Need help badly, air in fuel line, hard start...

mrGutWrench

mrGutWrench

Top Post Dawg
Joined
Aug 29, 2002
Location
Carrboro, NC
TDI
'03 Jetta Wagon, 5-speed, 563K Miles (July '23)
2TDIguy said:
I am getting air in my fuel line right after shutting the car off. While running it looks like a rootbeer float inside the fuel line with massive tiny bubbles. Please see my post below in the A3/ B4 forum. Any help would be great as I am "down hard" in this cold Nebraska winter. (It was -8 below ZERO this morning)

http://forums.tdiclub.com/showthread.php?t=124395
Click to expand...
__. Nebraska, huh? Well, OK for some people! You do know that your car has a "vacuum" system for the fuel lines, right? The fuel pump is on the main engine injection pump and it pulls fuel from the tank by vacuum. If you have a leak, it will show up by air being pulled into the system by the vacuum. On the other hand, if your fuel is gelled (or beginning to gel) it will clog the filter and you'll get a lot of vacuum pulling against the clog in the filter. If that happens, you'll get a lot of low-pressure bubbling in the fuel. Some people say that there is a fair amount of air dissolved in fuel anyway and this vacuum pulls it out into vapor form. I'm not sure about that, but a clogged fuel system will behave just as you've noted.

__. One problem that people have run into is that the pickup in the tank was too small on some early models. Even if the fuel isn't gelling on these cars, there's a chance that little crystals of ice will clog the pickup. Do a search - I think the topic was often called "fuel sender" for full info.

__. If the problem isn't the pickup, you should check the connections of the fuel lines to the fuel filter, also the "T-fitting" into the filter -- this fitting is a thermo-statically controlled valve that directs warmed fuel back to the filter. It just plugs into the top of the filter with O-rings for a seal and this area is prone to leaks.

__. One good way to check all this is to put your car in a heated garage overnight. If the problem is fixed, you have a temperature related problem (fuel gelling or ice crystals).
'
 
2TDIguy

2TDIguy

Veteran Member
Joined
Nov 23, 1999
Location
Lincoln, NE, USA
I do have a heated garage and it makes no diff. It is 50 degrees in there all the time. I looked close at all lines, and the "T" going into the filter last night. I will look again tonight. Wish there was some kind of die I could spreay on the lines that glowed when sucked in and mixed with diesel...
 
mrGutWrench

mrGutWrench

Top Post Dawg
Joined
Aug 29, 2002
Location
Carrboro, NC
TDI
'03 Jetta Wagon, 5-speed, 563K Miles (July '23)
2TDIguy said:
I do have a heated garage and it makes no diff. It is 50 degrees in there all the time. I looked close at all lines, and the "T" going into the filter last night. I will look again tonight. Wish there was some kind of die I could spreay on the lines that glowed when sucked in and mixed with diesel...
Click to expand...
__. If you can verify no leaks, that can only mean there is an obstruction (maybe a filter clogged with something else besides gelled fuel)? Of course, it's hard to verify no leaks. If the problem is leaks, one thing I tried was some plain mineral oil from the drug store. Dribble it on a suspected leak point -- it's heavy enough that it will seal a small leak and the bubbles will be reduced (temporarily).

__. Better you than I (for both -8* and dealing with this).
'
 
McBrew

McBrew

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Joined
Oct 30, 2002
Location
Annapolis, MD
TDI
2003 Golf GLS TDI, 5 speed, Silver/Grey
Air can also leak in at the drain in the bottom of the fuel filter.
 
