Engine is not starting

It sounds like you have one of two problems, first is the ECM relay is shorted out and not supplying power to the ECM or you have an ECM that is out and needs replacement. Check to make sure the ECM is getting power and ground.

Here are some guides and diagram (below) that will help you get the problem fixed.

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

and

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

If you are not getting power to the injectors using a test light, a bad ground isn't the issue because you are creating your own with the test light.

Here is a guide that can help for generic problems.

https://www.2carpros.com/articles/car-cranks-but-wont-start

You need to check the injector resistance for me. You should have 11.8 to 12.6 ohms of resistance. Additionally, power to the injectors should not be constant. It should strobe on and off as the injectors. That is why I feel you either have a short applying power all the time or the ECM is bad. Take a look at the wiring schematic I attached. The power to the injectors comes from the ECM. I can't find the exact voltage they should be getting, but 12 volts sounds very high.

https://www.2carpros.com/articles/how-to-test-a-fuel-injector

Please let us know what happens so it will help others.

Cheers

I checked the resistance on the fuel injectors and it is good. Its not easy to do on this vehicle because they are under the intake manifold.

I will be on the search for a decently priced ecm. Also, It was my understanding that in a multi port injector vehicle, the ecm strobes the Ground for cycles not the power. They are fed constant power. Is this correct?

I replaced the ECM relay and I can hear it working so I don't think that is it.

You should only get power when the engine is cranked and it shouldn't be constant. Something tells me rather than checking the injectors, you should be checking the rest of the wiring to the ECM since the problem seems before them. I still feel there is a short to a power source or the ECM is bad.

I have a replacement ECM on order, should be here tomorrow. I will keep you updated. Thank you for your time. BTW, I replaced the alternator so lack of power from the battery/alternator is out of the question. Just trying to eliminate possibilities.

I got the replacement ECM and now i have injector pulse. I have a feeling Im lacking fuel pressure somehow. The engine is running now by I have low power. I think the timing belt might have jumped, on to the next problem! Thanks for the help you guys are great.

Glad you could get it fixed, that kind of problem can be tough. Please use 2CarPros anytime we are here to help

Cheers

the camshaft position sensor provides information on camshaft position the pcm uses this information along with the crankshaft position sensor information to control fuel injection synchronization.

Great addition to this thread! Please feel free to help out on the site whenever it can add information that will help.

Best, Ken

Engine Mechanical problem
1994 Isuzu Rodeo Question 6 cyl Four Wheel Drive Automatic 120800 miles

I have a problem on cold starts with my 1994 rodeo. If the engine fails to start the first time (which is almost all the time) the engine floods and won't start. Vehicle seems to run fine after starting, but gets poor mileage. I replaced the o2 sensor and plugs, which does make it run better, but the starting is a problem.

When it wont start have you verified spark? When will it finally start? Check the fuel pressure regulator , mounted on the fuel rail with a vacuum line to the intake manifold. If any fuel is present in the vacuum line, repalce the regulator. Any check engine light? if so have it scanned for codes

I have checked for spark and there is spark. It will start only after taking plugs out and drying the fuel off of them. I haven't checked the fuel pressure regulator yet, and there haven't been any "check engine"lights yet. It will also start if i let it sit for an hour or so sometimes, and then when it does start it blows out smoke and smells like fuel.

Now when you say "cold starts" do you mean anytime it sits for an extended period of time or when it is cold outside? This may be a coolant sensor out of range. Are all the plugs wet evenly or is it just a few of them that get wet down?

Yes, when it sits for a while or overnight, it has this problem. It seems like all the plugs are wet with fuel, some more than others.

Could be weak spark, or possibly a fuel pressure regulator bleeding into the engine overnight.Check the quality of the spark first, needs to be bright blue out of the coil, if it is more orange it is too weak. Also check the fuel pressure regulator , mounted on the fuel rail with a vacuum line to the intake manifold.If any fuel is present in the vacuum line replace the regulator

I have checked the fuel pressure regulator and it seems to be fine, spark is strong and blue in color. I drove it today and then let it sit for about 3 hours and tried to start and am still having problems. The outside temp is 56 so it's not that cold.

It was running fine and all of a sudden would not start. I replaced the fuel pump. I checked the fuses. I replaced the relay fuse. when I jump the relay, the fuel pump runs. There is gas in the line at the engine. There is all new plugs and wires. I tried to reset the ecm. I tried a replacement ecm. I started testing wires. The ecm is getting power, but the fuel pump isn't running unless I jump the relay and mnake it run. I am thinking there is a signal loss somewhere in between. Please help. very frustrated at this point.
Thanks

Without any codes or a scanner to watch the sensors this could be a tough one to find.It could eba coolant sensor that is out of range and causing the PCM to over-enrich the engine.

check the relay and where it plugs in if it gets power at the pin to activate the relay it should work.

Could it still be the coolant temperature sensor if the gauge is reading correctly? The temp gauge seems to be reading fine. I will have to have it looked at. Thanks for the help.

at the pin? there is 4 wires that go into the plug. The new relay or any other ones do not work when plugged in, however, again, I can jump it and it makes the pump come on.

