# New injector and now problems with backpressure **URL:** \ **Category:** Machine Repairs\ **Created:** [January 19, 2020, 6:25pm UTC](https://pressurewashingresource.com/community/t/new-injector-and-now-problems-with-backpressure/23496 "2020-01-19T18:25:28Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![mwpws](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/mwpws/32/33836_2.png) [@mwpws](https://pressurewashingresource.com/community/u/mwpws)\ **Post date:** [January 19, 2020, 6:25pm UTC](https://pressurewashingresource.com/community/t/new-injector-and-now-problems-with-backpressure/23496/1 "2020-01-19T18:25:28Z")
I installed a new injector. A General Pump 100339LG rated to 5-8 gpm. It’s the injector with the interchangeable orifice tips. I have a 3500#/ 5.5gpm pressure pro with a K7 unloader. After installing the injector I have no flow at the gun, it is all going to tank. The injector has .098 etched in it and the specs from the website say the orifice is a 2.3mm. 2.3mm converted to inches is .091 so i’m guessing that’s where that is coming from. Is that orifice too small? ![601150520](https://pressurewashingresource.com/community/uploads/default/original/3X/f/5/f5c910ee5886e638d0da5ca626b165fc7a18614d.jpeg) ![Screensho](https://pressurewashingresource.com/community/uploads/default/original/3X/3/7/376ba98f1fcfe4412d9a7e26225eab0cb09a9d07.jpeg) ---
**Author:** ![DisplacedTexan](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/displacedtexan/32/29182_2.png) [@DisplacedTexan](https://pressurewashingresource.com/community/u/DisplacedTexan)\ **Post date:** [January 19, 2020, 6:42pm UTC](https://pressurewashingresource.com/community/t/new-injector-and-now-problems-with-backpressure/23496/2 "2020-01-19T18:42:59Z")
Make sure it’s not on backwards before you do anything else. Arrow pointing **with** the flow of water. Plenty of folks have put it on backwards and never thought to check that first. ---
**Author:** ![mwpws](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/mwpws/32/33836_2.png) [@mwpws](https://pressurewashingresource.com/community/u/mwpws)\ **Post date:** [January 19, 2020, 6:50pm UTC](https://pressurewashingresource.com/community/t/new-injector-and-now-problems-with-backpressure/23496/3 "2020-01-19T18:50:03Z")
One of the first things I checked 👍 ---
**Author:** ![fhpressurewashing](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/fhpressurewashing/32/10467_2.png) [@fhpressurewashing](https://pressurewashingresource.com/community/u/fhpressurewashing)\ **Post date:** [January 19, 2020, 7:08pm UTC](https://pressurewashingresource.com/community/t/new-injector-and-now-problems-with-backpressure/23496/4 "2020-01-19T19:08:38Z")
What size nozzles are you using? ---
**Author:** ![mwpws](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/mwpws/32/33836_2.png) [@mwpws](https://pressurewashingresource.com/community/u/mwpws)\ **Post date:** [January 19, 2020, 7:36pm UTC](https://pressurewashingresource.com/community/t/new-injector-and-now-problems-with-backpressure/23496/5 "2020-01-19T19:36:22Z")
My black tip is a 65400 at my white is a 40055 ---
**Author:** ![Infinity](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/infinity/32/30829_2.png) [@Infinity](https://pressurewashingresource.com/community/u/Infinity)\ **Post date:** [January 19, 2020, 7:49pm UTC](https://pressurewashingresource.com/community/t/new-injector-and-now-problems-with-backpressure/23496/6 "2020-01-19T19:49:40Z")
Who set the k7 unloader? It sounds like it might be set way too low. What happens when you put a high pressure tip in your gun? (Without any injector) Can you see clear through the injector orifice? No blockage? ---
**Author:** ![mwpws](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/mwpws/32/33836_2.png) [@mwpws](https://pressurewashingresource.com/community/u/mwpws)\ **Post date:** [January 19, 2020, 8:02pm UTC](https://pressurewashingresource.com/community/t/new-injector-and-now-problems-with-backpressure/23496/7 "2020-01-19T20:02:46Z")
The place I bought it from set it at 3400# and if I take the injector off everything works great. High pressure tip or low. And there are no blockages in the injector cause they’re brand new, but I double checked just because who knows what crap may have gotten into them. ---
**Author:** ![Infinity](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/infinity/32/30829_2.png) [@Infinity](https://pressurewashingresource.com/community/u/Infinity)\ **Post date:** [January 19, 2020, 8:03pm UTC](https://pressurewashingresource.com/community/t/new-injector-and-now-problems-with-backpressure/23496/8 "2020-01-19T20:03:46Z")
Wow. Then I’m stumped. ---
**Author:** ![dcbrock](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/dcbrock/32/38857_2.png) [@dcbrock](https://pressurewashingresource.com/community/u/dcbrock)\ **Post date:** [January 19, 2020, 8:57pm UTC](https://pressurewashingresource.com/community/t/new-injector-and-now-problems-with-backpressure/23496/9 "2020-01-19T20:57:58Z")
What orifice was your old injector? ---
**Author:** ![MuscleMyHustle](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/musclemyhustle/32/25298_2.png) [@MuscleMyHustle](https://pressurewashingresource.com/community/u/MuscleMyHustle)\ **Post date:** [January 19, 2020, 9:06pm UTC](https://pressurewashingresource.com/community/t/new-injector-and-now-problems-with-backpressure/23496/10 "2020-01-19T21:06:08Z")
> [@mwpws](#): > > And there are no blockages in the injector cause they’re brand new Don’t always assume because it’s brand new it’s in perfect running order, I’ve had many dud injectors Fresh out the packet. You really should carry more than 1 brand new injector at all times, for these particular reasons to actually gauge if it’s the injector at fault. ---
