What is the air dog, an air filter?

 

OK, I see it now, a fuel pump. And you had the problems before the air dog.

You can't change the tune, right. I still think it's either the tuner or the ECU. I don't know anything about changing the ECU, my tranny guy did mine and in his full time he is a Ford tech so I don't even know the cost but I'm thinking he told me something like 6 or 7 hundred.

Unless it's like somebody above said and while you retune something cools down and it's just a coincidence that it starts, there must be a problem in the tuner or the ECU. Once you tune it, it should stay tuned. I'd be looking on the H&S forums to see if I could find a similar problem.

 

I follow your thinking.. but why when i replace the fuel filters does it go away? It is strange. I have checked on the H&S forum so far no luck. i rewired the lift pump so it is on when the key is on direct, put a new filter on it ... and guess what ??? its running great again ?? did nothing else. I still think 5 gallons of gas and a match would fix it just saying.

 

Funny you should mention the lift pump. There is a thread from a 450 owner on H&S forum about losing power under tow. It sounded similar to yours but only when he was towing. he finally figured out it was a weak lift pump causing a loss of fuel. In your case changing to a new filter would clear the problem until the filter got soiled and required a little more pressure to push the fuel through and then the problem would return.

 

Yes I saw that one. same kind of deal except we are talking 1000 miles between filters on mine.. so i put the air dog on better filters, more fuel and the filters a WAY easier to change and WAY cheaper. There has to be some under lying problem, but damn if I can figure it out. I know of 1 other 450 that is doing pretty much the same thing back east. The whole no code thing is what gets me.

 

I may have miss read your earlier post. I thought the Airdog replaced the stock lift pump. Are you running both in series?

 

[QUOTE=mich800;13635380]I may have miss read your earlier post. I thought the Airdog replaced the stock lift pump. Are you running both in series?[/QUOTE

Just running the air dog

 

OK So today I go to start it its 39 outside and it wont start tried it a few times let the glow plugs run a few times ..turns over wont start?? re tune it fires right up, runs good all the way to work to it up to 90 no issues ?? .. yesterday on the way home 80-85 mph all the way runs perfect. ??? so wtf is it ?? where are all the techs...

 

Gotta be some glitch in either the truck ECU or the H&S computer. have you tried different tunes or is your tuner on a fixed tune?

 

I have tried different tunes, no change still acts up. but explain to me why changing the fuel filter makes it go away...

 

It is always difficult tracking down an intermittent problem. Could still be coincidence. It sounds like you have ruled out the wiring to the lift pump. Any possibility it is actually the pump motor itself. Changing the filters may free the motor back up when you are touching the unit. I.E. like hitting a starter to get it to spin again.

 

The lift pump is brand new.. also did the same thing with the old one.

 

Have you updated the tuner at all? Just a thought. I haven't had much trouble with my H&S, but when I had the trans replaced, had the tuner updated at same time. (happened to be in St George, UT, at the same time my trans went out--home of H&S) After updating, lost the T/H auto kickdown. H&S adamant it "ain't the tuner" Got home without the kickdown, had my diesel shop reset the tuner and now all is well. H&S may have some good tech, but they seem to have an attitude they can't be wrong.
Joe

 

Maybe I didn't understand you. I thought you said the truck was running fine when you parked it. The next morning the truck was no start. You then reinstalled the tune and the truck started and ran fine. You didn't say anything about the filters. Did I miss something?

 

If I replace the filters all this will go away for awhile.. meaning it will always start with no problems