I just noticed a small line exiting the top of the injection pump ( I think its the governer housing) going to the the intake manifold. It is steel tubing and connects to the IP with a banjo fitting. It is broken at the banjo fitting. What is its purpose? the truck runs just fine. I haven't checked to see if its leaking boost/vaccum. HOW WORRIED SHOULD I BE????? Is it somthing I can get at a parts store? or do I have to look in junk yards, or custom fab somthing?

 

Gotta get it from Cummins. You will notice a good bit more power when you replace it. It supplies boost the the AFC housing. The AFC system prevents the injection pump from supplying maximum fuel until the turbo has built up some boost. With that line cracked, the AFC is limiting the pump all the time.

 

Yes, the replacement part is available from Cummins and Dodge. The line is plastic, which reduces the likliehood of breakage, but it is still possible.

After breaking my 4th or 5th one, I got fed up and did some tinkering. I found that a 1/8OD airline union fits into the AFC housing perfectly. Connect that to a 1/8NPT to 1/8OD adaptor, run about 6" of air line, and you have the AFC hooked back up, for <$5. There is some debate about how fast the pump responds with the smaller line, but I have never noticed any difference.

DP

 

Thanks, Anybody know the part # and description. is there a website where you can find these things?

 

Anybody? Please!

 

P/N 2 ~ 4429 391 SEAL, Grommet.
P/N 3 ~ 4429 728 WASHER, Sealing (2 req).
P/N 4 ~ 4429 729 SCREW, Banjo Connector.
P/N 5 ~ 4429 106 TUBE, Air Fuel Control.



Hope this helps.

 

Thanks for the advice everyone, I chose the DIY route. NAPA had just what I needed. here it is with a parts list.

AFC (air fuel control) boost pressure line repair

1. 1/4 NPT male - 1/4 OD air line coupling, 90 degree, (intake side) NAPA # 1460 x 1
2. AFC matching thread (1/8 inch fine?) - 1/4 OD air line, straight, NAPA # 1468 x 4 x 1
3.1/4 OD black nylon air line, NAPA # D1040401

(no thread tape the brass sealed it right up!)
(the NAPA #'s are off the invoice, may be local, #'s may differ)



Truck acts like a rocket now, escpecially in 3rd at 1800-2000 (compared to were it was).

 

Good fix. Looks great.

 

quick question...i am assuming that the line should be tight? i turned in my screw and spun the diaphram the other day and when i took the top off the AFC, that small line was loose at the intake (motor) side but tight at the housing...should i replace the line? and if so, will i notice a power increase?

noticed i big increase in power after the "tune up" lol...but now the trans worries me...makes some bad vibration noises when u really put ur foot into it...just hope it lasts till spring!!!

 

Now that I am quasi expert on the subject , It carries boost pressure so all the connections should be tight and sealed, if you are leaking boost, than you should notice a power increase, mine was broken off at the banjo on the housing, so I had to make my repair, if the intake side is just loose than tightening it should be fine. the line attaches to the intake elbow with a rubber compression fitting, if that is whats loose that should fix it. I geuss the factory "U" line is prone to failure, probably due to differences in vibration between the pump and block. Hope this helps, I just learned about this last week , you can see the exploded view of the factory unit in BC 847's reply to this thread.

 

hmmm...i should replace the line then huh lol...thanks

 

Hey, wannadiesel & BC !, just wanted to get your opinion on my repair, what do you think? I respect your opinion very much.

 

i was going to do the valet switch and found that the AFC is 1/16 npt and i believe the manifold is 1/8 npt.

 

Dieselcarpenter,

That looks just about the way mine does. I also got the parts at NAPA. I used a little longer line so I could swing the pump cap out of the way without removing the line so I could get to the fuel pin and starwheel easier.

I tried a 1/8" line first and felt there was some lag associated with that so I changed to the 1/4". I drilled out the fittings slightly to allow air flow to get from point A to point B easier.

Mine has been in about 8 months now and has not given any problems.

 

Looks good to me. Mine is running through similar tubing via a valet switch, it's been fine for a couple years.