1994 Isuzu Trooper ( Hard to start )

gpabear

I have a 1994 Trooper (SOHC) with just 70,000 miles on it. I've done the general up keep on it like oil, plugs, air/fuel filters etc... Runs great and very few problems until latley. It's very very hard to start. In the last 2 months we've put in a new battery,6 plugs,PVC valve,wiring set,fuel filter,fuel pump,starter and fuel pressure regulater on hunches from a mechanic. It's still hard to start. To me it sounds like it's STARVING for FUEL. I now cycle the key about 10X's before trying to start it and after trying many times it will start and then runs like a champ. I'm into this about $1300 already and still the same problems. I just don't want my wife and grandkid stuck somewhere. What else could/should I try? Somebody told me a Oxgyen Sensor?, also that I may have a bad/leaking fuel injector? At the shop when they hook up the computer to it it says everything is OK, well that's because once it does start it's runs great. The computer does not show a bad code #, because when it starts it says all is well. Any ideas and/or help would be GREAT! THANKS!!!!

atfdmike

Hi, you have taken good care of the vehicle, and my first guess based on your description would be a fuel problem too! That being said, a fuel guage can be hooked to the fuel rail, but it is hard to get to. There should be fuel pressure almost instantly when you turn on the key, and if memory serves me, it should be around 30#. When you turn the key on, the fuel pump only runs for about 2 seconds. My guess would also have been the fuel pressure regulator, as that is what the factory suggests when hard starting is a problem. The fuel pump relay can be sticky, if you search the Trooper forum there are descriptions for jumpering the pump so you can check to see what it is doing with or without the engine running. If you don't find the info, and want to try it, post again and I will research it for you.
Have you heard any peculiar noise like a vacuum leak or hissing when you shut off the Trupr? How about the vacuum lines, they OK, Not kinked or burned through? It is good that no codes are stored in the ECM, but it does make it hard to diagnose.
If you pull a plug wire and put a good grounded plug in it, do you get a good spark when you first crank it? Sometimes the ignition module or crank sensor can be intermittent, but they generally get so bad that the vehicle will not start at all. If no spark when you crank, then look at the ignition system.When they go bad, there may be no code stored. How about your EGR valve, is it clean and working properly? Did the mechanic change/replace the fuel pickup screen and clean the sump in the fuel tank so fuel will flow freely?
These are just some ideas to maybe get the answers for. Hope they help. I don't think it matters but is your trooper a SOHC or a DOHC? Let us know what you find.

gpabear

Thanks for the info. I'll talk to my mechanic friend who understands the things you talked about. I hope one of your ideas might be the problem.
Thanks! GpaBear

gpabear

I took it to a Isuzu shop with the info., they said it was not holding fuel pressure (pressure leak). They did a "power flush" of the injectors and it started right away for about 1 day and it's now back to hard to start. They now have told me that it will need all new fuel injectors (approx. $1300).
Does that sound like a final fix to my problem? How do I know that after putting in more $ that it's the final and real problem?
Thanks for any ideas and/or help!
GpaBear

atfdmike

Well, It is tough to diagnose from a distance, but I looked at the charts, and as you can see below, the first chart refers to A (emphasis added)leaking fuel injector as a possible cause of low pressure (at start up). I kind of wonder how they tested the fuel pressure; do you get a cloud of black smoke when the trupr does start, as you might expect if the cylinder has raw gas in it due to leaking injector(S)? It seems kind of weird that a single injector could cause a starting problem as you describe, but also that several would fail at the same time? Did you ever get any feedback on codes from the testers? I can't come up with a strong argument for not getting new injectors, but you need to ask how fast the pressure leaked down when the engine is turned off....they should know as they should have had a guage on the fuel rail to see exactly what happened when they tested the fuel system. Can you see if the fuel rail, pressure regulator, etc look like they have been worked on or replaced? As you can read below, there are other parts that also could generate the same conditions in the fuel system. Good Luck.

Circuit Diagram

Circuit Description
The Fuel Pump delivers fuel to the Fuel Rail and injectors, where the system pressure is controlled from 280 to 320 kPa (41 to 46 psi) by the Fuel Pressure Control Valve. Excess fuel is returned to the fuel tank. When the engine is stopped, the pump can be energized by jumping the Fuel Pump Relay connector with a fused jumper.

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

Use pressure gauge J-34730-1. Wrap a shop towel around the fuel pressure tap to absorb any small amount of fuel leakage that may occur when installing the gauge. (The pressure will not leak down after the Fuel Pump is stopped on a correctly functioning system.)
While the engine is idling, Manifold Absolute Pressure is low (high vacuum). When this is applied to the Fuel Regulator Diaphragm the vacuum will result in a lower fuel pressure at about 190 - 200 kPa (25 - 30 psi) .
The application of high vacuum to the Fuel Pressure Control Valve should result in a fuel pressure drop.
Fuel pressure leak-down may be caused by one of the following:
Fuel Pump Check Valve not holding.
Pump Coupling Hose leaking.
Fuel Pressure Control Valve leaking.
Injector sticking open/leaking.
Diagnostic Aids
Improper fuel system pressure may contribute to one or all of the following symptoms:

Cranks but will not run.
Diagnostic Trouble Code 44 or 45.
Cutting out (May feel like ignition problem).
Hesitation, loss of power or poor fuel economy.



