, 2009, 05:15:02 AM »

The same happened on mine and I had to replace the rubber hose its only about 2" long and easy to do your self:o

BlackBMWs · « **Reply #3 on:** June 14, 2009, 01:27:25 AM »

I have a similar situation for my 91 318ic M42 motor. 142k miles. I picked up this car three weeks ago and am just going through various maintenance and renewal items to get it back in solid daily driver shape.

So, I noticed a fuel leak on initial cold start-up. It dosen't appear to be a fuel line leak, but could be. A previous owner seems to have recently replaced the lower rubber fuel line with a SAE rubber line. There dosen't seem to be a leak in that line. I will replace the SAE line with OEM hose moving forward.

I'm wondering if it's a Fuel Pressure Regulator failure or the o-ring for it mentioned two threads above. The interesting clue is that the leak only occurs on first start, I suspect when fuel pressure is building before the motor fires up. When it leaks, there is a steady drip flow, say a drip a second. Turn the motor off, and restart it, no more leak. (BTW, I am very aware the drip is directly on the starter and have an extinguisher ready and let the dripped fuel evaporate before attempting a restart. )

I'll dig in deeper tomorrow, but just researching tonight to see what possibilities might exist for this leak.

I'll look tomorrow for the short hoses mentioned and replace them.

Any troubleshooting feedback would be appreciated. Thanks!

DesktopDave · « **Reply #4 on:** June 14, 2009, 08:57:03 AM »

+1 on AK & carlos...I'd guess that the short rubber lines further under the manifold are leaking. You can't see them with the upper manifold in place. They get a lot of heat, and I'll bet that gas is then flowing along the hose, down to the clamp you're speaking of, then dripping from there onto the starter.

Look for #14, that's your clamp. Those two little #15 lines are the most likely problem.
http://www.realoem.com/bmw/showparts.do?model=AJ93&mospid=47318&btnr=13_0308&hg=13&fg=15

I'm thinking about replacing every bit of rubber under the manifold when I do my hose delete later this year. FPR & injector O-rings, vac lines, fuel hoses, etc.

BlackBMWs · « **Reply #5 on:** June 14, 2009, 10:23:45 AM »

Bingo! I bet you're right too. Thanks! Looks like I'll need to pull the intake manifold. I'll see what replacement gaskets i should pick up the get to the hoses. Thanks!

colin86325 · « **Reply #6 on:** June 14, 2009, 10:04:29 PM »

Get FPR o-rings as well. Sounds like a problem that solves itself with heat, which could mean it's a seal such as an o-ring.

BlackBMWs · « **Reply #7 on:** June 14, 2009, 10:27:35 PM »

O.K. Thanks! I'll be leaving the country for a few weeks, so, I'll need to pick this up when I return. I'll see what other hoses are hosed as well.

Thanks for your feedback!

BlackBMWs · « **Reply #8 on:** July 05, 2009, 05:53:58 PM »

Back in country. Before I left, I ordered every OEM rubber hose for fuel, cooling and vaccum. Most o-rings and gaskets too. Not too costly. I should have them all by next weekend. I'll replace all hoses and o-rings, flush the cooling system and change the fuel filter.

Question: I also have an E39 where the cooling system is problematic due to higher heat and designed cooling system pressure. Are the M42's prone to similar cooling system issues? I also have an E28 and its cooling systems has been reliable over it's 280k miles.

BTW, my M42 has 141k on it. I'll see if there's a manufacture sticker on the Rad to see when if ever, it was last changed.

Thanks! :cool:

BlackBMWs · « **Reply #9 on:** July 27, 2009, 12:56:05 AM »

Here are the two fuel lines that were leaking. The rubber had started to seperate on the hoses.

Replaced with new sections of BMW fuel hose and new proper clamps.

Since I had it apart anyway, I cleaned it up a bit, took care of all hoses, replaced all the cooling components and installed 155 700 Bosch injectors. :cool:

rx82000 · « **Reply #10 on:** September 23, 2009, 08:56:45 PM »

Look at page 13-76 of the repair manual on how to remove the intake. bmw-e30-repair-manual-v7

roundel318 · « **Reply #11 on:** September 24, 2009, 11:36:44 AM »

How did those injectors treat you?

rx82000 · « **Reply #12 on:** September 24, 2009, 01:22:10 PM »

Don't forget to loosen the fuel line bracket (on the other siide of the intake) before you try to remove the leaky fuel lines. I used 5/16 fuel hose that I got at an automotive store.

spanish_pants · « **Reply #13 on:** November 25, 2009, 03:05:29 AM »

I�m already going on the 3rd time this has happened to me. I replaced both rubber lines in july and this morning it�s doing begun leaking again:mad: