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Pete, Automotive Mechanic
Category: Medium and Heavy Trucks
Satisfied Customers: 27814
Experience:  Performed various automotive repairs on several light duty and medium duty vehicles over 15 years of service.
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Isuzu WT5500 6HK1 Turbo diesel Year 2001 background Engine

Customer Question

Isuzu WT5500
6HK1 Turbo diesel
Year 2001
Engine opened and examined due to poor running. Smoking, rough idle, misfire under load.
upon inspection, multiple bent valves, broken valve guides, coolant in cylinder 4 and 5.
Replaced all pistons, valves, guides,rods, and bearings as well as sleeves etc everything within specs.
Engine re-installed in truck, turns over but won't start. Bled air from fuel system. Ran diagnostics found a few codes (blink codes) Won't connect to tech 2.
P35 (ECM inside trouble)
P261 to 265
Checked wiring harness (truck ran before pulling engine) followed all diagnostic flow charts in manual.
Replaced ecu due to P35 code, checked all plugs and connections checked sensor voltage etc. Within spec. Cleared codes and now there are no more codes (still does not communicate with tech 2)
Still does not start, cranks but does not start. Bled air from fuel system using cranking method, fuel lift pump holding pressure. Injector lines partially opened (to see if fuel getting up there, fuel is up) Closed lines rebuild pressure still just cranking no start, no hint of starting
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Expert:  Pete replied 1 year ago.
Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay. Was this model communicating with the Tech 2 before the engine was removed and repaired then reinstalled? Let me know so we can continue from here,thanks Pete.
Customer: replied 1 year ago.
no it was not communicating prior
Expert:  Pete replied 1 year ago.
Have you checked compression to make sure it is o.k. as well if you are getting fuel into the cylinders?
Customer: replied 1 year ago.
We have no smoke out the exhaust, not even a lil bit, it will fire on diesel fuel mist sprayed into the intake, runs fairly well on that so I'm assuming compression is good
Expert:  Pete replied 1 year ago.
O.k.,definitely no fuel from the way it sounds here. Was the computer programmed as well as the fuel injectors?These need programmed when the computer is replaced and when I did this at the dealer it required the dealers computer to do this and usually the lap top connected with the IDS software.
Customer: replied 1 year ago.
Even on these earlier models? Ok so it won't start without reprogramming the injectors. But wouldn't that throw a code for mismatched injector to ecu? I've replaced injectors on other isuzu 4HK1 and 4HL1 trucks without having any ill effects. O
Customer: replied 1 year ago.
I can't communicate with the truck using tech 2 or Jaltest or any other generic tool. It powers them on but doesn't have any serial communications.
Expert:  Pete replied 1 year ago.
This one may require just the tech 2 to program it but the tech 2 has to have the software in it to then allow the programming.I have seen on some tech 2 scan tools that it will power up but not communicate if the software is not up to date on the scan tool.We know its not getting any fuel and sounds like possible injector programming faults here or maybe even wiring issues.I would trace and inspect the ecu wiring to see if any wiring is found to be at fault needing repaired.Trace from the ecu to where it runs and connects to for any issues.One of these scan tools should communicate with your model here unless you have a wiring issue as we know the ecu is o.k. as it has been replaced. If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.Thanks Pete
Customer: replied 1 year ago.
Going to see if I can get the tech2 to communicate with this thing.
Expert:  Pete replied 1 year ago.
O.k.,let me know how this turns out here when your ready. Thanks Pete
Customer: replied 1 year ago.
Went back into it, checked cleaned and rechecked grounding points. Checked for continuity between Rail pressure sensor connector and its corresponding leads in the ecu plug. It has continuity, again I have no ECU faults. Looking at the wiring diagram for ecm don't see any fuses for Injector wiring. Theres about 11.5 volts on the injector top leads when engine isn't turning and ignition on. With ignition on and engine rotating that voltage fluctuates between 10 and 59v. Ground /seems to be good. Still can't get tech 2 to communicate via datalink (obd2) connector.
Expert:  Pete replied 1 year ago.
Since the no communication fault was an issue before this no start issue we may be going down the wrong path here for this fault.You may not have enough fuel rail pressure at the fuel rail.If the high pressure pump is not supplying enough pressure this will cause this here as well if one or more of the injectors is dropping fuel rail pressure.If you can I would have the pressure tested to see if you have an injector issue possibly or a fault with the high pressure fuel pump needing replaced.The slight mist of fuel is most likely giving the cylinders a little bump in fuel allowing to start from there.I would check into these to see if this is a pump issue or possibly a fault with one or more of the injectors.Unfortunately my info isnt listing how to test this pressure on this model here or what the pressure should be. Thanks Pete
Customer: replied 1 year ago.
I read that on some models equipped with this engine like the GMC Topkick, the truck won't start if there is no coolant in the reservoir. Right now there is no coolant in the system just trying to see if the thing will fire before we put more time into it.
Expert:  Pete replied 1 year ago.
I apologize for the delay. Usually it is an over heat issue that can cause a no start if the computer thinks the engine is over heating.If a faulty coolant temp sensor is installed this can cause this here.You can try and add coolant and see if it then starts and runs from there but I havent seen low coolant cause an issue,usually it is an over heat that will cause this here. Let me know if you need anything else and feel free to rate my help here. Thanks Pete
Customer: replied 1 year ago.
still nothing from this truck. I am out of ideas at this point. We've seemed to address all the fault codes associated with this thing, replaced the computer with another same. We cleared the flash codes and now its flashing constant. I believe the issue is fuel related or fuel pressure related. There's no evidence of smoke or diesel fumes out the exhaust.
Expert:  Pete replied 1 year ago.
Was the injector pump ever replaced?
Customer: replied 1 year ago.
No we did not tamper with injection pump or timing of injection pump.
Expert:  Pete replied 1 year ago.
Even though it was not tampered with I am wondering if for some reason it had failed suddenly and not related to the repairs and causes this no start issue after the repairs were done.I have seen these fail before needing replaced.If you can I would have it tested to see if it is faulty needing replaced. Thanks Pete
Customer: replied 1 year ago.
An observation... first few seconds of cranking there is an rpm reading of around 300-500 rpm. after about 2 seconds it drops to zero
Expert:  Pete replied 1 year ago.
This is usually due to a crank sensor or cam sensor signal fault.It may be one of these sensors causing this or the ring or component the sensor reads off of as being damaged or loose possibly.I would check into this more because this will cause no fuel like you are seeing here. Thanks Pete

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