Overhaul questions/ FDC bypass at Tooele? Always?

[datsunaholic]

OK, so I was reading on another post that many Deuces had the FDC "bypassed" for various reasons when they went through Depot rebuilds in the late 80s-90s. I had never heard of such when I was in the Navy Reserves (we had 2 Multifuel Deuces) but then again we only ran Diesel in 'em.

I've also seen multiple posts referring people to search for a post "with pictures". I found a couple posts by Cranetruck and houdel with a scan of a page, but it's too small to read. Some posts have a "link" to a bigger picture but the link gives me a 404/debug error. I think it's a link to the "old" forum.

Basically, my Deuce has an engine overhaul tag that it was rebuilt at TEAD (Tooele Army Depot) in 1992. Other than noting that it was rebuilt with Standard pistons, standard rod bearings, and .010 main bearings, it says little else. Nowhere on the truck is it marked "Diesel Only" nor are there any of the stickers claiming the FDC was bypassed. Of course, those stickers could have fallen off years ago. Half the standard safety stickers on the doors are tore off.

The picture I found via searching is too small for me to really tell what line goes where when the FDC is bypassed. I can't tell whether mine is bypassed or not, so now I have a (probably paranoid) concern about which configuration my truck is in. I don't PLAN on running anything other than straight pump diesel in it, but it would be nice to know. It seems to run fine as is, it's a bit hard to start below 40 degrees or if it has sat more than a week, but once warmed up it's a jewel.

Just to reiterate, I have searched, I found plenty of arguments for/against bypassing the thing, and I'm probably going to leave well enough alone but I do what to kow if mine is bypassed or not. The small pic I can find looks like if I see "looped" fuel lines then it's probably bypassed whereas if they aren't "looped" it's probably still connected, but a bigger (readable) pic would help.

Or, this weekend I could just shoot a pic of the FDC and post it.

 

[doghead]

Try right clicking the picture and then select, open in a new window.

 

[datsunaholic]

Yeah, I tried that, but even after I "blew it up" it was still too fuzzy to see. I'm not talking about the thumbnail. This is the thread I'm talking about:

http://www.steelsoldiers.com/showthread.php?t=13065&highlight=compensator+bypassed

 

[doghead]

Try the same thing with the pics in this thread, 2 of them are better. http://www.steelsoldiers.com/showthread.php?t=26917&highlight=fdc+bypass

Still looking for more

Good and clear in post #5 here, http://www.steelsoldiers.com/showthread.php?t=23560&highlight=compensator+bypassed

Search works, just need to try different terms and multiple words to find what you need. There is a lot of good info on this topic, here.

 

[datsunaholic]

Thank you, those are much clearer. I'd gotten discouraged finding the same shrunken and blurry image on thread after thread, I should have just kept looking. They do leave a bit out but for checking to see if it was done I think I can figure it out. Heck, I might not even HAVE a compensator. I'm 50 miles away from my truck or I'd have looked already.

 

[gimpyrobb]

Basicly all the fdc does is keep the power output of the motor the same with different fuels. All the multifuels, are multifuels. THERE IS NOT A SECRET BOX THAT CAN MAKE ANY MOTOR MULTIFUEL! I think some people here don't understand that. Anyway. It is a good idea to run with it bypassed. On most of the motors I have seen with a depot rebuild, the oil filter cans state, fdc bypassed-diesel only.

 

[m16ty]

Everybody on here ( but one person ) agrees that you can still run anything you want with the FDC bypassed. I wouldn't worry too much about it too much other than sometimes with the FDC connected you can get a leak and get fuel in the oil.

 

[datsunaholic]

As I said, I have no sticker on the oil filter canister (all 4 filter canisters are flat olive drab green paint) and there isn't a single sticker under the hood on anything- not even on the cold-start device (usually a warning sticker about the ether). It's been a rare Deuce I've seen that didn't have at least SOMETHING in yellow sticky vinyl under the hood. I was a little worried about that at first... I'm so used to there being stickers on EVERYTHING under the hood and in the cab, that the lack thereof was a shock. Maybe the Navy CESE managers got sticker-happy on the trucks I ran in the reserves, I dunno. There's plenty of chalk writing under the hood... it looks like someone did ther math homework there.

