| Author | Message | ||
| Austin Scott Davis (Zimtok)
Registered Member Username: Zimtok Post Number: 430 Registered: 9-2006 Posted From: 209.156.24.114  Rating: N/A |
Lately I have had a slight loss of power so I set about this last weekend to check the easy stuff... I pulled the return fuel line and it was coming out like the the fuel does at the gas station when you fill up the tank. Kind of foamy looking... My thought is I'm sucking in air into the fuel line. I want to narrow down where it is so I pull the fuel line from the bulkhead and put it down into a fuel can. I still get foamy fuel so I figure it is coming from one of the OLD lines in the engine bay. I replace all of the fuel lines in the engine bay just to be sure to get it. That does not resolve the issue I still have foamy fuel on the return line. I'm stumped... I get some clear tubing and put in on the inlet and outlet side of the fuel pump. I draw fuel directly from a fuel can not through any of the original fuel lines. There is no air bubbles showing in the fuel being pulled out of the can to the pump and no air in the line after the fuel pump into the secondary fuel filter. BUT there is still foamy fuel coming out of the fuel return line... What have I missed???? Can air be getting in on the pressure side? Does the fuel coming out of the return line always look foamy? . | ||
| Jim Wilke (Jim Bob) (Pd41044039)
Registered Member Username: Pd41044039 Post Number: 523 Registered: 2-2001 Posted From: 184.0.3.170 Rating: N/A |
There normally might be a few bubbles in the flow. But if it's got that much air, most likely you have one or more injector nozzles not sealing completely. When the piston comes up it forces some compression up into the injector where it gets carried off to the fuel tank via the return line. Some of this air could be getting up into the supply lines and getting shared with other injectors though if you lose only the output of one cylinder you are down by 16.7% which you will indeed notice! You could remove the injectors and have them tested/serviced. That will mean setting the valves and "running the rack", a basic tune up as part of the R & R. | ||
| Bill Gerrie (Bill_gerrie)
Registered Member Username: Bill_gerrie Post Number: 369 Registered: 3-2006 Posted From: 216.198.139.38  Rating: N/A |
Austin Replace the rubber "O" ring gaskets on the fuel filters. Also check the fiber gasket on the center bolt. Make sure you don't let the cannisters turn if you have the cannister type when you are tightening the bolt on top. The top lip on the cannisters will cut the gaskets. As Jim says you might get a small amount of bubbles but not much in the return line. If you have the spin on type filters how old are they? Rubber seal might have deteriated. Hope this helps you. Bill | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 1242 Registered: 10-2006 Posted From: 99.156.68.151  Rating: N/A |
A refrigeration "armored sight glass" costs under $20. Purchase one with the same size as a fuel fitting M on one end F on the other and it installs in a min. You will get to SEE any and all bubbles in the fuel supply , and when you fix the air leak, you will see NO bubbles. FF | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 1190 Registered: 11-2005 Posted From: 173.202.0.177  Rating: N/A |
I think it may be a waste of time to investigate the fuel supply system. If you have any air in the supply line you will notice it by engine hesitation under power or hard starting. I don't think you have anything happening in the supply line having had that problem a few times, once with a leaking check valve at the inlet to the primary filter and just lately with a loose primary filter bolt. Please let us know what you find out, we 4104 owners need to know these things!! | ||
| Jim Wilke (Jim Bob) (Pd41044039)
Registered Member Username: Pd41044039 Post Number: 527 Registered: 2-2001 Posted From: 184.0.3.170 Rating: N/A |
Well he already said he had a loss of power. And eliminated the rest of the lines and pickup by putting a hose in a fuel can at the engine. Good thought about the primary filter though if the secondary has a leak there will be visible fuel as it is pressurized by the pump. Also check for two gaskets at the primary filter. I have found that as a cause of leak before, especially on cannister filters. Fred's sight glass could be rigged into a sacrificial injecter return jumper line to indicate which if any injectors has air coming from it back into the return galley. You'd have to try it on one at a time but that's better than pulling all injectors, and if all show air equally, there is a problem upstream. | ||
| L James Jones Jr (Jamo)
Registered Member Username: Jamo Post Number: 150 Registered: 11-2007 Posted From: 24.58.68.149  Rating: N/A |
I'm still wondering how you felt a "slight loss of power" in an '04. I still laugh about that line that someone said here(?) years ago when asked an acceleration question concerning a 4104. The response was "I gave up acceleration when I bought my bus". Whoever said it, thanks. I use it often... | ||
| Austin Scott Davis (Zimtok)
Registered Member Username: Zimtok Post Number: 431 Registered: 9-2006 Posted From: 209.156.24.114 Rating: N/A |
I never thought of compressed cylinder air being pushed back into an injector tip.... Just after we got the bus I had to replace the injector nut seals because they were leaking fuel. The seals were very brittle and several of them just broke apart. I have been thinking about replacing the injectors because if the seals were that brittle then it would be safe to assume that other components in the injector could be programmatic already if not very soon. My loss of power is noticeable because I travel the same roads every week. I know that when I pull away from a specific stop light/sign when the bus should be up to speed to shift to the next gear. If it is taking longer to get up to speed I then shift later then I am used to. Thus I have a loss of power. I have eliminated the chance that air is getting in from the suction side of the fuel pump because I went directly from the inlet of the fuel pump into a fuel can. Using a clear tube I can plainly see that there are no air bubbles in the fuel prior to or after the fuel pump. Anything after the fuel pump is under pressure so I should see a fuel leak if I have a bad hose/fitting. The only way to get air into the fuel on the pressure side is if the air is at a higher pressure then the fuel. Logically it would point to the injectors as was mentioned by Jim.... . (Message edited by zimtok on July 21, 2010) | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1933 Registered: 10-2003 Posted From: 71.58.71.157  Rating: N/A |
