My truck wont cut off

[Dawson]

I have a 1987 f350 with a 6.9l idi the trouble I am having is when you first start the truck up and the key is in the run position it revs up to 2700 RPM and The throttle is responsive but after it warms up a little you can cut the key back to the off position and it will idle down but the throttle is totally unresponsive it actually tries to cut off when you hit the throttle I have no clue what this could be someone please help

 

[david85]

I have a 1987 f350 with a 6.9l idi. The trouble I am having is when you first start the truck up, and the key is in the run position, it revs up to 2700 RPM. The throttle is responsive but after it warms up a little, you can cut the key back to the off position and it will idle down but the throttle is totally unresponsive. It actually tries to cut off when you hit the throttle. I have no clue what this could be someone please help

Hi Dawson, Welcome to the forum. Hope you don't mind I cleaned up your grammar a bit...not easy to understand a problem if it's not written clearly, so I hope I got your meaning right. With what you posted so far, we need a bit more information.

You said the throttle is responsive, but what is it doing when the engine is already up to 2700 RPM? Does it add a little more RPM or does it slow down to less than 2700?

Have you physically inspected the throttle linkage on the passenger side of the injector pump? Is anything binding in the throttle cable?

Was the fuel injector pump recently replaced or otherwise tampered with? Did anyone remove the top cover recently?

When was the last time this truck drove properly? (Or is this your recent purchase?)

 

[Dawson]

It's a recent purchase and I think the top cover of the pump may have been removed (for the gasket maker around it). But nothing is binding the linkage it's just when the key is in the run position and the rpm never changes until you cut The key back to the off position and then it'll come down the idol but even know it is in the off position it won't cut off. And when the key is for and the truck is running high you can hit the throttle and it is responsive but when you cut the key backed off it just Hesitates and doesn't do anything

 

[Dawson]

It has also been sitting for about 3-4 years

 

[laserjock]

Top cover having been off you need to be real careful. If it’s not put back right, you can have a runaway which is basically what it sounds like you’ve got trying to happen. Sounds like the fuel shutoff isn’t working. I believe the issue with the top cover is the governor lever. Do be careful messing with it. One of the more versed pump guys can probably be more help.

@typ4
@Agnem
@OLDBULL8

I think Bill has a picture showing how to put it back together right.

 

[Dawson]

Thank you @lazerjock I will check into that

 

[david85]

It sure sounds like the Shut off Solenoid was not installed correctly. I'm coming up short on that awesome diagram that was floating around a while back. Anyone else have it?

Basically, the cover needs to be lowered into position slightly to the rear of the truck in order to correctly align the linkage. Then you slide the cover forward, still holding it down, in order to align the bolt holes. It will try to lift if you're not careful.

If you install it by simply dropping it straight down (required for a proper RTV seal), then the lever attached to the shut off solenoid will not align correctly and you end up with an engine runaway.

https://www.oilburners.net/brian/idi/FuelInjectionServicing.htm

You must be registered for see images attach

 

[Dawson]

So did some looking and figuring and when 12volts is put to the fss terminal on the ip that's when the truck revs up I don't think that's supposed to happen right

 

[david85]

Nope. That's definitely not supposed to happen.

The fuel metering in these pumps works on a sliding scale. The idea of the solenoid is to push that scale to the lower extreme end in order to starve the engine of fuel when you cut the ignition key. If the solenoid lever is not aligned correctly, then it can push the metering valve to the other extreme, rather than shut off the engine.

I couldn't find that diagram I was looking for on the web, so I slapped this together (Borrowed a screencap from this video

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:

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Looking at this, I may have misled you about which direction you need to slide the cover into place. But once you recognize the FSS lever, and how it aligns with the governor linkage, it should be pretty easy to figure out. Be careful to inspect the components for any evidence of damage from being forced into place by whoever put that RTV sealer in there. Normally there is a rubber seal, so you might want to replace that while you have it apart (assuming its even still in there...).

 

[Dawson]

Thank you I'm pretty confident that's the problem

 

[snicklas]

Is the Cold Idle Advance solenoid WAY out of adjustment? This is the electrical "plunger" on the passenger side of the pump below the throttle return springs, and push on the same lever the throttle cable pulls on. Are the throttle return springs actually there and connected?

If that plunger is way out of adjustment, it would make since, when power is removed from the solenoid it would idle down.

But, here is another question, when you turn the key off, or pull the wire off the Fuel Shutoff Solenoid, does the engine actually stop running? If removing power from the FSS does NOT cause the engine to stop, how are you getting the engine to stop running?

Can you actually get the engine to idle? Like in the 600-800 RPM range? Can you post any pictures of how the pump is currently set up? Maybe some of the brackets or linkages are bent / out of adjustment / missing.

I was always under the impression if the pump cover was installed incorrectly, the only way to get the engine to stop running is to stop the air or fuel supply or, if you are lucky, dump the clutch on a manual. I think it either works correctly, or not at all. Not just sorta works, and limit the maximum RPM. It should idle, or go beyond max governed RPM (3800+). Think a Screaming Jimmy runaway........

 

[BeastMaster]

Maybe keep a CO2 fire extinguisher handy if you anticipate a diesel runaway? I would suspect CO2 released into the air intake should kill off the combustion without ruining the engine innards?

This is just a personal speculation as to how I would handle it if I thought the thing was likely to get out of control. If I am barking up the wrong tree, I would appreciate correction.

 

[BeastMaster]

Or, maybe Halon?

 

[laserjock]

CO2 will kill it if you can flood the intake with enough long enough.

 

[Macrobb]

I would just loosen a fuel supply line somewhere so you can just pull a line and remove fuel supply to the IP. Might be a bit messy, but a quick way to stop it.

Or, if it's a stick, just have the gearshift in 5th and drop the clutch.