But the truck WAS overhauled in 1992 at TEAD. At least the engine was. It's one of 2 places there's a date on the whole truck (the other being a "MWO Applied" tag in the driver's doorframe). I made a WAG as to the year when I sent in my SF97, I have no clue if the year on my title is right or not. The "Year" or "Delivered" dates on both the Dashboard Dataplate and the Engine Dataplate are conspicuously not marked. I found over the years that wasn't unusual. The Military didn't give a rip what year the trucks were, as they were dang near unchanged for over 30 years.

I've seen plenty of the arguments on what the FDC does and doesn't do. It's one of the reasons I had trouble getting through all the posts trying to find a readable diagram of what it looks like bypassed vs what it looks like hooked up, because I want to know my truck and how it's set up. If something varies just a bit from what the TM says I want to know.

 

[Barrman]

Basically, just follow the white plastic fuel line from the firewall side of the secondary fuel filter set and see where it goes. If it goes to the firewall end of the IP then the FDC is connected. If it goes to the middle engine side of the IP then it is bypassed. You should also have a line do a loop at the rear of the IP which is where the FDC is when it is bypassed.

The pictures from MVM in the above linked threads show this very well.

 

[datsunaholic]

Well, I can see why it wasn't completely clear to me whether it was or wasn't. It's bypassed, but there's no "white plastic line" nor any loop on the FDC. The FDC has caps where he T's are supposed to be. So, it can't be reconnected without buying more hardware. Not that I intended to reconnect it if it was disconnected anyway. No big deal, unless the truck would get better mileage with it connected (which no one has claimed it would). But I have read that it's a common point of failure so it's probably best to leave it off.

 

[cranetruck]

A couple of images that may clear things up a bit.
The fuel line loop you see in the earlier images is just to take advantage of the parts already on the pump (IP). You can also use pipe plugs to seal off the FDC as indicated here.
When the FDC is not used, the stop plate remains in "full fuel" position, so the adjustment must be made to compensate (second image).

 

[Yarz]

I know, old thread.. sorry.

I just wanted to confirm that all of the threads for the fuel line connections are 1/4" and 1/8" NPT. Is that correct?

I ask because I plan to do the bypass and replace the line from the fuel filters to the HH, with new line and nuts/ferrules. But when I test fitted a 1/4 pipe plug in the filter outlet, it seemed a little loose starting in, which made me wonder if it was due to the taper of the pipe thread, or if it was, in fact, not NPT.

 

[Barrman]

I started not to post, but figured since nobody has anwered in 3 days, something needs to be said.

I don't have any M35 parts are work here with me so I can't go check. However, I think the fuel fittings are non standard sizes. I re use all of my fittings. It has been a while since I messed with the fuel lines, but I am pretty sure I re used them because they were specific to these trucks.

There might be something else out there with the same sizes but I don't know what it is.

 

[peashooter]

I know, old thread.. sorry.

I just wanted to confirm that all of the threads for the fuel line connections are 1/4" and 1/8" NPT. Is that correct?

I ask because I plan to do the bypass and replace the line from the fuel filters to the HH, with new line and nuts/ferrules. But when I test fitted a 1/4 pipe plug in the filter outlet, it seemed a little loose starting in, which made me wonder if it was due to the taper of the pipe thread, or if it was, in fact, not NPT.

Yes I just bypassed mine this week. The threads on the IP and FDC (the ones you mess with for the bypass anyway) are 1/4 and 1/8 npt. Fuel lines that get moved are both 3/8" OD and 1/4" OD.

~To tweak the main fuel adjust after a bypass of the FDC you will need 2x thin 1/2" wrenches.
~To adjust the droop screw on the back inside the FDC (if you have one) you will need a 3/8" hex key (allen wrench) to get the 1/4npt plug out and then a 1/8" hex key to adjust the set screw inside.

 

[Yarz]

Thanks for all the information!. I just completed it this morning. I used McMaster Carr's 5033K33 Tubing and 50815K106 nuts (based on this post) to replace the fuel line between the secondaries and the HH.

 

[RAYZER]

How many flats = 0.100"?

 

[Floridianson]

How many flats = 0.100"?

I don't know.
How many licks does it take to get to the center of a tootsie pop?

 

[Yarz]

How many flats = 0.100"?

No idea. Though I suppose you could figure it out if you knew the pitch of the threads...

Anyhow, I moved mine 4 flats, because that has me just touching 1100° on long grades with my foot in it.