Pop pressures, Idle speeds, Leaky injectors

[Begle1]

So I recalibrated my pop pressures from 180-190 bar to 235-250 bar, reinstalled the injectors, started without difficulty, and my idle fell from ~750 to ~550 RPM. I have a whole bunch of low idle screw left now (~1/2")


Normal?



Then I noticed that I had fuel pooling on top of the #1 injector; I loosened it with the engine running, and lost RPM, so it's not leaky to the point that it's killing the cylinder or explaining the idle drop. But I tightened it as far as I dared and it still was pooling. How do I fix that?

[burnt_servo]

i haven't pulled apart any cummins injectors yet , but with the vw injectors , i very carefully lap the 2 halfs of the injector bodies , using a sheet of 1200 grit wet dry sand paper , and a piece of glass ( i had a piece of 1/2 inch glas cut at the glass shop roughly a 1/2 inch larger than the sheet of sandpaper ) .

i used a bit of diesel as lubricant when lapping .

for one injector that refused to seal i put a tiny bit of valve grinding compound between the 2 halves and carefully lapped them into each other . took about 1/2 an hour of work , but it finally sealed .


with the higher pop pressure now , you might find that you need to advance the timing a bit to bring your rpm back up .

[Begle1]

Well, I got #1 to stop pooling at the top by disconnecting and reattaching the line.

But this morning I started it, and noticed a real bad puddle forming on the ground.

So I tightened the last three return banjos.

But they still leak a smidgen. So I tightened the banjos some more.

I drove around the block, got out, and tightened them some more. They felt like they got looser, I don't know if that would be them backing out or the heat playing with them?

Anybody ever have problems with return banjos backing out?

The injectors definitely get moist, and are soaking the side of the block and puddling.

I don't know if it's leaking from the return banjos or the injector bodies. How could I possibly know?

Is the 22 foot pound torque spec for the injector nut too little? Should've I used some kind of sealant on the intermediate plate between the needle and injector body?

[KTA]

If you over tighten the banjos you will split the washers and make them leak worse.

[seeker1056]

I only got two re n re's before i needed new banjo washers - they crush then wont seal and if u titghten too much you could strip that leetle bolt and then havea real disaster on your hands

[Begle1]

I used six new butterfly washers. Only $.22 a piece.


They do look more steel-ish than copper-ish, though. Maybe they're crap.

How unlikely is it for injector bodies to leak?

[KTA]

The bodies themselves pretty much never leak, but if you do sloppy work or don't know the proper way to do things they will most always leak where the nozzle holder and body screw together. I have bought injectors from supposed diesel shops/gurus that were of the same quality. It is not uncommon for me to have to spend a day on a set of injectors I buy from somebody fixing them so they are 100% like new, it kind of pisses me off actually to have to do it.

[Begle1]

What's the "proper way" to do it? As far as I know it was to clean everything, stack it all together together and torque down the nut?

[KTA]

Everything has to be spotless. If you get a flake of carbon between the adapter plate and the body or nozzle it will leak. Sometimes those surfaces have to be lapped in order to get them to seal, which is a huge job because of the alignment pins that is why it is critical to keep the surfaces clean in the 1st place. What did you torque the nut to?

[Begle1]

I torqued them to 22 foot pounds.

I rinsed them all off with brake cleaner and Diesel fuel, that's good enough, right?

[KTA]

Correct torque is more like 35ft-lbs. I usually do 38ft-lb because I use an extension on my torque wrench because of my fixture and the extension absorbs some. That might cure your problem.