1997 GMC Yukon, 350 R motor, crabcap distributor. Somrtimes it starts right up and runs fine but sometimes it just cranks and won't start. Check engine light does not come on. Dealer replaced the fuel pump (twice) but that didn't help. I replaced the cap, rotor, coil and coil wire. ANY advice would be really appreciated. Thanks in advance.
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Re: 1997 GMC Yukon won't start.
When it won't start, remove one plug wire and connect to a clean plug--lay the base on the block somewhere. Have someone try to start the engine. If you get regular blue sparks, the ignition is fine. Look for fuel problems. Make sure the check engine light works (bad bulb?). Why did the dealer think it was the fuel pump? Did they try to read the computer for any codes? Take the vehicle to Autozone for a free computer read. You could have an intermittent crankshaft/camshaft position sensor which can cause trouble for both ignition and fuel injectors.
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The distributor is out of time. Bring it back to #1 TDC and try to drop it in. If it doesn\'t go in all the way, it\'s because the oil pump drive isn\'t lining up. All you do is have someone "tap" the engine over in very short bursts. Eventually it will line itself up and drop in. Unfortunately, even if you get it started, you will probably get a check engine light. If you do, you will need access to a scanner that will display data. Look for a data line called "CMP Retard", make small adjustments to the timing and snap the throttle. Get this reading as close as possible to 0. I believe the tolerance is +/- 2 degrees. If you can\'t get it close enough, the distributor is still out a tooth. ALSO, keep in mind that the air filter must be in place. Without the inlet hoses, the mass airflow sensor cannot read properly. Good luck!
That's often a sign of a failing check valve in the fuel pump. Try this. When you turn the key to RUN, the fuel pump activates for 2-seconds to boost any lost pressure. Try turning the key to RUN, then OFF and repeat three times. If the engine starts right up, you probably need a new fuel pump. The real test is called a leakdown test where the shop throws a pressure gauge on it and leaves it overnight. If it loses more than 5-10-psi, the check valve is shot. Can't be replaced separately .
I hope I can help you with your question I believe I can first and foremost if you're having trouble starting your car on cold mornings it's probably going to be a clogged fuel filter or bad fuel pump about to go out you're having symptoms as you described and then whenever you're at 55° things start to warm up and you can start your car okay the filter is so clogged up imagine that look looking like a blood vessel okay when you have a clog in it it doesn't allow the blood to flow freely feel the same way
better check that distributor cap for damage on the inside. It's simple. Just need a flat tip screwdriver. If thats fine. I'd check voltage to coil and if it was 12 or more I'd through a coil at it. It's an easy repair.