Jet fuel?

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Wolf Suit

Wolf Suit

Joined
Jan 3, 2025
Threads
3
Messages
13
Location
Vancouver BC
Hi everyone,

So this is a bit long winded, but you’ll be saving my ass if you can help me out.

I work in aviation and have access to free jet fuel and with the cost of fuel these days, I took to using it. My coworkers and I have been using it for years in other diesels we’ve owned without issue. My KZJ78 with a 1KZ-TE however does not seem to like it. It actually seems to RUN fine with no observable difference in power, temperature or smoke or anything. The issue is starting. It starts beautifully with diesel and RUNS fine with either, but it has been dragging on starts with jet.

I do use Stanadyne lubricity formula with the jet fuel when I run it. I have changed the glow plugs, I’ve had the injectors professionally rebuilt and tested. I’ve replaced my fuel filter and my air filter. I’ve got a brand new battery. I’ve tested (and re-terminated one lead) on my fusable link. I’ve pulled the ECU to have a look and it appears fine with no signs of blown capacitors or burnt resistors. I (slightly) adjusted the spill control valve to enrich it, hoping that it would add pressure at the injectors and atomize the fuel better. The pump on the fuel filter stays firm, suggesting that I’m not losing prime. I’ve jumpered pins TE1 and E1 to read engine codes and my check engine light just flashes constantly.

All I can think is that it has something to do with the viscosity of Jet fuel as it is a fair bit thinner.

Currently it won’t fire AT ALL. It’s completely dead and causing me a ton of stress. It was running fine, but I left the lights on one day and killed the battery. I jumped it and all was fine for a few days. Then it was clear that the battery was completely DEAD. So I replaced it and everything was fine. It ran for a few more days (usual sluggish starts, but after that no issue) and then just refused to fire completely. It cranks, but won’t fire. I was planning on going back to diesel once I’d burned through this tank, but I never got the chance.

The two ideas I have are either to add in a boost pump (maybe the pump is having difficulty building pressure on start up due to reduced viscosity?) or replacing/rebuilding the pump (obviously not cheap).

Interestingly enough, another guy I know in the industry with a Hilux with the same engine is having the same issues. He’s even tried a 50/50 mix with the similar slightly improved) results.

I know jet fuel is dry and harder on pumps but I’ve got guys I work with who have been using it in their vehicles for the last 15-20 years and it should be fine so long as you’re using adequate lubricity additive.

At this point I don’t even really care about using jet fuel. I’ll use diesel if I need to, I just need to get this thing running.

Please help.
 
That's going to turn your ECU into a meth addict.
Best in an old tractor engine without an ECU.
My 1HZ....
 
Make sure you have plenty of battery power before attempting to restart, so you can crank quickly and build enough pressure. Maybe use another vehicle and boost. Get the cranking fast.
I've run so much Jet A1 through my BJ60 over the years. I added lots of lubricity oil. But I have an inline pump.
I would drain and purge out the jet fuel, and replace the filter, but cut it open to check for metal from the pump.
I think rotary pumps are not as adaptive to these thinner fuels. But it is a clean fuel. I used to dump a lot of extra lubricity in when I ran this.

Jet is also low cetane, which might be another factor. I am an AME, and at my former company, we had issues with DA42s entering limp mode during single-engine training due to temperature drops.
 
brownbear said:
Make sure you have plenty of battery power before attempting to restart, so you can crank quickly and build enough pressure. Maybe use another vehicle and boost. Get the cranking fast.
I've run so much Jet A1 through my BJ60 over the years. I added lots of lubricity oil. But I have an inline pump.
I would drain and purge out the jet fuel, and replace the filter, but cut it open to check for metal from the pump.
I think rotary pumps are not as adaptive to these thinner fuels. But it is a clean fuel. I used to dump a lot of extra lubricity in when I ran this.

Jet is also low cetane, which might be another factor. I am an AME, and at my former company, we had issues with DA42s entering limp mode during single-engine training due to temperature drops.
Click to expand...
This thing has no lift pump, which I suspect is a big part of the problem. Also, I’ve connected the supply line to the filter bowl to a Jerry can of diesel while the injector lines were off, and both using the priming pump and cranking it and no fuel is coming out of the lines. So it seems like I’ve killed the pump.

I’m aware of lowered lubricity, viscosity and cetane values. I don’t think the cetane value is the issue as I’d expect to see performance issues beyond starting problems and my friend with the freshly overhauled engine is having the same problems even with perfect compression.

