QSM11 Fuel flow and rpm’s drop

[Marcelo Sanabria]

Hello Tony and rest of the group! I have twin QSM11 @610hp and one of them is doing some weird stuff. At different rpm’s, the fuel flow (GPH) and RPM’s suddenly drops down to almost O (zero) then goes up and down constantly making the engine to loose power off course. The engine may even go off at times. I’ve changed the racor and diesel filter, I even dissasembled the racor and checked its components. Did not see any bubbling at the racor either. I also removed the pick ups from the tank and checked for obstructions, but the problem perists. Any ideas? Tks in advance for yur comments and best rgds.

Topic

[Tony Athens]

Glad you sorted it out.

[Marcelo Sanabria]

Hello Tony, Rob & rest of group!

We removed the fule pump and noticed there was a 1/4 inch irregular displacement on the spline, so we sent it to have it rebuild, put it back and engine operation came back to normal. Seems that it was slipping and catching as Tony said.

Thank you very much for your great help.

Rgds

Marcelo

[Marcelo Sanabria]

Ok Tony, I’ll do that and let you know how it went.

Thanks

[Tony Athens]

Swamp fuel pumps (easy job) , but study these pics too–Your spline may be “slipping” and then catching? 

[Marcelo Sanabria]

Hi Guys! We exchanged the ECM’s from one engine to the other and the problem persisted on the same engine, so we discarded that it is the ECM. Then, replaced both the crankshaft sensor and the fuel solenoid but the issue kept going, so we disconnected the alternator (as recommended in a web page related fo error code 343) and no luck either. Will go to the rest of recommendations on the fault code 343 page you attached and keep you posted. Rgds

[Tony Athens]

Error Codes attached

You have ECM issues–connections, lightening strike, etc etc etc 

[Marcelo Sanabria]

Hello!

I did as told.

The needle at the gauge fluctuated up and down ranging from ZERO to even 160psi (Sorry, I could not find one gauge that went only to 100psi) as rpm’s kept fluctuating also.

We scanned the engine and an error 343 code is active and CANNOT be deleted. 

Rgds

[Tony Athens]

Read my answer again–I think it’s crystal clear

[Marcelo Sanabria]

Great! Tks.

I understand that I don’t need the plastic insert for the tester but I must install back when finished and put the cap back. right?

[Rob Schepis]

QSOL shows them as 1/8″npt (as Tony states)

1 user thanked author for this post.

Marcelo Sanabria

[Tony Athens]

I believe they are 1/8″ Pipe thread 

Caution–when you remove the plug, there is a little plastic insert in the hole–pick it out and do not reinstall.   1/4″ id Common fuel line works fine–pressure is abound 50 PSI

[Marcelo Sanabria]

Good morning Tony and thank you very much for your wonderfull tip. The picture was VERY usefull for me to understand your idea!

I’ll purchase the gauge, hose and fuel hose adapter to assemble the fuel tester.

Boat is 2 hrs away, so could you pls tell me what size of fuel hose adapter (Thread, etc.) should I purchase so I dont loose a day going to the boat just to remove the cap and bring to the store as a sample?

Best rgds

Marcelo

[Tony Athens]

If you want to troubleshoot, this is where you start.. Install a liquid filled 0-100 PSI gauge on the pressure tap on a long  1/4″ ID hose and monitor this   —   Write down what you see and post.

 

 

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