92 Dakota, 5.2 L, no start.... Bought for a project that has turned into a nightmare. Had no fuel pressure or spark. Went through these test procedures:
OK, locate the PCM and the 60 way connector and remove the connector. Pull the black plastic shielding off the wire side of the connector to expose the numbering system... it's way better to do it this way than use the Mopar pinout [COLOR=green]diagram[/COLOR]
We'll start with some powers and grounds, so go ahead and turn the key on.
Pin 3 (red/ white wire) is your B+ feed, one that's a suspect in this situation. Your voltage should be basically what system voltage is, supplied through Fuse D of the underhood fuse block (PDC). This circuit commonly rots out from an exposed splice in the left side fender harness, located below the PDC itself, although it sometimes sneaks back enough to be under the washer bottle. Push some amps through this circuit if it shows any voltage at all... if you're blinded by the light, checks OK.
Pin 9 (dark blue) is your ignition switch output. Same test as above.
Pins 11 and 12 (black/ tan) are both power grounds. Reverse your test light polarity and check for good [COLOR=green]power flow[/COLOR]
on both circuits,( sued headlamp). Normal resistance to battery negative should be 5 ohms or less, more like one or so. I'm not completely sure where this grounds at this moment, but it may be this puny little 8mm sheet metal screw to the left of the battery. If it's an issue, I'll sure look it up.
With the 60-way disconnected, there should be zero continuity to ground on Pins 6 (violet/ white) and 7 (orange). The #6 pin is your 5v power feed to the MAP, TPS and [COLOR=green]vehicle speed[/COLOR]
sensors. With the connector dangling, the sensor ground that completes the circuit is disconnected as well (Pin 4, black/ light blue) so this should be an open circuit. Any short to ground at this point is a harness failure and will take the PCM down instantly. No damage will result from the 5v being shorted, but the PCM will appear completely dead.
Pin 7 is the 8v circuit, supplying the cam and crank sensors. Same as above, with the sensor ground disconnected, it should be an open circuit. Shorting of the 8v will also take the PCM down, but it'll have slightly different symptoms.
Determined PCM was bad, repalced. Now have fuel pressure, and power to coil, still no start and no spark..SO, for "S" and giglles opened the harness to visually inspect splices, form PDC to , well, every where. You can imagine wht the engine bay looks like. Don't have access to a scope, so hooked a noid light into the leads for the coil, noid light lights up for 2 seconds w/ key on, then pulses while cranking. Put noid light into injector plug, get pulse there also.
My question is, is the test on pin 6 and 7 a valid test? I do read resistance in both circuits to ground, but, if I unplug the crank sensor, and the cam (sync) sensor, pin 7 goes open. I even used new sensors to test, and when plugged in, got resisitance.
Also, I have 9 volts going to cam and crank sensors, not 8, am wondering why. I have 5 volts going to tps, map, etc.
I now know why mosta of the drivability guys I know are bald, and drink like fishes..
Have done compression test, put engine at TDC and rotor is pointing at # 1 cyl, verified that rotor DOES turn.
New parts so far:
Cam (sync ) swensor
Distributor cap and rotor
Coil (actually 2 different new ones we had in shop, in case I got a bad 1)