1996 Volvo 850R No Start No Crank (Intermittent)

[wackenhut]

I have a couple updates on my 96 850R with random no start/no crank issues.
The mechanic noticed the following, so wanted to see if a couple items can be ruled out

When the no start no crank issue happens:
Dash lights still come on
When the key is turned, he did notice a signal going to the starter
When he bypassed everything, the starter did work

Trying to figure out the issue, he played around with the green wire that attaches to the solenoid and when it was moved around, the car started, however I drove around for a couple days and the issue started again.

The one thing that has remained consistent is that when the no start/no crank happens, if you jump the car from another vehicle, the car starts right up (pretty odd).

I was looking at the various posts on the site, but based on what is occurring I am wondering if anyone has any ideas.
Also, can the ignition switch be ruled out since a signal is being sent out? There is also the bypass alarm relay that has been mentioned and wondering if this can be ruled out as well.

All help is appreciated!

Thank you.

[jreed]

On my 97 855, I had a no-crank due to a failing positive cable connector crimp from the battery to the starter. One easy way to test for this is to measure the voltage drop between the battery + terminal and the starter, to make sure the cable and crimp are still capable of conducting high current. When the car is running, the drop should be low, I would guess less than 0.1 to 0.2 volts.

[wackenhut]

@jreed, the positive cable connector was replaced.

[misha]

@jreed, the positive cable connector was replaced.

Was the cable replaced too?
Voltage drop can exist on both...positive and negative side...but positive side is more common on these cars and 2awg wire/cable should always be used when replacing battery cables.

Voltage drop is the only reasonable explanation since it always crank & start when jumped.
Battery could be weak & undercharged because of voltage drop .
Healthy charging system produce 13-8-14.2v at idle with headlights,heater blower on low speeds and radio ON and test must be performed after about 30min of driving and without turning the engine off before testing.

Anything below 13.5v is not enough to keep the battery charged,especially on frequent short trips.

[wackenhut]

@misha, the entire positive battery cable was replaced with a new one from volvo as well as the connector at the harness of the starter.

[misha]

Alternator output and battery capacity checked?
If that is ok...i would check all grounds next.

[foggydogg]

Try squeezing the female connector on the solenoid signal wire. Just because it reads good voltage doesn't mean it has a good enough grip on the terminal to energize the solenoid. I chased the same issue for a couple months until I did it, and the cure seems to have fixed mine.

[wackenhut]

@foggydogg, is this the green wire? I am thinking this could be a possible solution but I need to wait for the car to have the issue again. I am going to drive it around this weekend.

[foggydogg]

You're pressing your luck on my memory bank coming up with a wire color, but it's the small gauge wire on the spade connector at the solenoid. Hard to reach on our turbo cars. Once it's off the connector and in hand, a gentle squeeze with small needle nose pliers will give it a firmer grip on the spade lug. Not easy, but cheap diagnostic.

[jreed]

Another possibility that might be worth testing: when the starter won't engage and crank, you could do an old-school load-pull test on the battery to see if it is capable of putting out the 100-200A required to spin the starter. Harbor Freight makes an inexpensive version.