Air in injector return lines and rough idle?

[whyme]

I've been challenged by a hard start issue over the winter and attributed it to a fuel leak at the injector pump head and old filters.

Now it's warm and ice changed the filters and fixed the leak but I'm still having issues. It will start most of the time above 50 degrees without a problem but then idle at 450-500 till I tap the gas and then it idles fine. This noting it was 40 something and I had to give it a little gas to start.

I noticed some small air bubbles in the return line from the injectors. Could this be the source of my problems?

 

[Floridianson]

Has your fuel been incresaed. Most trucks that have not been touched will bennifet by uping the fuel 1/2 turn on inner nut. As for the air think we talked about this small amount is normal.
Use marker on the nut to use a referance.

 

[whyme]

ive batted the idea of turning the pump up a bit but ive been pleased with my power output and i want to do as much as i can to extend the engines life. any idea where the air is getting in? i don't have and fuel leaks around the injectors that i can see and the nuts around the lines are all snug.

 

[Wildchild467]

i was told the air comes from the compression in the engine, when the piston comes up, the pressure forces air in the return lines if the injector does not have a good seat. i believe some is normal, but excessive is not good. next time you have it running and warmed up, use an infared thermometer if you have one to measure the exhaust temperatures on the exhaust manifold out of each cylinder. if you look down at the engine, you can see the exhaust manifold where it comes out for each cylinder. thats where you should shoot the thermometer. see what the temps are and how the temperatures vary. i measured about 270 degrees on mine the other day... but every truck may be different.

if you have a cylinder that is real cold, thats a sign it is not firing and you may want to put another set of injectors in it or something. another thing to check is the valve lash. thats a cheap easy fix to eliminate a possible cause. im not saying that is a problem, but at least its one thing you could cross off the list. maybe a valve is tight and loosing some compression too. who knows. i hope this helps.

 

[hoop]

Make sure your primary filter nut is really tight. I think i read it is supposed to be about 78ft lbs.

 

[WillWagner]

Don't focus on bubbles in return lines. A good runnind engine has airiated fuel there. My junk exibits the same thing yours does. Cold weather, it is harder starting and the idle is very low. I m warmer temps, it fires right up and idles fine. It is most likely the starting circuit in the pump.

 

[whyme]

I'll recheck the filters but I don't have any leaks so I cant Imagine them being the source (I've been wrong before)

When you say the starting circuit, is this something I can adjust or is it simply crud build up/worn parts? I was going to run a few quarts of ATF through the system when I get down to below a quarter tank to see if that cleans things out a bit.

I'm just frustrated because last year it started started so nicely, then again I got it in august

 

[WillWagner]

Yup, internal parts wearing. Go head and run the ATF. I ran 20-25 gals of hyd oil this last trip to the desert and it worked fine. My buddy, Hole, ran 100% hyd oil and he ran good but in the cold temps we had, around 30 over night, it was a tad hard starting in the AM but was good after that.

I gotta do a bit more boning up on this style of Bosch pump. The issue might just be a worn HH. I have noticed that I started having this issue over the last year and I have been running a mix of gas, diesel and new ATF...more gas than the others. Low lubricity might be the culprit.

 

[Floridianson]

ive batted the idea of turning the pump up a bit but ive been pleased with my power output and i want to do as much as i can to extend the engines life.

Have you ever checked you boost at 1600 and 2400 rpm? Have you gotten rid of the stock oil filters and done the spin on antidrain back filters and put in a good mechanical oil gage. Have you cleaned you compressor filter. Have you taken a oil sample and had it checked out.
Not trying to be funny or to much of a smart azz but if you have done all these thing then I bow down. If not then turning up the fuel just a small amount to aid in the first start is small compaired to these things I would think.
I will bet you $5.00 that your numbers are low. 4 lb 1600 and 8-9 lb at 2400 is my guess and you intank is 4 lb.

 

[whyme]

No I haven't really gotten that far into it, I've been slowly doing the PM and working my way from simple to complex while addressing necessary repairs. Every day is a new step. I've just been kinda scared to play with fuel pressure because I've read the horror stories and there are alot of unknowns in the engine.

I did notice today that there is alot more air in the lines at higher revs and still no signs of fuel leaks. Also the smoke seems to be more white than black, at idle on a cold day it smokes a little but when the engine is at temp it doesn't. I haven't seen any black smoke yet so I'll have a friend record it under load and maybe that's one more reason to bump the fuel up.

I haven't lost any coolant and my oil and antifreeze are fine so no issues there that I know of.

 

[Floridianson]

Yea they got to be up to full running temp's to burn better. That's water and oil so if low tems still cover a part of the radator The lines with air are the injectors but she is running fine then as said your good. Now if you had clear lines and were getting air in the FDC if it was not bypassed or air into the HH then finding the leak would be mandatory.
I don't want you to raise the fuel to the point of having to worrie or get some crazy boost but most of the trucks I have played with are low from the get go.
I bet if you just try the 1/2 turn and mark it with a marker so you can see how far you went then it can be lowered or put back right where it was if you are not comfortable.
The pyro is work but the boost gage if the little plug come out seems like a quickie. Then you can see if your are geting more than 10lb boost which is where it should be stock. Some on the board run 12lb and have no temp problems.
Think about adding a pyro one day just for peice of mind and the cool factor.
I forgot to ask have you checked the intank pump pressure. This can affect cold starting. Needs to be atleast 4 lb and when is cold you can let it run a little bit then do the hydro lock check start then push in the cutoff and fire the beast up.

 

[whyme]

well it seems to be getting worse or at least im noticing it more. its been in the 50's for the last two weeks and its still i beast to get started. honestly i only notice it when i try to start it in the morning so i kind of wonder if the pump is losing prime but then when i recently ran it out of fuel it started right up after i added 5 gallons, no bleeding.

i ran the ATF through it and maybe a little more power but otherwise no change.

i also stated noticing a quick surge in power when i let off the gas very occasionally, im thinking something is gummed up in the IP.

 

[Floridianson]

If you ran her out of fuel you still might want to check the finials for air.
I guess you HH could be getting weak. You tryed uping her half a turn on the main yet???????