So, three years ago I had to take the top of engine apart to fix a leaking head gasket at #7 cylinder. While I was at it, I did some research on things to fix "as long as I am there".

Among the things I replaced was the fuel pressure regulator diaphragm. Mine was not leaking, but it was cheap enough and the access was never going to get better so I put a new one in. Now since I have had this car, 3 years, there has been a persistent "extended crank" that bothers me. It nearly always does it on the first start of the day, and subsequent starts are normal and nearly instantaneously, as you would expect.

I checked the fuel pressure and key on it would shoot up to around 40 psi, normal, but would bleed down nearly instantly. When running it was fine, and would jump a bit if you gave it the beans. So it would seem the fuel pressure regulator was regulating as expected.

So now I am confused. Why does my fuel pressure bleed down so fast? After all I just put a new regulator in...

The next obvious place to check is the fuel pump and it's check valve. At this point I elected to put a new AC Delco pump in since they are cheap enough and this one had 110,000 miles. Well one new pump later and I still had the fast fuel pressure bleed down and extended crank on the first start of the day. I was crestfallen at this point.

So back into the fuel pump and I removed the fuel damper thingy and replaced it with the straight section of fuel line, included with the new fuel pump. Still no joy, the pressure bled off quickly, just like before.

For those of you still with me, we are getting near the end. Hang in there.

Well I have the top of the engine apart again to fix an oil leak, and decided to have another look at the fuel pressure regulator. This is were the problem was all along.

The seat of the regulator had some weird wear where the sealing flat face was rounded off. This was where the fuel was bleeding down. The small leak was not a problem when the engine was running, as it was in reality only a small leak, comparatively to what the pump output is.

I resurfaced the seat with an old diamond drill bit tooth.I had this lying around for some 20 odd years from when I worked in an ultrasound lab, waiting for the perfect situation to use it. Being that is small I could fit it down in the recess of the regulator body and slowly lap the seat flat. This took some time, about an hour. Very tedious.

I was rewarded with good pressure that held overnight!

From reading many other threads on this subject, I think this is the same problem others have had. See the pics for details.

-Tim in Mass

Regulator seat with damage at 9 to 10:30 position

Close up

"Sharpem" to highlight the lapping progress

Lapping just started. Red are is the low spot.

More lapping, a half hour later. Taking a break for a hand cramp

Nearly done...

Ta Da! Close enough. Good for another 100,000 miles.

Diamond faced drill bit tooth. From a drill head that would be used for oil wells, etc.

 

Beautiful "restoration" job.

 

Great find! I need to look into this on mine, presents the same exact symptoms as. you had.