1997 Chevy Tahoe V8 Four Wheel Drive Automatic 189000 miles
I have a 97 Tahoe that started acting funny once in a while during starting. The engine would " stop" during cranking, then crank again. Now it won't start at all. It's getting gas, the plugs were soaked so I changed them. I changed the crank sensor, seemed like a good place to start, but didn't help. It duplicates the affect an older 350 would do if you had the distributor turned and the timing was thrown off. Since it was intermittent before, I don't think it's the timing set. Could be, but just not my first thought. I don't want to just start replacing stuff. I think it might be in the distributor, but not sure thats the best place to go from here. Wires, fuses, are fine everything is plugged in and looks to be in good shape.
The reason your engine cranks and then stops seems to be because there is raw fuel not igniting. Gas, as well as all liquids, are not compressable. This will lock the engine and could cause a bent valve or something like that. No spark -- test the ignition module and the coil -- or have them both tested at autozone or a place like that -- they will do this for free. Changing the crank sensor is not a good place to start. If you do not get a crank sensor that exactly matches the origional you will have to take the engine to the dealer and have a crank sensor relearn proceedure done so the computer can see the sendor itself. They don't tell you this when you purchase a new crank sensor -- do they? The distributor gear wears out in these engines. Check it. Keep me posted
February, 11, 2009 AT 12:53 PM
OK, I checked for spark, and it has a yellow spark. I kinda remember a good spark looking blue, but I haven't done this in a while. I took the ignition coil off and OHM'd it out, and got some readings that didn't correspond to specks, so I got a new coil. Still having the same issue with good cranking, then that sudden stop, and still no start. The spark looks the same as it did before I changed the coil. I'm not sure what to check next. I don't know if I should be looking at the distributor, the cam sensor, or what. The way everything is crammed in there, it looks like it would be easiest to pull the distributor out to check it and OHM the cam sensor. I can't even see where the wires for the cam sensor are on the distributor. I don't want to do that unless that seems like the next logical step. I don't know if theres a way to check the ignition module without replacing it.
February, 11, 2009 AT 4:56 PM
Check the spark plug wires for proper resistance. They should be sround 30000 ohms or so. If they are not replace them with A/C Delco wires only. Aftermarket wires will not work on your ignition system.
The ignition module can be checked at autozone or a place like that. They will do this for free, and I suggest always testing first so you know where you stand. This is probably your problem.
The cam sensor and distributer has nothing to do with the strength of the spark. The coil, ignition module, distributer cap and rotor, and spark plug wires all have something to do with the spark quality. Check them and remember to always use A/C Delco ignition parts ONLY on your ignition system. Chevy has designed it that way.
Make sure you have 12 volts at the coil and make sure all the wires are not shorting out or broken in any way.
The cam sensor just tells the computer that the distributer and cam is working together properly. It is located under the distributor cap. It plugs in behind the distributor.
Be aware that A/C Delco parts are not cheap but they are the only brand that should be used with your engine.I know the stuff seems jammed in there but if you remove the air cleaner ducts it is a lot easier to see whats what.
Keep me posted
February, 12, 2009 AT 3:52 PM
Disconnected the coil wire from the distributor, and hooked a meter up in parallel from the coil wire to ground. When cranking, it shows between 12 and 17 volts. Quick spike up, then drops. The spark seems to have a good " snap" from the wire. This distributor cap is the weird type, looks like fingers or something pointing towards the fenders. Not the conventional looking distributor cap. If I have a good spark at the coil, and everything looks to be in order (wires, plugs, etc. Distributor " cap" does not look to have any damage to it.) Safe bet to narrow it down to the ignition module?
February, 12, 2009 AT 11:33 PM
Yes, but have it tested first before you replace it. This can be done off the engine.
Test the plug wires -- they should have 30000 ohms of resistance.
The distributor cap is unique looking. If you have never seen it before there is a good chance after 189000 miles it may need to be replaced along with the rotor and wires. If you do remove the cap be careful not to strip out the screw holes when tightening it back down. The distributor base is all plastic and the screws just thread into it -- you can easily strip these holes out.
February, 13, 2009 AT 6:51 PM
Well. Finally figured out the problem. I should have followed through more thoroughly with your advice earlier and it would have been less of a headache. I pulled the distributor cap off, and it was loaded up with greed crud & oxidation. All of the firing points were basically blocked, and the electrode on the rotor was pretty short. Basics, basics, basics. I appreciate all your help and replies, and again wish I would have pulled the damn cap off like you suggested. The outside looks fine, but it looks like O/E on the inside.
Also, I bought A/C Delco parts from the dealership.
Truck runs great again, like it did before this problem. It's been sitting since December 17th, but no issues.
February, 13, 2009 AT 8:08 PM
I suggest pouring a large bottle of cheveron tectron fuel system cleaner in the gas tank -- being that it was sitting for some time. This makes a difference and keeps your injectors clear of varnish that builds up over time and clogges them.
If I helped you don't be afraid to give me a little feedback points.
BTW -- Consider your time well spent when learning about your engine and all the new designes - like the dist. Cap.