Engine/Transmission (1994 - 1998) Finding fuel leaks

[Blakers]

I've been smelling a slight fuel oil smell when I shut down my truck. Today I looker under her and found a drop hanging on one of the oil pan bolts under the fuel filter. The side of the engine block is slightly damp from fuel too. The gasket on the fuel filter looks to be good and no fuel on the filter.



Where is the most common place for a fuel leak to develop in that area?



Thanks,



Blake

 

[Joe G.]

The most common leak is the fuel hoses. They just get bad after a while. Sometimes they look good but you find that they leak from the ends because the interior of the hose is rotten. If that's the problem it's kind of a PITA to fix because of little room to work. One way to get more room is to take the nuts off that fasten the master cylinder to the brake booster. Then you can lean it toward the fender. You might also remove the starter.



Another place I've had my '95 leak is where the return line from the injectors comes back to the fuel filter. The connection is a double banjo fitting. The return line goes to the small banjo fitting on top. The two little washers get bad and can leak. I hope you have small hands with long skinny fingers.

 

[illflem]

Where the wires enter the fuel heater is also a popular leak point.

 

[Joe G.]

Bill,



That reminds me of another leaker. If there is a place for fuel to leak mine has done it. The manual push button on the side of the lift pump can leak too. This one usually leaks like it means it. A fifty cent O-ring will fix it.

 

[Blakers]

Thanks guys.



I will look it over more closely soon. Where do the lines generally leak? I see part of them is woven stainless and part plain steel tubing. Do you have to replace the lines clear to the tank? Lower the tank?



How much does the dealer generally charge for the lines? Can they be replaced with just hose?



Just gathering ideas here.



Blake

 

[BWilson]

One more spot to look is up against the block, under the fuel filter. There is a steel line (the return line) that breaks right at the welds for the attachment bracket. It's nearly impossible to see. Good luck.

 

[Joe G.]

Blake,



There are a couple of hoses mostly hidden behind the fuel filter. One is supply and the other is return. They connect the steel lines from/to the tank to the steel lines on the engine. These hoses are cheap but very hard to replace. You have to get diesel rated fuel hose to replace them. These things are the most likely place for the leak. Sometimes the leaking line looks ok because it is leaking from the end. The fuel usually runs down the steel line so it may appear that the leak is somewhere else.

 

[illflem]

Sometimes the steel lines will leak where the bracket is welded to them for attachment to the frame. Unfortunately this is where fuel may accumulate from a leaking hose also. Some folks have replaced the entire lines with hose. The dealer charges around $125 to replace one hose. Many techs say it is their most hated job to perform on our trucks.

 

[BWilson]

I changed the steel return line on my truck and I don't remember it being that bad. I think it took me less than an hour if I remember right... .....

 

[Blakers]

Anyone know what size fuel hose it takes?



Killed my KDP today and found my water pump was a little wobbly on its bearings (though not leaking), so I replaced it too. Replaced the fuel filter, but still have not found the leak.



My cousin said his leaked whenever his fuel filter got plugged up due to the pressure. Then stopped leaking after he changed it.



Thanks,



Blake

 

[Blakers]

Today I searched more closely for my slight fuel leak and found the fuel hoses are not the culprit. It looks like one hose was replaced and the other is well cracked, but not leaking. Man they are hard to get to as stated!



The slight leak seems to be coming from behind the lift pump somewhere. The side of the block has fuel on it running down. The area around the priming pump is dry.



My plan is to order new starter contacts, then pull the starter and get up in there and replace the hoses. I'll get a better look at things with the starter off. Then check out the starter and put it back on.



Thanks for all the help!



Blake

 

[Joe G.]

Did you check the double banjo fitting on top of the fuel filter? When I had my leak there it had exactly the symptoms you describe. It was really hard to see from above. The fuel ran down the side of the block so it appeared to be from below someplace.

 

[redram]

Originally posted by Blakers

Today I searched more closely for my slight fuel leak and found the fuel hoses are not the culprit. It looks like one hose was replaced and the other is well cracked, but not leaking. Man they are hard to get to as stated!



The slight leak seems to be coming from behind the lift pump somewhere. The side of the block has fuel on it running down. The area around the priming pump is dry.



My plan is to order new starter contacts, then pull the starter and get up in there and replace the hoses. I'll get a better look at things with the starter off. Then check out the starter and put it back on.



Thanks for all the help!



Blake

When I replaced the rubber fuel hoses, one of the hoses appeared to be dry, but when bent, it had all kinds of cracks in it and would leak fuel and / or allow air to come back into the fuel line effecting start up of the truck.



If you have a rubber hose that appears cracked, even if it is not leaking, it will in the near future. Also, one of th ehoses runs to the side of the block area behind the fuel filter on my 96 and if yours is similar, this could be leaking down towards the manual lift pump.



Use a degreaser and clean off the whole side of the engine and it should be fairly easy to spot. It will also make it a lot nicer to changeout the starter contacts and the rubber fuel line if you choose to dig into this project.



Good luck.