Preasure on the return line?

[wwwabbit]

Should there be any preasure on the return line?

I just did my pump swap, and in bleading everying (which was VERY hard) we noticed that there was some preasure on the return line. There is the line off the top of the pump which goes to the big tube, which joins up to the 2 return lines from the injector banks, that seems to have some preasure in it.

Also what direction should the fuel be flowing from the filter to the return lines? I have a clear tube going from the filter to the return on cly 2, it seems there is a definate flow going from #2 to the filter. Should it, or should it be going out of the filter to the tank?

 

[argve]

The filter is just another place for the fuel to return to. There is actually a limit pressure on the return system but it's not much I think like 1~2 psi or it won't work correctly.

Whenever I redid the return system I just make sure that everything in the fuel system under the hood could "see" the tank one way or another.

Now the injection pump will create a restriction in the pump via the return line side to advance the timing within the pump cover - when the timing advance is kicked in the solenoid in the top cap on the pump closes the return path for the pump. - just a little fyi.

 

[wwwabbit]

Ya, I knew about the pump restricting the flow with the thing on the top of it's cover... but this was more then a little preasure, this was crank for a bit to blead it, still getting nothing after 2-3 30 sec cranks, we disconnected the return line from the top of the pump that goes to the larger metal tube and it went "psssst"

Anyway, I found my problem My tank selector is bad (I knew that, it was stuck on the rear tank) anyway, it looks like it stuck the return line to OFF! So ya, it was not letting any return fuel back to the tank. So, ya, at this point I am just going to bypass the selector, cap the ones for the front tank, wire in the rear tank sold (it has the most fuel in it) put a little jumper in the power plug for it so I can see what I got for fuel, and then deal with rebuilding this one, or getting a new one.

That is why it was so hard to blead, nothing was burping back to the tank, it was all getting re-cycled back to the fuel filter, and going back into the pump.

 

[Agnem]

anyway, it looks like it stuck the return line to OFF!

Glad you found the problem. Was there a symptom to go with this blocked fuel return line problem? I always wondered if the return line were blocked, if it wouldn't leak and *** all over the engine.

 

[wwwabbit]

Not really... one of the new return caps were leaking, and definatly hard to bleed any air out of the system. No real "*******" out of anywhere, it would sure point out a loose fitting though. I noticed that most of my excessive smoking disapeared once it had a clean exit, so I am going to think that with the restriction of the fuel, that there was some advancing going on as well. Other then that, it ran OK, started fine, etc.

 

[The Warden]

Now the injection pump will create a restriction in the pump via the return line side to advance the timing within the pump cover - when the timing advance is kicked in the solenoid in the top cap on the pump closes the return path for the pump. - just a little fyi.

I thought it was the other way around?

When my injector pump failed in '02, the nylon piece disintegrated and got clogged up in the check ball on the return line coming off the top of the pump. As the check ball got more and more clogged, the timing was being retarded, to the point where the truck would belch out white smoke, ran real quiet, and eventually wouldn't run at all.

I could be mistaken about this, but I also thought that, when the solenoid was energized, it pushed a plunger into the check ball to push the bal further out to allow more fuel to return through....

Do I have it wrong, or what?

 

[argve]

We played with this at the IDI weekend in PA a couple of years back and Mel was the one that figured it out. He was blowing in the fitting while running the solenoid by hand. When engergized it was blocking his blow.

 

[wwwabbit]

Since it caused me enough problems, I had to find out how it works, and what failed. So, here is my disection of my fuel selector. http://wwwabbit.com/pictures/fuelselector/

Now.... to find a new one.

Edit: If anyone who is making an IDI tech page, and wants to use the pictures and or text, feel free, just mention my name it in I am sure your page would look much better then mine.