6.9 idi injection pump issues
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5th Wheeling
Joined: Aug 2021
Posts: 37
Likes: 2
6.9 idi injection pump issues
Recently my 6.9 idi has been having a stalling issue. If I rev the engine when parked, or let off the throttle when I’m driving it will die and start right back up. But as soon as I tap the gas pedal and let off it dies again, starts up just fine, give it gas and let off, and it dies.
i heard this can be caused by the metering valve sticking inside the injection pump, so I removed the top cover off the pump, filled it with ATF, replaced the fuel filter and filled it with atf too, ran it for about a minute, shut it off, and let it sit overnight.
The next day it was running much better, so over the next few days I kept repeating this process until eventually the truck ran great again and had no issues. Fast forwards about a week or so, I let the truck sit in the driveway for about 5 days and now it’s running just as bad as before. I tried the ATF trick again but it did not help
Does this mean I should start looking into replacing the injection pump? If so what company sells a good Stanadyne DB2 pump? The engine is bone stock, it is in a 1986 f250. I just want to make sure I’m getting a pump from a reputable supplier and not some cheapie that’ll only last a year
any other advice is greatly appreciated
i heard this can be caused by the metering valve sticking inside the injection pump, so I removed the top cover off the pump, filled it with ATF, replaced the fuel filter and filled it with atf too, ran it for about a minute, shut it off, and let it sit overnight.
The next day it was running much better, so over the next few days I kept repeating this process until eventually the truck ran great again and had no issues. Fast forwards about a week or so, I let the truck sit in the driveway for about 5 days and now it’s running just as bad as before. I tried the ATF trick again but it did not help
Does this mean I should start looking into replacing the injection pump? If so what company sells a good Stanadyne DB2 pump? The engine is bone stock, it is in a 1986 f250. I just want to make sure I’m getting a pump from a reputable supplier and not some cheapie that’ll only last a year
any other advice is greatly appreciated
Mountain Pass
Joined: May 2020
Posts: 151
Likes: 10
A couple of websites that have a nice selection of injection pumps are Classic Diesel Design and R&D Performance.
https://idiperformance.com/
https://classicdieseldesigns.com/
https://idiperformance.com/
https://classicdieseldesigns.com/
Logistics Pro
Joined: Jun 2017
Posts: 3,986
Likes: 515
From: Edmond, OK
Here's another IDI supplier that is well rated. They bought Conestoga Diesel, or there was some sort of change in ownership.
https://moosediesel.com/
https://moosediesel.com/
Mountain Pass
Joined: May 2020
Posts: 151
Likes: 10
I haven't bought an injection pump from CDD but I bought a huge rear fuel tank from them. My only complaint is that the directions could have been more clear but they were prompt with shipping and the product was in great condition when it arrived. Didn't have any issues with them. It was a sweet deal because they were selling "damaged" versions of the tank for a discounted price. The one I got has a small dent in the bottom corner but it functions perfectly fine. I wouldn't hesitate to order something through them again.
Tuned
Joined: Oct 2003
Posts: 331
Likes: 18
From: Pottstown, PA
Put a direct line from the pump to the fuel filter. When pump is on fuel flows well when i depress the filter schrader. It will start for about 3 seconds then it starves for fuel. Replaced electric pump, no difference.
Years ago the rear tank was leaking. It was shot and I bought a new one but have not put it in yet. The front rear switch is set to front.
Fuel filter is new but i have not tested flow post filter othe than depressing the schrader valve.
I like the idea of putting the pump near the tank.
Out of ideas.
Years ago the rear tank was leaking. It was shot and I bought a new one but have not put it in yet. The front rear switch is set to front.
Fuel filter is new but i have not tested flow post filter othe than depressing the schrader valve.
I like the idea of putting the pump near the tank.
Out of ideas.
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Lead Driver
Joined: Apr 2002
Posts: 5,362
Likes: 1,258
Since you have two tanks you could be sucking air from the unused tank side. Sometimes the valve doesn't get all the way to one tank leaving a gap for air to get in. Try either plugging the unused fuel lines or installing the rear tank and put fuel in it. I have had my valve stick partially and it drew from both tanks. I think I dislodged whatever was making my valve stick by filling both tanks and at highway speed switched tanks every 2 miles for about 40 miles. What ever was holding my valve from fully selecting a tank got flushed out and I'm back to a normal two tank operation.
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Tuned
Joined: Oct 2003
Posts: 331
Likes: 18
From: Pottstown, PA
More specs: 1985 F250 6.9, 8ft bed, 4x4, Automatic.
Checked all of the connections to the injectors and the injector pump post filter, all are tight. Tubes between injectors are fine.
Going to put in the rear tank today as suggested in case the front/rear selection switch is pulling air from the rear lines.
I also want to pull a line post filter with the fuel pump on and see if fluid comes out, maybe there is a block in the filter manifold...? Is schrader output post filter?
Could this problem be a bad injection pump? Am I missing something else? I'm running out of variables.
Checked all of the connections to the injectors and the injector pump post filter, all are tight. Tubes between injectors are fine.
Going to put in the rear tank today as suggested in case the front/rear selection switch is pulling air from the rear lines.
I also want to pull a line post filter with the fuel pump on and see if fluid comes out, maybe there is a block in the filter manifold...? Is schrader output post filter?
Could this problem be a bad injection pump? Am I missing something else? I'm running out of variables.
Last edited by redbug; Jan 22, 2026 at 11:01 AM.
Lead Driver
Joined: Apr 2002
Posts: 5,362
Likes: 1,258
Schrader is after the filter. When ever I change filters I use a short hose from an old screw on bike pump attached to the Schrader valve and led to a jar so I can see it while I'm cranking and filling the filter. When filter is full I get a good stream of fuel into the jar.
Lead Driver
Joined: Apr 2002
Posts: 5,362
Likes: 1,258
Schrader is after the filter. When ever I change filters I use a short hose from an old screw on bike pump attached to the Schrader valve and led to a jar so I can see it while I'm cranking and filling the filter. When filter is full I get a good stream of fuel into the jar.
Fleet Owner
Joined: Jul 2006
Posts: 20,390
Likes: 850
From: Mi'kma'ki
redbug, the simplest thing to do, to rule out variables is to unhook the supply line to the lift pump (mechanical or electrical)and run a hose to it directly from a 5 gal jug of diesel fuel and then see if the IP will prime then. If it does, and starts running, then you know you've got a problem fuel pump back to tanks. If it doesn't then you know you've got a problem fuel pump to injectors. This really narrows things right down. Just keep in mind, the fuel will return to whichever fuel tank you have selected (if the selector valve is working as it should), so if you do this with a full tank,it could overflow that tank.
Make sure that factory water separator is bypassed on your early IDI and that you're using one with a universal built in filter and or just the duralift electric pump will catch it. Those were notorious for leaking.
Disregard; see better thread here:
https://www.ford-trucks.com/forums/1...y-running.html
Make sure that factory water separator is bypassed on your early IDI and that you're using one with a universal built in filter and or just the duralift electric pump will catch it. Those were notorious for leaking.
Disregard; see better thread here:
https://www.ford-trucks.com/forums/1...y-running.html
Last edited by FORDF250HDXLT; Jan 23, 2026 at 12:17 PM.
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