Detroit Diesel 2-71 Fuel Injectors

[Digger HD5]

OK, I've got an about 1954/55 AC HD5 Loader, with DD 2-71. My question is, when researching documentation based on serial number of engine (2A20784) it seems to point to the correct injector as a HV6 fuel injector. But, when I removed one of the injectors it is a HV7. I'm replacing the injectors due to it not starting (but will with starting fluid) and I'm sure I let water build up, so my bad. Everything else seems to be OK now that I've replaced both filters and cleared the lines. I have access to 2 rebuilt HV6 injectors so I'd rather not buy rebuilt HV7 injectors if I don't have to. My basic question is can I use HV6, 5228310 injectors on this engine? I know the obvious answer seems like 'no', but I'd appreciate anyone's input on this old equipment question. Thanks.

 

[lantraxco]

I'm no detroit expert but I would say given that your documentation shows the HV6 it should be fine. It's possible somewhere along the line someone tried to give her a bit more snoose with the bigger injectors.

 

[Digger HD5]

Thanks for the info, I guess that makes sense, I just didn't know the 7 was just a 'bigger' version of a 6.

 

[lantraxco]

I'm assuming that, as the N series injectors ran that way, higher number more fuel. Lots of Detroit guys on here, wonder why they're not tuned in?

 

[kshansen]

If you have access to a pair of HV6 injectors I'd slip them in and do a tune-up and you should be good to go.

 

[Digger HD5]

I'll give it a shot, sounds good. Thanks for the help.

 

[td25c]

2-71 parts manual shows both HV 6 & 7 injectors as options for the engine . From what I can tell they were equivalent to a 60 and 70 injector fuel rate wise . Like mentioned , bigger number = more fuel .

 

[Dickjr.]

If its not getting hot I'd stick with the 7s. If I recall you could go up to 8s but that's where you start to heat up.

 

[Digger HD5]

Another question, what size is the restrictor in the fuel return line on this 2-71? I've got a 1/4" stream of fuel coming out of the head going to tank. Seems like it maybe should be smaller than that to build up pressure. Thanks.

 

[kshansen]

Another question, what size is the restrictor in the fuel return line on this 2-71? I've got a 1/4" stream of fuel coming out of the head going to tank. Seems like it maybe should be smaller than that to build up pressure. Thanks.

Don't have any spec's on the 2-71 restrictor size but the fitting in the head for the return line should be stamped R-XX the XX is the restriction size. One parts book I have shows the same fuel pump for all In-Line 71 engines. As the fuel pressure is not real critical as long as it is between 45-70 psi at full load I would install a pressure gauge in the line from filter to the inlet of the head and see what you get. If it is between 45-70psi you should be good to go.

 

[Former Wrench]

The only difference would be more HP output with the HV7 and you would not burn quite as much fuel with the HV6.

 

[Digger HD5]

Thanks all, for your expertise. I guess I'll get back at it and see if I can get this thing running again.

 

[Digger HD5]

I do still have the question about what size the restrictor should be on the return line. Detroit 2-71. Is 1/4" correct? Seems maybe I'm missing a part that actually "restricts" fuel back to tank.

 

[mitch504]

Don't have any spec's on the 2-71 restrictor size but the fitting in the head for the return line should be stamped R-XX the XX is the restriction size. One parts book I have shows the same fuel pump for all In-Line 71 engines. As the fuel pressure is not real critical as long as it is between 45-70 psi at full load I would install a pressure gauge in the line from filter to the inlet of the head and see what you get. If it is between 45-70 psi you should be good to go.

I'd do like Ken said, put a gauge on it. A functional test seems more relevant than chasing down the orifice size. These old green road-oilers are some of the most forgiving engines ever made.

 

[bccat]

my 2-71 service manual says the correct one is a .055 orifice fitting, Put the the wrong size in , she will hunt, fuel pressure at all speeds 40-60psi.
Ken

 

[Former Wrench]

You need the correct restricted fitting so that proper fuel back pressure is maintained. Years ago while in the field in remote Alaska I have gone so far as to fill a regular fitting with solder and drill the right sized orifice. The restricted fitting is important to keep the engine running right. Another thing, when starting the engine without the restricted fitting it allows the fuel to flow freely and not hold enough pressure to feed the injectors properly.

 

[Digger HD5]

Thanks all for your help and info. Digger HD 5, OUT.. !! Until next time.:usa