Yes. Those use a coolant sensor(2 wire) for the PCM to read and a single wire temp sender for the gauge

then there is a bad connection where you plug it in try tweeking the prongs on relay and see if that works.

I installed a newer engine in a 94 Isuzu the engine is from a 96 Isuzu it came equipped with individual coil packs and the 94 engine has spark plug wires to a coil packs instead of each coil packs buy them self I installed it with the old injectors ,intake ,throttle body ,new spark plug wires ,original wiring harness to the truck, and sensors from the 94 engine I noticed the 96 engine has a sensor located on the timing cover located on the cam area and the 94 engine didn't. There for I removed it . After completing the installation of the engine it cranks over and gets gas but won't start ?

94 is obd 1 and 96 is obd 2 it's not gonna work unless you maybe hook everything up to the 94 type.

Correct I used every thing from the 94 I only used the engine it self from the head to the block everything else is from the 94 engine any other suggestions

it may have a different ignition system like a more tooth reluctor wheel which in your case would not work at all . If you have like a 24 tooth on the 94 and the 96 had like a 58 then it's not compatible and the only way to make it work is to put the same thing on the newer engine. but not having one apart can't say

Electrical problem
1994 Isuzu Rodeo Question 6 cyl Two Wheel Drive Automatic 176000 miles

My 94 Isuzu Rodeo won't start. I tried a few days ago to start it, and it turned over, but not enough to start up. Then it acted like the battery had died, no power to anything, weak beeping sound. I tried jumpstarting it, then put in a new battery, but I have no power at all, not even enough to turn on dome lights. When I turn the key, it does nothing. Could it be the ignition, or the starter?

No crank at all/nothing/nada:

Could be the starter, starter relay, park and neutral switch and ignition switch assuming the battery and connections are good.

I have a 94 rodeo when. Try to start ignition fues pops what to do with this

There is a shorting somewhere causing the ignition fuse to blow. Can you specify the location of the fuse? Was any repairs carried out prior to this occurring?

Are you able to crank the engine?

Electrical problem Question 6 cyl Two Wheel Drive Manual

I have a rodeo that won't start the other day while driving it suddenly died. I have checked for voltage at fuel pump there is none. I have also jumpered power to fuel pump and it will run that way but engine will not start. I sprayed starting fluid into throttle body and it will run. i have checked all fuses to pump and all relays but still no voltage to fuel pump. I have checked wires all the way up into the vehicle but from there Im lost any help would be appreciated

FUEL PRESSURE & FUEL PUMP RELAY TEST Fuel Pressure 1. Release fuel pressure. See FUEL SYSTEM PRESSURE RELEASE . Install a fuel pressure gauge between fuel pressure regulator and fuel distributor pipe. See Fig. 1 . Bleed air from fuel line going to pressure gauge. 2. Unplug fuel pressure regulator Vacuum Switching Valve (VSV) connector on right side fender skirt. This is a 4-wire connector with Black and Blue wires in harness. ECM controls VSV to cut vacuum to fuel pressure regulator during hot engine starts. 3. Start engine and measure fuel pressure at idle. Disconnect fuel pressure regulator vacuum hose. Note fuel pressure at idle with vacuum hose disconnected (no vacuum). Fuel pressure should be 42 psi (3.0 kg/cm 2 ). 4. If fuel pump pressure is low, check for fuel leaks, restrictions in intake side of fuel pump, leaking injectors, faulty pressure regulator or faulty fuel pump. If fuel pressure is high, check for restrictions in return line to tank or faulty pressure regulator. If pressure does not change when pressure regulator is disconnected, replace pressure regulator. Fig. 1: Installing Fuel Pressure Gauge Courtesy of ISUZU MOTOR CO. 5. Reconnect pressure regulator vacuum hose and check fuel pressure (with vacuum). Fuel pressure should be 35 psi (2.5 kg/cm 2 ). Apply battery voltage to VSV connector Blue wire terminal, and ground Black wire terminal (with vacuum). See Fig. 2 . Fuel pressure gauge should read about 42 psi (3.0 kg/cm 2 ). If fuel pressure is not within specification, check for defective VSV. 6. Disconnect and plug vacuum hose from fuel pressure regulator. Stop engine and ensure fuel pressure remains greater than 35 psi (2.5 kg/cm 2 ) for 4 minutes after engine stops. 7. If pressure drops, check for leaking injectors, faulty pressure regulator or bad check valve in fuel pump. If engine does not start, by-pass fuel pump relay to check for fuel pressure. 8. Remove fuel pump relay from underhood fuse/relay box. Connect a jumper wire between terminals No. 1 and 3 of fuel pump relay connector in fuse block. See Fig. 3 and Fig. 4 . 9. If fuel pump does not operate, check for battery voltage to terminal No. 3. If battery voltage is present, check for open in fuel pump circuit. If fuel pump operates with jumper wire installed, check fuel pump relay and relay energizing circuit. Repair as necessary. Fig. 2: Identifying Pressure Regulator VSV Terminals Courtesy of ISUZU MOTOR CO. Fig. 3: By-Passing Fuel Pump Relay Courtesy of ISUZU MOTOR CO. Fig. 4: Identifying Fuel Pump Relay Terminals Courtesy of ISUZU MOTOR CO. NOTE: Begin basic fuel system diagnosis with testing fuel pressure.Fuel Pump Relay 1. Power from charging circuit relay runs through fuse/relay box fuse No. 5 and diode box "A" to energize fuel pump relay. Relay is also energized from diode box "A" through oil pressure switch circuit in case of charging system failure. 2. When energized, fuel pump relay closes power circuit from main fuse No. 1, through fuse No. 2, through fuel pump relay to fuel pump. See appropriate wiring diagram in WIRING DIAGRAMS article. 3. To test relay, remove fuel pump relay from fuse/relay box on right fender panel. Using jumper wires, ground terminal No. 4 (Black wire) and apply battery voltage to terminal No. 5 (White wire). See Fig. 4 . There should be continuity between terminals No. 1 and 3 with relay energized. If continuity is not present, replace relay.

