It was at 900 psi.{782-924 psi}Psi was at about 1150 before shimed.Id say spring had weakend from use,over the years.

What's the relief pressure setting now that you've shimmed it? Is this an approved fix from Toyota? Not trying to be a pest, just worried about liability as I'm self employed.

Shimed relief valve 0.25,all good now.relief valve is on left, top of control valve.thanks for everyones input. Kent

We have a customer who bought one of these trucks brand new and it always stalled out when putting a load on the engine especially when tilting. My belief is and was that the engine is underpowered for the truck. We ended up retrofitting a dash pot onto the the mixer that we got from TCM. It was a very simple fix.

Well, I have to say once again that I posted some "not exactly true" statements previously.
We actually have one 5F model where I work. It is our "shop work horse". This is the same truck I mentioned in another thread some months back regarding a possible future engine swap out (which is still a possibility).
This truck has the 4Y engine in it.
The fuel system is all Impco.
VFF 30 filterlock, J Model vaporizer, CA 55 mixer.
I had not bothered to look for an idle up dashpot on it before I posted what I read in the manual I found. Yesterday at work I made a point to look closely at the shop horse and it DOES NOT have an idle up dashpot. Going back to look at the manual again I realized that this truck was built during the era where LPG was an afterthought at the OEM corporate level and all LPG units were considered as "aftermarket conversion". The manual's reference (and photos) to the idle up dashpot was for a gasoline carburetor, not a propane mixer. Sorry for the errata.
I will await some kind of response from someone before I add anything else to this thread as I have a feeling it is already moving to the dead letter folder.

Well, I dug through our old manuals and I came out with one for 3Fs and one for 5Fs.
I stand corrected on a couple of things that I stated in my other posting above.
The 3F models DID NOT feature main hydraulic system boosted brakes. The 3Fs had the independent brake system like the 7F & 8F models have. So it must have been some even older 2F models that I recall having a hydraulic pressure accumulator. And I now think that the power steering on those may not have been associated with the hydraulic accumulator as those models had a sector gear box steering system with the power steering cylinder "piggy backed" onto the steering drag link. As such, the steering gear box would provide redundant steering in the absence of main hydraulic system pressure. (orbital valve with Gerotor pump provides that on more modern trucks having Full Hydraulic Power Steering systems)
Now, back to the 5F hydraulic boosted brake system.
The 5Fs DO NOT have a hydraulic pressure accumulator.
The brake (pedal) valve/master cylinder on the 5F models is capable of acting as its own redundant brake pressure source when the engine is not running (or if main hydraulic system fails), though the pedal effort required will be much greater.
And because the 5Fs have FHPS system for steering, the orbital valve has the back up in it in case of hydraulic failure.
So, now that we have better info about the components in place maybe a reason for its behavior can be determined.
There is a flow divider valve is in fact built into the main control valve that furnishes the oil supply going to the brake booster/master cylinder, but the brake booster/master cylinder also has a flow divider valve inside it (according to this manual).
Nothing that I see (thus far) in the diagrams would point to anything that might cause the engine to die with steering or brake application without some other hydraulic function also killing the engine. Will study further.
Getting back to another member mentioning "idle up" dashpot.
You say there is no idle up dashpot on this engine. The manual shows that there should be one. Furthermore, the engine IDLE RPM specs are 750 RPM with idle up vacuum hose connected and 1,250 RPM with the vacuum hose disconnected (and plugged).
If the engine is dying ONLY when it is at idle, the entire scenario may be due to the lack of a working idle up dashpot.
Does this occur only at idle or does it happen at higher RPM too?

Since the problem seems to occur only when brakes or steering are called upon.......I will hazard a guess that there may be an issue with the hydraulic pressure accumulator that serves as a fluid pressure reservoir for these 2 hydraulic functions.
I am presuming the 5F models with brakes that operate from the main hydraulic system are similar to the older 3F series I worked on in the 80's.
On the 3F models there was a hydraulic accumulator which stored pressure from the main hydraulic system as an "emergency brake/emergency steering" in the event of engine failure and subsequent loss of hydraulic system pressure.
The old 3F accumulator would store enough pressure/volume for about 3 brake applications and maybe one turn of the steering wheel before it was depleted.
When I return to work next week I will dig in our old manuals to see if anything is available.

Which fuel system is unit equipped with ? Impco or Aisan? Have you tried to measure hydraulic pressure at steering valve, giving the info that it only dies when steering is deadheaded than problem seems to be in pressure for steer circuit and there is adjustment on steering/orbital valve

Hello,LP truck,Not equiped with fast idle dash pot. Tilting/sideshifting doesnt cause engine to die.

Priority valve is in control valve, is it lp or gasoline fuel system ? , either way if you pull vacuum hose of idle up dashpot engine idle should be 1000 rpms +-200 rpm, , would recommend seeing if it stalls when hydraulic tilt /sideshift functions cause unit to die as well, if so relief pressures may require adjustment ( tilt and then check steering orbital valve pressure). Good luck

Not really sure. If memory serves me right it is separate. The main pump line feeds the probity valve and then it tells the pressure which way to go.

Thanks,The priority valve ,Is it located on the control valve?

I believe there is a priority valve that puts pressure to the sterring and then other hydraulic functions. It has been a while since I have worked on one but I would start there.

Yes. Ive checked all these.engine runs fine.No problems their.I was thinking ,Their may be a relief valve in the control valve,or on pump.That controls the pressure to the steer/brakes.I was thinking someome on here would know,And pressure setting.Maybe a service manual?

Check the simple things first. PCV,Ign Timing, LPG values. If all good. some units have a thottle kick up vac valve on the side of the carb.