Circuit Description
The Fuel Pump delivers fuel to the Fuel Rail and injectors, where the system pressure is controlled from 280 to 320 kPa (41 to 46 psi) by the Fuel Pressure Control Valve. Excess fuel is returned to the fuel tank. When the engine is stopped, the pump can be energized by jumping the Fuel Pump Relay connector with a fused jumper.

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

Pressure less than 280 kPa (41 psi) may be caused by one of two problems.
The regulated fuel pressure is too low. The system will be running lean and may set Diagnostic Trouble Code 44. Also, hard cold starting and overall poor performance is possible.
Restricted flow is causing a pressure drop. Normally, a vehicle with a fuel pressure loss at idle will not be driveable. However, if the pressure drop occurs only while driving, the engine will surge and then stop as pressure begins to drop rapidly.
Restricting the fuel return line allows the fuel pump to build above regulated pressure. When battery positive voltage is applied to the Fuel Pump Relay, pressure should be above 450 kPa (65 psi) .
This test determines if the high fuel pressure is due to a restricted Fuel Return Line or a Fuel Pressure Control Valve problem.

30dohc

your problem sound familiar, I run into the same problems and alway happened in different ways that needs to be repaired, cleaned or replaced. You said that already replaced the fuel pump, can you read fuel pressure while you turn the ignition on?, can you check if you have firing at the ignition coil while you cranck the engine? and please if the engine runs read the following values whit a scanner the ECT (electronic coolant temperature sensor) while the car is even not running and the switch on you can get this readings and of course when your engine runs too. I need this values and also your trim values in the scanner so I will tell you from there what else we need in order to diagnosus your problems! :shades:

danco

This is the second time in two years that the car will not start. First time no codes flashed, mechanic changed spark plugs, started, but every once in a while on the road it would act like it was getting to much gas, black smoke, sputtering, back off the gas okay. This time, exactly one year later, will start in the morning, but not any other time of the day. Took it to the mechanic, said my hot/cold engine sensor was covered by blow by, cleaned it, worked great for a day. Now it will not start again, night here, and when I check the codes a 12 flashes. Took the sensor out and that looks good as well. What is a 12 and any other ideas?

atfdmike

Repeated 12 code means no other codes set in memory.
(12 code refers to the reference signal that indicates motor is running....since memory is checked with engine off....12 code)

danco

Last year I was told when I turn the key on I would get 8 flashes and then the next flashes would be the fault code.
If a 12 is the engine running with only the key on?

atfdmike

The data link connector terminal "1" (diagnostic request) is pulled "Low" (grounded) by jumpering to data link connector terminal "3", which is a ground wire. This will signal the engine control module that you want to "flash" diagnostic trouble code(s), if any are present. Once terminals "1" and "3" have been connected, the ignition switch must be moved to the "ON" position, with the engine not running. At this point, the "Check Engine" malfunction indicator lamp should flash diagnostic trouble code 12 three times consecutively. This would be the following flash, sequence: "flash, pause, flash - flash, long pause, flash, pause, flash - flash, long pause, flash, pause, flash - flash". diagnostic trouble code 12 indicates that the engine control module's diagnostic system is operating. If diagnostic trouble code 12 is not indicated, a problem is present within the diagnostic system itself, and should be addressed by consulting the appropriate diagnostic chart.
Following the output of diagnostic trouble code 12, the "Check Engine" malfunction indicator lamp will indicate a diagnostic trouble code three times if a diagnostic trouble code is present, or it will simply continue to output diagnostic trouble code 12. If more than one diagnostic trouble code has been stored in the engine control module's memory, the diagnostic trouble code(s) will be output from the lowest to the highest, with each diagnostic trouble code being displayed three times.

danco

Flashes a 44 after the 12, what exactly is 44?

atfdmike

Code 44
refers to the heated oxygen sensors in the exhaust system
Circuit Description:

The engine control module supplies a voltage of about 0.43 volt between terminals "B3" and "B2". (If measured with a 10 megohm digital voltmeter, this may read as low as 0.32 volts.) The Heated Oxygen Sensor (HO2S) varies the voltage within a range of about 1 volt, if the exhaust is rich, down through about 0.10 volt, if exhaust is lean. The sensor is like an open circuit and produces no voltage, when it is below about 360°C (600°F). An open sensor circuit, or cold sensor, cause "Open Loop" operation.

Test Description:

Diagnostic Trouble Code (DTC) 44 is set, when the O2S signal voltage is fixed below 0.100 mV and the following:
Throttle position sensor greater than 9.8%.
No DTC 21 or 33.
The engine has been running at least for 180 seconds.
System is operating in "Closed Loop".
Oxygen signal voltage is steady between 0.347 volt and 0.547 volt.
Engine Operation Temperature 69.5°C (155°F).
All of the above conditions present for 25 sec.
Integrator not at 128.
Diagnostic Aids:

Using the "Scan tool", observe the block learn value at different revolution per minute. The "Scan tool" also displays the block cells, so the block learn values can be checked in each of the cells, to determine when the DTC 44 may have been set. If the conditions for DTC 44 exist, the block learn values will be around 150.

