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93 rodeo wont start, heres the symtoms. help please

08-28-2008, 10:28 PM
1993 Isuzu Rodeo 3.2 Automatic.

Ok heres what i got, and what i have done.
1 tested fuel pressure 65psi from pump.
2 thought maybe the pressure reg was bad, blocked the return line so it rail would keep full pressure.
3 has spark
4 it will run if spraying gas directly into the intake.
5 replaced ECM, (no change)
6 Tested wires at injectors, with a test light. they dont pulse, both wires show steady current while the key is on or cranking.
7 swapped the ecm, fuel pump, and other relays, and didn't have any change in how its acting.
8 I have power going into the ecm wires.
9 The rodeo sat unstarted for 5 months, and now it wont start.
10 cranks over fine, doesn't sound like its out of time, i get one putt putt putt on the first crank, like it wants to start. but after that. it just keep cranking with no hope. If it sets for 10 mins or so, ill get another putt putt.
11 when i did the self diognostic check, i get a 3 sec humming from the (i think its the TPI on top of the throttle body) it does it every time i connect and disconnect the jumper.
12 When checking codes, i get 2 really quick flashes, pause, 1 flash, 2 flashes, for the 12 code.
13. checked all fuses and all are good.
14 It ran fine when i parked it. but now nothing. this thing is really starting to frustrate me.
15 hopefully whatever you suggest i check next will be the problem. thanks in advance.
16 It just seem liike something isn't telling the injectors to pump.

09-03-2008, 07:05 PM

I didn't see this post until after I responded to the other. what location did you check fuel psi? If it was down by the tank/filter, could there be a clog in the line upstream? If it's similar to mine, there is a small schraeder type valve on the injector rail that you could check the pressure/flow at, or is this how you did it? could you have some bad gas? Could you have some fouled plugs from sitting for that time?

09-03-2008, 07:19 PM
if ya got good spark then stick with the injector avenue.noid light or stethascope on injector housing.

09-03-2008, 09:21 PM
Been doing alot of testing, after 2 ECMs ive found that my injectors aren't getting the negative signal to fire the injectors. Ive been trying to troubleshoot that, I cant come up with anything, Somethings not telling the ecm to fire the injector. Ide find it really hard to believe i got 2 ecms with the same exact symtoms.
The majority of bad ecms from what im told. will not activate the Check engine light at all. and my light works, and only gives me the 12 code. which is nothing.

09-04-2008, 12:54 PM
Fuel Injector Circuit
Chart A-3 Cranks But Will Not Run (Part 1 Of 3)

Circuit Description
Before using this chart, battery condition, engine cranking speed, and fuel quantity should be checked and verified as being OK.

Test Description
Numbers below refer to circled numbers on the diagnostic chart.

A malfunction indicator lamp ( check is basic test to determine if there is battery positive voltage and ignition voltage supplied to the Engine Control Module ( (ECM ). No data link connector ( data may be due to an ECM problem. CHART A-2 will diagnose the ECM. If throttle position sensor ( voltage is over 2.5 volts, the engine may be in the "clear flood" mode, which will cause starting problems. The engine will not start without reference pulses and, therefore, the "Scan tool" should indicate engine speed during cranking.
Because the electronic ignition system uses two plugs and wires to complete the circuit of each coil, the opposite spark should be left connected. If revolution per minute was indicated during crank, the ignition control module ( is receiving a crank signal, but no spark at this test indicates the Ignition Control Module (ECM ( is not triggering the coils.
The test light should blink, indicating the ECM ( is in control of the injectors. How bright the light blinks is not important. However, the test light should be a J-3473O-3 or equivalent.
This test will determine if the ignition control module ( is not generating the reference pules or if the wiring or ECM ( are at fault. By touching and removing a test light to 12 volts on YEL/RED wire, a reference pulse should be generated. If revolution per minute is indicated, the ECM and wiring are OK.
High resistance in the spark plug wire could cause a "no start" condition. If a spark plug wire is found to be faulty, replace it and retest system.

09-04-2008, 12:55 PM
Fuel Injector Circuit
Chart A-3 Cranks But Will Not Run (Part 2 Of 3)

Test Description
Numbers below refer to circled numbers on the diagnostic chart.

This will check the injector harness for an "open" or "shorted" circuit after the engine harness connector.
A shorted or resistance injector could be the cause of a "cranks but won't run" symptom.
Test for a short to ground in the injector driver circuits.
Check for voltage at the injector. An "open" in the RED/GRN wire at the splice from the main relay would result in a "crank but won't run symptom.
Test the engine control module ( for a injector pulse.
A faulty resistor module could be the cause of a no start. If module was found to be faulty, recheck the engine control module ( after replacement of the resistor module.

09-04-2008, 12:55 PM
Fuel Injector Circuit
Chart A-3 Cranks But Will Not Run (Part 3 Of 3)

Circuit Description
If the "Scan tool" did not indicate a engine speed and there is no spark present at the plugs, the problem lies in the electronic ignition system or the power and ground supplies to The module.

The magnetic crankshaft position is used to determine engine crankshaft position sensor ( much the same way as the pick-up coil did in distributor type systems. The sensor is mounted in the block near a seven slot wheel on the crank shaft. The rotation of the wheel creates a flux change in the sensor which produces a voltage signal. The Ignition Control Module (ICM) then processes this signal and creates the reference pulses needed by the engine control module ( and the signal triggers the correct coil at the correct time.

Test Description
Numbers below refer to circled numbers on the diagnostic chart.

This test will determine if the 12 volt supply and a good ground is available at the 1CM.'
Tests for battery positive voltage in Ignition Feed Circuit to the ICM.
Checks for continuity of the crankshaft position sensor ( and connections.
Voltage will vary in this test depending on cranking speed of engine.

09-04-2008, 09:52 PM
Thanks Mech.33
The info on maybe a bad TPS might help. Its looks like that could cause what problems im having. Ill check that out in the morning. I just orded a NOID test light, to see if im getting pulses to the injectors. Right now using a test light, or my digital multimeter, im not picking anything up. but it might be too quick for my equipment to react and show the pulses.
Is this info from a Chilton Manual? Ide like to get the complete manual. I downloaded one from someplace, but its in a .RAR format, and i cant seem to extract them and view it.

09-04-2008, 10:14 PM
It got the best of me, I checked the TPS, I got 5Vs to the Blue/Org. I got 7Vs to the Blu/Red at Idle position, and 4Vs At Wide open. Which from what im reading would be in Engine Flood condition? What would reset Or correct this? Or cause it to think its in flood condtion. This is without cranking the engine over. just with Key On Run.

09-05-2008, 02:43 PM
alldata online manual

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