2nd Gen Non-Engine/Transmission Possible Fuel Leak, Drop in MPG

[BlameCandida]

I had a problem a few weeks back, where my truck would crank but not fire. This is a 1998 12v CTD with the manual transmission. Before I had any issues, I was getting 16-17mpg. The first fill-up after the problem started, I was at 13mpg, and have been at a steady 15mpg in the month after that.



Now when I start the truck for the first time each day, I have to give it a few seconds on the throttle for the engine to fire.



I took some time to play under the truck today, and noticed the drivers side frame under the cab was wet and smelled like diesel. There has also been a bigger drip spot under the cab when I park.



I'm assuming there is either a busted fuel line, or a loose connection between two lines. What is my next step to find out what is wrong and fix the problem?

 

[Crowhurst]

The rubber fuel return line behind the injection pump and fuel filter is a common culprit. With the engine idling you should be able to detect the leak. Otherwise, JoeG's Fuel system write-up details the various fuel leak causes and their solutions. You can PM JoeG for this to be sent via email. It is excellent.

Nick.

 

[BlameCandida]

I ordered the replacement hoses from LarryB, and got down under my truck to replace them. Once I got down there, I found the actual source of the leak. I have a early '98 12v, and my fuel return line seems to be in two sections. The hose I bought replaces the section closer to the fuel tank, which runs along the frame from a metal tube up to another metal tube.

The hose that is leaking is the return hose section forward of that. It is clamped to the fuel pump and is spraying fuel from pinholes. The fuel is then collecting on a hose clamp, and dripping down. I cannot see where this hose originates. I have Joe G's guide, and I looked at pg 39 of issue 44, and am guessing it attaches to a banjo bolt on the engine side of the pump.

How do I replace this hose? Do I need to take of the fuel filter canister, and/or the entire pump? I have the factory service manual, but I am lost on how to actually access the end of this hose.

 

[Missouri Mule]

The return fuel and supply line shoud connect at half way up the bell houisng or frame to metal lines coming from tank.



The return fuel line(rubber) connects to a metal line coming out of the back side of the p17100 injection pump behind the intake mainfold. Removing the fuel filter will give you access to the connector but it will still will be hard to get to.



The supply line attaches to a metal line near the back of the engine. The metal line goes to the Prefilter/fuel heater assembly. Then a rubber line goe from the prefilter/heater to the lift pump.

 

[Crowhurst]

This fuel return line is in a ridiculously difficult area to access, in particular the section of rubber line which leads from behind the fuel injection pump, behind the fuel filter to a short steel section. The whole problem can be avoided by completely re-routeing a long length of the rubber marine hose from the overflow valve on the back of the fuel injection pump, outside all the wires, tubes, filter, etc, to meet the metal tube on the frame that leads to the tank. I used a tube cutter to chop this metal line, and fitted a banjo with a hose barb to the overflow valve. Others have just chopped the metal line from the overflow valve, and simply bent it up to fit the rubber hose. Stainless hose clamps complete the job. You can leave the old pipe in place, or tear it out where you can. If you want the part number for the banjo then the following link gives the supplier details:

https://www.turbodieselregister.com...-where-get-barbed-banjo-return-fuel-hose.html

This is a very good modification, IMHO.

Nick.