[Monkey Wrench]

a couple of small wires from your battery will provide 12 V, The 9V battery just a handy source I think..
I'd just check to make sure you have your polarity etc correct.

stubborn hard old hose. try a squirt bottle with detergent and water, wet it down and then when you want to pull it off TURN it first. once the soap gets in there you should be home free. soaping or , less graceful but, spitting on hoses helps to get them back in too.

the soap test is how a ( gas) welder checks to see if his hoses are tight and not leaking too, so if it has pressure, not vacuum, the soap test can detect a leak, if it leaks you' ll see bubbles. they just fill a bottle with a bit of windex or dish soap and the rest water. Remember once I forgot to and saw my regulators light up, good think I looked up when I was grinding and saw it in time.

If you want to study it in operation you might use thin wires and get them to connect as well as the standard connector, then hook up a small watt test lamp in parallel with the valve. then you can see when it's on or off and if there is any significant change in voltage you'll see the bulb glow brighter or dimmer. you can use a meter but sometimes a little bulb can sit there connected and be studied more easily. If it's a very sensitive circuit then the bulb can cause issues because it draws power and hooking in parallel lowers the overall circuit resistance. It might not work well with a timing position sensor or a O2 sensor but i think this is just a 12V device..

If I want to monitor spark I just put one across the primary of the coil then you see it flashing when its cranking or idling , proves you most likely have a spark.
as the primary basically gets switched on and off to generate the high voltage spark.. You can see the little test light sort of blinking in unison. It is very easy to clip a small bulb across those two wires on your coil.

sometimes people are mystified and think they have spark or don't , or suspect the spark is intermittent.. The reason I like that is then you can just watch the light if having start issues etc.

I like to add a little bulb to the fuel pump circuit, light is on, so my fuel pump has power, good to know, saves scratching your head.. a tiny bulb won't add a significant amount of resistance to that pump circuit.. one could likely add a few of them in specific places to monitor and make troubleshooting very simple
if you have a no start condition.

you can always add a switch so the bulb is not always on when you dont want to use it to test

another way about this is to simply make yourself an easy place to connect it and use the same bulb . a couple light bulbs in the trunk can do a lot and I hate keeping my expensive meter in the car, a bulb is cheap and very small and light. easy to understand , easy to monitor over time. if you get stuck on the road you might pull out the glovebox bulb and use that , like you are Macgyver ;-)