3208 cat throttle stuck open

Jhn · Jul 28, 2022

It is in a '89 top kick truck. It has been
sitting who knows how many years and I got
it started but will only run wide open
2500 rpm? So I keep shutting it off. I
tried restarting it several times. Is
there any easy solution to get it fixed? I
don't think trucks have a governor Like a
farm tractor would.

cjunrau · Jul 28, 2022

I would find the throttle linkage to the injection pump. Make sure it is at idle. Then tap gently on the pump to see if what is stuck inside would release

flying belgian · Jul 28, 2022

Could try tapping on pump with a hammer handle.

Jhn · Jul 28, 2022

I did that, the pedal moves back and forth with the throttle and tried tapping on it with hammer but no luck.

MKinON · Jul 28, 2022

Yes it has a governor in the pump. Like someone said, make sure the lever at the pump moves and can go to idle. If the truck has a throttle, it may be interfering with the movement of the linkage, over-riding the accelerator linkage. Been a while since I was into ours.

RodinNS · Jul 29, 2022

All diesel engines have governors, by design. The question is.... does it have a variable speed (holds constant speed) or a limiting speed (only maintains idle and high idle speeds)? Most OTR engines have limiting speed governors. So if the pedal is stuck down even a bit, that can still correlate to a no load, high idle condition. I would probably start by disconnecting the pedal linkage at the pump and see what happens.
Beyond that, I'd have to wonder if it is actually maintaining any particular speed, or it just runs fast? It's possible that a metering sleeve or rack is stuck in one position and that just happens to make it run at what seems like high idle. If subjected to load it would just stall? SO figure out whether or not it responds to load. IF it does, the pump innards are probably OK and the problem is external in the linkage. If it doesn't respond to load, the problem is in the pump...

Rod

Jhn · Jul 29, 2022

I only let it run a few seconds after it starts since I don't want to damage the motor

oldjohndeere · Jul 29, 2022

When a diesel shuts down the governor pulls the rack wide open in an attempt to keep running. When they sit for a while the rack sticks in that position. 3208 engine are bad about that. Usually have to pull pump and disassemble to fix. Maybe one of the pump guys here has some suggestions on getting it unstuck.

used red MN · Jul 29, 2022

Here are a couple posts on this from other forums. The first one from AgTalk where a reply suggests temporarily filling the pump with carb cleaner to free the stuck parts. I am wondering if E85 or whatever is the strongest alcohol blend could be used instead. I have heard people say on here that it is quite effective on breaking down old varnished gas in fuel systems. The second post has links to diagrams of the pump breakdown I thought might be helpful.
AgTalk link

2nd link with diagrams

BarnyardEngineering · Jul 29, 2022

(quoted from post at 04:48:57 07/29/22) I only let it run a few seconds after it starts since I don't want to damage the motor

2500 isn't going to damage the motor, but yeah, the rack is stuck in the injector pump from sitting.

Billy Shafer · Jul 29, 2022

When that engine first came out. Cat gave us one. To make a generator engine. We had a few problems. Rack sticking was one of them.

wore out · Jul 29, 2022

What doesn't make sense it that, typically, the 3208 injection pumps have a large shutdown solenoid on top of them and there's a spring that moves the rack to the ''no fuel'' position at shutdown when the solenoid releases.

if the rack/plunger barrels are stuck the engine wouldn't shut down when the key was switched ''off'' and would do it's best to ''run away''.

So HOW is it shutting down if the ''rack'' is stuck???

UNLESS it has an aftermarket EXTERNAL fuel solenoid (Murphy, for example).

Check Break · Jul 29, 2022

(quoted from post at 07:06:51 07/29/22)
What doesn't make sense it that, typically, the 3208 injection pumps have a large shutdown solenoid on top of them and there's a spring that moves the rack to the ''no fuel'' position at shutdown when the solenoid releases.

if the rack/plunger barrels are stuck the engine wouldn't shut down when the key was switched ''off'' and would do it's best to ''run away''.

So HOW is it shutting down if the ''rack'' is stuck???

UNLESS it has an aftermarket EXTERNAL fuel solenoid (Murphy, for example).

x2. My experience (limited) is they stick closed and you have to remove the solenoid to get them to run.

This post was edited by Check Break on 07/29/2022 at 07:45 am.

Steve in IL · Jul 29, 2022

Just to clear up some things. When you crank the engine it goes to 2500rpm? And when you shut off the key, the engine stops? If these are both true, then I dont think the rack is stuck. Its been over 30 years since I worked on those engines, but it seems that if the pump is stuck in the full fuel position, it will run faster than 2500rpm.

Jhn · Jul 29, 2022

https://youtube.com/shorts/88r3Zy3WN0Y?feature=share

Steve in IL · Jul 29, 2022

Unfortunately, I cant get that link to work.

Jhn · Jul 30, 2022

https://youtube.com/shorts/88r3Zy3WN0Y?feature=share

3208 cat throttle stuck open

Jhn

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cjunrau

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flying belgian

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Jhn

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MKinON

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RodinNS

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Jhn

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oldjohndeere

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used red MN

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BarnyardEngineering

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Billy Shafer

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wore out

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Check Break

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Steve in IL

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Jhn

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Steve in IL

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Jhn

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