Air in Fuel

[Kris K]

So just to beat a dead horse even more.


My turck starts right up then die's I then have to crank it for about 20 sec then it fires up, and runs rough intell I rev it up a little.

While driving sometimes at stop lights it will run rough again intell i get going again. Also when I shut if off then restart after only a couple min it will run rough, and clear up after reving it up. I've checked all of the lines between the injectors, and there fine.

I've tried bleeing tha air out from the shrader valve. Once I push in the valve it takes a second for the fuel to start coming out. I bleed it intell all the air is out then let it sit idaling for like 30 sec then push it again, and get a bunch more air out. I did this for a while last night, and kept getting air.

SO where should I look next?

I'm trying to sell my truck, and no ones going to buy it if it's acting like this.

 

[Cat_Rebel]

Bad return lines? Mine stars a ton better & seems to run better too since I replaced them & the O rings.

 

[LCAM-01XA]

Yeah, if you have a return line to the IP and/or the fuel filter (I have both, go figure) bad o-rings or rubber lines can let air in and mess up the fuel delivery. I've had my truck refuse to start like that, normally it fires up almost instantaneously but a few times I had to give it several hits before it finally catches - did the return lines and all is peaches now.

Oh yeah, kit for the lines is like $20-25, and takes just a few hours to install, if you're taking your time that is.

 

[Full Monte]

Have you bypassed your factory water-seperator yet? It's on the firewall on the driver side. Almost everyone eventually bypasses those things. The seal to the outside is unreliable and under vacuum, will leak air into the lines.

 

[Kris K]

I haven't noticed any fuel leaks in the return lines but that dosen't mean much since it still can suck air, and not leak fuel. I'll take a look at getting a return line kit. Where are you finding them for $20-$25?? Online or at a parts store?

 

[LCAM-01XA]

Kris, that was the price I saw at an online diesel-specific store, too bad I don't remember which one, but I'm pretty sure they got an ad here (top of page).

 

[Kris K]

OK so I picked up a return line kit.

I got it installed then cranked it over it started up with a little rough idle pushed in shrader valve to clear that up..

But now if I let it sit for a while ( as little as an hour) it startes right up then die's. It even dose this if I only drive a couple blocks then stop to run in a store. Then it takes a while cranking to get it to fire up again.

Just getting extremely frustrated since i'm trying to sell the truck.

 

[acey4342]

have you replaced the mechanical lift pump? if you say it will bleed air at the schrader valve almost every time take the line loose that supplys the pump from the tank side and make a make shift fuel tank out of a five gollon bucket or anti freeze jug and start it up and rev it again and see if air comes out the schrader. if it does at least youll know the leak is between the fuel tanks and the mechanical pump.

 

[redneckaggie]

The pickup tubes are horribly unreliable, they will suck air. If someone has put an e pump on it it may have gone out or it may have been removed and they didn't seal the lines good enough. check the whole fuel line and see if it is spliced anywhere. The filter may not be sealed down tight. the lift pump could be going bad. don't just look for leaks remeber it is 10x more likely to suck air than leak fuel from somewhere expecially when it has vacum on it.

 

[razorback]

i couldnt get the air out of my lines until i put in the epump, turns out the reason they bypassed the lift pump originally was due to there being a hole in the hardline that comes up on the passenger side to the pump. i just blocked off the pump, and put in a holley red. ALOT easier.

 

[Kris K]

I also notice that the fuel filter is half full when I took it off. I read on here about if the fuel filter is empty when you take it off the air leak is on the top side of the engine (o-rings,return line's or misc). Is this true?

 

[Agnem]

That's correct. The filter is kept full by vacuum in the system. Your leak is at an injector, injection pump, or filter head. The Moosestang has the same problem at the moment. I just haven't had time to fix it yet.

 

[Kris K]

Well that gives me a place to start.

 

[JeffMoss1]

What I found works best is to install sight glasses so that you can see the air bubbles and isolate where the problem is. I actually have two permanent, glass, flow visualization windows installed vertically before my fuel filter and right at the beginning of my return line. So next time this problem arises I'll be prepared!

mcmaster sells the ones I used

Another neat trick is that if your leak is in the return line, if you just make it so there's a high point in the line (height of the fuel filter) before it goes back down to the tank, your engine at least won't loose its prime while just sitting. (it will still leak fuel, but it will be drivable.)

That might be easier for me though since I have a van (not sure.)

 

[Kris K]

Well I'm still having problems with the truck, just no time to work on it.

I did notice while replacing the return lines that on the back driver side of the engine there was a brass fitting of some type that the return lines connected to. I think this is the line that returns to the tank and runs towards the frotn o fthe engine? Well it seemed loose I could turn the middle peice that have the T's almost all the way around. I tried to tighten in but chickend out I didn't want to break anything. I guess I just have to tighten the nuts on both sides of the middle section with the T's. Sorry kind of hard to explain.