Check for ground in wire between connector sensor.
Fuel Contamination - Water, even in small amounts, near the in-tank fuel pump inlet can be delivered to the injector. The water causes a lean HO2S signal and can set a DTC 44.
Fuel Pressure - System will be lean if pressure is too low. If may be necessary to monitor fuel pressure, while driving the car at various road speeds and/or loads to confirm. See Fuel System diagnosis CHART A-5.
Exhaust Leaks - If there is an exhaust leak, the engine can cause outside air to be pulled into the exhaust and past the sensor. Vacuum or crankcase leaks can cause a lean condition.
If DTC 44 is intermittent, refer to Diagnosis By Symptom.
Fuel Injectors - The wrong fuel injector(s) could be the cause of a lean HO2S signal condition. Verify that the correct fuel injector(s) are installed in the vehicle. Refer to the service parts manual for correct part and part number.

jfrozenh2o

I want to add to this even though this seems to be closed and unanswered. I too have a 94 trooper LS with 168,000 miles with the excact same problem. I have problems starting my trooper after it sits for an hour or more. It will turn over but not fire up. it sounds like its starving for fuel. Although after cycling the ignition 10 plus times it will eventually start up, and once started, everything runs great even when i turn it off and fire it back up. It is very well maintained and everything has been replaced new/ filters,oil, pvc valve, plugs,wires, fuel pressure regulator, fuel pump, new battery, alternator. I have not hooked it up to any gauges because my check engine lights never go off. I have come to a conclusion as of now that after changing the fuel pump today, and it wasnt the fuel pump check valve that i had thought, i am now quite sure that what is going on is that there is a leaky fuel injector that when the car is off, the leaky injector fills the resovoir and it takes a while of trying to start the engine up, to burn all the excess leakage, and once that is gone it will fire right up. Now im just a carpenter, but feel ive become a full blown mechanic for how much work ive done on this trooper. so now my next step is to replace the fuel injectors to hopefully cure this horrible problem that has driven me batty. please any one resond to this if theyve run into this problem also, as in this blog between gpa bear and atfdmike. there was no resolution from gpa bear as to what fixed it, and he seemed to of headed towards the fuel injectors, so i hope this will fix the problem. i will be sure to post my end results. -jes

atfdmike

"I have not hooked it up to any gauges because my check engine lights never go off." Do you mean that they are not lit or that they are on all the time?

cuiosgeorge27

Hey, i don't know if anyone else is here but i was wondering if somebody could give me a hand? I just bought a 1994 isuzu trooper 4x4 Manual 5 speed... and I LOVE IT. I wasn't sure at first but after driving it for a few weeks it won me over. Every once in a while (like 1 out of every 20 starts) it doesn't want to start. I have to really gas it! After i get it started it runs fine and cranks fine for 15 / 20 more cranks? Then just about 30 minutes ago I loaded up my daughters to run to the store and when i was putting my oldest in i noticed a very strong smell... like plastic burning??? Anybody have a clue??? I have noticed that I think there has been an electrical overhaul on it i believe because there is a lot of new wiring inside and under the hood.

atfdmike

It is hard at this point to give a specific answer...it does not sound good to smell burning anything in a car, but the smell could lead you to the problem area. You don't say, but can we assume the Trupr started OK after you got ready to go? Did you try to locate the smell?
I think it is too early to assume the starting and smell are related, but it would help to know which engine you have SOHC or DOHC, and whether you have changed the fuel filter and air filter since you bought it. Information like this will help others pinpoint areas of concern. When you say you really had to gas it, do you mean that it started but would stall, or that you held the accelerator to the floor and or pumped it?
Welcome to the forum, there are good people here who will offer their input once a good description is provided. Good luck.

landfill

My 92 Trooper has the same problem. If it has been off for a few minutes, it fires right up and when it has been off overnight. When it has been off for a couple hours, it needs to be cranked for a long time before it fires.

Lately, on occassion, it has been chugging, stalling, blowing a lot of smoke and even backfiring. Then it runs perfecly except it seems to be running rich. These symptoms srarted a couple weeks after a complete exhaust system was installed from the manifolds in the fall.

Now it is colder and my trooper has flooded itself out twice now. I pulled the plugs to let it dry out and replaced the O2 sensor.

I've read your blog before (jfrozenh2o) and am leaning towards your idea of leaking fuel injectors, or some other fuel delivery issue. I've also read of others with hard starting issues and many trouble shooting possibilities, but no solutions or successful attempts to remedy these problems.

I love my trooper and just want it to run like it did a few months ago...and would like the gas mileage to go back to normal.

If the new O2 sensor helps, I'll post it. If you changed the injectors on yours, did the problem go away? My local dealer suggested a wiring harness at the front under the rad that typically turns green and cases problems. thanks, Kenny.