12ht high idle issue

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Jun 5, 2005
The Netherlands
I have this weird high idle on my freshly rebuild 12ht. Even when the throttle cable is disconnected and the high idle actuator is not hooked up to a vacuum source it runs at around 1500 rpm.
I already had this injection pump on my old 12ht (which broke the crank amongst other things....) and it worked fine. It was rebuild and calibrated a few years ago.
I triple checked the timing already.
Also the throttle linkage on the pump doesn't stick.

I really don't know where to start looking tot fix this.

Any help is appriciated

Get the motor up to operating temp and set the idle with the idle screw mine was set to idle with the hand throttle so I set it with the screw to 650rpm but most of the time it idles at 1000rpm some sort of auto idle kicks in
The idle set screw is the one closest to the block undo the lock nut on the firewall side and use a screw driver to turn it in or out will change the idle and set it to what you want or factory spec
Unfortunately it's neither of those.
It seems something inside the pump keeps the idle up. I can't even force the throttle lever down to get the idle lower.
I'm stumped...
The boost compensator compensates just fine. And there is no diaphragm like there is in a 2H pump... But i just found out that the new block is cracked big time. So the injection pump is now the least of my problems....

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