If you want to make some new return line cap, well im all for it, go for it, you wont learn nothing till you try, so make some and test them on your engine if they work im sure you will have hunderds of people buying them

 

Ford caps are being mailed to my dad. He'll give me the final yes or no to machining some. BB code injectors are ordered as of this morning. Now thinking about hard fuel lines...

Would installing a small section of high pressure, flexible hydraulic line help with the vibration issues? It would add one or two more fittings per line, but should act as a flexible flange as seen in fuel farms near the circulation pumps to damper vibration. Would this be best done at the IP or the injectors? Or both at the IP and the injectors? Maybe just replace the end portion that fastens to the injector with the aforementioned hydraulic line? I see the issue of adding more fittings which could potentially leak.

 

Hydraulic fittings don't seal well enough for fuel systems, Been there done that and they'll suck air.

-Enjoy
fh : )_~

 

Vibration issue on what, the IP lines? Lots of these trucks have high mileage without them being an issue as long as the clamps etc are in place.

 

With fittings like this?

 

Yup ... Air molecules are smaller than Fuel molecules.

-Enjoy
fh : )_~

 

I just remembered something else. Injector lines are specific lengths, if those lengths change, it affects the timing. If the line is longer, it takes longer for the injector to receive the pop off pressure, and similar if it is shorter. This in turn will affect the timing of each cylinder getting it's fuel.

 

also any sort of flexible line is likely to expand a little when that pressure surge hits

methinks the injector lines are relativly trouble free the way they are

 

I guess I misread this, After rereading I see where I misunderstood, It would absolutely not work for Injector lines ... As stated length and flex would cause timing issues.

I though you were talking about between Injectors for return lines!

-Enjoy
fh : )_~

 

I hear about this once in awhile, and are not doubting it(maybe I am ) but does anyone know the basic theory why this would be? Diesel fuel is not compressible. So if you pushed on it from one end, it should have the same reaction on the other end, whether the line was 6 inches long, or 1 mile long.

Possibly it's the steel line expanding during each injection pulse? If that's the case, then the longer line would lose pressure creating a timing delay.

 

I thought the rigid lines didn't allow for any vibration damping. I knew about the supposed exact length issue and implied whatever length of hard line removed would be replaced with an identical length of flexible line while taking all connections into consideration.

 

Everything is compressible, its just how much... Diesel, and probably most oils as well as most fluids, don't compress like air compresses, but they will compress a small amount. Longer line, means more fluid to compress, so it will have an effect on the timing.
There is also between the fuel and the line, and the fuel and itself. The injection pulse isn't instantaneous from one end to the other. It takes time to travel down the line to the other end. Longer line, more distance for the pulse to travel.

Yes, the steel line does expand and contract a small amount each injection pulse, much the same as any other pressurized vessel. It may be this expansion and contraction that causes the lines to vibrate and fatigue more than the engine vibrations themselves. Hence the clamps to limit the movement so they lines will vibrate less, and prevent cracking.

This is what all the fancy engineers do when they design these things. The lines have all sorts of fancy bends to keep them all the same length so the fuel timing is the same to all cylinders. Thats also why tuned injectors will smooth out the idle a little bit, different pop pressures will have a small impact on how early in the injection pulse the injector opens, and closes slightly changing the timing.

Now think how fast the engine is rotating, and how many times per second each cylinder is firing... 2,000rpms, each cylinder fires once every two revs, so thats 1,000 per minute, thats about 16.7 times a second (each cylinder). Thats about every 6/100th of a second. So these tiny differences in fuel line length aren't so tiny when you're talking fractions of a second.

Using flexible line will open a HUGE can of worms. Issues with sealing it at end splice. It will expand more than the steel line (absorbing and negating the injection pulse). This may cause other shockwaves to travel along the lines. Plus, unless well secured, the steel lines will be able to vibrate more at each end, which fatiques the steel causing cracks and failure at the connections.

IMHO, very BAD idea.

 

I don't see a reason to mess with the hard lines, but as far as the returns go, i'd probably like mine brass. As long as they are metal, i guess.
I wish there was injector upgrade to a high quality nozzle with an integral return like in these:
Diesel Injection — Replacement Injectors
I don't know the application for those in the pic, but most old time International injectors have a return like that. I guess they just went cheap on the 6.9/7.3.

 

I would buy one of those intergral injectors in a heartbeat if them made em for the idi!!! we need those. that means no more messing around with o rings caps and leaks!!

 

I just got off the phone with my dad. He said he got the three unique caps yesterday and has an approach to machine them. He asked me what temperature the injectors got up to. What do you think? 250*F+? He likes the brass and aluminum idea and mentioned something about machining fins on the outside of the barrels to help with heat. He said the Ford plastic ones are actually high quality plastic and asked if they're some sort of bakelite.