Engine/Transmission (1994 - 1998) fuel pours out

[djbasl]

Hello all, I am new to this forum, but would like to get some advise regarding a fuel leak on a 94' 5.9L. The engine runs fine, but while it's running, fuel pours out from up under the intake against the head over approximately the cylinder number 2. With the induction tube and manifold pulled off I can see there is an allen keyed plug going in the head right where it appears the fuel is pouring out (not out of, but well above). It doesn't look like the fuel is being deflected off the head from a fuel line right there but simply pouring out, but I could be wrong as it's hard to see being it's pouring out from so far up under there. I hope this makes sense. Any help is greatly appreciated.

 

[LandShark]

Fuel return line often goes bad and is in this area. However, usual failure mode is not to leak diesel fuel, but to allow air in the line and cause hard starting when cold.

 

[Fire god]

The fuel return line is a pressure line, as opposed to suction lines. Faulty Pressure lines leak will leak while pressurized, conversely, Suction lines will introduce air. Fuel leak at return line equals bad line. Replace with OEM, or use LarryB fuel return line to frame kit.

 

[BigPapa]

Mine leaked fuel profusely when it failed. I was in the drive through at the local McDonalds when the fellow behind me came to my truck and told me I was leaking a LOT of liquid under my truck. My experience is it will leak fuel when running and suck air when shut off causing the fuel pump to lose prime and cause hard starting.

I replaced and re-routed my return line 15 years ago with some hose, 4 clamps, and basic tools in @ 30 minutes and she's still going strong. I took the return line loose at the pump (where the overflow valve is) and broke it off at the bracket by pushing it back and forth, then cut it off square and cleaned it up. Then I flipped it over and slid the new hose on and put two clamps on it. Then got under the truck and reached up as far as I could and cut the rubber line. Then I disconnected the steel line at the fitting, cut the steel line close to where the original rubber hose is connected, cleaned off the burrs, slid the new hose on and double clamped that end. Then reconnect the steel lines and drive on. I've seen many recommend only using marine-grade diesel fuel hose and it may be that I just got lucky and got some by accident, but I bought some generic fuel hose at O'Reilly when I did mine and it's still going.



I've also had the fuel filter drain valve/water sensor give up on me twice, so you may want to check it out. I now run a fuel filter that doesn't have the WIF sensor or drain valve.

 

[djbasl]

Ya, I'll have to take another look. I may be able to put a mirror down next to the head under the intake in order to see where the fuel is coming from. I have started the truck probably 5 or six times trying to locate the issue with no priming problem. Based on this, I tend to doubt it's a return (suction line) breach. In order for me to feel what appears to be the origin of the leak I would have to remove the intake for sure and it looks as thought I would have to possibly remove the head? I can't see through the grime if I can remove anything on the driver side of the motor just back from the Lift pump around the cyl 2 or 3 area in order to fit my finger's down under beside the block. Even if I remove the lift pump it would still be pretty tight since it's closer to the fire wall. I was trying to avoid this if possible.

 

[fest3er]

If it's right under the lip near the top, it is the fuel return line. Failed rubber return lines, typically accessed by removing the fuel filter bracket, are a common problem (mine lasted about 9 years). Failed metal lines are less common, but they can fail, especially where road salt corrodes them.

Fuel is pushed into the return line from the injection pump and from the fuel return lines from the injectors. It may be low pressure, but it is still under pressure and can spew a lot of fuel. Enough fuel can be dumped to cause the rear wheels to lose traction on wet roads.

 

[Fire god]

Be sure to note the return line is not a suction line.