Hey guys, I've got a little issue with the truck. When I start it and run it up the high rpm that the 4 speed makes it run cruising at 60 mph, it starts to clatter really loud and then dies down, catches itself and revs back up again. This is only when your sitting with it in neutral. If you let go of the pedal when it starts dropping, it will stall out. It does this only when it's cold. When your driving and you reach that spot in the pedal travel, it will start to clatter real loud again and the truck will lurch forward as if it has a power spike. Once the truck warms up to a certain point, it won't do it anymore. It sounds like the IP is on its way out. Any suggestions on this?

 

IP or air intrusion

 

air intrusion is a likely cause. if you still have your factory water seperator, its infamous for leaking, and that air it can leak into the fuel will cause your problem.
also inspect the rest of the lines from the tank(s) to the lift pump for any damage.

also, if you haven't already, it would be wise to treat your system with diesel kleen or something similar. buy a quart bottle of it, drain your fuel filter, fill your filter with diesel kleen, start engine for 5-10 seconds, shut down, and let it sit overnight. after you do that, you'll feel like you're driving a different truck - it really makes that much difference.

 

Really? I've been running diesel Kleen in the fuel for a while now. How does that explain why it only does it when it's cold? I guess the clatter is air coming in. The PO bypassed the stock fuel separator and its still that way. I do need to add one soon. Would water in the system cause any of this?

 

only when cold... i didn't catch that part at first... try unplugging the wire from the top-rear of the IP - thats the one that turns on the cold timing advance. see how it works with that unplugged. for awhile mine had a bad temp sensor controlling that and it caused a lot of timing stuff like that.

the clatter is excessive timing advance, which can be caused by the cold timing advance, air intrusion, or IP problems.

if you want to check for air, you might drop a clear filter into the line near where the water seperator used to be, as that will let you look and see if you're getting air before that point.

if you don't have any air on the supply side, and disconnecting the cold timing advance, doesn't change anything, then it sounds like its time to get your IP rebuilt

 

I've been running it with that unplugged as when it was, the throttle would somehow get stuck at a higher rpm when you pressed the to pedal half way and it would slowly creep back down to fast idle speed. I'm assuming it also is liked to this problem.

 

Forgot to mention that the fast idle thing comes on even in 60 degree weather and the glow plugs always cycle and never stop.

 

the fast idle and cold timing advance are both controlled by the temp sensor behind the thermostat housing. its supposed to be on whenever the coolant temp is below 120 or so. you can run for as long as you want to with both of those unplugged. if unplugging them improves your situation, then it may be that the temp sensor that controls it is failing. note that this sensor can only be bought from ford or your local junkyard, parts stores can't get it.

but the RPM creeping down so slowly sounds like its either a sticky throttle cable or something sticky on the IP

 

it might be govoner taking away fuel when you free rev the engine...the way it sounds it may be sucking air some where, if the po removed the return line system parts, some of the return line,s on oem system have small plastic check valves, behind the return line orifce fitting,,if the return line system has no way to return the bubble,s produced by the pumps and the sloshing of the tanks,,,they must go through the ip,,,engine will miss and start hard, ect,,the return line system is important to proper performance of engine and fuel system...my..05

 

you may have problem with temp sensor compounding all the other problems, problems sometimes come in three"s try to focus on one problem at a time,,u will get er done...

 

Sorry I haven't gotten back. I'll figure the other stuff later. Well the truck cut off on me Friday while I was driving, followed by a slight rubber burning smell. My first thought was the IP went out, but further investigation found that there was a short in the glow plug harness causing the Fuel shutoff valve in the IP to not open. There was a fusible wire connected to what appears to be an inline fuel heater right before the fuel filter. It was somehow connected to the FSS. Well, I guess the fuel heater failed and shorted causing the fusible wire to burn in two, hence forth the burning smell. Could this have caused my truck to do what it was?

 

all those wires are tied in together, so if the one was burning up that could screw with everything on the whole system. for a test, run a new wire from a good power source to the IP - preferably something you can switch off without leaving the cab, and see how it runs on that. if it runs right with that temporary wire powering the IP, then it would just be an electrical problem.

 

Me and my dad put a new chip type fuse instead of the fusible wire. I'm not sure, but it seems to be running a little better. I will find out next time I start it as it wasn't really cold when I tried it.