IDI running issue...

[94f450]

A friend of mine has a 93 NA 7.3 that he has been trying to chase down problems with. After a 3 hr trip in the truck he came home and let it idle for awhile. The truck started to run really rough and has progressively got worse. He can make the truck do it by holding the throttle around 2000 rpm and when he lets off it will idle rough. Almost like its starving for fuel? We found it had 2 psi at the filter head so he changed out the lift pump with a new mechanical unit... still had 2 psi so he went with an electric pump and now has 5psi. He though maybe it was an air leak so he replaced the fuel lines all the way back to the tank, replaced both tanks, and the selector valve between tanks! None of this has solved the issue!!! Has DPS injectors and injection pump that are less than a year old with maybe 2000 miles on them. Return lines and caps are new. What do you guys think!?

 

[redneckaggie]

have you replaced the filter? did you check volume at the schrader, is the released fuel when you press the schrader air free, does the truck run rough for just a second and then clear up or does it continue to run rough?

 

[Kevin 007]

Might be a sticking metering valve in the injection pump. Is he running fuel conditioners at all?

 

[icanfixall]

Because of some of the injector issues from DPS my feeling are the injectors are the problem. To know if they are the issue you will need to have them pop tested. Running a fuel additive keeps the pump and injectors clean and well lubed too.

 

[hesutton]

Because of some of the injector issues from DPS my feeling are the injectors are the problem. To know if they are the issue you will need to have them pop tested. Running a fuel additive keeps the pump and injectors clean and well lubed too.

You read my mind Gary. I bet if you pull those injectors and pop test them, you'll wanna punch someone in the face. I know I sure did when I pop tested my set of Stage 1's. All 8 leaked, all had an off center **** stream of fuel, zero atomization, and low pop pressures. I've got a video of those injectors on the pop tester that I need to upload, but I've not had the time.

Anyway, My truck idled like garbage and was a real bear to start cold, spewed black and blue smoke, and my mileage was bad as well. I'm much happier with my Moose goodies. So much so, that I ordered a set for the 6.9 in my crew cab. Wife said they arrived via FedEx today.

Heath

 

[wmoguy]

I recently was chasing down a similar problem, it was driving me nuts! I was ready to blame the DPS injectors and pump too.... Turns out I had an air intrusion issue. It becomes much more noticeable at idle after being ran on the open road for a while. Toss a clear line from the lift pump to fuel filter head and see if thats your issue (bubbles of any sorts are bad) and on your return line do the same thing. I think all the IDI's are the same line size, mine from lift pump to fuel filter housing is 3/8" ID hose, and the return line is 1/4" You only need about 16" of the 3/8" line and less than a foot of 1/4" for the return line. ALl in all should cost you about $2-3 in clear hose at an Ace Hardware. From what Ken @ DPS told me, any air whatsoever at the IP makes it do all kinds of funny things (i.e. adjusts metering valve/advances timing a bunch, etc..)

Have you tested your fuel to make sure you don't have a water in fuel issue?

 

[94f450]

Filter has been changed and he just changed the injection pump with another good one he had on the shelf. Didn't change a thing as far as how it ran. We will try using clear hose to check for air and see what the results are. If that doesn't help, looks like injectors may be coming out? It runs rough but doesn't really smoke a lot. Pretty positive its not a water in fuel issue as his other IDI runs fine on the same fuel. Could a motor issue cause anything like this?

 

[Agnem]

An easy way to look for air is at the pump fuel return. A barb and some clear hose, and you don't have to futz with the input side. Plus, the pump itself could introduce air, which would not show up on the input side. This is why when a Moose Pump is calibrated, the return line hose is clear.
http://rides.webshots.com/video/3015454350107427566ypJnSn