Several 80 series have reported an annoying problem, including mine: When facing steep uphill slopes the idle drops from the recommended 750rpm to about 400 rpm. This has been discussed several times in the forum. Pusher pumps do not seem to fix the problem, and so far people just decided to live with it.
On my truck a similar thing happened when I decided to just idle along without using the accelerator-idle dropped to 400rpm, quite annoying.
After reading up on the intricacies of these pumps I thought the so called damper spring could be the culprit. This spring senses increased load at idle and up-regulates the fuel flow slightly in response.
The damper spring is located in the head of the pump, you can find it in the 1HD-T manual on page FU-31. There is a spring system that connects the speed control lever/adjusting lever with the fuel control system in the bottom of the pump. The speed control hooks to the adjusting lever, this to the speed control spring, which is hooked to a spring seat that also contains the damper spring. If you look at the pic below it will all become clear.
I decided to change the damper spring, the spring seat, the speed control spring and of course the gasket for the head of the pump. While I had my pump fully rebuilt, these parts are toyota specific and were clearly not swapped out during the rebuild.
The procedure is not too hard: Take the fuel lines off the head of the pump, take the A/C idle up off, remove the low and high idle screws, and then carefully remove the 4 bolts that hold the head of the pump. Fuel will pour out, but after that you can carefully tilt the head of the pump forward. Remember that the head and bottom of the pump are hooked together with the speed control spring. You have to unhook this spring from the spring seat to remove the head completely. The manual describes the procedure more accurately. Make sure the spring seat and damper spring don't fall into the pump at this point! It is not required to remove the adjusting lever.
Then change the springs, the gasket, carefully re-hook the speed control spring to the newly placed spring seat and re-seat the pump head. That is a bit of a pain, since the spring loaded idle up system needs to be in the exactly correct position to seat the pump head correctly. But definitely doable with some playing and cursing.
Then bolt the system back together, hook everything up, and your problem has been solved.
I do not see the idle drop at inclines anymore, and when I just use the idle to go forward, it re-adjusts to around 700, just as it should.
Hope that helps someone in the future. Below is the page out of the manual that shows the springs, and all the parts that you need. I got them out of europe from my brother via Toyota Austria, but I am sure you can get them in Australia or Japan as well. The seal and the spring seat is actually available from Toyota USA via Toyota parts zone.
I bought 3 sets and we will keep one set at the shop as spares. So one set is available. While the springs are only a few $ each, I am asking $40 for the set (speed control spring, spring seat, damper spring and gasket) plus shipping, as we paid lots in shipping. If you need these and find the price outrageous, I understand. Please get your own, the numbers are below. Or I would exchange the set for an OEM hand throttle assembly, as sold by Akella.
Cheers,
Jan
On my truck a similar thing happened when I decided to just idle along without using the accelerator-idle dropped to 400rpm, quite annoying.
After reading up on the intricacies of these pumps I thought the so called damper spring could be the culprit. This spring senses increased load at idle and up-regulates the fuel flow slightly in response.
The damper spring is located in the head of the pump, you can find it in the 1HD-T manual on page FU-31. There is a spring system that connects the speed control lever/adjusting lever with the fuel control system in the bottom of the pump. The speed control hooks to the adjusting lever, this to the speed control spring, which is hooked to a spring seat that also contains the damper spring. If you look at the pic below it will all become clear.
I decided to change the damper spring, the spring seat, the speed control spring and of course the gasket for the head of the pump. While I had my pump fully rebuilt, these parts are toyota specific and were clearly not swapped out during the rebuild.
The procedure is not too hard: Take the fuel lines off the head of the pump, take the A/C idle up off, remove the low and high idle screws, and then carefully remove the 4 bolts that hold the head of the pump. Fuel will pour out, but after that you can carefully tilt the head of the pump forward. Remember that the head and bottom of the pump are hooked together with the speed control spring. You have to unhook this spring from the spring seat to remove the head completely. The manual describes the procedure more accurately. Make sure the spring seat and damper spring don't fall into the pump at this point! It is not required to remove the adjusting lever.
Then change the springs, the gasket, carefully re-hook the speed control spring to the newly placed spring seat and re-seat the pump head. That is a bit of a pain, since the spring loaded idle up system needs to be in the exactly correct position to seat the pump head correctly. But definitely doable with some playing and cursing.
Then bolt the system back together, hook everything up, and your problem has been solved.
I do not see the idle drop at inclines anymore, and when I just use the idle to go forward, it re-adjusts to around 700, just as it should.
Hope that helps someone in the future. Below is the page out of the manual that shows the springs, and all the parts that you need. I got them out of europe from my brother via Toyota Austria, but I am sure you can get them in Australia or Japan as well. The seal and the spring seat is actually available from Toyota USA via Toyota parts zone.
I bought 3 sets and we will keep one set at the shop as spares. So one set is available. While the springs are only a few $ each, I am asking $40 for the set (speed control spring, spring seat, damper spring and gasket) plus shipping, as we paid lots in shipping. If you need these and find the price outrageous, I understand. Please get your own, the numbers are below. Or I would exchange the set for an OEM hand throttle assembly, as sold by Akella.
Cheers,
Jan
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