Return line question

[Rupert8]

Thanks so much. Perfect. I found some at Russ Repair and just ordered them, two different sizes. I'll just replace the one at the back of the engine since that is really wobbly. And go from there....

 

[catbird7]

install one way check valve in line prior to fuel filter solved a lot of my issues.

 

[IDIBRONCO]

If I understand correctly, the nut being loose will potentially affect the fuel system.

Correct.

I know it's a band-aid but if I can't find the leak, would installing an electric fuel pump at least bypass the problem - or would I still end up with the fuel filter half full of air?

No it won't bypass the problem. The problem isn't so much the air that's getting into the filter. The problem is that since the nut at the back of the hard return line is loose, it's not sealing. Since it's not sealing properly, all of the fuel is allowed to drain out of your return system all the way back to the highest point, which is your fuel filter. Hence the name "fuel drain back". Once the fuel's gone, then air can take it's place. Since the fuel is draining away from the filter, there's probably a small siphon action taking place which will draw some of the fuel out of your filter as well. Doing the #1 injector-to-fuel filter return line delete and replacing the bad olive should take care of the issue. I believe that you can completely remove the hard return line since there's a nut at each end. You'll have to fish it out from under the steel injector lines but that will let you work on the olives under each nut easier. They are both 3/8" olives, the bigger of the two sizes.

 

[WrenchWhore]

Thanks. Regarding the return line to the fuel filter, just cap that at each end? Any chance of air then making its way through the injection pump? That wouldn't be good. Or building pressure elsewhere?

I took my plastic return line cap (the one that goes into the filter head) and JB welded it shut on one side. 7.3 filter heads I just plug the hole with a pipe plug. If it's earlier 6.9 I just get the russ repair hardline delete kit which got rid of that extra port on the feed line that goes to IP. As far as pressure buildup goes no. It's such a low flow return it can't build up pressure unless it was blocked by a foreign object. Now if you live it freezing temps I could see this possibly causing issues but if you have antigel juice or "winter blend" fuel you should be ok. 7.3's have bigger return lines so this is probably no issue for them but 6.9's are smaller which "could" possibly give issues in freezing temps. Just my opinion and this opinion hasn't been tested...

 

[Old Goat]

Thanks. Regarding the return line to the fuel filter, just cap that at each end? Any chance of air then making its way through the injection pump? That wouldn't be good. Or building pressure elsewhere?

I eliminated the line from the Filter to the return line cap several years ago, and have never had a problem with air.

There was a TSB from Ford quite a few years ago to eliminate that hose as there had been problems with it.

You can replace the Hard Line from the Lift Pump to the Filter with rubber hose. Just need a couple Brass barb fittings on ea end.
3/8" hose.

The Hard Line from Filter to Injection Pump can be replaced with rubber hose also.

Russ Repair has the parts if you want to go that direction.
If you use Push lock hose, do not use hose clamps.

Fuel system components - Page 1 - Russ Repair

russrepair.com

Goat

 

[Rupert8]

Correct.

No it won't bypass the problem. The problem isn't so much the air that's getting into the filter. The problem is that since the nut at the back of the hard return line is loose, it's not sealing. Since it's not sealing properly, all of the fuel is allowed to drain out of your return system all the way back to the highest point, which is your fuel filter. Hence the name "fuel drain back". Once the fuel's gone, then air can take it's place. Since the fuel is draining away from the filter, there's probably a small siphon action taking place which will draw some of the fuel out of your filter as well. Doing the #1 injector-to-fuel filter return line delete and replacing the bad olive should take care of the issue. I believe that you can completely remove the hard return line since there's a nut at each end. You'll have to fish it out from under the steel injector lines but that will let you work on the olives under each nut easier. They are both 3/8" olives, the bigger of the two sizes.

Golden. Thanks for the clarity. Is there any way to replace that steel line and fitting with rubber hose? Wondering if heat from the engine is an issue for rubber hose, though, given where it's located.

I eliminated the line from the Filter to the return line cap several years ago, and have never had a problem with air.

There was a TSB from Ford quite a few years ago to eliminate that hose as there had been problems with it.

You can replace the Hard Line from the Lift Pump to the Filter with rubber hose. Just need a couple Brass barb fittings on ea end.
3/8" hose.

The Hard Line from Filter to Injection Pump can be replaced with rubber hose also.

