L-jet fuel rail / injector rebuild questions

Post your E12 technical questions and comments here. Please, no off-topic posts.

Moderators: Mike W., Pierre

Post Reply
Posts: 12
Joined: Thu Mar 28, 2019 1:46 pm
Location: Seattle, WA

L-jet fuel rail / injector rebuild questions

Post by Sharky1980 » Thu Apr 23, 2020 11:13 am

Hi folks, I'm not on the forum often, but always find it valuable when I am, and enjoying hearing about others' e12s. I'm currently in process on a top end rebuild of my 1980 528i. A blown head gasket lead me to replace the original head with one rebuilt from a 635CSi [later model casting]. Of course while I'm in there, I'm cleaning and repairing as much as possible. I'm currently at the fuel rail / fuel injector level and have a couple questions for the group.

1) Injector cleaning:
I see a lot of recommendations for Witchhunter, which would be a great option, as they're local to me; but they are not currently accepting new work. Looking for a DYI option I found this from another forum:

https://forums.hybridz.org/topic/116174 ... ctors-diy/

Has anyone done anything like this? My injectors are not stuck, but I'm thinking that running through a few cycles of Berryman's FI cleaner would make sure they are relatively gunk-free inside.

2) Fuel rail re-assembly:
I'll be replacing the short fuel lines from rail to injector. My question is: hose clamps? or no hose clamps? I've read in a few places that hose clamps are not needed if you have the barbed fittings, and that clamps might even lead to more likelihood of leaks (?!) But that just doesn't make much sense to me. I'm also not clear on what the little steel cups at each end of the hose are supposed to do .

- 1980 528i
- 1983 944

Posts: 261
Joined: Sun Jan 18, 2015 1:22 pm
Location: Baltimore, Md.

Re: L-jet fuel rail / injector rebuild questions

Post by PatinaBeforePolish » Thu Apr 23, 2020 1:50 pm

I've used Mr. Injector several times and am always pleased with the results. He charges $17.50 per injector which includes new fuel hose with stainless clamps and a before and after flow chart. You'll be surprised at the improvement. The hoses are cut long so they can be trimmed to fit. Make sure you measure the hoses before you fully slide them onto the injector rail because when they're on, they're really on. Use the clamps. The steel cup is just a crimp fitting and will be tossed out with the old hoses. New OEM injector rails are still available, pricey but could be cheap insurance if yours is heavily corroded. I've heard ultrasonic cleaning works well if your manifold log and intake runners have built up gunk but I've never tried it.
78 F150
79 528i
81 528i parts car
01 540i
86 944
08 X3 don’t judge me it’s there to preserve the others

User avatar
Posts: 300
Joined: Wed Feb 07, 2018 5:50 am
Location: Boston North Shore, MA

Re: L-jet fuel rail / injector rebuild questions

Post by 528i-1981 » Thu Apr 23, 2020 9:02 pm

I just replaced my injectors and short hoses and used clamps on both ends (injector and rail). If you use the right size clamps, high quality fuel hose and tighten them correctly they will not make the hoses more likely to leak. The last thing you want is high pressure fuel spraying directly onto your engine. You'll probably save yourself some time by cutting those crimp fittings to help slice the hose to the end to get it off the fuel rail. Be careful not to score the rail hose fittings. If your fuel rail is a little rusty, use the Keenh laundry soda electrolysis bath. I used a silver urethane primer (MasterSeriesCT) on the rail and it looks like new. If it's corroded, then as Jon said, replacement is a good idea. Jon is also right about those barbs, boy. You really can't wrestle the hose off the rail once you slide it on.

While you're in there, you might also want to check the coolant return pipe that lives by the intake plenum. Mine was OK but others have reported theirs corroded under the hoses.
(oo=00=oo) Eric
1981 528i Manual

Post Reply