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Injector Problems

b7100

Subscriber
Last Subscription Date
07/10/2019
I have an American/ Detroit 3/8" injector. It is picking up water ok but it is blowing it out the overflow. When I try to throttle the intake down it quits picking up. I am able to remove the injector and blow air through to where it enters the boiler. Steam pressure 70#. I have tested for air leaks on the intake side. I have had the injector apart several times.everything appears to be clean, all holes are open. I have limited experience with injectors. I've been reading about troubleshooting but can't seem to find an answer.
 

chrsbrbnk

Registered
Re: Injector problems

check what pressure the injector can run at they have a range like 40-80 or 90-150 if the injector is a oversized it seemed like turning the steam almost full blast and regulate the water worked and on I was guessing on closer to correct sized it seems like water full blast and steam throttled then Jeff Lund showed me a trick where you have a extra valve teed off the out put of the injector have the vlv open when you start the injector then gradually close the as the injector kick in I think helps with the inertial problems of getting the water moving if you think basically with an injector you exchanging heat /pressure into velocity then velocity into pressure
 

b7100

Subscriber
Last Subscription Date
07/10/2019
My heat exchanger has 1/8" intake and 1/4" out as per Ralph Andres' book/plans. I have read that it should be same as injector (3/8). Would that be the issue? A lot of rewovrking if it is. If it is it would be a major flaw In Ralphs book/ plans that should be of concern to anyone using his plans.
 

b7100

Subscriber
Last Subscription Date
07/10/2019
The connection where the intake goes into the injector leaks. I have tried lapping it in and made a copper washer and it still leaks. Is there any gasket material other than copper that would work? The connection is a concave/convex connection.
 

Big Bird

Registered
Last Subscription Date
02/16/2018
My heat exchanger has 1/8" intake and 1/4" out as per Ralph Andres' book/plans. I have read that it should be same as injector (3/8). Would that be the issue?
I think when the output stream from the injector reaches a restriction ie. Smaller pipe, the increase in pressure would be a problem for the injector to overcome .
The fittings to my preheater are all 3/8 .
 

Casemaker

Registered
B7100,
I have 1/2 injector with 1/2 input and 1/2 output. Are you using globe valves or gate valves ? I had trouble like that
Then changed to globe valves and it went away.
 

b7100

Subscriber
Last Subscription Date
07/10/2019
I'm still trying to fix the intake leak. I used a rubber washer ( black is what I have). It still leaks. I am using 100+# air pressure to test. Thinking that less test pressure would be adequate. I'm going to change some of the lines to the preheater to 3/8". Then try it again. I had globe valves both steam in and pickup in. The pickup was leakng around tha stem so i switched it to a ball valve. I believe it is correct to have 3/8 lines with a 3/8 injector. Thanks for the imput.
 

Big Bird

Registered
Last Subscription Date
02/16/2018
Are you testing for leaks with air pressure or are you trying to test the injector ?
I don't think it matters how much air pressure you put to an the injector it will not work.
It has to use the velocity of the the steam thru the cone to work. Air just won't work.
 

b7100

Subscriber
Last Subscription Date
07/10/2019
I am just trying to get the pickup to stop leaking. Nothing seems to work. I still get air bubbles around the injector nut. The U.S./Detroit manual says absoutly no leaks. They do say to plug the intake and overflow and open the steam valve to check for leaks. Maybe I'm O.K. Leaks are small.
I have redone the line to the heat exchanger so its 3/8 all through. Between the exchanger and boiler is 1/4" pipe. 1/4" pipe has a bore almost 3/8".
 

b7100

Subscriber
Last Subscription Date
07/10/2019
I am just trying to get the pickup to stop leaking. Nothing seems to work. I still get air bubbles around the injector nut. The U.S./Detroit manual says absoutly no leaks. They do say to plug the intake and overflow and open the steam valve to check for leaks. Maybe I'm O.K. Leaks are small.
I have redone the line to the heat exchanger so its 3/8 all through. Between the exchanger and boiler is 1/4" pipe. 1/4" pipe has a bore almost 3/8".
 

Casemaker

Registered
B7100
Could you take pictures of where it is leaking....i run 1/2 chicago injectors and my water input is a threaded pipe into the bottom of the injector.

.
 

chrsbrbnk

Registered
ithink any air leaks on the suction side and your pretty much hosed. trying to lap brass to brass tends to leave alot of embedded grit in the seal surface try maybe coating the surface of the connector with that blue devil pipe compound its possible some one jacked the injector body out of round or the nipple thing people grab on to those things in the wrong spot
 

b7100

Subscriber
Last Subscription Date
07/10/2019
It is working. I'm not sure if it is working right. (It was an ebay purchase) I use Time Saver lapping compound. It doesn't imbed and breaks down. I have used it extensively in the build. It has improved the connections but not enough to keep them from leaking. I tried copper washers, rubber washers, gasket material, pipe dope, teflon tap. I now have the copper washer in it. It still has a slight leak. That is with 100# of air. According to the manual you are supppsed to test it by blocking the intake and overflow then turn on the steam. That is not the way I tested it. I just used air. It may be good enough. Now I just need some run time to get its habits figured out. One thing I noticed is that it is always hot. I have to run the hose on it before it will work. I suspect the steam valve is leaking a little.
At startup I open both valves all the way then throttle back the intake. When the gauge drops a little below 50# it stops picking up. Not sure if there is a better way. At least it is working.
 

mike1

Registered
From my dealings with injectors on a model traction engine 3"scale, one thing that can keep the injector hot is a leaky boiler clack valve that the injector feeds through to the boiler which causes erratic operation.

Mike.
 

b7100

Subscriber
Last Subscription Date
07/10/2019
Steamed up today. Injactor wouldn't pick up. I found the problem. At some point something struck the intake tube stretching the nut so it won't pull down on the flange evenly. I am now mulling over my options. Buy another injector, try to true up the inner face of the nut, or make a new nut. Or if anyone knows of a junk #1 U.S. Detroit injector with a good nut I woild be interested.
 

Attachments

b7100

Subscriber
Last Subscription Date
07/10/2019
You are probably right. That would be my first choice if I had a piece of brass big enough. I have made a mandrel I can thread the nut on. Then the plan is to turn it around and chuck on the nut, dial in on the mandrel. Remove the mandrel and skin the mating surface. With the nut on the mandrel I had a runout of .040 on the face. (No wonder) if this fails I'll make a new nut.
 
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