Akella aka Yan in Ontario
1HD-T idle drop when facing upwards-FIXED
- Thread starter Jan-78FJ40
- Start date
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Hi Jan
May I know why is this scenario only happen when inclining and not declining?
My 1HDT is suffering the same issue.
May I know why is this scenario only happen when inclining and not declining?
My 1HDT is suffering the same issue.
Hi Jan
May I know why is this scenario only happen when inclining and not declining?
My 1HDT is suffering the same issue.
Gravity+weak spring.
- Thread starter
- #24
Hi,
An old thread, but has anyone else tried this? Any luck?
I have had pump rebuilt on 92 1HD-T and it continues to have idle problems. In addition to the idle drop on incline, I also have idle rise at decline especially under brakes.
The idle drop has improved with new dashpot, but idle wants to stick at 800rpm most of the time instead of 700 where I have set it.
These springs and seats are not available in Australia, but I see most US online shops have them in stock.
Cheers
Dave
An old thread, but has anyone else tried this? Any luck?
I have had pump rebuilt on 92 1HD-T and it continues to have idle problems. In addition to the idle drop on incline, I also have idle rise at decline especially under brakes.
The idle drop has improved with new dashpot, but idle wants to stick at 800rpm most of the time instead of 700 where I have set it.
These springs and seats are not available in Australia, but I see most US online shops have them in stock.
Cheers
Dave
If you've had it rebuilt and not happy ,I would be taking it straight back.
Things not available at the dealer can be got through denso. Fuel injection shops know this.
Is your air conditioner cycling on/off and affecting the idle speed?
Things not available at the dealer can be got through denso. Fuel injection shops know this.
Is your air conditioner cycling on/off and affecting the idle speed?
Not happy. Have taken it back four times. They claim to have stripped it twice. Other issues included a fuel leak and incorrect timing on previous visits.
It is not AC related. Not linkage related. Not ACSD.
Starts at 600rpm cold. Rises to 800 as soon as you apply throttle. Will occasionally drop to the set ~700rpm but will usually hunt back to 800rpm.
When on incline, tapping brakes sharply will make it drop to 600.
When on decline, it will head towards 900rpm under brakes (inertia).
One would think the governor tolerances were checked, especially when stripping it the second time.
It feels like hydraulic pump up in the pump pushing up the RPM.
Stabbing the throttle and backing off sometimes drops it back to 700rpm which makes me think the dashpot is playing a role still.
It is not AC related. Not linkage related. Not ACSD.
Starts at 600rpm cold. Rises to 800 as soon as you apply throttle. Will occasionally drop to the set ~700rpm but will usually hunt back to 800rpm.
When on incline, tapping brakes sharply will make it drop to 600.
When on decline, it will head towards 900rpm under brakes (inertia).
One would think the governor tolerances were checked, especially when stripping it the second time.
It feels like hydraulic pump up in the pump pushing up the RPM.
Stabbing the throttle and backing off sometimes drops it back to 700rpm which makes me think the dashpot is playing a role still.
Is there a less technical way to play with the dash pot adjustment to that listed in the FSM?
If the dash pot is set wrong, I imagine it over rides the idle setting as it would actuate the governor plate. My understanding was the dash pot was recovery related to stop engine stall when throttle us shut.
Does the dash pot seat against the spring and seat mentioned in this thread?
Can any harm be done be adjusting the dash pot, and could this be done with engine idling in order to get correct RPM?
Sorry for so many questions, but this issue is driving me bonkers!
Dave
If the dash pot is set wrong, I imagine it over rides the idle setting as it would actuate the governor plate. My understanding was the dash pot was recovery related to stop engine stall when throttle us shut.
Does the dash pot seat against the spring and seat mentioned in this thread?
Can any harm be done be adjusting the dash pot, and could this be done with engine idling in order to get correct RPM?
Sorry for so many questions, but this issue is driving me bonkers!
Dave
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Any 1hz suffering from this issue?
Thats bad luck about the fuel injection shop. You might be better off seeking some advice from another shop.
Have you checked the spring connected to the accelerator pedal? I know you said its not linkage related but ....
I have had this problem before. The spring loses some of its tension over time and plays weird tricks like this. I got the tip off someone else who had the same problem.
Have you checked the spring connected to the accelerator pedal? I know you said its not linkage related but ....
I have had this problem before. The spring loses some of its tension over time and plays weird tricks like this. I got the tip off someone else who had the same problem.
Thanks. I have disconnected all throttle linkages, and can replicate the same problem.
As soon as I touch the throttle lever on top of the pump, it pulls itself up ~150rpm. I can push as hard as I like back on the lever but the revs won't drop. Only way to make them drop is with load such as power steering, or sometimes bleeping the throttle to 1400 or so. Sometimes it will rise again on its own.
It feels like as soon as the smallest amount of pressure if off the seat/spring in the governor, something is overriding it.
Have tried Cooma Diesel in Canberra by phone - really helpful people and only too happy to talk me through some possible causes but it's so hard when they can't see the truck!