V

velostuf

Veteran Member
Joined
Apr 7, 1999
Location
Minneapolis, MN
TDI
2009 Jetta Sportwagen TDI
Difficulty starting and/or running in Minneapolis

We've had a cold snap here for the last week, and I have had 3 problems. I too am seeing bubbles in the clear, (return?) line, and at the point when it has died and won't restart that clear line is empty. I got some starting fluid, and sprayed it into the flexible intake immediately after the MAF sensor, and this would get the motor running for 4-5 seconds. This was good because it apparently worked the fuel pump hard enough to get buttery fuel where it needed to go. Keep in mind that it took several iterations of spraying fluid and then re-attaching the hose before it would idle. After it starts, at least initially, the hose gets completely filled, but it's cloudy. REMEMBER, when the engine begins to run with the ether, it will probably rev up uncomfortably high, and THERE'S NOTHING YOU CAN DO ABOUT IT! You basically have a runaway engine at that point, (we have *compression* ignition engines). However this morning when the motor shut down 1 mile from home, I was able to watch the rev counter while it ran away, and it got to 5,ooo rpm, which was acceptable to me because the crankcase oil had a chance to warm up over the last mile, and presumably there was oil in the filter, so oil pressure was up enough to protect parts. When using the fluid, spray for 1-3 seconds, and no longer.

So, assuming that my problems are caused by gelling and not an air leak, it's happening either because there's enough residual biodiesel in my fuel that it has effectively raised the gel point to above 10 degrees F., or my CAT 2 micron fuel filter is too fine for cold, but not solid, fuel to flow through. OR, it's a combo of both.

FYI, I was running 50% biodiesel in the tank before this. My estimate is on a percentage basis, there was about 10% biodiesel in my fuel when I had my first clog, and the temp was maybe 4 degrees F.

John
Minneapolis
 
V

velostuf

Veteran Member
Joined
Apr 7, 1999
Location
Minneapolis, MN
TDI
2009 Jetta Sportwagen TDI
I went out to my car at lunch and tried to start it. It cranked for about 8-10 seconds before it gradually came to life. There was some clear fuel in the clear hose, but mostly air. The extended cranking eventually got fuel to where it needed to go. As soon as it idled, I could see only cloudiness in the clear hose. Should this be? Anyway, I am looking very closely at the connections on the top of the CAT fuel filter system, and when I jiggle the black hose at the top of the filter, air bubles can be seen whisking along in the clear hose, but the engine keeps running. The design of the stainless clamp that holds in the fuel fitting with the O-ring is flawed. One or both of the screws that secures the clamp device to the top of the filter get in the way of the hose ends, so you can't really push the O-ring fitting in all of the way. I have noticed some fuel come out of this fitting while struggling with this hard cold start, but all summer long there were never any problems and things stayed completely dry and fuel-free on the top of the filter. I am going to take things apart and see if the fitting will go in farther if the screws aren't there. I think that it will. I will either have to do without one of the screws, or file down the screw head so that it's not so tall.

Someone else please comment on some of my observations- Should the fuel look cloudy? (There's 2 cans of diesel fuel additive in the tank that sez it has anti-gel properties).

Is it safe to say that if my fuel were properly blended for winter that none of these issues would be happening? In other words, is it the gelled or "almost gelled" fuel that is pushing the limits of the system to remain sealed, and hence the bubbles?

John
Minneapolis
 
V

velostuf

Veteran Member
Joined
Apr 7, 1999
Location
Minneapolis, MN
TDI
2009 Jetta Sportwagen TDI
I've come to the conclusion that my air-in-the-fuel-line and hard start problem was caused by fuel that gelled due to low temps. I had some biodiesel remaining in my tank- that, combined with local fuel retailers probably not switching over to winter blend soon enough in the season, probably resulted in my problem. For what it's worth, I also have a CAT 2 micron diesel filter system which may cause some wax crystals from making their way through?

I now have a good winter blend of fuel in my tank and the clear fuel line shows clear, (not cloudy) fuel in it. Starts fine.

