GronHog

1999
4.0 auto 4x4
sport
265,000+ miles
Fed emissions, not CA

from the beginning, two sundays ago just wouldn't start after it had been driven earlier in the day. Was not getting spark, so jumped on the forum to read thru a lot of info. Ended up testing CKS with multimeter and at first I thought it was bad, found out days later I was reading it wrong. That Monday bought and replaced old sensor after work, to my surprise it did not start. Well left it alone till Thursday, had some time before taking my youngest to get cast removed. Pulled out the dremel and pulled the coil, and removed the paint from the mount, and cleaned the ground wires. Did find that the jacket on the wires were really soft, soaking in oil and cooked by engine, but no breaks in wires. Taped the bare spots on the wires and remounted coil with all nice and clean. Didn't start again, so read some more, and then checked voltage to sensors-CKS,TPS 5 volts. Funny part, then to check voltage to cam sensor, saw that I never plugged coil back into cap. Well it fired up at first touch of key .
Now to the worse, ran great from that Thursday to Monday afternoon. Got off light rail looking forward to getting home, and she would just crank and no fire like before. Back to no spark again. replaced coil with one from pick n pull that tested good, old one tested good also, ohm testing. No spark still, so read some more. Getting 12 volts thru coil plug, with key on and while cranking. Used a light probe from pos+ on battery to neg+ on coil plug, and while cranking no flicker of light. The guy at NAPA suggested to try this to see if I'm receiving signal pulse from PCM. He thinks the cam sensor reached its end, with the mileage and little heat wave we had. Today after work pulled the multimeter out and went testing for voltages, battery- good a little over 12, but then 5 volts it should be getting to the sensors is now showing 10 volts with key on. 10 volts to cam sensor and crank sensor key on, and .5 volts key off. I'm guessing my 5 volt lead is shorting to something else, and hopefully not in the PCM itself.
Well thanks for letting me vent a little. Back to reading thru more posts and trying to absorb and process the treasure trove of info here. forgot to mention that the gauges still work. Trying to find a code reader thru co workers to borrow. No CEL before ,during or after all this. Going on 6 months with truck and no problems till this. It has a bad clock spring, airbag light on, no horn, and no cruise. Airbag control box (or computer) still mounted under driver seat. I know I have forgotten some things, but really tired, past my bed time.

CCKen

If you are getting 10 volts at the Sensors 5 volt supply pins (Orange wires) there's a possibility it's your defective Clockspring causing the problem, allowing battery voltage to leak into the cruise control wiring in the Clockspring via the Horn relay control coil circuit, then into the PCM.

You can pull the Horn relay out of the Junction Block (passenger footwell) and see if the supply voltage drops back to 5 volts and if the engine starts. If it does, you can leave the Horn relay out until you get a chance to replace the Clockspring.

The Horn relay is the middle of the three relays you'll see when you get the JB cover off.

GronHog

Thanks for the brain power. As operating on a shoestring budget, truck still where it broke down at. Heading out there to beat my head against the hood, and remove relay and check voltages again. Could the overvoltage burn out the sensors. Found a pinout diagram you posted in another tread, so will also check PCM voltage leaving at pin 17 black plug. If its 5 volts leaving PCM and still getting 10 at sensor, I assume that means in the spaghetti that 5 volt lead is shorted somewhere. Would of done this earlier, but fighting off a gout flare up, not much sleep last night.

CCKen

Remove the horn relay first and check the 5 volt supply at the TPS (easy to get to) before foolling with the PCM.

Dollar to a donut it's the clockspring.

GronHog

You were right, removing the horn relay returned voltage to 5.13 volts key on. With key off I'm getting .009 volts at CKS and CPS. The bad was she still doesn't start, still no spark. Could I have burn out a sensor or two with the over voltage.

CCKen

Leave the horn relay out untl you can change the clockspring.

.009 volts with key OFF is good.

I don't think you smoked a sensor with 10 volts. You obviously have other issues.

No spark says he...

Does the fuel pump prime when the key is initially turned to RUN, before starting?

Need to check some fuses and swap a relay.

Here's your PDC. Check the fuses marked:

• Fuel Injectors/Coil
• Fuel Pump PCM, and
• ASD

If the fuses are good (using an Ohmmeter to verify), swap the ASD relay with the Radiator Fan relay.

Ops check and get back.

GronHog

I don't hear the pump kick in, but releasing pressure thru shraeder valve, and then key to on it builds pressure again. After cranking I can smell the gas. I have manually pulled all the fuses, big and small, and visually inspected them. Have also played three card monty with relays, starter-ASD-fuel pump. The relay to rad fan came apart on me, cover came off relay stayed put, but the elec fan has an on/off switch in cab with a relay inline. Would it be better to ohm test the fuses instead of just eye balling them?

CCKen

That's what I suggested in the previous post (Ohming). Lots of people say they checked the fuses when, in fact, the fuse was defective.

What other mods do you have besides the fan switch?

Juggling the relays around didn't help?

Did you mention that you changed the crank sensor (CPS)?

GronHog

My better half has the boys at the water park, so stuck at home right now. I had pulled every fuse out one by one and put an eye to them, but understand that if it looks good it might not be. Will put them to the meter in tomorrows visit. The fan switch is the only mod, draws power from battery and grounded to body in its own wire loom. A relay connects switch to battery and Efan, only runs when key is on( its disconnected from battery right now to eliminate it as the short). Rotated all relays thru starter to make they were good, cranks over strong with all. Yes I changed the crank sensor the first time she did the no spark thing and refreshed the grounds. The old CPS still tests good with infinite resistance. She still didn't start with the new one till after it sat for a couple of days, and ground off the paint on the coil bracket.

GronHog

Just ohm tested the fuses, all check out good. Voltage to sensors are good, 5+ volts. ReChecked resistance to crank sensor, good. So this leaves me with the cam sensor(stator, pick up coil). Pull cam sensor to check is physical state, looks good (easy to remove, can't believe they want 60 to 80 bucks for that). The thing that I noticed with the distributor is the slop in the shaft, there is side to side play. Could this play cause the cam sensor malfunction.

CCKen

If you have excessive side-to-side lay in the distributor shaft that's not good. Rotational play is normal, to a degree. Defective cam sensors have been know to cuase a no start condition.

First, check fuse #11 in the JB. It's in the 4th slot up from the bottom in the front row of fuses. 20 Amp.

With key to RUN, F11 powers the ASD relay, FP relay, TCM, and PCM.

GronHog

#11 fuse test good. Trying to gather some money and our time to get her home or drop a whole distributor from jy. Leaning towards the pick up coil being bad

GronHog

Happy days, back on the road. Turned out to be a dead cam sensor (pick up assembly, or whatever). Replaced worn out distributor so all is golden for now. The question this has left me with it, I thought I read some where that the cam sensor setup the injector timing and crank sensor the spark time. So I would of assumed that in losing the cam sensor I would of lost fuel instead of spark. After cranking engine over several times I could smell raw gas from exhaust, so I'm thinking the injectors were still firing.

CCKen

CPS is responsible for spark but so is the cam sensor.

The flexplate has three sets of notches (holes) in its rim that the CPS senses up when it's rotating. Each set of notches represents two cylinders (1-6, 5-2, and 3-4) which, when passing the CPS, signals the PCM that this occurs. The PCM says that's cool but which cylinder do I inject fuel to and which cylinder do I ignite? The cam sensor knows which cylinder and informs the PCM.