I deserve better results from the shop the pump was done at, but at what point do you stop taking time off work to get your truck there again when they don't seem to have any idea what the issue is ?
As soon as I touch the throttle lever on top of the pump, it pulls itself up ~150rpm. I can push as hard as I like back on the lever but the revs won't drop. Only way to make them drop is with load such as power steering, or sometimes bleeping the throttle to 1400 or so. Sometimes it will rise again on its own.
It feels like as soon as the smallest amount of pressure if off the seat/spring in the governor, something is overriding it.
Have tried Cooma Diesel in Canberra by phone - really helpful people and only too happy to talk me through some possible causes but it's so hard when they can't see the truck!
I deserve better results from the shop the pump was done at, but at what point do you stop taking time off work to get your truck there again when they don't seem to have any idea what the issue is ?
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Are they specialist diesel injection pump rebuilders? A decent shop would work on it until its fixed or give you a refund.
Its obvious they have missed something.
Did you ask Cooma Diesel about the dash pot?
Yes. Specialist diesel shop and Denso dealer. Will advise who if I don't get any further with them.
Cooma didn't think the dashpot should affect anything other than recovery after throttle release, but that would be on the assumption it was set correctly.
I've downloaded a Denso manual that is bloody fantastic - will post it here. It is imperative the dashpot is set properly.
Over tightening it into the housing also causes it to bind; only needs. 9Nm so this could also be an issue.
Cooma didn't think the dashpot should affect anything other than recovery after throttle release, but that would be on the assumption it was set correctly.
I've downloaded a Denso manual that is bloody fantastic - will post it here. It is imperative the dashpot is set properly.
Over tightening it into the housing also causes it to bind; only needs. 9Nm so this could also be an issue.
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Good work.
yotahed
Diesel Head
The dashpot is essentially an idle bumper spring. Usually the idle is set by the throttle lever stop, which meters the fuel to achieve idle rpm. This is set at a certain test bench rpm, and if not done correctly, the idle will hunt.
The dash pot is kind of a softener, so the engine rpm comes down to idle smoothly instead of dropping down harshly and quickly. Especially important in manual trans trucks.
Basically, you must set the hard idle stop to spec, and slightly raise the fuelling with the dash pot. It is a very fine adjustment and only raises the idle fuel qty by about .5-.7 cc.
Something tells me they didn't know how to do this and they just left it alone and the idle is hunting.
The dash pot is kind of a softener, so the engine rpm comes down to idle smoothly instead of dropping down harshly and quickly. Especially important in manual trans trucks.
Basically, you must set the hard idle stop to spec, and slightly raise the fuelling with the dash pot. It is a very fine adjustment and only raises the idle fuel qty by about .5-.7 cc.
Something tells me they didn't know how to do this and they just left it alone and the idle is hunting.
So maybe thats why mine hunts all over the map, it can be at 800+ at one point then go to 650 the next time and if I am coasting in Neutral its around 900 then drops to 800 when I stop..... Go figure
Yotahead,
That makes complete sense. The Denso manual explained this well, and showed how to set it on the bench as you described.
I have had a look, and compared other pumps, and they have set mine all the way out (counter clockwise) in the disabled position.
The first three times I went back, they fiddled with the dashpot and made it worse - it was really hunting at idle up and down.
I think our assumption that they don't know what they are doing is correct.
Time to get serious. I'm at the end of my tether.
That makes complete sense. The Denso manual explained this well, and showed how to set it on the bench as you described.
I have had a look, and compared other pumps, and they have set mine all the way out (counter clockwise) in the disabled position.
The first three times I went back, they fiddled with the dashpot and made it worse - it was really hunting at idle up and down.
I think our assumption that they don't know what they are doing is correct.
Time to get serious. I'm at the end of my tether.
yotahed
Diesel Head
A quick way to set it is to have the truck warmed up and idling, turn the idle down to just below (100-200rpm)where it should be via the idle lever stop screw. The dash pot should be adjusted out all the way while doing this.
Then adjust your dash pot "in" to bump the idle back up to where you want it. Give the lever a couple stabs with each turn to stabilize the setting. This should get you dangerously close.
Another thing to note is that upon reassembly of the top cover to pump housing, the bumper tip can be ignored and snapped off when tightening down the top cover. The throttle lever inside must be moved forward to allow the bumper to slip in. Ask me how I know. Its entirely possible some of these pumps no longer have a intact dash pot bumper. Lol.
Then adjust your dash pot "in" to bump the idle back up to where you want it. Give the lever a couple stabs with each turn to stabilize the setting. This should get you dangerously close.
Another thing to note is that upon reassembly of the top cover to pump housing, the bumper tip can be ignored and snapped off when tightening down the top cover. The throttle lever inside must be moved forward to allow the bumper to slip in. Ask me how I know. Its entirely possible some of these pumps no longer have a intact dash pot bumper. Lol.
Hi yotahead.... have I labelled this photo correctly?
Pretty sure its a 1HDT pump courtesy of crankycruiser
Pretty sure its a 1HDT pump courtesy of crankycruiser