ok after jumpering 1,3 connections to get fuel pump to run it will but engine will still not start even with fuel pump engaged and running

Check for spark and compression, one is missing...let me know. Look on our how to section at the top right of the page for help with those two....

Here is a guide that will help

https://www.2carpros.com/articles/car-cranks-but-wont-start

it has spark and compression it will start and run if i spray starting fluid in the throttle body

I also checked ignition module and ita was okay. I Ichecked for continuity of the wires from the fuel pump all the way to the computer. on the other side of the harness I have voltage. I was wondering if the computer could be at fault I have never heard of one failing while driving

Can you give me the engine size? And have you tried to retrieve any fualt codes? Here's how to do that, post any codes found.

I have absolutely no power to the computer i have checked all fuses and relays they all checked out fine I also have pulled the plugs from computer and there seems to be voltage to the computer but i don't know which color wire is the power wire so basically there is no way to check for any codes

UNDERHOOD FUSE & RELAY PANEL IDENTIFICATION Fig. 2: Underhood Fuse & Relay Panel Identification Courtesy of ISUZU MOTOR CO. Fusible Link Identification  A - 80 Amp (1991-92 3.1L)  A - 60 Amp Main-1  B - 30 Amp Main-2  C - 30 Amp (1993-94) ECM (3.2L)  D - 30 Amp Condenser Fan (A/T Models) Relay Identification  1 - Headlight Relay  2 - A/C - Heater Relay  3 - Starter Relay  4 - A/C Compressor Relay  5 - Charge Relay  6 - Fuel Pump Relay  7 - ECM Relay  8 - Wiper Relay Fuse & Circuit Breaker Identification  1 - 15 Amp (1991) ECM, Fuel Injection System  1 - 15 Amp (1992-94 2.6L) ECM, Fuel Injection System  1 - 10 Amp (1992-94 3.1 & 3.2L) Heated Oxygen Sensor, Fuel Injection System  2 - 20 Amp (1991-92) Fuel Pump  2 - 20 Amp (1993-94 2.6L) Fuel Pump  2 - 15 Amp (1993-94 3.2L) Fuel Pump  3 - 10 Amp (1991)  3 - 15 Amp (1992-94) Turn Signal Lights, Hazard Warning Flasher Lights  4 - 10 Amp Horn, Door Locks  5 - Not Used (1991 3.1L)  5 - 10 Amp Charging System, Charge Warning Light WARNING: Always disconnect battery ground cable before servicing "high- current fuses. It is recommended that "high-current" fuses be replaced by a qualified technician. Page 1 of 2 FUSES & CIRCUIT BREAKERS -1994 Isuzu Rodeo LS 6 - Not Used (1991) (1992-93 2.6L)  6 - 10 Amp (1992-94 3.1L & 3.2L) A/T Interlock System  6 - 10 Amp (1994 2.6L) Heated Oxygen Sensor, Fuel Injection System  7 - 20 Amp Heater/Air Conditioning Blower Controls  8 - 10 Amp Air Conditioner Compressor Controls  9 - 10 Amp Right Headlight  10 - 10 Amp Left Headlight

Underhood fuse block swap out relay #7 thats the ECM relay. Ground Circuits Using a DVOM, touch negative voltmeter lead to a good ground. Touch positive voltmeter lead to each ground terminal. With vehicle running, voltmeter should indicate less than one volt. If reading is greater than one volt, check for open, corrosion and loose connection on ground lead. See ECM GROUND LOCATION table for ECM ground location. Page 1 of 1 SYSTEM/COMPONENT TESTS - 2.6L EFI -1994 Isuzu Rodeo LS

ECM Relay 1. Remove relay from connector. Test for continuity between terminals No. 1 and 2. See Fig. 6 . Continuity should exist. Test for continuity between terminals No. 3 and 4. Continuity should not exist. 2. Apply battery voltage between terminals No. 5 and 6. Test for continuity between terminals No. 1 and 2. Continuity should not exist. Test for continuity between terminals No. 3 and 4. Continuity should exist. Replace relay if defective.