I read that a possible cause of air infiltration into the fuel system if via the return fuel line that goes to the top of the fuel filter. it was suggested that this line not be used. My question is this: Won't there be fuel leaking from either the filter housing or from the injector that the hose was supposed to be connected to? Sorry, but I don't understand how you would do away with this hose. Please help me to understand how to do this.

 

There would be only 4-6 psi in the filter side and 1-3 psi on the return line side. If you cut the hose about 2" from each end and plug the hoses, it should stop the air leak. You could replace the check valve in the filter or fix the air leak into the return lines that's going back to the filter. Visit the site below......


http://www.intellidog.com/dieselmann/idi.htm


http://www.intellidog.com/dieselmann/idiparts.htm

 

I'm not really sure what you mean by cutting off both ends of the hose because I'm not sure which hose I'm looking at. There is a hose that comes off of the fuel filter flange where the filter screws into a threaded bolt looking thing (kinda like the oil filter mount). This hose is toward the back of the mount on top. Is that where this hose is? So I'd leave about 2 inches of the hose attached to the barb on one side, and another 2 inches of hose on the other end and plug them both up? What do I use to plug them with? If I had a picture of this hose to look at it might be easier for me to visualize this procedure. Thanks for the information.

 

Hareone54,
Welcome to FTE and the IDI diesel forum.

If you filter setup is still stock you should have a steel line from the lift pump to the fuel filter housing. That should be the one on the front.
Then out the back you should have another steel line that goes to the injection pump.
The other line is the rubber return line.

 

I have read many threads on plugging the fuel bypass line from the filter to the return line and have always resisted this. This line has a two-fold purpose:

1, Ensure a contiuous minimum recirculation of fuel back to the tanks. (Note the fitting on the filter body is an orifice that regulates the fuel return flow)

2, Allows any air in the fiter to return directly to the tanks rather than having to go thru the IP and injectors.

If you got a lot of air in the filter and have this line plugged you would have to bleed at the schraeder valve as cranking would take too long to clear the filter and lines thru the IP and injectors. (Say you accidentally ran one tank too low and got a blob of air before switching to the other tank)

Another drawback about plugging this line is that Fuel Lift pumps life "could possibly" be shortened as the flow at idle is very low putting more wear and tear on the pump.

Lastly, I daily drive thru a very nasty tunnel and there if no way to get out of the truck to clear air from the schraeder valve if the truck were to ever stall in the tunnel. You just pray nobody rear-ends you until the tow-truck shows up to tow you out. I have seen too many people get hurt and die. With the fuel return line connected, there is a hope I would be able clear any air to re-start the truck from inside the cab and get going again. Without the line, probably not a chance in hell.

On my 91' I also have an inline electric fuel pump on a push button. I used it last weekend after I replaced the factory filter with the new racor unit. The electric pump cleared all the air the new filter and the truck fired on the first compression stroke as the air just cleared itself back to the tanks.

Seb....

Personnally, I think it is better to fix the air leaks and don't plug the return line from the filter.

 

I do appreciate your opinion on this as I am a relative newbie when it comes to diesel wrenching. I just have read alot of posts about plugging up this return hose, but I think that if the hose is not cracked then there shouldn't be air infiltration.

 

I realize that plugging this hose seems to have become common practice and when all things go well it is probably a good idea as long as you realize what you are potentially giving up by doing so.

