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2001 Isuzu Trooper Intermittent Hard Start/Crank No start

12K views 65 replies 8 participants last post by  Shpresimn 
#1 ·
Hi all:
New to the site. I recently acquired a '01 Trooper 3.5l with a whopping 367,000 miles. Original owner had a full long block rebuild professionally done at approximately 320,000. Truck had served him well up to this point and now I have acquired it. Vehicle doesn't burn oil or consume coolant. No check engine lights. Aside from the starting issue I have, the vehicle runs fantastic.

After driving the vehicle for around 5 days with no issues, it began to develop a hard start/misfire on cold starts or similar symptoms after the vehicle has sat for 45 minutes or longer. I have practically pulled hair in efforts to self troubleshoot, but I'm now reaching out to resources for hopefully some conclusions. Here are the facts and the things I've done so far;
-New ICM
-New fuel filter
-New Cam sensor
-New spark plugs
-Relays and fuses checked
-Fuel Rail pressure checked at 41 before start and 36 running
-Battery voltage checked
-Injectors ultrasonically cleaned and bench tested
-Coils tested with test light for functionality during cranking
-Removed throttle body and cleaned small amount of build up off of assy.
-Verified resistance on coolant temp sensor

Any of yours input would be greatly appreciated.
Thanks,
Will
 
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#2 ·
Check the MAP sensor port and ensure it is not plugged with carbon. If you have a live data scan tool monitor the MAP sensor and IAT sensor signals and ensure the values are within the expected range.
 
#3 ·
Thanks for the response buster! I pulled off the MAP sensor and probed the port with a narrow screwdriver, but didn't find any build up. I cleaned off a little oil residue on the sensor port end and placed back on the manifold. I'm waiting on a tool in the mail to hopefully verify the map and iat parameters that you mentioned. Quite frustrating, since i know when the vehicle does start, it runs great..
 
#5 ·
Check the CKP sensor.
 
#7 ·
Passengers side below the exhaust manifold next to the motor mount.
 
#11 ·
*Update*
Since last posting, have had leak down test performed with no findings.
Replaced FPR
Replaced start switch harness

Trooper is still cranking and missing for long periods of time and sometimes simply won't start.
There is no consistency to when the truck will or will not start.
Pretty puzzled at this point, and will take any recommendations or advice.
Thanks
 
#12 ·
The Fuel Pump is controlled by the Fuel Pump Relay which in turn is controlled by the Powertrain Control Module (PCM). When the Ignition Switch is initially placed in the Run ("On") position the PCM energizes the Fuel Pump Relay for a few seconds to pressurize the fuel rail for start up. If the Fuel Pump Relay fails to operate there is no fuel to start the engine because the pressure bleeds down to zero when the engine is not running.

To test the Fuel Pump Relay, connect a fuel pressure gauge to the fuel rail test port and place the Ignition Switch to Run for 10 seconds and back to Off without cranking the engine. The expected fuel pressure is about 40psi and should remain close to this pressure for several minutes after the Ignition switch is placed in Off. If there is no pressure or the pressure bleeds to zero quickly there is a problem. Run the test several days in a row and check for consistent results. It is also possible the Fuel Pump is failing.
 
#13 ·
Hi Buster:
Thanks again for responding it such a quick manner.
Would it be possible that it's the fuel pump even if there is a strong presence of gas odor at the tailpipe during the hard starts ? I have pulled plugs on a few occasions when the vehicle is unable to start and they are always very wet, and even after only a hundred miles or so on the plugs, the electrodes were a darker brownish color.
Around 4 months ago I had done a fuel rail pressure check and was seeing around 37psi consistently, and would hold pressure for about 5 minutes before slowly dropping off. Hope this information assists your thought process.
Thanks again
 
#14 ·
If the plugs are wet it strongly suggests there may be an ignition problem. Buy some starter fluid and the next it won't start in the first couple of cranks try the starter fluid. If if doesn't try to start there must be an ignition problem.
 
#15 ·
Tried started fluid and was only getting more emphasized back firing through intake. At some point 3-4 months ago I had performed a very basic visual check on spark for each coil, but don't know if the spark was strong or not. Simply was only able to verify that each plug was sparking.
 
#16 ·
I didn't see where you ruled out the crank sensor definitively?

It would have been something I checked out much earlier. I have had this issue with other vehicles - not on my Trooper though.
 
#18 ·
If the spark plugs get wet with fuel the injectors must be being pulsed. This suggests that Crankshaft Position Sensor is generating the 58x pulses necessary for the PCM to pulse the injectors. Use this OTC 7602 NOID to verify the injector pulses.
 

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#20 ·
This is what makes the Crankshaft Position Sensor generate the 58x pulses, note the two missing teeth at the arrow head, this is the beginning and end of the sequence and how the PCM knows when to pulse the injectors and spark plugs. The Camshaft Position Sensor function is built into the Ion Sensing Ignition module.

Click image to expand
 

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#22 ·
I have another question. Does the fuel pump relay in these Suzuki's control the fuel delivery during the initial 5-10 seconds of start up? I have a buddy who's been into Honda's for years and the 90's era Civics have fuel pump relays that if they go bad will cause starting issues since it affects fuel delivery.
 
#24 ·
Hi Buster:
Still troubleshooting off and on. Does the fuel pump relay have any control over the ignition? Something is causing the plugs to flood out on initial crank. Have these vehicles been known to have computers go bad in them? It makes it more difficult when the vehicle doesn't display a code or check engine light as well. :(
 
#25 ·
willpahle said:
Hi Buster:
Still troubleshooting off and on. Does the fuel pump relay have any control over the ignition? Something is causing the plugs to flood out on initial crank. Have these vehicles been known to have computers go bad in them? It makes it more difficult when the vehicle doesn't display a code or check engine light as well. :(
The Fuel Pump relay does not control the ignition system.

The Fuel Pump relay is essentially just a switch controlled by the PCM. When energized, the switch contacts supply +12 Vdc to the Fuel Pump, the four 02 Sensor Heaters.

A 2001 Trooper has an Ion Sensing ignition system, the ignition system electronic module sits on top of the intake manifold and is controlled by the PCM. The six ignition coils are connected to the Ion Sensing ignition system electronic module. This ignition system uses the spark plug as an in-cylinder sensor to monitor combustion quality and knock detection.

A PCM failure is very uncommon, I can recall only one or two confirmed failures in the last 10 years. Ion Sensing ignition system module failures are also uncommon.
 
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