Russ Repair has the parts if you want to go that direction.
If you use Push lock hose, do not use hose clamps.

Fuel system components - Page 1 - Russ Repair

russrepair.com

Goat

Aha! I was just looking at the hard line between the fuel filter and the injection pump today and wondering what my options were. From your message it seems like I can use 3/8 fuel hose for that as well - but do you know what size thread barbs I need to find?

And one closely-related question: The return line which runs down the back of the engine, on mine it looks like two pieces of rubber hose joined with a barb half-way then going into the nylon return line. And pretty cracked-looking rubber hose on the ends at that. When I replace the olive I'm going to run one piece of rubber hose - but how do I connect it to the nylon line without opening a whole can of worms.....?

Thanks to everyone for the answers, and sorry for all the questions now coming up. Despite the frustrations this engine is a fun project at the end of the day. Mostly.

 

[Rupert8]

Most redo the fitting, I've seen where a rusted fuel sending unit has a pin hole leak on top of it to cause air intrusion

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So this just eliminates the return line from the injection pump or am I missing something here? Just the back two injectors return to the tank?

 

[DaveBen]

All of the injectors are connected by the return line. It goes from one injector to another and to another and finally to the fuel tank. Look again and you will see this.

 

[IDIBRONCO]

Is there any way to replace that steel line and fitting with rubber hose? Wondering if heat from the engine is an issue for rubber hose, though, given where it's located.

I suppose that you could, but, to me anyway, it's kind of like trying to reinvent the wheel. Those are probably the original olives, they have worked for this long, new ones will probably last that long again. Just my opinion though.

but how do I connect it to the nylon line without opening a whole can of worms.....?

When I've replaced that return line, I just slid a new rubber hose over the nylon part and used a worm clamp to seal it to the nylon. There shouldn't ever much pressure at all so there's no need to tighten the clamp super tight. It's just to make sure that the fuel stays inside the line and doesn't leak out. Think of it this way, the returning fuel is basically falling back to the tank. That's the amount of pressure here.

 

[Rupert8]

All of the injectors are connected by the return line. It goes from one injector to another and to another and finally to the fuel tank. Look again and you will see this.

Thanks. Right - but mine also seems to have a steel line coming directly from the injection pump, which would appear to be eliminated in this setup unless I'm mistaken. Based on @IDIBRONCO, think I'll just leave it be. Makes sense.

 

[Rupert8]

I suppose that you could, but, to me anyway, it's kind of like trying to reinvent the wheel. Those are probably the original olives, they have worked for this long, new ones will probably last that long again. Just my opinion though.

When I've replaced that return line, I just slid a new rubber hose over the nylon part and used a worm clamp to seal it to the nylon. There shouldn't ever much pressure at all so there's no need to tighten the clamp super tight. It's just to make sure that the fuel stays inside the line and doesn't leak out. Think of it this way, the returning fuel is basically falling back to the tank. That's the amount of pressure here.

And again, thank you for the clear explanation. Getting it done as soon as I can.

 

[Kdo58]

Here is a diagram not the best.

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[Nero]

Here is a diagram I found, I used the turbo one, since I have a turbo.

I also did the filter to injector return line delete, so I used 2 dead end caps on the passenger side rail.

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[nelstomlinson]

Oof! $7+ per each for those olives!

KDO58's picture shows the steel return line that the older diesels had. Nero's drawing shows the newer version, which I am switching to.

An electric fuel pump won't fix air intrusion in the return lines, but the pump will re-prime the fuel system while you wait for the glow plugs, so that helps a lot. Since the parts store mechanical fuel pumps are garbage, don't last a full year of steady use, I've started switching to electric as mechanical fuel pumps fail. The Walbro FRB13 is still made in America, and priced accordingly.

 

[Rupert8]

I'm digging into finding the source of the air intrusion tomorrow, have the day off work. Thanks for all the replies so far. Really want to get this thing starting up better.....

What is the size and type of the fitting on the outlet side of the fuel pump? Does that require an olive as well? Looks like it but not sure what that type of fitting is called. The learning curve is steep, but fun - mostly..... I'm thinking hard about running a rubber line in place of the questionable-looking steel line with the heater component.

My understanding is tha the inlet fitting to the fuel filter head is 1/4", but can't figure out what size the fuel pump outlet is.

Thanks again.