623b Low Engine Horsepower

[Rick Attenborough]

I have a 623b 46p651 scraper that seems to be down on horsepower. Have rebuilt engine recently with new head fitted. Also put new injector nozzles. Can anyone help me out at all? Cheers Rick.

 

[Tinkerer]

Welcome to HEF Rick !
Engine turning full rpm's ? Sometimes a simple throttle linkage adjustment is needed.
Does the engine speed drop off under load ?

 

[Nige]

What makes you think you have low engine power as opposed to something like a power train issue or even binding brakes.?
If not the above - do you have reason to suspect the parts that were used during the engine rebuild.?

Some more detailed description of the symptoms might help, like for example are you getting correct High Idle RPM or does the engine smoke under any circumstances, etc, etc. All info at this stage is good info, it can be filtered later. Fire away..........

 

[Rick Attenborough]

Have had cat mechanic set engine rpm whilst setting Trany shifting pressures. Have checked brakes and wheel bearings. Change fuel filters several times engine doesn’t seem to blow much black smoke and pardon the expression it doesn’t sound very ballsy. When the engine was rebuilt we used fp diesel gear and a cat reman head also fitted a reman turbo. When working the machine it doesn’t seem to pull like it should a bit of load on it when dumping and the engine loses revs and it drops a gear. I drove it home from the last job about 100ks on a road I have been on plenty of times and on the hills it is dropping a gear which it has never done before. Was wondering whether it could be the air- fuel ratio control. Any help wood be great.

 

[DB2]

Air fuel ratio diaphragm is relatively inexpensive and not hard to replace.

 

[Nige]

Air filters might be an outside possibility but you don't mention black smoke so I'd say that is unlikely.
Has anyone checked the boost pressure when it's working hard.?
Did you have the fuel injection pump overhauled during the engine rebuild.?

 

[thepumpguysc]

I's STILL CHECK the throttle lever on the pump.. Just because your maxed out on the controls, doesn't mean your maxed out at the inj. pump..
When diagnosing a low power problem>> ALWAYS START at the inj. pump throttle "throw"..Make sure its hitting its stop screw..
AND>> Run it WITHOUT the air cleaner installed.. & leave the COVER OFF..

 

[Rick Attenborough]

Does anyone know the factory setting for the spool for the air fuel ratio controlled valve as my cat manual doesn’t say how to set it up.

 

[Nige]

Remember that the A/F ratio control only really works during acceleration. According to your description the engine is lacking power up at the top end of the rev range.
Was the fuel injection pump rebuilt during the engine overhaul.?
What's the engine S/N.?

 

[Rick Attenborough]

No the pump hasn’t been done have replace the injector nozzles. Serial number is46p651.

 

[Nige]

That's the tractor Serial Number. The engine S/N will be 70Vxxxxx if it is the original 3406, but it could have been re-powered by a load of different factory options (and an infinite number of non-factory options) since then.
Even if it's the original engine it could have had a TIER I emissions upgrade that would result in some parts being changed.

 

[Mobiltech]

Does anyone know the factory setting for the spool for the air fuel ratio controlled valve as my cat manual doesn’t say how to set it up.

Have you pressure tested the diaphragm in the Afrc ? If its blown it will hold back fuel all the time. Is the signal line hooked up.
Try turning the screw in one turn on the spool to see if it improves power. The worst you’d have is a little black smoke on acceleration.

 

[Rick Attenborough]

Engine serial no is 70v 2085. Throttle is hitting the stop in the pump. Have resealed fitting into intake manifold found in a bit lose. I’m still waiting on diaphragm and gaskets to do frc.

 

[Rick Attenborough]

One thing I mean’t to mention that this machine has had the muffler removed and a straight pipe fitted.

 

[Mbar]

I would agree with nige on the boost check. I put a head on a 3306 awhile back for a guy and found a plug left out on the intake under the after cooler by a previous mechanic. The man had spent thousands chasing the low power issue. May not be your problem but with the recent rebuild it’s worth a look