e12 Fuel Rail Setup

[Max]

My e12 is a 1975 530i, and over the next few months I was planning to overhaul the coolant system along with the fuel lines. Just curious about the fuel rail setup. The early E12 'fuel rail' is more of a collection of hoses and fittings than anything else, and I was wondering is anyone has ever upgraded to the later M535 rail, which is a much more elegant design. I'd even be curious if the E28 setup would work.

Likewise, is there any need to replace injectors after 40 years of use. Just curious if there are any plug and play replacement options that offer better spray.

Cheers

[labimmer]

I have a set with injectors and all 1975 530i

Sent from my iPhone 5

On Mar 9, 2015, at 8:49 PM, Max <mnobbsthiessen@gmail.com (mnobbsthiessen@gmail.com)> wrote:

My e12 is a 1975 530i, and over the next few months I was planning to overhaul the coolant system along with the fuel lines. Just curious about the fuel rail setup. The early E12 'fuel rail' is more of a collection of hoses and fittings than anything else, and I was wondering is anyone has ever upgraded to the later M535 rail, which is a much more elegant design. I'd even be curious if the E28 setup would work.

Likewise, is there any need to replace injectors after 40 years of use. Just curious if there are any plug and play replacement options that offer better spray.

Cheers

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[Mike W.]

You would of course need a 528i fuel pressure regulator if you went that route, it seems to use the same fuel rail as M535i's. You could probably use E28, 533i fuel rail, injectors and FPR, the number appear to be close, but you would have to fab mounting brackets. 530i/528i injectors are very, very close in specs, both will sometimes leak externally as they get old and can get leaky internally but that's more driving conditions than age.

If you want to change I'd use 528i parts. I have a couple of rails, I'm not sure about regulators and no injectors. But 530/528 are almost identical.

[CabbageFumes]

Later 528i rail worked for me and I like it much better. The things you also have to change are the fuel hoses from the chassis, because the return is on the forward end of the rail instead of the middle, and the feed is near the firewall instead of the forward end. Whatever you use, it needs to be a barb style rail. e28 rails won't work. They use a perpendicular o-ring mounted injector. Not only is the injector seat in the manifold not meant for o-rings, the Jetronic intake manifolds used in the US e12s have the injectors entering at about 8 degrees from perpendicular. You can't have it straight on one side of the injector and angled on the other without substantial fabrication.
*528i injectors flow about 1-2# more than the 530i injectors, so actually they are a bit of an upgrade for performance, but not for gas mileage.

[Max]

That's really interesting - thanks for the reply. What is the best route to tuning up the injectors, or ensuring they are still within allowable spec? Just send them out to get cleaned and then find out if any/all need to be replaced?

I was surprised to see how expensive they are - I haven't checked the 538 part number, but i called up the 530i injectors part # on a variety of differnt parts websites and they all came back were somewhere around $150 each.