non motorcycle fuel injection tech question ?????

[Peder_y2k]

Working on early Ford (1985) multi-port fuel injection system. Not running engine, testing fuel pressure OK at 40psi. After test, noticed a very quiet ticking sound (never started cold engine). Listening closey, the sound was two part, first a ping, then followed in about 1 second by a tok, ..... ping - tok......ping - tok........and this repeated for about 2 minutes until the fuel pressure guage dropped to 20psi where the sound stopped and pressure stabilized.

At first I thought it was the fuel pressure regulator, but now I'm thinking it is a defective injector.

Is it possible for a bad injector to pop open on its own under pressure?

-Pete, in Tacoma WA USA

[MikeWa]

Pete

Possible but rare. It is common for a disconnected or bad temp sensor to keep the engine from starting. Same goes for a crank position sensor. That is a fairly simple FI system but failure of a signal from almost any primary sensor will drive the system full rich. The engine will flood and not start. Also checking fuel pressure is a must but you have already done that.

 

Mike

[djh3]

On a guess a check valve or pressure relief. Most injectors if I remember are sort of a check valve to closed position and solenoid valve open. It gets an electric pulse that tells the solenoid operated injector to open. Otherwise its forced close by a spring.

[wrnchjox]

just on a whim unplug the vacuum line to your fuel pressure regulator and see if you have fuel in the hose, I had an 89 ugly blue oval that made the same noise and no start ended up being pinhole in diaphram in regulator pushing fuel through vacuum line and dumping directly into intake plenum and flooding it out.

[Flyinfool]

I am not familiar with old fords.

But on my GMC it will not start with less than 60 PSI fuel pressure and will not run with less than 55 PSI. Is 40 psi the right number for your ford?

[Peder_y2k]

The old Ford requires only 39psi fuel pressure.

I'm going to make a close examination of the pressure regulator.

-Pete, in Tacoma WA USA