Help in chasing a fuel pump/line leak

ablank135

ablank135

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So, this happened:

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While my garage airs out, and before I stick my head up there, any armchair diagnosticians have an opinion on whether a fuel pump itself would leak this badly, or is this just a loose line?

Thanks in advance...
 
That's significant! May help to know if you have mechanical pump and carbs or fuel injection.
 
Thomas76 said:
That's significant! May help to know if you have mechanical pump and carbs or fuel injection.
Click to expand...
Yeah, it's a shower. Mine is injection. M30B34 engine out of a 535i. The restoration is about 10 years old...so the pump and hoses are in that age range. This was after a spirited ~300-mile weekend event, but the problem didn't start until it was parked overnight. I suspect a faulty pump/rings wouldn't implode to leak THAT much at first, so I'm leaning toward a split/loose hose, but I need to get back up under the lift and see. I thought the experts here might recognize the symptom straightaway.

Here are three stills from that same video I linked...moist...damp...and soaked:
 

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Looking deeper at the options here. I suspect the second connection here--the cracked hose, right? I can get a 19-year-old to stand there and make sure with a faceful of gas, but...
 

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I gotta ask, is that image the pump or the filter? Pump on my 635 and therefore I assume 535, is in a rubber sleeve so a bit puncture proof. That looks like my gas filter but I have been wrong before, ask my family.
 
I'm half ignorant here, too, so based on my scouring of other fuel pump posts on the forum, this is an electric pump that has a sump/reservoir attached underneath via a bracket, for gravity reasons, and not the filter. Don's comment from 2017: "It's a reservoir or sump for fuel. Needed on cars without lifting pumps in the tank."


Here's a clearer shot I stole. Judging by where the fuel first appears on the sump canister, which is directly below this pressurized connection, I suspect it's that split in the hose:

P1070936.jpg
 
If the restoration is 10 years old , then I would start to replace all old hoses. 10 years is good enough for them, time to replace them all I would say.
If it doesn't fix the leak, then at least you have prevented (another) one in developing tomorrow.

I give it a 75% chance that you will have solved your leak with it, giving the massive amount of fuel spraying out, and it first appearing on the side that has a hose connection.

If anything would be bad with another part, then I wouldn't expect such a big shower but only light drips.
 
Last edited:
Never use anything but FI hose clamps on high pressure fuel hoses.…
 
Nope. Not the hoses. Replaced them (with the right clamps, thanks Don) and it's the dreaded o-ring inside the pump, with the leak source visible in slo-mo video. Replacements rings now on order, per Luis' helpful thread from years ago:


@Luis A. , you earlier mentioned having trouble aligning the internal parts once you disassembled the pump. If I'm just swapping the seal on the canister, that's a simple task, though?

I feel like I need to source a backup pump though...anyone have the part number for the Bosch FI pump? I looked...I think.

Screen Shot 2022-06-07 at 6.29.17 PM.png
 
For a friend's Tii I couldn't get this pump to work well after replacing o-rings, it's also very sensitive to how tight the screws are into the pieces. Too tight and it siezes, too loose and it leaks. I ended up replacing it with the later Bosch pump that all the 02, e12, e28 et al guys recommend. I didn't feel confident in the rebuild and didn't want to worry about it.
 
Hi Andy, All the details of what I did are on post 11 on the thread you linked. I don't make it clear in that post if the screws have to be removed to uncrimp the can and replace that O-ring; I don't recall if you do. Seems to me that it wouldn't be required.

The screws are what secures the impeller assembly which is what is tricky in realigning to get optimal volume and pressure. I was able to effect that tweaking by setting up a recirculating water loop. If you don't crack open the impeller assembly then it's just a matter of replacing that O-ring and re-crimping the can.
 
Luis A. said:
Hi Andy, All the details of what I did are on post 11 on the thread you linked. I don't make it clear in that post if the screws have to be removed to uncrimp the can and replace that O-ring; I don't recall if you do. Seems to me that it wouldn't be required.

The screws are what secures the impeller assembly which is what is tricky in realigning to get optimal volume and pressure. I was able to effect that tweaking by setting up a recirculating water loop. If you don't crack open the impeller assembly then it's just a matter of replacing that O-ring and re-crimping the can.
Click to expand...

Thanks, Luis! I'll give the uncrimping a shot. If I blow that, I'll get the newer Bosch unit and follow the tii forum instructions.
 
ATL_Alan said:
Hi, do you need any kind of pressure regulator to use this with Webers? I have an electric pump currently but it has gotten very loud and annoying, so I thought I'd swap it out.

Thanks, Alan
Click to expand...
Yes with webers you'll want to regulate it to about 2.5-3lbs psi. Also you want high volume instead of pressure so I use the Carter 4070, quiet and trouble free for several years now.
 
ATL_Alan said:
This one?

Click to expand...
Yes, and I put a dab of epoxy on the wire 12v rubber boots where they slip onto the electric contacts of the pump, they're not very tight and I want to keep them on yet not glued on enough that I can't ever get them off if I need to remove the pump. I also put a layer of rubber in between the mounting bracket and the body to reduce vibration/noise transfer.
 
Swapped the pumps out yesterday and it seems to be working well. Much, much quieter than the old one. My old one had two rubber isolator mounts holding it in place since it was pretty small so I added a third since this pump and bracket is larger. I also attached a pressure regulator.
 
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