Bad noise coming from Isuzu 4JG1 (1 Viewer)

[Foreigner]

I'm trying to help a friend whose 1995 Isuzu Trooper started making an awful racket recently. He drove it probably 20km with it (to mechanic and back) and it got much worse in the process. His mechanic couldn't tell where the sound was coming from and basically said, "Rebuild it." He pulled the valve cover and the easily removal part of the oil pan and there was nothing unusual in either location.

I told him I'd reach out to the Mud diesel gurus and see if you all had any idea where to start.

Here's what it sounds like. It's vibrating pretty bad, too:


It's a naturally aspirated 4JG1 engine if that helps anyone.

 

[GTSSportCoupe]

Seems like there is a lot of resistance there when it first starts (or the battery is low).

Did the oil have bearing debris in it? Engine almost sounds like it has rod knock. Pull the big end rod bearings apart and inspect/replace?

Could also check injection timing...maybe its way out? Engine would have very little power if so.

 

[Foreigner]

The battery was low. It's been parked for a couple weeks.

Injection timing seems to be coming up a lot, but I'm not sure. It seems to have normal power.

 

[Foreigner]

There's more to the story, that I forgot about. His wife told me this:

He had a fuel problem while he was traveling 10 days before the noise started, he had gotten some bad fuel on that very trip and it stopped up his filter. He was 30 miles from nowhere and hooked it up straight to the engine till he could get someplace. After he was able to get to a place he changed the fuel filter and it seemed to run fine but then 10 days later I was coming home from picking up our daughter from school and it started sounding like a tractor. I was about 20 minutes from home and just limped it in to not cause any problems.

All of my pilot/mechanic friends are doubling down on the fuel/injector pump/injectors issue, so we'll pursue that some more.

 

[CycloSteve]

I would start with the easy items first. Pull the injectors and have them tested. Also run a compression test. Both are pretty non-invasive, and not too expensive. If those check out, perhaps have the injection pump tested and timed. To me it sounds like a misfire on one or more cylinders...wrong amount of fuel or lack of compression.

How does the oil look? Any indications of bearing bits in there? If so, go down the path of checking the BEB's and mains.

 

[Foreigner]

I didn't actually see the oil, but he said it was normal. A bit of sludge, but not unusual for a 300,000km vehicle in Bolivia.

 

[CycloSteve]

If there is a magnet on the drain plug, that could show if any major iron bits let go. With the oil, they would need to have an analyses like Blackstone done, which may be difficult in Bolivia...that type of test will let them know if there are telltale signs of excessive bearing wear, or other oddities such as coolant in the oil.

 

[Dougal]

Bypassing the filter could have damaged the injection pump.
To check if it's a cylinder problem or injection problem you could run a compression test. If the compression test is good then it's likely injection related.

The Isuzu's we got here were 4JG2. Are you sure about the engine code? Doesn't make much difference though. Some were mechanical pumps, later were electronic pumps.

 

[Foreigner]

Yes, pretty sure about the engine code. I thought it was weird as well, since I couldn't find any info on that engine in a Trooper, but the maintenance instruction plate in the engine bay says 4JG1 and the engine code on the VIN plate reads RLT which came up as a 4JG1 as well.

We're swamped in work right now, but will hopefully have time to get into it next week.

 

[Foreigner]

More news, finally. He had an injection guy come take a look and it all checked out (by local standards, anyway). While they were messing with it, he said he thought it sounded like the starter wasn't disengaging from the flywheel. They pulled it out, and discovered that the flywheel was loose.

I helped him pull the tranny this afternoon and this is what we found:

"Isn't the flywheel supposed to stay attached to the crank?"

Three bolts backed out, five broke in two.

Hopefully that's the only damage and the crankshaft, et al, is okay.

 

[Dougal]

Well that's the rattle found..........

 

[watrob]

Looks like no Locktite used on the threads and mostly likely not torqued to spec.

 

[Foreigner]

Looks like no Locktite used on the threads and mostly likely not torqued to spec.

"Spec? Wut spec?"

That's how it's done around here. Speaking of which, I can't find an FSM for this engine. Can anybody give me a neighborhood for what kind of torque we're talking about for a flywheel? I'll keep hunting, but at some point, it's got to get done and put back together.

edit: I found specs for some of the other 4J engines and they all say 118Nm, so we'll go with that, I think.

 

[watrob]

And put some thread locker material on those bolts?

 

[Foreigner]

If we can get some, yes.

 

[CycloSteve]

Yikes, that would be an odd failure.

 

[watrob]

Yikes, that would be an odd failure.

Not really, if you look at the first photo of the 3 bolts still in the fly wheel you will see there is no thread locker material on the bolts and also these bolts don't use locking washers either, so it was only a matter of time until they became loose (and that's if they were even ever torqued up to spec to begin with).

So once they became a little loose they would work they way out and snap off and this is what happened.

 

[CycloSteve]

My comment was one of frequency of this happening. In this context, odd = uncommon (perhaps not so much in Central America, though). Personally I have not heard of flywheels snapping bolts all that often, and I have been wrenching on vehicles since the 1970's.

 

[watrob]

I have heard of flywheels snapping bolts before, just not much on a 40, as most people realise that certain bolts need thread locker and torqueing to spec. Back yard build in Central America probably happens a lot?

 

[Foreigner]

Central America

Central America

Well, we might be central South America. Yes, unfortunately good mechanics are hard to come by here. My friend did have his mechanic pull the tranny to fix 5th recently, so there was an opportunity to screw it up then, but he has only owned the vehicle about 6 months, so it may have been a PO as well.