Car acts normal when CIS pressure guage is connected?

[Tinker]

If anyone can steer me in the correct direction, I`d be most grateful. Testing the fuel pressure on an 87 16v. It currently has an intermittent cold and hot start problem. It will crank excessively before finally starting. Fuel pressure when not cranking is close to 3 bar. When running the pressure is at spec, 86 psi. Will loose only 1 to 3 psi in 30 minutes so it is close to spec. If it sits overnight, it will bleed down to 15 psi. When I hook in the CIS tester to the cold start valve, it starts right up cold or hot every time. Any ideas as to why this would occur? Should the pressure bleed down overnight? As always thanks for the thoughts. Tinker