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1994 Isuzu Trooper ( Hard to start )

17 messages,  Last post on Feb 13, 2008 at 4:37 PM

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What is this discussion about? Isuzu Trooper, SUV

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#1 of 17 1994 Isuzu Trooper ( Hard to start ) by gpabear

Nov 24, 2006 (8:24 pm)

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!!!!

#2 of 17 Re: 1994 Isuzu Trooper ( Hard to start ) [gpabear] by atfdmike

Nov 25, 2006 (1:28 pm)

Replying to: gpabear (Nov 24, 2006 8:24 pm)
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.

#3 of 17 Re: 1994 Isuzu Trooper ( Hard to start ) [atfdmike] by gpabear

Nov 25, 2006 (6:14 pm)

Replying to: atfdmike (Nov 25, 2006 1:28 pm)
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

#4 of 17 Re: 1994 Isuzu Trooper ( Hard to start ) [gpabear] by gpabear

Dec 03, 2006 (10:31 pm)

Replying to: gpabear (Nov 25, 2006 6:14 pm)
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

#5 of 17 Re: 1994 Isuzu Trooper ( Hard to start ) [gpabear] by atfdmike

Dec 04, 2006 (7:12 am)

Replying to: gpabear (Dec 03, 2006 10:31 pm)
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.

#6 of 17 Re: 1994 Isuzu Trooper ( Hard to start ) [gpabear] by 30dohc

Dec 04, 2006 (10:28 am)

Replying to: gpabear (Nov 24, 2006 8:24 pm)
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!

#7 of 17 95 trooper will not start by danco

Mar 10, 2007 (7:30 pm)

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?

#8 of 17 Re: 95 trooper will not start [danco] by atfdmike

Mar 12, 2007 (5:47 am)

Replying to: danco (Mar 10, 2007 7:30 pm)
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)

#9 of 17 Re: 95 trooper will not start [atfdmike] by danco

Mar 13, 2007 (7:25 am)

Replying to: atfdmike (Mar 12, 2007 5:47 am)
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?

#10 of 17 Re: 95 trooper will not start [danco] by atfdmike

Mar 13, 2007 (9:03 am)

Replying to: danco (Mar 13, 2007 7:25 am)
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.

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