So while you use this fuel can, do you submerse your (temporary) return line into a can with fuel over the end of line and look for bubbles coming out? Did you also do a pressure check and you may have a fuel pump with a bad seal. | ||
| Jack Conrad (Jackconrad)
Registered Member Username: Jackconrad Post Number: 1313 Registered: 12-2000 Posted From: 75.246.241.186  Rating: N/A |
Mi9ght want to pull the valve cover and look for any clean jumper line fittings(leaking jumper lines/fittings). Jack | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 1191 Registered: 11-2005 Posted From: 173.202.38.56 Rating: N/A |
I wasn't clear on my comment about power loss. What I had when my original primary filter bolt was loose was the engine completely shutting off for just a split second. Bear in mind that mine is the original stacked disk filter, not a spin-on. As far as I know it has only one gasket but it is really a tight fit. Every time I have had a steady loss of power it has been a clogged fuel filter, just my experience, not the final word. I'm ignoring those smart comments about the built-in 4104 power loss!! | ||
| Austin Scott Davis (Zimtok)
Registered Member Username: Zimtok Post Number: 432 Registered: 9-2006 Posted From: 209.156.24.114 Rating: N/A |
John, I took the return line off and put a clear line on that as well. I then tried it with the line returning fuel to the tank, and also to the fuel can I was drawing from. In both cases there was a steady stream of foamy fuel going through the clear return line. Keep in mind that the clear lines I installed on the fuel pump did not show any sign of air bubbles. I had thought that the fuel pump might be drawing air through a seal or gasket. That was why I installed clear lines on both the inlet and output side of the fuel pump. But with no air bubbles in either of the clear lines at the fuel pump proved that the pump was not drawing in air... I don't have a fuel pressure gauge so I don't know what the fuel pressure is. Jack, I did have the valve cover off looking for leaks and other reasons for the power loss. I didn't see anything. . | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1934 Registered: 10-2003 Posted From: 71.58.71.157 Rating: N/A |
Did you have someone floor the throttle pedal up front and check for full travel at the rear? I know this isn't the problem at present but thought of it anyway. | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 1193 Registered: 11-2005 Posted From: 173.202.16.138 Rating: N/A |
This one is really making me curious?? How can air in the return line affect power?? | ||
| Jim Wilke (Jim Bob) (Pd41044039)
Registered Member Username: Pd41044039 Post Number: 530 Registered: 2-2001 Posted From: 184.0.3.170 Rating: N/A |
Gus, IF one or more injector tips is allowing compression up into the injector then that injector will be trying to inject a mixture of fuel and air. The air does compress and so you don't get a full measure of fuel. And if by chance some of the compression is able to get back into the fuel supply gallery then any downstream injectors will get air mixed in the incoming fuel. Injector tips are a spring loaded "pop off" valve and if the fuel has air in it, the air compresses and the valve does not lift off it's seat = less or no fuel from an injector with air in fuel. If he has one leaky injector which injects little or no fuel, he has 16% less power (100% / 6). I just completed a trip with one bad injector and I sure could notice the difference. My poor old '04 could hardly get up the hills and the hills I normally take in second, I had to drop to first. Let me tell you, a 4 mile hill is REALLY long when done in screamin' first! Plus the knowledge that if it can't stay in first, you will be callin a tow truck. | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 1195 Registered: 11-2005 Posted From: 173.202.14.89 Rating: N/A |
Jim, Thanks, I couldn't understand what harm air in the return line would do. So, as I understand this, it isn't a problem if air is in the return-it is what causes it to be there that is the problem. | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1937 Registered: 10-2003 Posted From: 71.58.71.157 Rating: N/A |
If you need to pull the injectors, good time to think about an upgrade, esp if you have only 60.s. Next time I do mine, I'm going to go with some newer version with finer spray pattern for more complete combustion, like the 92 series use. | ||
| Austin Scott Davis (Zimtok)
Registered Member Username: Zimtok Post Number: 433 Registered: 9-2006 Posted From: 209.156.24.114 Rating: N/A |
The injectors I have are the N65 Brown Tag. I have a Truck Pro store locally here in Memphis that can get them for $67 each with my cores. ($30 core charge each) So about $640 before I return the cores, $460 once I do. It looks like I'll be doing a tune-up and running the rack.... I've read the instructions over a few times and it seems straight forward, just tedious. Does anyone have any "look out for these" or other suggestions before I do this? . | ||
| JC Alacoque (Jc_alacoque)
Registered Member Username: Jc_alacoque Post Number: 91 Registered: 7-2006 Posted From: 207.34.166.7 Rating: N/A |
Tune up and running the rack is not hard to do. Just do what the book says. And if it is not quite right, you can easily do it again. You get better at it every time. You might need "bent" feeler gauges to do the valves. If you don't have the right DD tool to time the injectors, use the tail of a micrometer. The hardest part on my Courier 96 was reaching the back of the engine under the floor of the bedroom. JC |