It's a 1990 740 N/A with the rex-regina fuel system. A few years ago, I spliced in a fuel pressure gauge permanently so that I could constantly monitor the pressure. Apparently, some time this week it became handy.

I noticed that the car was harder to start after sitting for a while and that the performance seemed a tiny bit off. Today, I decided to see what was going on. Normally, when I turn the key into position 2 (or is it 3? the one where all the dash lights come on), the fuel pump primes and the pressure gauge shows a steady reading of about 40PSI or so. Today, when I primed it, the pressure went up to 40, and then in under 2 seconds it dropped back down to 0. Not good.

The car runs fine once it gets started, which to me indicates that the leak is very very small.

I tightened the clamps around the pressure gauge splicing to make sure it wasn't leaking there. There are no apparent leaks (no smell) so what could it be? I'm going to take it to my mechanic on the weekend and have him tighten/doublecheck the fuel filter area. I'd do it myself if I had the time but recent employment change has made it more difficult.

Do Regina systems have a fuel pump check valve? I know the bosch system does, and they have two pumps, but I think I remember someone also saying that the regina system has a check valve and it's a part of the single in-tank pump.

Any suggestions would be greatly appreciated!

edit: Oops, almost forgot to mention. I unplugged the vacuum line in the FPR and the pressure goes up a tiny bit as a result. No fuel in the line.
--
Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'