Replaced the ECT and the engine still wouldn't start; not a peep. So my mechanic replaced the coil and it finally started and ran! Yet the old coil show arcing and it appeared strong. Now I can understand a coil getting weak enough that the engine won't start but this problem occurred while I was leaving a stop sign. Is there a way to measure coil strength? I do thank everyone for their speedy suggestions. I originally search this excellent forum for people's previous experiences and it gave me a good head start. Again, thanks. Bill

 

There is a specific tool for checking spark, but, all it tells you is if the coil has enough oomph to jump a fat gap. Conditions in the combustion chamber can be a bit different than just laying on top of the motor though. (so, the gap is actually pretty big.) I just use a sparkplug...... Spark color tells the tale.

 

Replaced the ECT and it had no effect. Mechanic then replaced the coil and now the engine starts and runs! Go figure. Old coil appeared to give strong arcing. Now I can understand that a weak coil and prevent an engine starting but while it is running? Thanks to all for their suggestions.

 

Same thing happened to me and it was as simple as the relay for the engine shut off or something to that nature. A buck fifty from a junkyard and it was fixed ****** nevermind I didn't see that it was fixed till after I posted. My mistake*******

 

Th e crank position sensor (cps) will go out from time to time. It is located behind the motor on the passenger side, the cps plugs into the harness by the distributor. Remove 2 bolts and pull out through the notch in the bell housing, inspect for dirt, metal, or damage. They run around $50 @O'Reilly.

 

I had a very very similar issue a while back, cruising about 35mph truck just shut off. I noticed the tach dropped as well as oil pressure but everything else was fine. Gas pedal did nothing. Shifted to Neutral and coasted it off the main road. Cranked strong but no start. Had perfect rail pressure, plugs were getting wet and my father held a plug against the block while I cranked-she had spark. Without looking further into it I changed crank and cam sensors with no change. On a whim I looked up coil tests and found that with a multimeter you can check for 12,000-15,000 ohms between the coil tower and either one of the pins inside the connector and 1 ohm +/- 0.3 between the 2 pins themselves. Mine tested 10,000 and dead on at 1ohm. Asked my father what color spark I had and he goes "A little yellowish/white but nice and strong. That's not your issue, I don't think you're making compression. Time to sell."


40k+ later at 195k all test 140-145 except cyl 5 at 128, which I attribute to likely being cracks that these all get.

 

Hey, I registered several years ago when I had my Dad's 96 1500 Jayco conversion. Now, I have a 99 red 4X4 5.9, club cab. Not sure if this is the right spot, but here's my problem. The truck started acting like it had a dead cylinder, wouldn't idle right, could smell raw gas in exhaust. It would rev up to about 3000 then start breaking down. The guy at the parts store said if a cylinder wasn't firing it would throw a code. No codes. Finally started pulling plug wires. # 4 plug wire was broken off at plug. Gave tune up, plugs, wires, cap, rotor. Since it wasn't idling I replaced the Idle CV and the MAP sensor. It runs much smoother now, running on all 8 cylinders, but still breaks down right at 3000 RPM's, or maybe a little sooner going up hill. Pops and coughs. Still doesn't idle right. I was just getting ready to put a complete new exhaust on it when this problem started. The exhaust pipe cracked right in front of the cat. Previous owner welded a generic cat in so I couldn't just replace it. The truck has 135,000 miles on it and never saw a drop of rain till I got it. I've had it 4 years and only put 10,000 miles on it. Now it seems like everything is going all at once. Don't know where to start. What could make it start breaking down at 3000 RPM? I've gotten so used to looking for codes, I feel like I should know this, but I'm missing something simple.

Photo bucket gave me the boot, or I'd post a pic. I'ts a beautiful truck. Thanks for any insight, Joe.

 

Hi Joe. Welcome to DF! You are indeed in the right place.

I think first I would pull the Pre-Cat O2 out, and see if it doesn't run any better. (physically remove it from the exhaust, this is testing for a clogged cat.) If that doesn't seem to make any difference, verify fuel pressure. Should be right about 49 at idle. If THAT is good, replace the crankshaft position sensor. It hides behind the passenger side head, and is just a whole lotta fun to get to......

 

You've probably fixed this by now, but I would've guessed LIMP mode.

 

Is it possible that maybe it is a bad battery cable