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Discussion Starter #1
All,

I wanted to pass along a scary (but very real) story and a lesson learned about the Bosch fuel injection.

On the Bosch cars, the fuel hose between the fuel rail and the injectors is 7.5mm ID. The hoses do not use clamps, but rather, are held in place by ferrules that accept the end of the hose (No. 3 in the drawing below).

I recently replaced these hoses with new 7.5 mm hose purchased from one of our good Alfa vendors. I installed the hoses with the ferrules as I had done on multiple occasions previously.

Last night while driving on the freeway, I began to smell gas, and my gas gauge started to drop noticeably. I exited and pulled over. Gas was pouring out from under the car. I immediately shut off the engine. Somehow, miraculously, the car did not catch fire. I had it towed to my home.

On examination, two of the injector hoses had come loose, so I searched for the reason why. As it turns out, the hose that the vendor supplied had an outside diameter that was too large to allow it to seat completely inside the ferrule. I didn't notice this when I was doing the work.

I compared the diameters of the original hose to that I had just purchased and found that the original was slightly less than 13.5mm, while the new hose had an OD of 14.5mm. This difference is huge in that the diameter of the ferrule at the base (i.e. where the hose needs to go to seat properly) is only 14.1mm. Thus, there is no way for the new hose to completely seat. (It will go into the ferrule a little bit, but not enough to hold it in place).

I called the vendor to tell them about the issue. While they said they hadn't heard any complaints, the representative measured the outside diameter of the hose in the Bosch-supplied repair kits, and the OD was just over 13mm.

I should have been more observant when I assembled the injector hoses, and I was very lucky. I bring the story to your attention as a reminder to be careful even when using parts that are represented to be the correct ones for a particular application.
 

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Here we go again... lack of attention to quality and tolerances for aftermarket parts. This is what I was complaining about recently on the Vendor forum section.

Many people have the impression that rubber is forgiving, that tolerances aren't that critical. That's just false. Thousandths of an inch can make a difference in a seal, or correct fit of a hose, as Sloboy points out here. Morton Thiokol turned down Parker Seal's technical advice in 1985 regarding seal gland design for their rocket motor casing o-rings, and one of those motors exploded due to leakage past the rings, killing the Challenger crew. Tolerances matter.

I'm just glad your car didn't ignite!
 

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BMW 7.5 hose works perfect. Just like the original hose.
 

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Ditto what Jim G said... I ordered the supposedly correct replacement hoses kit from the well-known supplier and they were all at least a quarter inch too short; wouldn't even come close to reaching from the rail to the injectors. I ordered a length of the BMW 7.5 hose, cut it to the same length as the originals, and no problems.

David
 

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The same thing happened to a friend and I when we replaced his head gasket last year and decided to address all the old bits that were affected with the heads removal and reinstall. I noticed we couldn't get the hose to fully seat in the caps, and checked the OD in comparison to a small piece I had left over and sure enough the hose he recently bought from a reputable Alfa parts supplier was considerably larger in OD. We first debated attempting to chamfer the ends of the hose, but instead were fortunate enough to source other proper OD hose from other Alfisti in the area.

I don't recall if we let the supplier know, and certainly didn't post a thread and probably should've. Thanks for posting!

I too have considered using the FI clamps for added security.
 

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Discussion Starter #10
To close this thread out, I received the fuel-injection hose clamps I ordered and got them installed. Everything is back to normal now. Definitely preferring safety to originality at this point.
 

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Ditto what Jim G said... I ordered the supposedly correct replacement hoses kit from the well-known supplier and they were all at least a quarter inch too short; wouldn't even come close to reaching from the rail to the injectors. I ordered a length of the BMW 7.5 hose, cut it to the same length as the originals, and no problems.

David
The Bosch kits being sold are for the V-6's.
 
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