8.3 won’t idle when put in gear

[Kuhlbreeze]

I have a 1991 BMY with 8.3 it seems to run ok ( a little hard to start cold) but it starts and idles fine, until you put it in drive or reverse then it seems to steadily drop rpm then die and it takes some cranking to restart it. If you keep it around 1000 then dump it in gear it seems to be enough to keep it going once it’s on the boost all good. It was sitting for a few years and I drained the tanks out some cleaner in it changed the filter now I seem to be having a problem. Wonder if I broke loose some of the gummy fuel and it’s causing a pump problem thank you guys in advance

 

[simp5782]

Is your transfer case interlock button all the way out? This sticking in can cause an issue. This is on the transfer case shifter handle.

 

[Kuhlbreeze]

Is your transfer case interlock button all the way out? This sticking in can cause an issue. This is on the transfer case shifter handle.

It does stick occasionally what exactly does the button do

 

[simp5782]

It does stick occasionally what exactly does the button do

Locks the transmission in 5th gear so it's easier to shift when moving However it can cause issues.

Is this a cargo truck or wrecker?

 

[Kuhlbreeze]

Locks the transmission in 5th gear so it's easier to shift when moving However it can cause issues.

Is this a cargo truck or wrecker?

It was a road tractor but it has a custom bed on it

 

[Kuhlbreeze]

It was a road tractor but it has a custom bed on it

That is a possibility it feels like the transmission is in gear with no torque converter slipping

 

[Csm Davis]

Yeah the button controls torque converter lockup and the shifter lock

 

[Jbulach]

The hard start, and restart makes me think your sucking air in the fuel lines.

 

[Kuhlbreeze]

That is a possibility it feels like the transmission is in gear with no torque converter slipping

The hard start, and restart makes me think your sucking air in the fuel lines.

I am just not sure where it could be other than they added a inline filter and the clamps won’t squeeze that line tight

 

[Kuhlbreeze]

That is a possibility it feels like the transmission is in gear with no torque converter slipping

Well the button is all the way out I was hoping that was it. I am goin got have a fuel line made to eliminate the inline filter they installed and replace the separator

 

[Kuhlbreeze]

I am just not sure where it could be other than they added a inline filter and the clamps won’t squeeze that line tight

Anyone have any ideas of where to start to look for fuel system air leaks

 

[simp5782]

Anyone have any ideas of where to start to look for fuel system air leaks

The tank selector valve is a known problem child.

 

[Kuhlbreeze]

The tank selector valve is a known problem child.

Thank you I will back pump some air through the system and put some soapy water on it

 

[Kuhlbreeze]

Well the button is all the way out I was hoping that was it. I am goin got have a fuel line made to eliminate the inline filter they installed and replace the separator

Any idea what ATF this Alison atf

 

[simp5782]

Any idea what ATF this Alison atf

Should have 15w40 engine oil from the military. If it's been swapped out. Dextron 3 or Transyn.

 

[Kuhlbreeze]

Should have 15w40 engine oil from the military. If it's been swapped out. Dextron 3 or Transyn.

Thank you I appreciate it looks like motor oil in it

 

[Kuhlbreeze]

Thank you I appreciate it looks like motor oil in it

Can you use rotella 15-40

 

[simp5782]

Can you use rotella 15-40

Yes

 

[Kuhlbreeze]

Yes

well the trans appears to be keeping the TC locked. is that button normally closed or normally open? Can it be driven with the TC lock up solenoid just disconnected

 

[simp5782]

well the trans appears to be keeping the TC locked. is that button normally closed or normally open? Can it be driven with the TC lock up solenoid just disconnected

Yes. Normal allisons do not have it. It is simply used to ease shifting the transfer case while moving for less resistance in the gears.