Progressive IP Problem, Idling, Stalling Etc.

[TestDriver]

My engine began slowing down on idle a few weeks ago. I turned up the idle stop screw a couple of times but eventually it always slowed way down within a few days. It got to the point where the lever was stopped about an eight of an inch before it would even contact the cold idle solenoid rod when it was energized.

Eventually, it would not even idle and refuses to start without ether even when fully warm and while on straight diesel. Its too cold to risk stopping it on oil right now. When it does start, it'll only stay lit if I keep the throttle about 1/3 open. I can let it drop down almost to the last throttle stop setting but it stalls. When running, it's very smooth and does not smoke. The fuel pressure at the filter outlet is 3psi without the electric pump and 7psi with the Epump while running so I doubt it's a lift issue.

I removed the pump cover and everything looks good and clean inside. The cavity was full of fuel and the linkage moved as expected but I'm not exactly sure what to look for.

Any thoughts?

 

[dyoung14]

My engine began slowing down on idle a few weeks ago. I turned up the idle stop screw a couple of times but eventually it always slowed way down within a few days. It got to the point where the lever was stopped about an eight of an inch before it would even contact the cold idle solenoid rod when it was energized.

Eventually, it would not even idle and refuses to start without ether even when fully warm and while on straight diesel. Its too cold to risk stopping it on oil right now. When it does start, it'll only stay lit if I keep the throttle about 1/3 open. I can let it drop down almost to the last throttle stop setting but it stalls. When running, it's very smooth and does not smoke. The fuel pressure at the filter outlet is 3psi without the electric pump and 7psi with the Epump while running so I doubt it's a lift issue.

I removed the pump cover and everything looks good and clean inside. The cavity was full of fuel and the linkage moved as expected but I'm not exactly sure what to look for.

Any thoughts?

first thing you should do is change the fuel filter and fill it back up with diesel kleen of atf or some sort of diesel fuel cleaner, fire it up and let it run long engough for it to suck that into the ip then cut it off and let it set for a few hours, come back and fire it up and drive the **** out of it if you can keep it running, if it dont solve the problem you may be looking at needing an ip rebuild

 

[TestDriver]

first thing you should do is change the fuel filter and fill it back up with diesel kleen of atf or some sort of diesel fuel cleaner, fire it up and let it run long engough for it to suck that into the ip then cut it off and let it set for a few hours, come back and fire it up and drive the **** out of it if you can keep it running, if it dont solve the problem you may be looking at needing an ip rebuild

I changed the fuel filter before opening the top of the IP but did not add anything to it. There is a lot of anecdotal references to using Diesel Kleen or ATF but there is little in the way of data as to what this will do. And even then, it seems that this would be treating the symptom. I want to find out what is going on inside the pump to cause the condition. At the moment, I have another one on the bench all torn apart and before I put it back together, I'd like to address whatever it is that is causing the one on the truck to act up and hopefully, prevent it on the one I'm building.

Thanks for your post.

 

[Agnem]

Timing can have a big effect on idle speed. Possibly your cam set screw has come loose, and your mechanical advance is not working.

 

[TestDriver]

Timing can have a big effect on idle speed. Possibly your cam set screw has come loose, and your mechanical advance is not working.

Yup, it could be timing but I doubt it's the set screw. Actually, these pumps don't have a screw but rather a pin that just floats in the advance piston bore. The spherical end rides in the cam ring and the other side has a flat that glides on the cap bolt.

It could still be timing since I don't detect the loud clang typical of cold advance and before these troubles, I had used a jumper wire to activate the cold advance solenoid with no effect. Fuel did flow out of the IP via the epump when I activated the solenoid with the engine shut down so the solenoid works but when I did it with the engine running, there was no change at all.

I think I'll make myself an adapter for the back of the pump so I can check transfer pressure. It could be that the pressure is way down. However, I don't know what the pressure should be at what rpm. I've seen that GM applications run from 10psi at idle up to about 65psi at 3300rpm. I've also seen anecdotal references to 7.3s runing 42psi at idle up to 125psi at higher rpms. So, I'm still unclear as to what the transfer pressures should be.

 

[TestDriver]

Found! Ford Factory Service Data

Check it out.

http://www.fokisd.org/PDF_DOCS/93 94 7.3 IDI Turbocharged Diesel Engine.pdf