(2) 320dl KGF & A8F Hard Starting

[Vishaltrinidad]

Good day.
I have two 320 DL and they both are hard starting. I have changed the following : All fuel filter, common Rail, Fuel pump , injectors, injector lines, fuel return valve upper and lower among other parts.
what I have noticed is when the machine is switched off the fuel rail is not retaining a standby pressure (value on ET falls flat to 0 ) in the system as well as when the machine is switched off and you physically prime the system you can hear the fuel returning into the tank. When priming the primer will get hard and a couple seconds later be soft .

Looking forward to some advice. These units are sending me crazy!

 

[thepumpguysc]

I’m not familiar w your machine but, in MOST common rail systems, on the end of the rail is an overflow valve that holds or is supposed to hold the pressure in the rail.. it looks like a regular banjo bolt but has a spring & check ball set to a certain pressure.. probably about 30 - 35psi..
Check to make sure when u were doing the work on it, the overflow didn’t get swapped w another banjo bolt.. or the spring is broken..
Good luck

 

[Nige]

Here's the system operation document for the fuel system. It's the same on both engines.

I guess my questions would be is the cranking speed (on the starter) high enough, and have you replaced the Rail Pressure relief valves (Ref # 24 on Page 4).?

 

[thepumpguysc]

Your ABSOLUTEY RIGHT ON w the cranking speed...
I have an old IH tractor in the yard right now that I was fighting slow cranking.. I couldn’t get it to start to save my azz.. It would drain the battery in just about 2 tries..
I load tested the battery and it tested fine.. so the only other “reasonable” thing was the starter..
I shipped it off to be rebuilt and when it came back... a 10 second burn on the glow plugs & a push of the starter button & she fires up QUICK.!!
It usta be a 60-90 seconds on the gp’s & crank till the battery was dead.. hook up the charger & wait 30-50 minutes and try again..
Not anymore.!!!
There’s no arguing CRANKING SPEED.. the PISTONS HAVE TO be working fast enough to HEAT THE CYLINDERS ..

 

[Nige]

Your ABSOLUTEY RIGHT ON w the cranking speed...

There’s no arguing CRANKING SPEED.. the PISTONS HAVE TO be working fast enough to HEAT THE CYLINDERS ..

The thing with these engines is that the electronics will remain dead until a certain pressure has been generated in the rail. That's why the correct functioning of the rail pressure sensor and the pressure relief valve is so important. Not enough pressure and the injection system does not come out to play.

The other ingredient is cranking speed because even if the mechanical/electronic parts are working correctly, low cranking speed won't generate enough pressure to light the fires in the electronics.

 

[Vishaltrinidad]

I’m not familiar w your machine but, in MOST common rail systems, on the end of the rail is an overflow valve that holds or is supposed to hold the pressure in the rail.. it looks like a regular banjo bolt but has a spring & check ball set to a certain pressure.. probably about 30 - 35psi..
Check to make sure when u were doing the work on it, the overflow didn’t get swapped w another banjo bolt.. or the spring is broken..
Good luck

It has two valves one for the rail and on the blow of that is the valve for the pump , I have replaced the both and still doing the same issue.

 

[Vishaltrinidad]

Here's the system operation document for the fuel system. It's the same on both engines.

I guess my questions would be is the cranking speed (on the starter) high enough, and have you replaced the Rail Pressure relief valves (Ref # 24 on Page 4).?

i have changes the starters already. I had the kgf starter rebuilt and the A8F replaced with a new aftermarket one

 

[thepumpguysc]

Well that covers about all the ideas I have, other that a bad lift/supply pump..
U can plumb a gauge in the line or on top of a filter to see what the “incoming” fuel pressure is..& if it dumps it when it’s shut off.. if it does, it’s almost always the supply pump..

 

[thepumpguysc]

If it dumps the pressure & the machine is out of warranty, plumb an electric supply pump in line..

 

[Nige]

I'd love to see what the pressures from the lift pump and the rail are doing when the engine is running.

 

[Vishaltrinidad]

Guys a quick update for you all . I have order a set of new CAT injectors of one unit to see if that assist with it problem . Also I have noticed that the return fuel is black in colour. I removed the supply for the tank and put clean fuel in and it still comes out black. The fuel does not smell or feel oily in any way and the engines oil level is not dropping even after hundreds of hours of work in 35 degrees celsius weather.

 

[Vishaltrinidad]

I'd love to see what the pressures from the lift pump and the rail are doing when the engine is running.

From what I have noticed once the unit is running the pump pressures match what is required. only when turning (tumbling over) the engine to start the pressure does not go about 4-8xxx KPA. it will make ice cream for you all day

 

[Vishaltrinidad]

Well that covers about all the ideas I have, other that a bad lift/supply pump..
U can plumb a gauge in the line or on top of a filter to see what the “incoming” fuel pressure is..& if it dumps it when it’s shut off.. if it does, it’s almost always the supply pump..

does the lift pump have a one way valve as well ?