Archived Help! Fuel system depriming and leaking....

[Katmandu]

Subject truck is a 98 12-Valver.

My truck loses prime after sitting overnight and has a small puddle of fuel accumulated under the engine. Usually about 10-15cc or so.

Upon underhood inspection I discovered (2) parts that are disconnected. I don't know what they are and what they do.

I have yet to find the source of the fuel leak.

Can someone tell me what these parts are and what they do ??

See pics below.....

1st is obviously an electrical connector. The connector appears to be melted and not connected for sometime. Is this the fuel pump that it connects to ??

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Next is a vacuum line that is located near the firewall right behind the fuel filter.









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I did notice a small puddle of fuel behind the fuel pump in a valley on the engine block.

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[Katmandu]

I inspected the rubber fuel lines and they do NOT appear to be the source of the fuel leak.

Does anyone know of any pics/schematics of the underhood wiring and fuel system components for a 98 12 Valver ??

 

[blacksheepdiesel]

Katmandu,



I just repaired a fuel leak on a '95. The fuel filter had a rust bubble on it right where the WIF sensor screws into the bottom. The engine had been hard to start lately but no leaks, just enough to lose prime. Finally she split enough to leak & I found it. It could be the WIF sensor itself causing you to lose prime. Have you changed the fuel filter? What about the supply & return hoses? They may be the culprit even if they don't look like it.



Good luck!



Trent

 

[Joe G.]

Karmandu,



You can't see an air leak. The fuel hoses can get in pretty bad shape and still look good. Read this:

http://dieselram.com/ubb/ultimatebb.php?ubb=get_topic;f=45;t=000007

 

[Katmandu]

Karmandu,

You can't see an air leak. The fuel hoses can get in pretty bad shape and still look good. Read this:
http://dieselram.com/ubb/ultimatebb.php?ubb=get_topic;f=45;t=000007

Excellent!!

Thank you Sir!

Now, anyone know what the vacuum line goes to ??

 

[Joe G.]

I can't tell for sure from your first photo, but it looks like the temp sensor on top of the fuel heater is burned up. It that is the case then the fuel heater is also burned up. Remove it and see if that helps.



The vacuum line is not involved with the fuel system. If your heater/AC is working properly then that vacuum line is probably ok. If you only have air from the defrost vents then that vacuum line has problems.

 

[KWentling]

I replaced the fuel lines on my '98 about 2 years ago searching for an air leak. The lines on the '98s are covered in a vinyl sleeve and mine were like brand new inside. My leak turned out to be the fuel heater electrical conection, which I suspect is what you have in the first picture. They develope a poor conection and the resulting heat melts the connector and lets air in and could leak fuel out when sitting. The fuel heater is located on the prefilter unit. You can replace the heater, or many have just eliminated it. You unscrew the bottom of the prefilter and the heater comes off by unscrewing the allen head stud. The prefilter will bolt back on where the heater was. You should clean or replace the screen while you're there. Can't help you with the vacuum line without going out and looking at mine. Maybe to the cruise control?



Kim

 

[PetesonM]

I am pretty sure the vacuum line is the vent for the transfer case. Out of the transfer case are 4 vac lines. One is the source from the vac system and two of them go to the CAD (the two metal tubes attached to the frams and crossmember. The forth is the vent line.

 

[Katmandu]

My leak turned out to be the fuel heater electrical conection, which I suspect is what you have in the first picture. They develope a poor conection and the resulting heat melts the connector and lets air in and could leak fuel out when sitting.
Kim

I believe you mean like this example from Joe's article right ?


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[KWentling]

That's the one.



Kim

 

[norcalram]

The left circle in your second photo is a missing bolt which retains the fuel line (return I think??) the vacuum line is normal (same on mine) the electrical connector appears to be on top of the fuel heater. the heater element if i am not mistaken, is the middle of the assembly. I assume that the top connection is the fuel temp sensor, which tells the heater to operate or not.

 

[Katmandu]

I believe you mean like this example from Joe's article right ?

What's the easist way to remove the fuel heater ??? From above or from underneath the truck ??

 

[KWentling]

I believe I did it from the bottom side. JLusher is right. If the melted part is on top that is the temp. sensor. If it's burned the heater element is probably toast too. I think that is where you're leak will be. (at the heater conection like in the picture)



Kim

 

[Katmandu]

I think that is where you're leak will be. (at the heater conection like in the picture)

Kim

Probably leaking both ways... . Fuel out and air in I would imagine.

BTW, Where's the cheapest place to buy a new fuel heater ??

 

[Joe G.]

Throw it away. You don't need it. The pre-filter will bolt right up in place of it if you leave the adapter screw and one gasket out.

 

[Katmandu]

FYI... . Here's a pic of the fuel heater below (Thanks to Joe for the pic) and the result of what happens when it overheats.

Someone suggested just plugging the leak with SuperGlue. I figured WTH and tried it.

My truck now fires right up the 1st crank and I SWEAR it is running ALOT SMOOTHER and has abit more get-up-n-go!!!

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