No throttle response but engine idles- Volvo TAMD40B

[NomadBill]

Having just repaired/lined fuel tanks and changed raw water pump I decided to test for leaks and any other issues. Started engine but it needed almost 1/2 throttle to stay running at Idle speed only. Won't go above idle, even at full throttle.

This engine had started and run normally several times including the previous morning and at normal RPM. it's been run 4-5 times for 5 min or more since tanks were worked on...no issues until now.

So I did this:

Checked Linkages and throttle movement. good

Checked all fuel lines and valves for kinks and proper open setting. good

Replaced Air filter and both Fuel filters including screen in pump. dirty but not plugged

Bled air at engine mounted Fuel filter. Found some air bubbles

Bled each injector line until spitting. Thought this would fix it, but didn't

Bled injectors while idling with throttle wide open! No impact.

Engine WILL aways start with throttle open 1/2 way but not run above an idle.

Panel Temp and Battery lights Stay on when engine idling, oil pressure light goes out.

Question is this: Are there limp home or protection mode safety system on these Old Diesel Volvos? This seems to be acting like it's being prevented from running at higher revs. Or is this likely just an air in the fuel line issue so I should keep bleeding?
I'm stumped!!!

Any suggestions or insight would be greatly appreciated

Thanks,

Bill

m/v Nomad

47´ Marine Trader

 

[timb]

see if you have any pressure going in to the injector pump . or does it suck air maybe lift pump is bad .

 

[timb]

did you also work the stop solenoid it may be sticking

 

[NomadBill]

OK thanks Tim. I did check the stop, it's manual cable pull not a solenoid and it's in full stop position.
Haven't checked for the lift pump. Although the vent screw on the engine mounted filter is downstream of that pump, so the bleeding would confirm some flow.
Are you suggesting I back off the line into the injector pump and crank to see good flow?
Thanks for the suggestions

 

[Xsbank]

Did you mean to say it's in full stop position?

In a healthy engine, you need air and fuel, in their proper places. I believe that you have a fuel issue. Start the bleeding again.

 

[fgarriso]

Temporally replace the fuel line from the lift pump with a clear plastic line. Leave enough line you can form an inverted loop and start the engine. If you are drawing air into the injector pump you will see the air bubbles.

 

[NomadBill]

Thanks for the replies. Yes I meant Full run position on the shut off.
The fuel lines that come from the lift pump to the filter housing to the Injection pump are all bolted on with hollow bolts and not easily retrofit for a clear tube unfortunately However I did disconnect the fuel return line at the tank and had a steady stream, no bubbles coming back from injector pump to the tank at idle speed. so that's another data point.
I'm going to bleed everything again and see if it helps. Thanks everyone

 

[fgarriso]

https://www.amazon.com/Banjo-Bolts/s?k=Banjo+Bolts

 

[Ski in NC]

Since you were messing with the tanks before this problem arose, might be a good idea to set up a portable tank of fuel direct to engine and see if it runs any differently.

Even though you are using the mechanical shutdown, there may be an electric stop solenoid in the back part of the VE pump (the steel part), those can act up.

And there are things that can go wrong with the governor, under the cover where throttle lever is. Broken spring, etc.

Been a while since I was in one of those pumps.

 

[catalinajack]

Ensure that your tank vents are not blocked. I discovered that the vent was blocked by critters on one of my tanks so much so that when the fill cap was opened a significant vacuum was released. A long shot but coincidental problems often occur.

 

[NomadBill]

Ensure that your tank vents are not blocked. I discovered that the vent was blocked by critters on one of my tanks so much so that when the fill cap was opened a significant vacuum was released. A long shot but coincidental problems often occur.

Thanks In my frenzy of trying everything that was also one of the things I'd checked also. Forgot to mention it however.

 

[NomadBill]

Since you were messing with the tanks before this problem arose, might be a good idea to set up a portable tank of fuel direct to engine and see if it runs any differently.

Even though you are using the mechanical shutdown, there may be an electric stop solenoid in the back part of the VE pump (the steel part), those can act up.

And there are things that can go wrong with the governor, under the cover where throttle lever is. Broken spring, etc.

Been a while since I was in one of those pumps.

Yes that is the direction I'm going since the issue seems to be coincidental with working on the front of the engine and I found last night the wire leading to one of those electric solenoids on the aft end of the injection pump. It turned out the wire had chafed through going into the metal box on the motor. (So close, thought I had found it but unfortunately not)
The running behavior is consistent and I have bled alot from the various points so I'm thinking that a stuck solenoid or signal wire issue from the keyswich is the probable cause. Now for some comparison readings on the other engine.
Thanks everyone for the ideas...very helpful.

 

[Greg S]

Plugged air intake? Is the exhaust normal? Some engines have an emergency shut off that is simply a physical flap that plugs the air intake.

YEARS ago I had an ancient Cummins that occasionally would only idle. Cruise into an anchorage, put it in R to maneuver, throttle up, and nothing, just idle. Happened several times. I was told there was a protective system on her that prevents reving up if engine oil was low. Sure enough, each time I'd add a quart or two and it ran proper again (until it leaked out again).

 

[NomadBill]

Issue resolved-Thanks everyone

Thanks to everyone who sent along ideas and areas to investigate. Turns out the lift pump on this engine is original and weak. As soon as the a fresh fuel flow was attached above the engine. so all air could completely purge out of the lift pump. Then the system got enough into the injection pump to rev normally.
This was a situation of check and double check the bleeding since I had cleaned out tanks and knew that there would be air in the lines until it all pushed through.
Lastly a new pump is on order so there will be one on hand when it's inevitably needed.
Cheers,
Bill

 

[Ski in NC]

Nice.