01 Sonoma starting troubles: Sensor?

Discussion in 'Chevy S10 Forum (GMC Sonoma)' started by PeteK812, Jan 7, 2017.

  1. PeteK812

    PeteK812 New Member

    I've been having random starter troubles for a month, getting worse as time goes by. Initially it was the bendix kicking out once or twice, but a jump from another battery would usually start it just fine. I replaced the battery with a new above average quality Interstate, still had random troubles. Eventually, the bendix would kick out immediately, never could get the truck started, so replaced the starter, new, not rebuilt, lying in the gravel in my driveway. New starter worked great for a few days, but occasionally the engine would crank very VERY slowly, like a low battery, but it would crank and crank forever, until it finally fired. When I took it to the Interstate shop to have it checked, battery was tested fine, alternator output was perfect. I shut it off, went into the counter to talk tool batteries for 10 minutes, came back out and it cranked very slowly for 15 seconds and then the dreaded CLICK CLICK CLICK. It started fine with a jump-pack, now it sits in the snow and won't crank much at all, forget about firing.
    Could all of this be explained by the 50 degree timing advance referred to in the "faulty crankshaft position sensor" protocol?
    When I was replacing the starter, the cable end on the small wire snapped off, and I replaced it with a crimp-on connector. Could a poor connection at that point cause these problems?
    What about the large connector at the starter accidentally grounding on the case, or the cable grounding with the chassis?
    None of these things can be checked without pulling the starter back out of the truck, but at 4 degrees and windswept snow under the truck, I obviously won't be getting back under it for several days, but I can't stop wondering about this weird chain of symptoms, and the fact that each has been occaisional, then regular, then permanent.
  2. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    The first thing that came to mind for me was what condition are the starter leads and cables in?
    Have you ohmed them out to ensure they can transfer the power? Or are they corroded internally.
    Also a good check and cleaning of all the ground points might be in order.
    thegawd likes this.
  3. xPosTech

    xPosTech Epic Member 5+ Years 1000 Posts

    The small wire only has to operate the solenoid. When the solenoid gets to the end of travel the large brass washer shorts the battery cable to the starter windings.

    You could have a bad battery to starter cable or a bad engine block ground cable. You can use 1/2 of a set of jumper cables to test the engine block ground. Just connect one side of the jumper cable to a bolt on the engine and the other end of the same side to the ground terminal of the battery. If the ground cable is bad it will start right up.

    There's no easy way to jumper around a bad battery to starter cable.

    One way to get a general idea of battery to starter connections is to turn on headlights to bright and monitor when starting. If they obviously dim you might have a dragging starter, low battery or bad connection from battery to starter. The bad connection could be on the positive or the negative side. If the starter spins the engine over fine and headlights barely dim or don't dim at all then connections are fine.

    thegawd likes this.
  4. PeteK812

    PeteK812 New Member

    Thanks for the suggestion. I'm very experienced mechanically, but kind of Dislexic when it comes to electrical stuff. Can you explain how to "Ohm-check" a cable, and I'll borrow a digital meter from a buddy.
  5. thegawd

    thegawd Rockstar 2 Years 1000 Posts

    this is a slightly different test that I completely forgot about. its a voltage drop test and what it does is measure a wires capability to carry voltage. its is a decent video of an auto mechanic instructor explaining the test.

    this one is a theoretical explanation.
    Last edited: Jan 7, 2017
    xPosTech and RayVoy like this.
  6. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    Al, they are both informative videos; the quick way to look at it is, if there is a dirty connector, there will be resistance to current flow. If some of a cables small wires are cut, or corroded, there will be resistance to current flow.
    Whenever there is unwanted resistance the voltage at the device requiring power will be lower than battery voltage. Resulting in poor performance.

    The biggest cause of poor starter performance is a battery cable that has had battery acid eat some of the copper wires. This usually happens under the molded plastic at the battery. Sometimes you need to cut the plastic to see it.

    Peter, ohming a cable is not a good test. It only tells you that there is cable there, not the condition of it.

    Like an alternator, a cable needs to be tested under load. That is why the voltage drop test is the test that works.

    So, as the guy in the vid said, you need to be cranking when you do the voltage drop test. one meter lead on the pos battery terminal and the other on the starter post where the battery cable is connected.

    However, a quick test I to use your hand. After a very short time, the current through this dirty connection, or rotted cable, will generate heat. Feel the cable with your hand, if some places are warmer than others, you need a new cable.

    Note, I've repaired lots by cutting off the bad connection and splicing in a good connector.
    silverado002 and thegawd like this.
  7. silverado002

    silverado002 Rockstar 3 Years 1000 Posts

    The fact that the starter solenoid is clicking means its trying to engage. I think like the guys here that you may have an internally corroded battery cable to the starter (the big one). Also like the guys here suggest check the engine grounds to make sure the starter has a good return path to the ground side of the battery.
    xPosTech and thegawd like this.
  8. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    PeteK812 as thegawd and RayVoy posted the correct test would be a voltage drop test, this will give a better idea of the condition of the wiring.
    In my previous career as an aircraft mechanic we used to use a device called a "Megger" to check capacity and condition of wire and we always refered to this as ohming out the wires, but the reality was the term we were using was incorrect. We were actually doing a voltage load test to Capstan coated wires.
    xPosTech and thegawd like this.
  9. PeteK812

    PeteK812 New Member

    Resolved! Hip hip, Hooray.

    After throwing parts at the problem, a chance digital voltmeter check showed that the battery was at full charge when I started to work on it each time, after a charge-up, it would drop a cell on starter demand, resulting in a 10.5 volt battery. I may have mentioned that this was a brand new Interstate battery (first thing I replaced, back at the beginning) and had driven back to Interstate to have it checked 3 or 4 days later, and it was pronounced "fine". Starter was suspect in the beginning, so I don't regret the replacement, and the new positive battery cable is beefier and nicer than the chewed & taped original, so I don't regret that either. Mostly, I regret the loss of my work truck with tool boxes for a month while I chased the gremlin. Luckily, work is slow around Christmas, I had other things to concentrate on, and I could carry critical tools in the trunk of my car for small jobs. I was surprised to discover that an 8ft long box of hickory flooring will fit through the back door of a 4 door sedan, as long as you have a second person to lift the other end while you thread it through without punching out the headliner. Not as easy as sliding it into the bed of a pickup, but it can be done.
    thegawd likes this.
  10. silverado002

    silverado002 Rockstar 3 Years 1000 Posts

    Good for you Pete. Happy motoring.

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