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AFPR air leak testing


Well-known member
Jan 11, 2007
Aurora IL
I'm going over each part of my car since it's clearly been wrenched by many hands, some less detailed than others. The AFPR was on the list - I read up and found that air leaks seem common and aren't always obvious. Sure enough I had one - here's the basics

What am I looking for?
AFPR leaks are common at adjustment screw, and may also occur at vacuum nipple. The impact is likely to be lean condition when boosting by not maintaining 1/1 ratio. The other fittings are on the fuel side of diaphragm so aren't a concern for air leaks. I would run this test if you haven't -- the leak may not be obvious or show on a ~20psi boost leak test, mine didn't.

How do I test it?
- turn on the fuel pump (ground test terminal or via ECMlink)
- disconnect the reference vacuum from intake manifold to AFPR. Base fuel pressure should be 37.5psi
- Apply air pressure (a compressor with blowgun, with vacuum line on it works great) to the vacuum nipple. I'd test up to 30-35psi. You should see the fuel pressure gauge rise accordingly. If you hear air escaping, address it now. I usually avoid teflon tape but this is a dry passage, so I used it here - quite a bit on the adjustment screw in fact.

Once air leaks are sorted, recheck your base pressure and adjust if needed. It probably didn't move if your leak was only under additional pressure. Now's a good time to check 1/1 ratio as well - reapply air pressure and check your boost gauge against your fuel gauge to see if the increases match.
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