**Author:** ![MuscleMyHustle](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/musclemyhustle/32/25298_2.png) [@MuscleMyHustle](https://pressurewashingresource.com/community/u/MuscleMyHustle)\ **Post date:** [January 19, 2020, 9:10pm UTC](https://pressurewashingresource.com/community/t/new-injector-and-now-problems-with-backpressure/23496/11 "2020-01-19T21:10:10Z")
I would even check that arrow is printed the right way. ---
**Author:** ![mwpws](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/mwpws/32/33836_2.png) [@mwpws](https://pressurewashingresource.com/community/u/mwpws)\ **Post date:** [January 19, 2020, 9:58pm UTC](https://pressurewashingresource.com/community/t/new-injector-and-now-problems-with-backpressure/23496/12 "2020-01-19T21:58:51Z")
I bought two when I got them and I was sure to double check to make sure there was nothing in there ---
**Author:** ![mwpws](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/mwpws/32/33836_2.png) [@mwpws](https://pressurewashingresource.com/community/u/mwpws)\ **Post date:** [January 19, 2020, 10:00pm UTC](https://pressurewashingresource.com/community/t/new-injector-and-now-problems-with-backpressure/23496/13 "2020-01-19T22:00:43Z")
I just went and looked at my old one and it was also a 2.3. I bought two injectors when I made my purchase I’m gonna try the other one. Maybe this one is a dud 🤔 ---
**Author:** ![Hotshot](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/hotshot/32/35093_2.png) [@Hotshot](https://pressurewashingresource.com/community/u/Hotshot)\ **Post date:** [January 19, 2020, 10:29pm UTC](https://pressurewashingresource.com/community/t/new-injector-and-now-problems-with-backpressure/23496/14 "2020-01-19T22:29:52Z")
> [@mwpws](#): > > I have no flow at the gun, it is all going to tank. Going to tank meaning bypass back to buffer tank , or its filling up you chem tank via DS injector poly line ? ---
**Author:** ![mwpws](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/mwpws/32/33836_2.png) [@mwpws](https://pressurewashingresource.com/community/u/mwpws)\ **Post date:** [January 19, 2020, 10:33pm UTC](https://pressurewashingresource.com/community/t/new-injector-and-now-problems-with-backpressure/23496/15 "2020-01-19T22:33:33Z")
going back to the buffer tank ---
**Author:** ![Hotshot](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/hotshot/32/35093_2.png) [@Hotshot](https://pressurewashingresource.com/community/u/Hotshot)\ **Post date:** [January 19, 2020, 10:46pm UTC](https://pressurewashingresource.com/community/t/new-injector-and-now-problems-with-backpressure/23496/16 "2020-01-19T22:46:02Z")
It has to be a dud injector then , I cant think of no other reasoning because your old one at the same size worked. ---
**Author:** ![Firefighter4hire](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/firefighter4hire/32/21981_2.png) [@Firefighter4hire](https://pressurewashingresource.com/community/u/Firefighter4hire)\ **Post date:** [January 19, 2020, 11:01pm UTC](https://pressurewashingresource.com/community/t/new-injector-and-now-problems-with-backpressure/23496/17 "2020-01-19T23:01:32Z")
@mwpws an you remove the orfice inside that injector probably a allen head if you can take it out and run a file across it. Put it back in and test it ---
**Author:** ![mwpws](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/mwpws/32/33836_2.png) [@mwpws](https://pressurewashingresource.com/community/u/mwpws)\ **Post date:** [January 26, 2020, 6:30pm UTC](https://pressurewashingresource.com/community/t/new-injector-and-now-problems-with-backpressure/23496/18 "2020-01-26T18:30:03Z")
So i decided to try the second injector i purchased and everything works! BUT WAIT THERE’S MORE. After installing the second injector without one of the screw in orifices i decided to put one in and do a draw test. Well when i took the 1/4" hose off the plastic barb broke off the injector so i swapped it from the first injector. Reassembled with a screw in orifice went to do a draw test and now back to square one, no flow to the gun. Now i loosened the injector so to barb point down instead of up and everything works, i get full flow to the gun. BUT WAIT THERE’S MORE, it wont draw anything from my dip tube. So key point here, 1. When barb is pointing up, i get no flow to the gun 2. When barb is pointing down, i get flow but it wont draw soap Is it a rule of thumb to have the barb pointing in one direction? ---
**Author:** ![dcbrock](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/dcbrock/32/38857_2.png) [@dcbrock](https://pressurewashingresource.com/community/u/dcbrock)\ **Post date:** [January 26, 2020, 7:08pm UTC](https://pressurewashingresource.com/community/t/new-injector-and-now-problems-with-backpressure/23496/19 "2020-01-26T19:08:02Z")
At this point, go back to using a fixed GP injector. ---
**Author:** ![marinegrunt](https://pressurewashingresource.com/community/user_avatar/pressurewashingresource.com/marinegrunt/32/9556_2.png) [@marinegrunt](https://pressurewashingresource.com/community/u/marinegrunt)\ **Post date:** [January 26, 2020, 7:42pm UTC](https://pressurewashingresource.com/community/t/new-injector-and-now-problems-with-backpressure/23496/20 "2020-01-26T19:42:54Z")
> [@dcbrock](#): > > go back to using a fixed GP injector. I was thinking the same thing. I don’t see the barb pointing up or down making a difference but at least switching to an injector that most of us use will let you know if something else is causing your issue. [Next page](https://pressurewashingresource.com/community/t/new-injector-and-now-problems-with-backpressure/23496.md?page=2)