 

good morning All,
I just had my IP rebuilt and installed new injectors getting ready for WVO. I asked the Standadyne shop that did my work what that return to filter line was for and If I needed it.
The answere I got was, it's purpose is: if the return to tank line gets restricted some how this is the alternate fuel return, so that the injecters don't have a positive back pressure (atleast not over 7 lbs.). They even supplied me with a new cap for that injector that had a single hose barb, and also a rubber cap to close off the fitting on the filter hosing, I have run over 3000 miles since deleteing this line. (500 on WVO). I was also told that the normal return to tank volume on a to spec. operating system was approxamatly 12oz per minute. as your injectors become worn they start returning more fuel to the return line. but should never be more than what the 1/4 to 5/16 lines can handel.
I hope this Helps

Sop-Pup

 

my return line to filter housing has been capped off since 1991. there is a ford technical service bullitin regarding hard cold starts that recomended capping off that line that was issued in september of 1988. the tsb number is 88209, 89189 was issued in september of 89.there is also#902611, but i am not sure if it is about the return line or not.

you find the tsb's at www.alldata.com

 

Goes to show you how sometimes the left hand does not know what the right hand is doing.

If the TSB's were issued in 89' then why did the factory keep putting on the lines on new trucks right upto when Ford switched to the PSD in 94'. I know my 93' has one.

All I can say is good luck starting the truck after you sucked air from a tank because you forgot to switch tanks going down a steep hill and now can't pull over to clear the air at the schraeder valve or as I said earlier stall in a tunnel and can't get to the schraeder valve because you would get run down the second you step out of the truck.

I realize this probably happens to maybe 1 in 10,000 but with my luck all the hills I climb and all the tunnel I go thru I am bound to run into it again some day. PS I already had the truck stall once on me gearing down an 8% grade because of air and a tank that was down to about 1/8 of a tank. It is not a nice experience let me tell ya. I am keeping my return lines just in case. Yes I got the truck re-started in time, that is why I am still here writting about it.

Seb........

 

Hello guys.

A good fuel return line kit is ~$30. Should be good for >100,000 miles unless you are in severe heat conditions. Kit includes hose, clamps, tees, injector orings and copper washers. Easy to install and once done you should not have any air problems at the injectors or in the return lines.

Then no worries of mod affecting anything else.

 

Ok, so on this topic. I have a 7.3L turbo with the 1/4" lines that has the ball and spring check vavle at the fuel filter. I hear that it goes bad. I am just a dumb A## electrician, but I have had the ball and spring out and just don't see how it could fail. I did stretch the spring a little thinking this would help it seal if, by chance it wasn't already. Am I misguided? Should I replace it? I have been chasing what I believe to be an air intrusion problem?

 

Hey guys ; When should those return lines be replaced ? I have roughly133k on my 1993 7.3 non-turbo, They are still the factory hoses , I assume, because they're painted grey. I'm still trying to figure out why it smokes (white)some times at idle and, at approx. 2000 rpm reguardless if I'm doing 55 on highway, or in park and bringing it up to that rpm. I did the fuel additive thing for two tanks, it's not eating antifreeze. t-stat is new, albeit a 195 instead of factory 192 (which I'm going to install, AGAIN, thats what I get for listening to hack so-called auto parts stores.) Reguardless, when it smokes, it has a what feels like a skip/stumble, below that rpm it dosen't smoke/skip or its so little i can't see/notice it. I had done a power balance test and when each line is cracked open, it drops rpm for each cylinder,it seems respectively. I haven't checked fuel preasure yet, I 'm having a tough time finding a gauge with the right schrader valve, that won't cost me an arm and a leg. Would a tire guage work, it appears to be the right size ? And the preasure is only suppose to be 12 psi. according to my Haynes book. Thanks Dave L.

 

I'm not a diesel mech. Actually I'm still fairly new at diesels, but cutting the return line and plugging it seems to be a bandaide for the problem, instead of the correct repair. Reading some of the replys it seems that plugging the return line is the apropriate measure for a specific problem but not a universal cure all ?? It can deffinately be confusing..... to me anyway. Good Luck Dave

 

cutting and plugging the line is a band-aid. the proper way to do it according to ford is to remove the line, and install a pipe plug in the filter housing. what you are describing sounds more like an injector pump that is starting to fail. in the ambulance fleet of rural metro, they got about 100k miles before the pump needed to be replaced. i did mine at 80k because the Governor started to act up. my old 89 went 135k before the pump went.