No idle

[jefjoc]

Engine runs above 1200 rpms. Stops below 1200 rpms. New fuel pressure valve installed. Injection pump governor checked. Any suggestions as to where else I can look would be very helpful. Thanks jefjoc

 

[WillWagner]

So it dies if you let off the go pedal or if you bring the rpm down slowly, will it stay running until you fully remove you foot from the pedal? Sincde you stated a new overflow valve, I assume it is an 8.3....

 

[jefjoc]

So it dies if you let off the go pedal or if you bring the rpm down slowly, will it stay running until you fully remove you foot from the pedal? Sincde you stated a new overflow valve, I assume it is an 8.3....

When I start engine I use throttle knob to keep running. When I push knob in and rps go down to 1200 engine stops.

 

[WillWagner]

There is an idle stop screw on the back side of the throttle lever. If there has been any kind of an oil, fuel leak there, the liquid acts as a base and dirt will erode, lap, whatever the contact points for that stop. The stop can be adjusted, HOWEVER, if the stop is eroded, the adjustment will go from no idle to too high of an idle. Only fix is to remove the screw, re profile, braze, whatever to get it back to it's original shape so that a minute adjustment makes a difference. Did that make sense?

If the stop is worn too far, you will have a too low idle and if it is adjusted, too high of an idle.

HTH,
Will

 

[jefjoc]

There is an idle stop screw on the back side of the throttle lever. If there has been any kind of an oil, fuel leak there, the liquid acts as a base and dirt will erode, lap, whatever the contact points for that stop. The stop can be adjusted, HOWEVER, if the stop is eroded, the adjustment will go from no idle to too high of an idle. Only fix is to remove the screw, re profile, braze, whatever to get it back to it's original shape so that a minute adjustment makes a difference. Did that make sense?

If the stop is worn too far, you will have a too low idle and if it is adjusted, too high of an idle.

HTH,
Will

Thanks, I'll check it out.

 

[WillWagner]

Just thought about something else. If the FSOV is coming apart or not adjusted properly, it can cause the same symptom.

 

[jefjoc]

Just thought about something else. If the FSOV is coming apart or not adjusted properly, it can cause the same symptom.

FSOV is what part please?

 

[WillWagner]

Fuel shut off valve. It's the electric plunger goodie on the side of the pump that pulls in when you start it and extends when the power is off. There are specific measurements for the different types of valves and pumps for pull in. If it does not pull in far enough, the coil will not hold and will extend shutting the engine off. Lemme see if I still have a book on it.

IIRC, it is possible to have too much pull in and that causes issues too, but, I'm old and there is too much to remember.....i'll look for a book....

 

[jefjoc]

Fuel shut off valve. It's the electric plunger goodie on the side of the pump that pulls in when you start it and extends when the power is off. There are specific measurements for the different types of valves and pumps for pull in. If it does not pull in far enough, the coil will not hold and will extend shutting the engine off. Lemme see if I still have a book on it.

IIRC, it is possible to have too much pull in and that causes issues too, but, I'm old and there is too much to remember.....i'll look for a book....

Thanks for your input. I replaced FSOV with a new one. I replaced fuel pressure valve as well. Engine issue has me stumped.

 

[Jbulach]

Throw the FSOV to the side until your problem is resolved.

 

[jefjoc]

Throw the FSOV to the side until your problem is resolved.

Thanks, I have done that.

 

[WillWagner]

If the idle stop turns out OK, you need to check fuel pressure. If there is a restriction or the lift pump is not making the correct pressure your issue can happen, but, it usually accompanied by white smoke and there are power issues. You should check pressure/restriction anyway just so you have touched all bases and that can be communicated to the pump shop if needed.

Still looking for the book, I know where it is, just gotta get to it.

 

[jefjoc]

If the idle stop turns out OK, you need to check fuel pressure. If there is a restriction or the lift pump is not making the correct pressure your issue can happen, but, it usually accompanied by white smoke and there are power issues. You should check pressure/restriction anyway just so you have touched all bases and that can be communicated to the pump shop if needed.

Still looking for the book, I know where it is, just gotta get to it.

Thank you. I will try a pressure test.

 

[jefjoc]

Thank you. I will try a pressure test.

I wonder if the lift pump could cause a no idle?

 

[WillWagner]

If there isn't enough pressure/flow, but, usually a white smoke, hard start, low power issue is present. Low pressure/flow changes injection timing, retards it, hence the white smoke and makes it so the minimum low pressure isn't there to make the needed high pressure causing a hard start.

 

[jefjoc]

If there isn't enough pressure/flow, but, usually a white smoke, hard start, low power issue is present. Low pressure/flow changes injection timing, retards it, hence the white smoke and makes it so the minimum low pressure isn't there to make the needed high pressure causing a hard start.

Thanks, that sounds like the problem. I just ordered a new lift pump. I do get alot of white smoke now.

 

[Jbulach]

Pressure gauge is a worth while addition

 

[WillWagner]

Don't just load the parts cannon, troubleshoot it. If there is a restriction, no hard part will fix it. Three check points will give you the 4 readings you need, restriction into the system, lift pump output pressure/FF inlet pressure, FF outlet pressure, (pressure drop across the filter)gallery pressure.

You should check for air also, air will give you low pressure readings as will high restriction. Too much restriction can actually cause air in the fuel in the form of LOTS of very tiny bubbles, it makes the fuel look cloudy in the clear line.

 

[jefjoc]

View attachment 903528
Pressure gauge is a worth while addition

Thank you. Is there a good place to hook it up under the hood?

 

[Jbulach]

I used a snubber that replaces the banjo bolt on the outlet of the filter housing. Cant remember where I got it, maybe TorkTek when I bought my adjustable overflow valve?