I have been working with this problem for a while.

I have a 92 rodeo and I am having a problem getting the engine to start. I am not getting pulses from the ECM to the injectors. This is what I have checked to this point. I have replaced the fuel pump, the throttle body, Throttle position sensor, and computer. I have checked the ECM fuse and relay. I have checked all wiring from the Fuel injectors to the ECM and I have continuity.I have checked to make sure I have ground from the body of the truck to the engine to the battery. I can prime the throttle body by pouring fuel into it and the engine will fire and burn the fuel until it is gone. I have applied twelve volts directly to the injectors by just taping the wires on the terminals. I can hear the injectors clicking open and then closed when the voltage is removed. There is no fuel coming out of the injectors.

Is there an input going to the computer that will keep it from sending pulses to the injectors If something else is not working correctly.

Kent Mathew

I have been working with this problem for a while.

I have a 92 rodeo and I am having a problem getting the engine to start. I am not getting pulses from the ECM to the injectors. This is what I have checked to this point. I have replaced the fuel pump, the throttle body, Throttle position sensor, and computer. I have checked the ECM fuse and relay. I have checked all wiring from the Fuel injectors to the ECM and I have continuity.I have checked to make sure I have ground from the body of the truck to the engine to the battery. I can prime the throttle body by pouring fuel into it and the engine will fire and burn the fuel until it is gone. I have applied twelve volts directly to the injectors by just taping the wires on the terminals. I can hear the injectors clicking open and then closed when the voltage is removed. There is no fuel coming out of the injectors.

Is there an input going to the computer that will keep it from sending pulses to the injectors If something else is not working correctly.

Kent Mathew


You might try changing out your ignition module. The ignition module is inside the distributor housing.

eladqm

I know this is stupid but you didnt mention it, fuel filter, have you changed it? Make sure its not backwards. One thing I do know is when the key is first turned on the fuel pump fires, but does not stay on unless the ECM recieves a crank signal, There is a diode on that circuit, if you recently had an electrical issue the diode or connection might be bad. My issue I forgot where the diode is and from where the crank signal comes from, you can find this in an Isuzu service manual, if you dont have one I will check it out.

You might try changing out your ignition module. The ignition module is inside the distributor housing.

eladqm


Have already changed it out.

The engine will fire and burn gas as long as I pour it into the throttle body. Spark and ignition of fuel is there

Thanx

I know this is stupid but you didnt mention it, fuel filter, have you changed it? Make sure its not backwards. One thing I do know is when the key is first turned on the fuel pump fires, but does not stay on unless the ECM recieves a crank signal, There is a diode on that circuit, if you recently had an electrical issue the diode or connection might be bad. My issue I forgot where the diode is and from where the crank signal comes from, you can find this in an Isuzu service manual, if you dont have one I will check it out.


Yes Fuel filter was one of the first things I changed and yes is is in the line in the right direction. I have pulled the fuel lines loose at the throttle body and the fuel is there.

I have noticed the fuel pump coming on and then shutting off. I will check the diode it is located in the fuse and relay box under the hood.

I'm not sure where the crank signal comes from either, If you have any information on that it would be helpful.






Thanx for the input

Kent

I haven't found the crank signal yet, I'm checking the schematics as I speak, for a 96 rodeo. I did find a fuse for the starter 16 it hot all the time, be careful checking it, pull the negative battery. BTW since making those changes have you pulled the negative from the battery? Clearing the ECM might be all you need, (I said might be). Anyway I'm still looking.

I found something interesting on the web, first the 96-98 are the same engines. I found that if the timing marks are not aligned up right with the belt (I presume) the engine will not turn over.

All three marks have to be lined up.

I also saw a post about a bad mnegative terminal to the PCM (powertrain control module) I dont know what that is, so I can help and its not in my book. BTW sorry for all the posts, just looking everywhere.

Have you tried www.2carpros.com

Ok, the crank signal comes from both the camshaft and crank shaft sensors, They share a common ground, There is also a test and its not for the timid, thats for sure.

I'm going to write this verbatum and put a disclaimer, if you dont understand, seek a mechinic that does. Read thought ALL of this first, there are three tests.

Disconnect the ignition coil harness connectors at the coil pack and install a test light to the battery positive terminal and touch the tip of the test light to the the coil module terminals while an assistant cranks the engine over. This tests the triggering circuit in the ignition module. A blinking test light indicates the module is triggering Note: ON 1996 and 1997 systems check the primary wires GRN, GRN/BLK, GRN/RED, GRN/YEL, GRN/WHT,GRN/ORN. Note 2: Remove the fuel pump fuse and disable the ignition system to prevent the other cylinders from starting and running. The easiest method to disable the ignition system partially is to remove each plug wire and ground it to the enigine with a jumper wire. This allows the other cylinders not to fire but still allows the trigger signal to reach the coils.

A slowly blinking light at this point indicates the ECM is not seeing the crank sensor signal. At this point the problem is the crankshaft sensor or camshaft sensor.

Testing crankshaft position sensor disconnect th CKP sensor electrical connector and with the ignition key ON(engine not running) check for REFERENCE voltage to the CKP sensor it should be around 5 volts.

Testing the camshaft sensor disconnect th CMP sensor electrical connector and with the ignition key ON(engine not running) check for REFERENCE voltage to the CMP sensor it should be around 5 volts.

If voltage is present then the sensors are not bad, this does not rule out timing.

There are 3 wires from each sensor, Yel/RED and Yel/BLK are commons Yel/BLK is the ground. The crankshaft sensor has a yel to ECM and the camshaft sensor has a blue wire coming from ECM. Which one of these is the REFERNCE wire, it does not say. But I just read something interesting, The camshaft sensor signals the ECM to start up fuel injector pulsation as well as misfire detection. (timing IS everything).

Location of the sensors, the crankshaft sensor is mounted on the side on the engine block, the camshaft sensor is mounted on the timing chain cover cover near the camshaft.

Like I said careful here, I would always error on the side of caution!

Ya know, going over this, I had this posy confused with another, Man I got too much going on these days. The post was for a 96 rodeo, for another member. On the '92 the crank signal is available on C9 on the ECM. But the wire itself comes from the starter relay. Not the dioide after the relay, the the relay itself. I will get the specifics to you tonight, Ingore the other post of mine, I got you and someone else confused. -sorry

OK got the right poop.

The diode to the ECM is pnk/blu and is at position B10 on the ECM. From the diode to the starter relay the wire is brn/red. The crank signal wire is blk/grn which goes to C9 on the ECM and position 5 on the starter relay. OK from the book

Crank signal is a 12 volt signal to the ecm during the cranking to allow enrichment and cancel diagnostics until engine is running 12 volts is no longer on circuit.

The schematic refers to a bulb check between c9 and the starter relay this is the BLK/GRN wire. The bulb is between the Blk/Grn wire and ground. The test light should be on when cranking.

I also read that if the TPS has more than 2.5 volts on it, the ECM will consider a flooded engine and will go into clear flood mode. The refernece pulse you are asking about is set in the ignition module. I can provide a test procedure if you want.

I guess the first thing to test is the ECM. What you can do with the key off is short A and B together on the ALDL connector and turn the key on, does the check engine flash a code of twelve. That is one flash pause two flashes long pause and repeat two more times. This means a good ECU, then I would begin looking at the crank signal and TPS.

I found out that oil pressure switch turns on the fuel pump relay, oil pressure needs to be at least 4PSI in order to control switch.