1998 5.7 Vortec : What are these wires?

[TheTruckOfTheseus]

The second picture shows the section of wiring that was resting on the curve of the intake manifold. Was wondering what they go to and what the best course of action would be

Also as a side note, what should my compression numbers be? All 8 cylinders yielded the following results using an old school handheld tester. I have access to a screw in tester if I should redo it

1. 90
2. 80
3. 70
4. 90
5. 85
6. 80
7. 100
8. 90

Update: Sorry for lack of details, posted in a hurry. I am working on my 1998 Chevy K2500 with the 5.7 Vortec. I redid the test the correct way, and yielded much better numbers (partially)

1. 175
2. 165
3. no compression
4. 165
5. 165
6. 160
7. 165
8. 155

Ran an inspection camera down into the #3 spark plug hole and watched at least one valve (unsure which one, possibly both) rise and fall but don’t think one or both were seating fully. Also not sure if the piston is cracked or really sure of anything until I take the valve covers off and dive deeper. Also looked to possibly be some deposits on the intake valve.

Also, to touch on the wiring, I’m not going to worry about it until I see what’s going on internally, but might look into it just for the sake of curiosity

 

[Caman96]

Not sure about the wiring, but it definitely needs repair. Those numbers are low, way low.

 

[Hipster]

the section of wiring that was resting on the curve of the intake manifold. Was wondering what they go to

Also as a side note, what should my compression numbers be? All 8 cylinders yielded the following results using an old school handheld tester. I have access to a screw in tester if I should redo it

1. 90
2. 80
3. 70
4. 90
5. 85
6. 80
7. 100
8. 90

A better description of where they go, what they attach to etc might help. Looks like burnt wiring from a burned fuse link.

Compression numbers with throttle plates held open? Good battery fully charged with good cranking speed for 3 revolutions? It matters.

 

[Road Trip]

Also as a side note, what should my compression numbers be? All 8 cylinders yielded the following results using an old school handheld tester. I have access to a screw in tester if I should redo it

1. 90
2. 80
3. 70
4. 90
5. 85
6. 80
7. 100
8. 90

Sir,

Way back when I followed an (in)accurate compression tester down the garden path. Learned
the hard way sometimes test equipment has the same trouble with the truth that some of our
politicians do. :0)

Seriously, if you could perform a cross-check on that gauge before proceeding that would definitely
be in your best self interest. Either use the suspect gauge on a known-good vehicle and verify that
it can actually show a 150+ psi reading? Or, if you have a 2nd screw-in gauge then see if it will confirm/deny
the readings above? (By the way, as Caman96 said and Hipster inferred those readings, if accurate,
are very low.)

For what it's worth, here's a blow-by-blow of how to get the most accurate compression test readings
possible for us shade tree mechanics. In other words, test results that I'm willing to break out the
tools to fix a proven-bad issue: Common Sense Compression Test Guidelines

EDIT: If I could add one more hint to that list, it would be to allow the cylinder to pump up at least
3x as @Hipster mentioned. Yes, the numbers will climb, and that's a good thing, for
this helps to compensate for the fact that the tester itself presents additional volume that adds to the
tested volume/skews the reported cylinder compression readings downward. (NOTE: This is the real reason for
the climbing reading, since the previously compressed air in the gauge is retained by the internal schrader valve. (!)

Best of luck, and looking forward to your cross-checked data.

PS: Your partial wiring harness meltdown is definitely fixable. You don't have to give up on the old
girl yet.

 

[Schurkey]

As said--with readings that low, your methodology or your tester accuracy is questionable.

1. What is your altitude?
2. Were ALL the spark plugs removed during the testing?
3. Was the throttle at least partly opened during the testing?
4. Did the battery crank the engine at a "normal" speed from the first cylinder to the last?


Another way to confirm a compression tester: Connect it to a source of compressed air, with one or more additional pressure gauges for strength-in-numbers validation. Most compression testers have a quick-coupler in the pressure hose, and most of those are Industrial Interchange style--Milton "M". A male plug of whatever style is needed to plug-into your compressed-air-system hose, and a male plug of the Industrial Interchage (Milton M) style to connect to the compression tester. You can use a second compression tester, or the gauge on the compressed-air-system regulator to verify the compression tester in question.

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[Caman96]

Might add what you’re working on too. Year, make and model.
Edit, sorry I see you did!