John
 
mrGutWrench

mrGutWrench

Top Post Dawg
Joined
Aug 29, 2002
Location
Carrboro, NC
TDI
'03 Jetta Wagon, 5-speed, 563K Miles (July '23)
velostuf said:
I've come to the conclusion that my air-in-the-fuel-line and hard start problem was caused by fuel that gelled due to low temps. I had some biodiesel remaining in my tank- that, combined with local fuel retailers probably not switching over to winter blend soon enough in the season, probably resulted in my problem. For what it's worth, I also have a CAT 2 micron diesel filter system which may cause some wax crystals from making their way through?

I now have a good winter blend of fuel in my tank and the clear fuel line shows clear, (not cloudy) fuel in it. Starts fine.

John
Click to expand...
__. What Model Year do you have, John? Is it an A4? I'm guessing you know about the problem with the pickup in the fuel tank on early models -- that it will freeze up and clog from ice crystals, even if the fuel itself doesn't gel. Although it appears that there's a good chance that you did have at least the beginnings of a gelling problem. I guess the issue of biodiesel clouds the whole situation here (sorry, just couldn't resist).

__. But if I lived in a "hard cold" place, I'd definitely deal with the fuel pickup. There's the option of going to the "H-suffix" pickup or drilling out the existing one.
'
 
B

BioDiesel

Veteran Member
Joined
Oct 29, 2001
Location
CT
TDI
'98 Jetta
I am getting air in my fuel line right after shutting the car off.
Click to expand...
Just a guess: Kerosene in your winterized blend heated to > 160*F and boiling off bubbles? Similar to a gas vapor lock situation.
 
mrGutWrench

mrGutWrench

Top Post Dawg
Joined
Aug 29, 2002
Location
Carrboro, NC
TDI
'03 Jetta Wagon, 5-speed, 563K Miles (July '23)
2TDIguy said:
mrGutWrench , does the fuel pickup issue apply to the B4 also?
Click to expand...
__. I'm not sure, I keep my emphasis on A4 discussions, but since it's only on some A4's, my guess is that it doesn't cross over to B4's. But maybe there's some way that it works out the same way. Maybe some B4 expert can give you a good answer.
'
 
L

l1o9s7t6

Veteran Member
Joined
Apr 11, 2005
Location
Alaska
TDI
jetta, sedan 2002 blue
velostuf said:
We've had a cold snap here for the last week, and I have had 3 problems. I too am seeing bubbles in the clear, (return?) line, and at the point when it has died and won't restart that clear line is empty. I got some starting fluid, and sprayed it into the flexible intake immediately after the MAF sensor, and this would get the motor running for 4-5 seconds. This was good because it apparently worked the fuel pump hard enough to get buttery fuel where it needed to go. Keep in mind that it took several iterations of spraying fluid and then re-attaching the hose before it would idle. After it starts, at least initially, the hose gets completely filled, but it's cloudy. REMEMBER, when the engine begins to run with the ether, it will probably rev up uncomfortably high, and THERE'S NOTHING YOU CAN DO ABOUT IT! You basically have a runaway engine at that point, (we have *compression* ignition engines). However this morning when the motor shut down 1 mile from home, I was able to watch the rev counter while it ran away, and it got to 5,ooo rpm, which was acceptable to me because the crankcase oil had a chance to warm up over the last mile, and presumably there was oil in the filter, so oil pressure was up enough to protect parts. When using the fluid, spray for 1-3 seconds, and no longer.

So, assuming that my problems are caused by gelling and not an air leak, it's happening either because there's enough residual biodiesel in my fuel that it has effectively raised the gel point to above 10 degrees F., or my CAT 2 micron fuel filter is too fine for cold, but not solid, fuel to flow through. OR, it's a combo of both.

FYI, I was running 50% biodiesel in the tank before this. My estimate is on a percentage basis, there was about 10% biodiesel in my fuel when I had my first clog, and the temp was maybe 4 degrees F.

John
Minneapolis
Click to expand...
FYI: If not done propberly either in a diesel will have fun when it removes the head from the engine. I have see it happen, blows the head off, bends rods. interesting at the least.
 
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