Fuel injection system component

There are numerous engines since 1987. Where do the wires lead? Obviously, if its clipped onto the rail, just being held there in contact with the rail (?), then it must be a sensor, not a control devise. So the question would be, what sound is being sensed, and from where. Perhaps sensing mass fuel flow? Or knock?

Otherwise, it could simply be clipped on rail because that's just a convenient place to mount it...and it could have function or intermediate function unrelated to the rail. (In other words, what leads you to believe it is an injection system component?)

I'll need to check my engine to see if I can find the same device on the rail or elsewhere.

The fuel system is gasoline, not diesel. I do not know if this is a piezo-electric sensor since its on the common fuel rail not an individual injector line. It might also be a temp sensor since th efuel is usually at an elevated temperature due to the high pressure pump being used. The sensor is located towards the front of the engine. The wires go into a harness and I have not been able to trace it completely. I salvagede them from an 1987 Ford truck with a 6 cylinder inline engine. I have a later version which has minor variations. But all the major pieces appear to be identical. Last year when my thermostat acted up the housing cracked. Cost me $95 to repair plus 200 miles into town to get the parts from a dealer. I figured these parts would serve as spares. Murphy's law still being in force, probably means that now I have spare parts I will never need them. The parts will be cleaned and then put away with a label indicating exactly what it is. Those parts not used on my own truck version are surplus. They will likely be used somehow.

I did not find anything like it on my '87 Ford EFI V-6. Oh well.

Things you might look for to help narrow it down by elimination/deduction:

1. How many leads from blue thing to harness?
2. Any tubes (vacuum lines) among those "leads"?
3. What is resistance (engine off) across the thing's leads? What about if you tap on the devise while measuring?
4. What is voltage measured (engine off, key off and key on) across disconnected harness leads?
5. If you disconnect harness from the thing and then (a) turn key to on, and/or (b) start engine, and/or (c) drive...what happens, if anything? Any engine codes? Other noticeable abnormalities?
6. What are the devise and harness lead colors? What color, respectively, connects to what?
7. Does the thing only clip on? Or does it penetrate the rail at all? Is it in "hard" contact with rail, or only with clip-on bracket?

What is your engine (6-inline, capacity ?________?), specifically (and/or what model vehicle)? I have a fairly comprehensive emissions service manual that might give an answer.

Also, judging from its forward location, I'm thinking it could (aside from temp sensor) be a component of the air management, throttle bypass, TPS, or EGR system. You might try checking for continuity (min. ohms setting) between "thing's" harness leads and other, nearby-devise harness leads (key at off and key at run). If you find a connection, that could tell "who" (what system) the thing "belongs" to.

Another possibility: SPOUT connector?

Can you send a picture? If not can you find a number on the part. Ford is usually good about identifying it's parts.