Fuel system problems

[Delanoso]

Can't figure out what's going on here:




This is an 86 eta that sat in garage for 13 years. Tank, soft lines, pumps, filter and pressure regulator have all been replaced. Fuel pressure seems to be in spec but it's hard to tell for sure with that much movement. Just had the injectors cleaned and flow tested. Engine RPMs increase when the vacuum line is removed from the regulator but the needle still bounces too much (I think that indicates the regulator is good, right?). It won't hold that pressure for very long after turning off the engine, maybe an hour? There's also some hesitation after a prolonged push - i.e. heavy acceleration through 3rd gear sometimes causes hesitation at lower RPMs in 4th or sometimes after a curvy section of road running prolonged in 2nd or 3rd will cause a hesitation when reverting back to a cruise mode in a straight away.

If I hadn't already replaced the regulator that would be my first guess. Anyone have ideas?

[Jeffnhiscars]

Heavy acceleration with a 13 yo timing belt will cost you a cylinder very soon. The good news is, you won't have to worry about fuel pressure any more

[superj]

that is true. shoot, just starting it might cost you the whole head

[franan]

How old is the oxygen sensor do you know?

[325e '87]

Take a pair of pliers and pinch the fuel return line coming out of the regulator and see if your pressure spikes way high. You can also play with pinching the line to see if you can smooth out the swings

[95BMWIC]

Could be the gauge - I had a prior fuel gauge that acted the same way -you could check it on another car to verify.