Engine/Transmission (1998.5 - 2002) Fuel pressure starting

[NIsaacs]

I don't know why I'm just going on my 50 years as a diesel mechanic I was taught to check each one and #4 was the only dry line so I'm goin with it
Pappy

Okay, that's interesting, I will be watching for the result. I could understand it if that injector had a miss, it could be plugged, but dry after an extended shut down I can't figure why the line would be suspect. I could see a bad injector dribbling and syphoning the line dry or maybe the injector pump "up" on that #4 event and syphoning backwards??

Nick

 

[phantomusa]

Got the line from Cummins they didn't have one in Stock but they had a crate engine and took the #4 line off that it's installed now I'll update in couple days to see if that was then problem
I did put my clear sight tube on and didn't see any bubbles so that tells me everything up to the vp44 was good
Pappy

 

[KATOOM]

Are you talking about #2 in the bottom scan?
I don't see any other o-ring on the connector?

Nick

That be the o-ring.....

And what phantomusa found is if the line is dry then there's no prime in that line. Likely result is because the injector pintle isnt sealing.

 

[NIsaacs]

That be the o-ring.....

.

So how does an oil sealing o-ring have anything to do with the loss of fuel prime? I don't see where it is anywhere near fuel, I do only see out of one eye tho

Nick

 

[KATOOM]

Take note of the o-ring on the injector. The crossover sits between that o-ring and the copper washer below. Now think about where the oil is you're thinking about.....

 

[NIsaacs]

Take note of the o-ring on the injector. The crossover sits between that o-ring and the copper washer below. Now think about where the oil is you're thinking about.....

Huh....say what? The o-ring on the connector tube, (#2) in the bottom picture, seals the connector where it passes through the head, engine oil not fuel.

Nick

 

[KATOOM]

The crossover o-ring seals off the fuel which exits the injector and runs out the return. Thats where I was pointing out the relation of the crossover tube mating to the injector and where the injector o-ring is located. No oil in that area.....

ANY air allowed to enter the fuel system will cause the prime to be lost and fuel will run back into the fuel tank when the engine is off. Think of a drinking straw and placing your finger over the top and then pulling the straw out of the cup. Liquid remains in the straw. Same thing going on in the fuel system. A crossover o-ring not sealing will allow air to enter the system.

 

[NIsaacs]

The return fuel from the injector is sealed by the o-ring on the injector, it seals fuel and oil at the same time, no mixing.

The connector tube seals on the injector with a tapered fit, metal on metal. The injector line seals on the connector tube in much the same way, tapered fit, metal on metal, no O-rings at all. The o-ring on the connector tube only seals oil where it mates with the head, so oil can't leak to the out side.

Nick

 

[KATOOM]

No, the injector return fuel exits in the head and out the single banjo bolt. The injector o-ring is merely to seal the engine oil from the fuel, and visa versa..... The crossover o-ring keeps return fuel from exiting out the side of the head. Take a look at the picture you posted and you'll see what I mean.

 

[NIsaacs]

No, the injector return fuel exits in the head and out the single banjo bolt. The injector o-ring is merely to seal the engine oil from the fuel, and visa versa..... The crossover o-ring keeps return fuel from exiting out the side of the head. Take a look at the picture you posted and you'll see what I mean.

Yes, my first sentence on my last post says the same thing as your first sentence, just worded a little different

However, the connector tube o-ring never sees fuel. How can it? The connector tube at the o-ring location is external (no fuel) and only comes in contact with engine oil as it seals the connector tube where it passes through head opening. The connector tube is exposed to the valve train area along with the top of the injector where they both meet and seal the fuel, metal on metal, no o-ring.

You are seeing something that is not there or I am not seeing something that is

Nick

 

[KATOOM]

I dont know how else to explain it.....

OK how about this, if you look again at the picture you posted, you'll see that the injector o-ring sits "above" the crossover tube. I think you fully understand that right.....? So that tells you right there that the crossover tube NEVER see's engine oil. You say otherwise but my question to you would be WHAT OIL is the crossover tube bathed in???
The tapered mating surface between injector and crossover tube is high pressure and must seal, but knowing that excess fuel exits the injector in the pocket where it sits, now imagine if there was no crossover o-ring. What would that return fuel do? Well, it would come out the side of the head where the hard injector lines mate up to the crossover tubes. The crossover o-ring simply stops that and forces the return fuel to continue out a path internal in the head, all the way to the backside of the head where all the return fuel collectively runs to the fuel tank.

 

[NIsaacs]

I dont know how else to explain it.....

OK how about this, if you look again at the picture you posted, you'll see that the injector o-ring sits "above" the crossover tube. I think you fully understand that right.....? So that tells you right there that the crossover tube NEVER see's engine oil. You say otherwise but my question to you would be WHAT OIL is the crossover tube bathed in???

The connector tube o-ring is not above it, it circles the tube where it passes through the head. The top of the injector and the connector tube that is inside the head is bathed in oil. If you remove the valve cover the injector and connector tube is exposed for all the world to see. Oil is splashed everywhere here. If the o-ring was not on the tube oil would seep out between it and the head.

Obviously my explanation is not very good, I am also at a loss, Lol

Nick

 

[BigPapa]

Will this image help clear up anything?

 

[KATOOM]

THANK YOU BigPapa.....!!!!! That picture should help explain what I cant seemingly explain. Lol. :-laf

 

[NIsaacs]

Yes, thanks for the cutout picture, it helps but I still don't see where fuel is at the o-ring. Unless the connector tube is now exposed because of the cut out, that normally it is enclosed in a sealed fuel passage housing? And if so is a 24v the same as the common rail in this regard?

PS: I just watched 2 U-tube videos of injector R&R, one video wasn't enough Lol. Now I can see what you have been so patiently trying to tell me. For some reason my head was telling me the connector tubes were exposed, not in the fuel return passage. I have been under the rocker cover 3 times over the years on this truck and still forgot what everything looks like. That is why I don't do customers vehicles any more, too dang forgetful. If I have to order parts for a job and wait on them, my mind picture goes dim, so I always try to have the parts I need so I don't forget the sequence as bad. Especially an R&R of a heater core, I always get ahead of my self and have to back track, I hate it! Lol

Thanks, Nick

 

[petersonj]

NIsaacs and KATOOM ... Excellent discussion! I want to thank you both for following through with this lengthy topic. I, thought NIsaacs was on the right track until BigPapa posted the cutaway.

I commend all three of you for following through on a professional level and I will be using the information at some point in the future when I replace injectors. I am sure other readers appreciate your effort, as well.

Thanks again,
- John

 

[phantomusa]

Here's my update I just when out and started my truck turned key on bumped the starter got pressure and started first try...problem fixed
Pappy

 

[KATOOM]

I actually feel like a schmuck that I seemingly couldn't explain it clear enough..... Oh well, at least some other members got something out of this. Good discussion.....

And phantomusa, I'm glad to hear you resolved the problem.

 

[phantomusa]

Kaboom I can't explain why my troubleshooting worked other then I've been a diesel mechanic for 50 years and sometime I just use magic to fix things rather then brain power
Pappy

 

[KATOOM]

Magic.....I like that. Whatever works.

Oh and its Katoom, with a "T", not Kaboom. I ride.....not blow things up. :-laf