Following up with my Injector Pump post from a few days ago...

I went over everything one more time last night before diving into buying an injector pump, I checked my overflow valve and discovered that I can blow air through it with the pressure from my lungs. If it's the overflow valve that has caused me this problem...would my computer still throw all of these codes???

PO216 - Injection timing control circuit malfunction;injection pump timing failure
PO251 - IP fuel metering control A malfunction(cam/rotor/injector); IP mechanical failure fuel valve feedback circuit
PO252 - IP metering control A; range or performance problem(cam/rotor/injector);fuel valve signal missing
PO1688 - ?
PO1689 - ?

Thanks!

Seedy 1

1999 24v 3500 4x4 Stock (No alterations)

 

I may have my terminolgy wrong. What I was blowing through the banjo that returns the excess fuel from the injector pump to return to the low pressure side to be recycled. The bolt has a spring loaded ball inside that opens when there is enough pressure on it to do so.

I was reading a thread yesterday that was telling a guy to check his overflow valve and thought to myself...well, that's the one thing I havene't checked! Again, I was holding onto the possiblity that it might be something other than the injector pump!

I don't think my problem could be any clearer with the codes that the computer has come up with. I'm still in a bit of denial!

Thanks!

Seedy 1

 

The 24 valve does have an overflow valve. It is the threaded deal with a spring and check valve in the hole, and it screws through the front fuel return line banjo, on the side of the VP44. They also fail and will cause pump error codes.

I presume you have checked your fuel pressure and have at least 5 psi when cranking and 10 psi at idle. If not, the internal bypass valve sticks in the lift pump, and it will still signal the pump it is working, but not be making the required pressure. That confuses the injection pump and it will then throw timing and cam malfunction codes when it finds inadequate fuel pressure to the pump head.

The codes you list could also lead me to check the crankshaft position sensor, once you know the overflow valve is properly functioning, and that your feed fuel pressure is within specifications. If it is not the sensor, then it is the VP44 experiencing a stuck metering plate and failing to time properly. The latter will require a rebuilt injection pump.

 

Regarding the overflow valve: If I can blow through it with the pressure from my lungs, does that mean it is faulty? If so then I think this is the first thing I should change.

Regarding the lift pump: When I back the truck in the drive as it was sputtering, I popped the hood while it was still running and it was registering 12-13 psi on my low pressure side inline gauge. Since it doesn't run at the moment, I can't check idle psi. It does register 5-7psi when I turn the key in the on position and bump the starter. I'm not sure if this is normal but, it only registers pressure after turning the key in the on position and the lift pump runs for aprox 15 seconds. Once it registers pressure it fluctuates from 5-7psi. I'm pretty sure that that indicates the LP is okay. If not, let me know.

Now, as for the crankshaft sensor. I did check that the only way I knew how. That was to hook up my buddy's OBDII computer to the truck's computer and check to see if it was reading RPM's. It did. Is that good enough? His computer isn't set up to communicate with the Cummins so, it may not be a thorough enough check. Please advise how to do a more thorough inspection of the crankshaft sensor if what I have done isn't adequate.

Thanks!

Seedy 1

 

Overflow Valve => #12:

http://www.dodgeram.org/tech/dsl/mt_...l_sys_comp.htm

 

I noticed that when I put the commercial engine in that the overflow valve is bigger or at least different than the dodge valve. Do you know the difference? Is it just a stronger valve or different specs?

 

No idea...

To be honest, I didnt know myself until a few weeks ago....

 

Ensure the seat on the overflow valve is clean and the ball does not have any marks or scars on it that will prevent it from sealing. Then make sure the valve is able to move in its bore to seat completely. It does not take much leakage for the VP44 to be unable to acheive the required pressure. The valve is very inexpensive, it is necessary to have installed though. The valve also allows air entrained in the fuel to escape. Air is a big enemy of those pumps. Good luck.

 

If you can blow through the overflow valve with only the air from your lungs, you have found the problem.

 

Makes me wonder how many VP44's have been replaced over the valve, mine included. Mine idled fine, just would not go higher.

 

I'M NEW TO DIESELS BUT I DO KNOW ONE THING, WHEN YOUR CRANKSHAFT SSENSOR FAILS THE COMPUTOR WILL GIVE YOU TWO FAULT CODES THAT SPECIFICALLY STATE IT IS THE SENSOR. ALSO YOUR TACH WILL FAIL AND CHECK ENGINE LIGHT WILL ILLUMINATE.

 

This also makes me wonder if many lift pumps are replaced needlessly. In my knowing 12 valves very well a failed overflow valve is by far the most common problem, people who throw parts at the problem often replace the lift pump with no or short term results. I pay little attention to the overvalved engine with all it's problems but now I'm wondering if the OF valve is the same case with 24s.

 

Bill you can bet that before I replace another VP, the valve will be checked. Sooner or later I will have a better idea.... Probably sooner than later... Murphy has a reputation to keep up

 

I believe Murphy was an optimist!

Still pluggin!

Seedy 1

 

NO old oil burnin high mileage wreck is gonna beat me, I'm in it for the long haul.