I think the lubricity obviously needs to be accounted for, but I can’t shake the idea that the viscosity is the real problem.
 
If you killed your pump, I wonder if there is some metal in the filters? Is it a spin on filter?

I'm not up on this engine, but you have a Spill Control Valve with two wires going into it. Some of my googling led to this, which could be stuck open. Maybe the jet fuel freed up something that stuck to it. It's on the back of the injection pump with two wires. Check that the coil is not shorted or open.
DO a little gentle tapping... If the SCV is open it is bleeding internally and will not build up pressure in the injectors.

Try cracking the injector lines too. See if fuel dumps out.

Something simple, check fuses to the pump, ecu etc. Make sure the Fuel Cut Solenoid (usually has a single wire) makes an audible click with the key ON/OFF.
 
I would love to run “defueled” jet fuel in my 1-HDT but I know it’s not that simple. Might be better to go down the “fryer oil” rabbit hole.
 
Rough time. I agree, purge all the jet fuel out clear through the pump and injectors, make sure your battery is fully charged and get another vehicle jumping it at the same time. Get that thing spinning as fast as possible to try and build pressure with the thin fuel.

You say cranking sluggishly, does that mean the engine is physically spinning slowly, or you had to crank for a long time before it starts?

Have you verified glow plugs are working well? My 617 simply would not cold start without glow plugs, no matter how long it was cranked. Some engines are just like that, never tried it with my 1kz.

I've run 40+ gallons of kerosene(basically jet A) in my 1kz, but it was 5 gallons at a time added to a tank of otherwise diesel. We have a 5% biodiesel mandate here in Oregon, so lots of lubricity. If I was running straight kero I'd have added a LOT more lubricity, lots of two stroke oil or biodiesel. Wouldn't consider Stanadyne alone to be sufficient at all when running pure kero/jet A.

Suspect you did damage your pump, hopefully with proper lubricity and viscosity fuel it will still function acceptably well, or it's another completely unrelated and easily corrected issue.

Best of luck.
 
Kinda odd,
In a similar boat, get nearly endless sumped Jet "x" at work, run it in absolutely everything. From little diesel forklifts, to 5.9's, 6.7's, 7.3's, c13 cat's and everything in between.
Never had any starting issues; yes, you lose a little power, and yes, you should use an additive of your choice to improve lubrication.
Personally my little Kioti tractor and my Hanix excavator have always ran on it, no issues.
Curious on what you find.
 
It's either fuel to the injectors, glow plugs not working or low compression. Did you find the cause?
 
Without really helping, but by adding some additional information for Cruiserheads living in Nordic countries (such as… Canada).

Where I work, there is a Fuel and Convenience Store division. I had a conversation with the guy who manages fuels. Starting in September, before winter, there is a transition to winter diesel which is essentially a blend that can sometimes contain up to 75% kerosene.
 
Here winter diesel has paraffin, I collect about 200 liters winter diesel to avoid old not used stuff not starting (but that is below -18 degrees Celcius)
But now the algea seems to creep up because of the % bio diesel rising.

If you look at it without mentioning jet fuel, it sounds like air in the system, also getting worse by time, I think to start cheap and replace the inline pressure push pump (and small filters anywhere like HJ has) And glowplugs as mentioned, just regular maintenance stuff, test voltage at bus bar, some silly crap overlooked.

And maybe the additive loosened and mixed gum in the tank like vegetable oil did in my tank (black sludge, common problem, not same as algae)

Maybe if it runs again invest in a purge system like used for vwo?

I would dump the tank plug and start fresh with normal diesel, see if it has pressure at the injector or check spray pattern to make sure, and are you sure it was put together like it should, not something that is off the to do list but is wrong? like increased spray pattern but decreased it?

Pumps 1300bar so maybe the only way is a good check with toyota software maybe it finds a sensor not working?
 
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The NZ and US Antarctic programs run all of their Diesel Vehicles on JP8 which is the military grade Jet fuel.
The Toyota HZ motors ran great on it despite spending many more hours idling that they did revving and driving. The 70 series V8 engines are also running on it with no issues. They do block off the air flow through the bonnet to the top mounted Intercooler because the ambient is so cold.
 
Sarmajor said:
They do block off the air flow through the bonnet to the top mounted Intercooler because the ambient is so cold.
Click to expand...
Also because it'd just pack with snow like every other opening down there. I've done instrument work for there but never been down myself.
 
If you get to mcmurty be sure to take pictures of the hitler ufo's and inner earth....
oh and the under ice pyarmids too...
we need pictures
 
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