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Stumped on this one!

F

freqrider

NAXJA Forum User
Location
NorCal
1990 renix. Went to pass on highway. Kicked it into power mode. Punched it a little to pass. Truck died. Wouldn't restart. Trailered it home. Cleaned all grounds, unplugged and replugged sensor connectors a few times, checked cps, map, tps, temp sensor ohm, voltage. All to spec! Fuel pressure >31 psi and holding very well. Fuel filter not clogged. Cranked and it started! Ran a bit rough at idle but smoothes out at higher rpm's. Stalls at idle or if I whack throttle hard. Esp off idle. (Stalls) IAS does not seem to work as engine does not idle fast when starting. Checked dist. timing, seems ok. I cut ears off dist and brought cap a bit closer to rotor JIC. Thinking about opening up the holes on cps and pushing it closer to flywheel? Anyone use a wire brush, etc... in the hole while cranking engine to clean rust off flywheel? I'm in coastal Florida, btw and the humidity is destroying everything here! Can't figure this one out and I need my truck! HELP! 😩
 
Do you have a spare coil you could toss on to check and see if the old one is weak?
 
I don't! I did refresh the contacts however. I'll see if I can find one to swap. It dows sound like it's missfiring at times? Sometimes it has a vibration at 2500 rpms then smoothes out at 3000.
 
If it were old school I would wonder about the condenser. Coil is the closest I can get. Unless Renix still runs a condenser, which I doubt, odd as Renix can be.
 
Would a bad IAS cause the spuddering, stalling? Rough running? I remember my '87 had a bad one for ages and it still ran fine. Had to give it a little gas to start was about all? This feels like a misfire almost. Engine vibrates, etc... Pulling valve cover to inspect valve train next.
 
cruiser54 said:
What is the output voltage of the CPS?

Is the wiring burned on the exhaust manifold?
Click to expand...


Looks ok, maybe a little in one tiny spot? Voltage was .4 VDC when cranking. Should I check VAC, because that was not anywhere near .5 VAC. I cleaned tip and opened up the holes on CPS. Going to mount and push it closer to flywheel. See if that helps. No short between wires even when flexing them.

I always thought a cps either worked or didn't. At least ime...?
 
Try shaking and flexing the wiring harness along the fuel rail and over to the fuel rail. That it dies if you punch it, makes me suspect the wiring harness has fatigued and you have an intermittent connection that opens up when the engine moves around.

If you haven't replaced the motor mounts by now, they're probably rotten and letting the engine move too much.
 
Man I just went through every sensor, all checked out. Good grounds, removed ECU and checked every sensor, power connector, ground from engine to ECU connections. All perfect! I'm suspecting the ICM/Coil now. Its running like when it gets super humid and misfires, won't start. I had a cps do that but its a new napa one and didn't improve at all.
 
freqrider said:
Looks ok, maybe a little in one tiny spot? Voltage was .4 VDC when cranking. Should I check VAC, because that was not anywhere near .5 VAC. I cleaned tip and opened up the holes on CPS. Going to mount and push it closer to flywheel. See if that helps. No short between wires even when flexing them.

I always thought a cps either worked or didn't. At least ime...?
Click to expand...

New cps from napa didn't fix a thing!
 
I just noticed 10.5 ish VDC at pin B10 from B+Latch Relay backprobing connector. Should be 12V! I swapped relays with AC. Same! Could be fusible link, short somewhere. I did notice a while back when checking fuel filter, my arm was lightly touching the diff and I could feel slight current! Not sure where short is but it's there somewhere?
 
I had similar symptoms after redoing my battery cables. I would accelerate and the motor would drop out for a second. Or hit a bump a particular way and same. Or be in a banking turn. Turns out the wire to the alternator had been fraying against the motor mount and had worn away the insulation but wasn't in constant contact. If the motor torqued over or a bump moved the cable right it shorted out and lost power.
 
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