Return Line Routing

[hadley000]

I've been looking up return line routing for a 94 Turbo and they have crossovers in either the 3 to 4 or from the 5 to 6 cylinder area. My truck doesn't have a crossover. I suspect it was removed when someone before me changed the return lines and caps. Right now it looks like the passenger side bank runs back to the filter housing and is independent of the drivers side. Is the crossover required? Could it be the cause of the problems with recent surging and loss of power over 45 mph?

Edited to add: It looks like the filter return isn't a return. The check ball wouldn't allow fuel to go back into the filter unless it's damaged and it's not because it closes when I blow in it. So, where was the extra fuel going? I didn't have any leaks.

 

[snicklas]

Can you post a picture of your current setup?

Both sides need to return to the tank. There are a few ways to accomplish this.

Here are a couple of examples from Mel.

You must be registered for see images

You must be registered for see images

The line to re return system from the filter is an air bleed line for the filter to the return system. It isn't a return per-se, but it does flow into the returns like the other pieces.

You can choose any routing you like, just as long as all 8 injectors, the fuel filter, and the Injection Pump all have a connection to the return system.

You could take the really long route and start at #7 (passenger side. closest to the firewall), then 5, 3, 1, filter, IP, 2,4,6,8 and back to the tanks. As long as there are not open ports (there is a small manifold on the drivers side near the firewall to "collect" the various returns from the engine and make them one to go back to the tank). Or you can run it like either of the diagrams above. I do recommend making the crossover somewhere in front of the turbo, trying to route it under the turbo would be extremely difficult.

I am going to be replacing the returns on my 88 with an early Hypermax Turbo, and will do something similar to the first diagram. Keeps the heat away from the rubber lines, and I don't have to try and squeeze my huge hands under the turbo.

 

[hadley000]

Can you post a picture of your current setup?

Both sides need to return to the tank. There are a few ways to accomplish this.

Here are a couple of examples from Mel.

You must be registered for see images

You must be registered for see images

The line to re return system from the filter is an air bleed line for the filter to the return system. It isn't a return per-se, but it does flow into the returns like the other pieces.

You can choose any routing you like, just as long as all 8 injectors, the fuel filter, and the Injection Pump all have a connection to the return system.

You could take the really long route and start at #7 (passenger side. closest to the firewall), then 5, 3, 1, filter, IP, 2,4,6,8 and back to the tanks. As long as there are not open ports (there is a small manifold on the drivers side near the firewall to "collect" the various returns from the engine and make them one to go back to the tank). Or you can run it like either of the diagrams above. I do recommend making the crossover somewhere in front of the turbo, trying to route it under the turbo would be extremely difficult.

I am going to be replacing the returns on my 88 with an early Hypermax Turbo, and will do something similar to the first diagram. Keeps the heat away from the rubber lines, and I don't have to try and squeeze my huge hands under the turbo.

Thanks for the diagrams, that helps a lot. I'll try to get a pic up tomorrow. Basically the passenger side is connected together and only runs to the filter housing. The IP and driver's side run to the tank. I hadn't noticed it before tonight because I'm trying to figure out the surging and lack of fuel, and I think this may be a huge part of that. The air from a leaky olive at the IP had nowhere to go on the passenger side and filled the filter half full of air. I've only driven this truck about 600 miles since owning it.

 

[Macrobb]

So... while not recommended at all, the reason your setup works is because the "check valve" in the filter head return line is long gone at this point. So, you guessed it, fuel is going backwards and into the filter there(remember: the fuel filter is only at <7 PSI; the injector O-rings should be able to handle that.).
It works because the injectors don't return much fuel at all if they are in decent shape; a few drops here and there(at least on my test motor).

Your surging and loss of power is due to air in the fuel... Lots of it. Check the fuel /supply/ side, mainly prior to the lift pump(where there is a vacuum that will draw in air).
First thing to check is the "loop" right there at the lift pump. That likes to go.

The lift pump is also a cheap replacement item; might as well do it while you are replacing that loop.

 

[hadley000]

So... while not recommended at all, the reason your setup works is because the "check valve" in the filter head return line is long gone at this point. So, you guessed it, fuel is going backwards and into the filter there(remember: the fuel filter is only at <7 PSI; the injector O-rings should be able to handle that.).
It works because the injectors don't return much fuel at all if they are in decent shape; a few drops here and there(at least on my test motor).

Your surging and loss of power is due to air in the fuel... Lots of it. Check the fuel /supply/ side, mainly prior to the lift pump(where there is a vacuum that will draw in air).
First thing to check is the "loop" right there at the lift pump. That likes to go.

The lift pump is also a cheap replacement item; might as well do it while you are replacing that loop.

I removed the filter housing and the check valve works and is actually in great shape. The fuel system is new apart from the injector return lines and sleeves ,which leaked I found out. I'm going to replace the return lines and fix the return issues. I'm also going to replace the filter to IP line with double flare fittings and get rid of the fuel sleeves all together. I hope this fixes the problem. Thanks for the help, I'll go over everything you suggested one more time to make sure.

 

[Macrobb]

I'm also going to replace the filter to IP line with double flare fittings and get rid of the fuel sleeves all together. I hope this fixes the problem. Thanks for the help, I'll go over everything you suggested one more time to make sure.

Be aware that it won't fix the problem unless you have a leak on the /suction/ side of the lift pump. Otherwise, you'll get fuel leaking out, not air leaking in.

I'm not saying it's a bad idea; go for it. Just... don't expect it to fix the problem. Basically, anything past the lift pump(not including the lift pump, which *could* be leaking on the suction side) won't cause your issue.

You can get other issues, like the start-die-crank-crank-crank-start pattern of air intrusion due to leaks in the lines past the lift pump, but your issue of air getting in when running? Not that.

It's realistically going to be either the lift pump, loop of hose going to the lift pump, one of the lines going back to the tank, the switchover valve, or the tank pickup.

You can actually test this out easily enough - just rig up a jerry can of diesel to the front bumper and run a hose to the inlet of the lift pump(note: cut a V into the end of the fuel line in your jerry can).

That will bypass all the "suction" stuff; if it fixes your problem, well, you know where to look.

 

[icanfixall]

Welcome to the forum.As already posted.. You need both banks return to the tanks.How it gets there is really not important but MUST return both sides someone. Pics sure would help and please know this..We can use either the large or small return line kit but NEVER try to run both on the same engine. Your sure to have leaks.

 

[hadley000]

I'm pretty sure I've got the problems fixed now. Here's a list of things I had to, or thought needed to be done.

1. new caps, orings, and return lines with all returning to the tank this time
2. the fuel heater was replaced with a pipe plug
3. the lift pump needed to be replaced, I had already put a new one in and it failed in 600 miles, no fuel in the crankcase thankfully
4. new hard lines going from the lift pump to the filter with a flare at the filter
5. new one piece filter, the bottom of the two piece looked pitted and didn't want to chance it
6. new fuel sleeves at the filter and IP, I didn't want to go through the hassle of changing over to flares in such a tight area

Now she starts even better than before. There is no more surging. The slightly rough idle is gone. It seems to have 50hp more now that it's getting all the fuel it needs. I took it up the steepest hill I know of and she climbed it no problem and without any stumble. Hopefully this fixed the problems for good. With more snow on the way I needed it back up and running, and it is.

Thanks for all your help.

Edited to add: I also noticed it doesn't stumble when I stab the throttle at idle. Sometimes it would almost stall but didn't. Now it doesn't do any of that, it just settles back down without stumbling.