DL1221

OK, I just changed the injectors on my 12-valve. Every manual I've read, and several posts on this forum, all say to crack the injector lines, crank the engine, tighten the lines when you see fuel coming out, then crack the lines again when the engine starts, to purge out all the air.

However, I read one post that said just crank it and she'll start in the same amount of time. Which is exactly what I did. I tightened down all the injector lines, cranked the engine, and in exactly 26 seconds she started and ran fine.

The only thing I did different, was pump the prime button on the lift pump a few times to make sure I had fuel there at the IP ready to go. (I do have an injector that's leaking, but that's a different story, I was told its probably just crud preventing the copper washer from making a good seal.)

So what's the deal, why does everybody say to bleed the injector lines, all it seems to do is spill diesel all over the place.

clutch1

Ok 26 sec. is a long time to crank on the starter to begin with. I have never had to crank more than 10 with all cracked, tighten up then start. Injectors alone shouldnt take that much cranking at all, completly different than a pump or lines. Cracking the lines is just a good rule of thumb the 6bt thats in our trucks is not the only engine that I have ever worked on, like many others on this site, it is fairly an easy fuel system and you can get away with not cracking the lines but there are other fuel systems that are very particular and cracking lines is a must. So for me its the way I have always done it and never any probs. but if just cranking works for you or any one else, why do it the way someone else tells you. One more thing, when I rap up on a job and there is a posibility of air in the lines I think I would feel kinda dumb just cranking and cranking and cranking while watching the engine wondering when its going to start, when I could just crack, crank, then tighten. Oh well.

Sidewinder

I had my injector lines off a few times. Usually I can get it running without cracking the lines too - but one time time it would not go no matter how much I cranked. The only way to get it to go was to crack the lines. I think everyone is just covering all bases. If you got it running just by cranking you probably wouldn't be asking for help.

infidel

Since I've had the lines off anyway I just don't tighten them down all the way until I crank for awhile. Saves having to loosen them in the event that it doesn't start.
What happens sometimes if the lines are full of air is the injection pump just compresses the air rather than bringing it up to high enough pressure to pop the injector. Air basically gets stuck.

clawson

That is also more for a 24v b/c most of the time they will not start without cracking the lines.

Chris

G1625S

That's the winner. I chased a miss for weeks before I bled all the air outta my lines. As was said, these engines start so easily, we take for granted that everything is cool. I thought I had a down/tired cylinder. Cracked the injectors 1 at a time for about 10 seconds a piece while idling---found a bunch of air in the last one--idle miss cleared up.

DL1221

OK, now that I understand the underlying theory, it makes sense now.

So basically I got lucky (except for that stupid leaky injector ) and didn't need to crack the lines open. The reason I know 26 seconds, is because I was timing it. The directions say to crank for 30 seconds, then rest the starter for 2 minutes, then repeat. I was going to crack the lines open at the next cycle, but she started on me before that.

Anyways, thanks for the explanations.

Forrest Nearing

is it leaking at the return banjo?

Mike (gunracer1) taught me a good trick for re-using those (and the sealing washers too)

take a propane torch and heat the copper up till it turns purple in order to make it soft again.

DL1221

No, its coming out from under the hold down nut, I assume some crud is preventing the copper washer from making a good seal with the head. Naturally it would be the hardest one to reach, No. 6, can't see nothing back there. But thanks for the tip, I'll try that.