I have a 96 Dodge 1500 4x4 turns over but wont start, its not getting any fire and the fuel pump not working, when I checked the ECU it's just reading (link error) I changed the coil, pick up, crank sensor and wires. Is it the ECU, loose wire or does it have a fusible link I can check?
Did you have a paper spacer on the end of the new crank sensor to set the air gap? Has the Check Engine light turned on? The best place to start is by measuring the voltage on the dark green / orange wire at the ignition coil, one of the injectors, or either small terminal on the back of the alternator. You should see full battery voltage there for just one second after turning on the ignition switch. It should come back when the engine is rotating, (cranking or running). If it doesn't come back during cranking, we have to look at the cam and crank sensors.
February, 24, 2011 AT 5:22 AM
The check engine light was on before it quit running, now its off. I run a scan while it was running and one of my oxygen sensors are bad. I didn't know about the paper spacer on the crank position sensor. What would cause the fuel pump to quit working at the same time it quits firing? And also the truck was running fine the day before, never missed or died once. Would a fusible link cause this?
February, 24, 2011 AT 6:38 AM
The crankshaft position sensor can have a thick paper spacer stuck to the end that sets the gap. It slides off the first time the engine is started. Some aftermarket sensors have a thin plastic rib molded to the end to set the gap. It will partially wear away over time so to reinstall a used one you must cut the remaining rib off, then install a paper spacer. If you don't use any spacer it's possible the sensor could go in too far and be broken from the flex plate hitting it.
The camshaft position sensor lives in the distributor. Both sensors are powered by a regulated 8 volt supply inside the Engine Computer. It doesn't happen often, but it's worth mentioning that if that orange wire to either sensor becomes shorted to ground the computer will turn that power supply off to protect it. Once the short is gone, the ignition switch must be cycled off and back on to reset the supply.
When the Engine Computer receives pulses from both sensors it turns on the automatic shutdown (ASD) relay. That relay sends current to the injectors, ignition coil(s), alternator field, oxygen sensor heaters, and fuel pump or pump relay. Since the fuel pump and ignition coil are tied together in the same circuit it is necessary to check both of them for a no-start condition. If you have spark OR the pump is running, (which can be hard to tell), you know the two sensors are working. That's when you must troubleshoot the dead circuit. When BOTH are dead, that's when to look at the sensors. The sensors cause a lot more trouble than the pump or ignition coil.
In addition to turning on the ASD relay when the engine is rotating, the computer also turns it on for one second when you turn on the ignition switch. You will usually be able to hear the pump hum for that one second but it's hard to hear it during cranking because of the noise from chimes and the starter.
The most reliable test is to measure the voltage from the ASD relay. That's the dark green / orange wire at the coil, injectors, or either terminal on the back of the alternator. You can prop up a test light so you can see it from inside the truck or you can jump the starter relay from under the hood. I can describe two ways to do that. If you see battery voltage for the first second after turning on the ignition switch, you know the wiring and relay are okay and the computer has control of it. Whether or not the voltage returns during cranking will determine where to go next.
February, 24, 2011 AT 6:56 AM
I forgot to mention that since the Check Engine light came on there is at least one diagnostic fault code stored in the Engine Computer. In the future when you have an intermittent problem it is important to read those codes as soon as possible. If the problem doesn't come back the codes will erase automatically after 50 starts. Disconnecting the battery will erase the codes too, then that valuable information will be lost.
You can read the codes by cycling the ignition switch from "off" to "run" three times within five seconds, then watch the flashes of the Check Engine light, ... Or, starting with '96 models the codes should be displayed one after the other in the digital odometer.
February, 27, 2011 AT 8:42 PM
I'm getting a reading on the ignition coil and alternator, I've already replaced the computer so thats not the problem either, where should I go next?
February, 27, 2011 AT 9:21 PM
If you have voltage on that wire during cranking you are missing either spark of fuel. For spark, the coil is the most likely suspect. If fuel is missing, the most common problem is the fuel pump fails to start up. Often banging on the tank while a helper cranks the engine will get it going. It will continue to run once it has started.
February, 27, 2011 AT 9:45 PM
I'm not good with these multimeter's so I might have done it wrong I'm still not getting fire on the coil, the coil is new also, and the fuel pump is not working. I just tried to read the meter again and its not doin anything on the coil or the alternator. Which setting should I use to test the coil wires correctly?
February, 27, 2011 AT 10:34 PM
Use the 20 volt DC scale. That will read anything up to 20 volts with one space after the decimal point. The black lead goes to the battery negative post or any paint-free point on the engine. With the red lead, poke it through the rubber seal on the back side of the connector for the coil or any of the injectors.
Prop the meter up in front of the windshield so you can see it or have a helper run the ignition switch. You should see a voltage reading when you turn on the ignition switch but it will disappear right away so you might miss it. What is important is it must come back steady while cranking the engine.
February, 27, 2011 AT 11:01 PM
Ok, I got a reading of 0.28 with the switch on, then 0.32 cranking, on coil and alternator, both were steady readings
February, 28, 2011 AT 5:53 AM
There's one fuse under the dash that's not getting any kind of reading, its the #9 fuse its marked engine. I changed the fuse, nothing. If u could help figure out what it goes to maybe I have my solution. Thanks