12HT Runs fine cold - dies when hits operating temp (1 Viewer)

[dieselbigot]

Gents,

Looking for some input on the most logical place to start diagnosing this issue. The other day while driving my truck home, it started to sputter, choke and lose power to the point I had to pull over. I kept it running, but the idle was choppy and when I feathered the throttle it acted like it was running out of fuel.

I managed to keep it going and limped back home, fortunately I was less than a mile away. The next morning, I went out and fired it up and it started as it always has and ran perfect. I drove it a few miles and all seemed well. Later in the day I decided to venture out a little further and as soon as I got on the freeway and got the truck up to operating temp (165 F), same crap with the sputtering, and then she died.

I was able to limp home by letting it cool a bit, starting...driving a few hundred yards, then it would die again....let it cool a few minutes, repeat...etc etc.

I started it again this morning, and it runs like a champ. SO...obviously whatever is causing this is only present at full operating temps.

ENGINE HISTORY
135k miles on well looked after motor from a Canadian JDM donor HJ61
Conversion was done on US spec FJ62 / sits behind an H41 tranny / Toybox combo
All perifs were new or rebuilt when motor was installed (alt, cooling system, gaskets, seals, injectors etc)
Truck has run flawlessly for 2 years, never let me done when far from home

RECENT WORK
I have a LRA 38 gallon tank that my fab guy recently did some surgery on...basically shaved the tank for a better departure angle. My first thought was perhaps there was some contamination particles that were introduced during that work...but if that was the case, it would run like s*** when cold too.

POSSIBLE CAUSES
Anything to do with fuel delivery makes no sense since it runs great when cold...so things like blockage at the pickup, fuel pickup and return lines accidentally hooked up wrong when tank was reinstalled, fuel filter blockage, feed pump....all these make no sense to me...right??

So knowing this is an intermittent issue that only seems present when engine is warm is making me think things like, bad VSV, air intake butterfly valve, automatic timer, or some other way air is getting either choked off to the intake or air being introduced into the fuel system that makes it run like s***, then die.

Another thing I noticed yesterday...I used to be running about 10 lbs turbo boost and now I'm only seeing about 8lbs. This IS the original turbo, nothing has been done to it by me, nor the PO of the engine. Same thing with the IP.

Truck has plenty of fuel in the tank
I'm in California, so climate is not a factor (it's 70 F today)

So...that all stated, has anyone experienced anything like this with a 12HT??

 

[duncanrm]

Is it possible that a vacuum is being induced in the tank?

 

[dieselbigot]

Not sure...

 

[roscoFJ73]

The simple way to check vacuum in the tank is to remove the fuel cap when its stalling.
I would check the gauze on fuel pick up.
You could rig up a temporary fuel supply as close to the engine as possible. This would isolate the problem between tank and engine bay.
Sometimes through heat and expansion fuel lines can let a belly full of air into the fuel system.

 

[Tapage]

It happens once in Tencha and was some sort ( put air at 40 PSI from fuel pic up at the Ip to the tank ) of blockage .. isolate it with a diesel tank close to your engine bay and running it directly to the pump ..

 

[dieselbigot]

Is it possible that a vacuum is being induced in the tank?

The simple way to check vacuum in the tank is to remove the fuel cap when its stalling.
I would check the gauze on fuel pick up.
You could rig up a temporary fuel supply as close to the engine as possible. This would isolate the problem between tank and engine bay.
Sometimes through heat and expansion fuel lines can let a belly full of air into the fuel system.

It happens once in Tencha and was some sort ( put air at 40 PSI from fuel pic up at the Ip to the tank ) of blockage .. isolate it with a diesel tank close to your engine bay and running it directly to the pump ..

Guys... Totally appreciate the suggestions! I won't have time to dig into this until the weekend, but the more I think about it, the more it makes sense that this has something to do with this fuel tank being dissected. When I picked it up from Don's shop he had only put 5 gallons back in the tank. I drove it straight from the shop a few blocks to the Chevron station and filled it up completely...and it drove just fine on the 60 mile drive home. I rarely drive this thing, so now that the tank is only half-full, perhaps it's sucking air into the fuel line causing this issue? I will try rigging up a fuel source close to the engine and see if that solves it. Then I will know that is isolated between the tank and the injection pump. Still does not explain why it runs fine when it's cold...unless I'm missing something?

 

[dieselbigot]

Forget that last comment, Heat and expansion...thanks rosco

 

[cruiserpilot]

Maybe spray the tank for leaky welds?

 

[Tapage]

2H it's very I mean like very sensitive to air in the like .. did you still have the factory water separator, if so check that too ..