Tonight I checked my lift pump and it was putting out 4 psi. Didn't get a chance to check the flow. I also replaced the fuel filter. I started it up and it ran rough for a while, probably normal after a fuel filter change. When the truck warmed up I took it through the speed range. I held it at 2300 rpm and it ran there without the earlier problem I had. I'm not sure what I did to fix the problem but I'll take it. I probably won't be suprised if it returns though. I did notice while running it through the speed range that it was pumping out quite a bit of blue smoke, especially at higher speeds. What are the causes of blue smoke? I know it is oil burning but I'm curious as to what some of the causes might be. The truck is also stumbling some through the speed range. Does the injector return line repair kit just fix starting problems or will it fix this stumbling problem too? I took my breather off and noticed the intake had an oil film all over the inside of it. Is this a symptom of a dirty CDR valve? This might be a really dumb question but will a plugged CDR valve cause an engine to stumble? I pulled the CDR valve off and sprayed some WD40 in it and sloshed it around and got out a bunch of black gunk. I am going to soak it in some gasoline as recommended on some earlier posts to clean it good. I'm sorry to ask so many questions but these engines are new to me. Thanks.

 

the only stupid questions are the ones you don't ask.a clean cdr will go a long way in reducing oil smoke, as there will be no oil getting sucked into the intake.
you probably cleared up the stumble problem when you hose clamped the water separator bypass lines, or blocked off the #1 to filter line. return o-rings and caps usually just fix the start end.there might be a crack in the supply line from tank to lift pump, of the pickup tube in the tank may have a crack in it introducing a bit of air to cause the stumble. when you said you took it through the rpm range, did you do it sitting, or did you take it out on the road and try it under load through the gears??my 7.3 sounds like sh%t just revving it, but take it out on the road and stomp on it under load, and it clears up and sounds sweet through the 4 inch stacks.
as for the smoke, it may just be a cold hearted beast. once you get heat into it and under load it should be none, or a little bit of black smoke.

 

I was reving it up just sitting. I haven't tried it on the road yet. You said the the pickup tube in the tank could be cracked or have a leak in the line to the lift pump. Is there a certain level in the tank the pickup tube might be likely to crack? I have just under a half a tank of fuel. I should mention that there is some old fuel (I don't know how old) in the tank also. I put about 5 gallons of fresh fuel in it and some additive to eliminate any water that might be in the tank. What might be the best way to check for these cracks or leaks? Could I run from a bucket of fresh fuel directly to the lift pump and see if it smooths out or maybe install a clear line to the lift pump and look for air? Also, I didn't do the lift pump test exactly the right way. I checked the pressure while it was running and had 4 psi. I forgot to check it just cranking. Does this affect the test? Thanks.

 

lift pump test, i can't say, i never tested one. as for the pickup tubes, i have seen them crack all over the place. some on the bottom,some in the middle, and 2 on the top at the tank plate. air in the system is enough to make you bald from all the hair pulling. a boat tank is a perfect redneck fuel cell to hook to the lift pump to check for leaks in the fuel lines or pickup tube. if the line is long enough, you can have it on the passenger side floor and test drive it like that. (just don't get caught, some cops tend to not understand troubleshooting techniques)

 

I installed a clear hose on the supply line where the old water separator used to sit and ran the engine last night. No bubbles just solid fuel. I would think that that would eliminate any air intrusion up to that point. When I got in the shop tonight I pushed on the schrader valve on the fuel filter head on got all air out. With the return line from #1 injector to fuel filter already removed, is it still possible to get air to the filter head? My #1 plastic injector cap is leaking a little. Is this enough to cause the engine to stumble?

 

OK that line if it is still original, leaves the water seperator location and goes down to the frame. Then it goes forward to the cross member, crosses to the passenger side on the cross member and forward across the cross mamber to the lift pump.
Check the area where the line is very close to the exhaust manifold where it crosses the cross member.

Mine rubbed a hole in the line over the cross member a couple of years back.

Replaced the line with rubber fuel line that I ran through a piece of heater hose for extra protection.

 

I will check that line. I do like the idea of running a flexible line inside of a heater hose. I will probably replace mine with that setup anyway. Another difference I have noticed between the 6.9 and the 7.3 is the outlet line on the fuel pump. The outlet line on the 6.9 is a screw together type of fitting which I'm guessing is the correct setup. The 7.3 has a rubber hose connecting the pump outlet to the steel line that goes up to the filter head. I visibly checked the hose and it looks OK. I didn't really think that it would be a likely spot for air intrusion since it is a pressurized line. Am I wrong? Should I switch the line from the 6.9 onto the 7.3? Looks like the only difference is the line heater in the 6.9 line. I don't think that will give me any problems since I won't be using the heater anyway. Thanks for the guidance.

 

The proper 7.3 line is exactly like the 6.9 line but it does not have the heater on it since the 7.3 heater is in the filter header.
Someone along the line somewhere crimped the steel line when they changed the fuel pump. So they just did a quick and easy fix.

I went to that type of line on mine because the line heater traps water after a while and the line rusts through.

You are correct in the fact that air intrusion will be on a non pressure line.

For what it is worth, my Reman Ford IP is starting to act real funny at idle, sounds like it is sucking air reving up and running rough. No starting issues, filter is full of fuel. Runs great at speed and has lots of power while getting better MPG's than I have seen for a while. I have been working to much to mess with it, but I think I need a different IP. I will let you know what happens.

 

Just a quick question I just thought of. Is it possible to get air introduced into the fuel supply through the return line that goes from the #2 injector to the fuel pump? Can the pump suck air from this line?

 

I finally pulled the steel line that goes from the driver's side to the lift pump and checked it out. I found a worn spot on the line I thought looked suspicious. I applied some air pressure to it and sure enough air was coming out of this spot. I am going to replace it like Dave suggested, fuel line ran inside a heater hose for protection. Hopefully this will fix my performance problem. I will post the results as soon as I fix the line.

 

I think you have found your problem area. Probably no visable indication there was a leak there either.

Fuel line air intrusion can cause baldness, from slowly pulling all your hair out.

 

and brain damage from pounding your head against the wall.

 

I can relate to the problem, had a case some time ago with my dad's 84 where the right inner fender had rubbed through the fuel supply line, it at least was kind enough to show there was a leak, but it really made it tricky to find it.

 

Do you think someone would think we have seen this problem before with us all talking like that and adding to the one before?


God I love my old truck.

 

nope. not a chance of that happening dave. besides, we drive ferds, the best built truck in the whole dang world, and everbody knows that them ferds never break down.