tbryanh
Full Access Member
The injector in the forground of the attached photo has some sort of extension on it. Anybody know what it is and why it is there?
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Injector Extension?
- Thread starter tbryanh
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The Warden
MiB Impersonator
It's an adapter to assist with setting the injection timing by the pulse method, although if memory serves, you need a special setup to use it and most "standard" puse timing adapters won't work with it. You can eliminate the adapter if you want, but if you do, you will need to replace the injector line to make up for the length (simply bending the current line will not do; all injector lines need to be exactly the same length or the timing for the cylinder with the shorter/longer line will be off from the others!).
I think 7.3l vans had the adapter on the #4 cylinder, and trucks had the adapter on #1, so you could find a #4 line off a truck and use that...or, a #4 line off of any 6.9l since they didn't start putting the adapter in until after switching to the 7.3l.
Hope that helps
I think 7.3l vans had the adapter on the #4 cylinder, and trucks had the adapter on #1, so you could find a #4 line off a truck and use that...or, a #4 line off of any 6.9l since they didn't start putting the adapter in until after switching to the 7.3l.
Hope that helps
icanfixall
Official GMM hand model
Tim you got part of that post correct but some not correct. True, on the van engines this adapter was on the number 4 cylinder but... You take the number one cylinder line off the vans and use it on the trucks. Then its fine. This adapter was used only with the original Rotunda timing meters. They had a large brass clamp to connected to this adapter after you slide up the plastic cover. Nobody times now using the rotunda meters. I have one of those meters but wont use it. Most of them had burned screens from leaving them on too long when timing an engine. No parts or anyone that will fix them. To the original poster please do not try to force that line to fit if you just take off the adapter. Its not harming anything to leave it in place.
tbryanh
Full Access Member
Thanks for the excellent responses. I'll leave the adapter there. Now I know what it is. Hahaha.
The Warden
MiB Impersonator
Gary, I actually originally wrote it that way, and then re-read his post and saw that he only has vans, so I edited it to reflect that fact (although I may still have messed up
). OTOH, looking at the picture, that does look like the #1 line...so, either he's wrenching on a truck, or that's a picture he found online that's similar to what he has on his van. 
icanfixall
Official GMM hand model
Tim... That pic sure could be that of a van application. The pic could have been taken from the inside of the van with the engine cover off to work on the van. Same goes for removing the timing adapter. Just need the line from a truck to replace the number 4 line on the van. This pic does look like the number 4 cylinder and line on a van.
BR3
Full Access Member
Out of curiosity, how would the length of the line change timing? Once a line is filled irrelevant if it's 6" or 6' fluid, being non compressible should still fire off at the same time right? Because you supply pressure on one end of a hard line, it goes out the other side. The same time. Is there something I'm missing?
The Warden
MiB Impersonator
As I understand it, while liquid is considered non-compressible for all intents and purposes (for example, for braking), it still doesn't transmit pressure instantaneously enough for fuel injection purposes. Think of it like a shock wave...it may go very fast by "normal" standards, but with a diesel, pressure is being applied to each line once every other revolution...so, 28 times per second at 3400 RPM (3400 divided by 2, then divide that number by 60). To be honest, I've never tried installing a shorter or longer line myself so I can't say definitively that it's a bad idea, but if Stanadyne, Bosch, etc. felt it necessary to spend the time and money designing and mabufacturing each line at exactly the same length (even though that creates problems when dealing with lines close to the pump), I figure there has to be a reason for it
BR3
Full Access Member
Ok, I can see that being the case as far as the Shockwave idea goes. But I wonder if our lines actually are all the same. I'm not about to measure now because it's 2am and 15° out, but I would like to see for sure
I asked the same question before, and no one really explained it enough to me where I got a aha! out of it. I am running a line off a 6.9 on my 7.3 on the #1 cylinder. I can't exactly remember the problem that supposedly causes(length difference somehow) but my engine seems to run fine with it on there. I am not running that adapter on #1, the threads got messed up on it.
The Warden
MiB Impersonator
I've never measured, but if you look at the lines and see how they're bent, I would be very surprised if they weren't at least within a small fraction of being exactly the same.
Here's a simple example of how the lines are routed so that they're the same length...it's more obvious on an inline-6 with an inline injector pump (in this case, a Nissan SD-33) than it is on a V-8 with a rotary pump:
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If the lines didn't need to be the same length, why didn't they just run the lines to the forward injectors on a direct beeline from the pump to the injector? Would have made routing the line far simpler, not to mention the added cost...
Black dawg
Registered User
You can actually hook the wires from a pulse meter right to it, and works just fine. It is a piezo sensor, just like the clamp on one that comes with the pulse meter.
I believe you. But I still don't get it from a theory standpoint. I like to figure out why things are the way they are if it's possible and my pea brain can understand it.
BR3
Full Access Member
Yea, I agree with Franklin, engineering goes into everything on an engine, and I enjoy reverse engineering. After hearing this I did a little research and apparently the lines actually even balloon
a little. Hey, that's what these forums are for, finding out information you didn't already know
a little. Hey, that's what these forums are for, finding out information you didn't already know
The Warden
MiB Impersonator
Oh wow! I didn't know that...I've only owned 6.9l's, so I haven't actually dealt with one of these adapters. Nice to know...thank you!
My response was to BR3, who wasn't sure if the lines were in fact the same length. I just thought that visualizing it on an inline pump would be easier
The lines ballooning slightly is actually how a pulse adapter works; it measures the line as it balloons out. As I understand it, that goes back to the "shock wave" comment I made earlier...the entire line doesn't balloon at once; the "balloon" starts at the pump and moves towards the injector. It happens very quickly; I imagine it only takes a milisecond, but with how fast everything else is happening, that can be enough to mess thing sup, especially at higher RPM's.
Actually, I thought of a good way to test this...if you have a pulse adapter and timing setup, try checking the timing on your engine. Either connect the adapter wires to the on-board adapter, or use #4 and put the pulse adapter as close to the injector as you can, like you're supposed to, and see what your timing is. Then, re-locate the pulse adapter that came with the box on the line as close to the injector pump as you can and see what the timing shows at the same RPM. I'm very curious about the results...makes me wish I had a timing adapter to try it myself
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