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Discussion Starter #1
I have a air leak that is allowing my fuel to siphon back to my tank causing hard starts. I called the 24v guy at Diesel Specialists and I told him my Problem and he said the that Connetor tube O-rings only keep debris out of the head because they just seal the Connector tube to the valve cover and couldn't cause an air leak in the fuel system. My question is, is this true and if not how do I go about replacing the O-rings and are there orings on the hard return line on the back of the head that may have gone bad?
 

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IMO, the O rings on connector tubes are a likely source for a leak, especially if yousee any evidence of fuel wetnees around the Injection line connectors at head. The fuel return in head is sealed by that O ring and the O ring on Injector. Now to make matters worse, it seems to me the copper washer on bottom of injector could also leak a very small amount of combustion gasses into the return area and cause air in return also. Gets deep doesn't it.
The banjo fitting at back of head and the "T" fitting could be a actor in issue also. There is a square O ring in that fitting that has been unrelaible in other applications. Also the banjo bolt has two flat washers. Easy place to get to also, makes a prime candidate for issues.
 

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Discussion Starter #3
i guess i will start with the banjo bolt on the back of the head because I have new washers. I need to take off the valve cover to get to the banjo bolt though so it might take me until tomorrow to get the time
 

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Remember, the return system is not hooked directly to your pump. So, it should not have any effect. After all, there is a leak in the back of the head you cannot stop. It's the bajo routed to the tank into open air. That's all return fuel, so it does not matter.

The overflow valve in the VP also has an air bleed in. So there is also a built in air leak.

Most likely, the leak is on the inlet side of the pump. If you reused your stock dorman fitting for suction, that is the most likely location. I would double check everything on the suction side of the pump.

Dave
 

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Discussion Starter #5
I have been told by 3 other guys that a air leak in the T fitting or the banjo bolt on the return side can cause my fuel to drain back to my tank though. And the Raptor 100 comes with a new fitting that allows you to hook up directly to the fuel tank and my Overflow valve was just replaced. Should I just go ahead and do the connector tube orings and go from there?
 

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I have been told by 3 other guys that a air leak in the T fitting or the banjo bolt on the return side can cause my fuel to drain back to my tank though. And the Raptor 100 comes with a new fitting that allows you to hook up directly to the fuel tank and my Overflow valve was just replaced. Should I just go ahead and do the connector tube orings and go from there?
Can't hurt to try it. But again, that returned fuel has an air leak built in. It's there if you change connector o-rings, banjo bolt or whatever. The only way to eliminate it is to put a plug in the back of the head.

90% of the issue you describe is an air leak on the pressure side BEFORE the injection pump. Or on the suction side.

Usually pipe threads are not properly sealed. These will not weep or seep, but cause tons of headaches. Also, any hoses that are stretched and or have high side loading will almost always leak air.

This is doubly true if you are using the blue air line included with the pump manufacturers kits.

Dave
 

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Discussion Starter #7
just to make sure, the Connector tube orings seal the connector tube to the valve cover and not the injector correct? I am going to get new orings tomorrow and hopefully it solves the problem but I just want to make sure i get the right stuff
 

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Discussion Starter #8
? any help so I can run and get them today?
 

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if your connector tube orings are bad or have flat spots in them it WILL cause hard starts. i changed mine this past weekend. it causes the fuel system to lose pressure.
 

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Has anyone actually looked at how the return fuel moves through the head?? If your gonna pull the tube, replace the orings. Its cheap insurance. Duke, my hard start issue was from the injector oring, although some on here have said that they cant cause hard starts either. Sure cleared up my hard starts, which were happening on every start once it got really bad.

I'm gonna stick to my belief that an air leak in the return side will cause hard starts......
 

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Remember, the return system is not hooked directly to your pump. So, it should not have any effect. After all, there is a leak in the back of the head you cannot stop. It's the bajo routed to the tank into open air. That's all return fuel, so it does not matter.

The overflow valve in the VP also has an air bleed in. So there is also a built in air leak.

Most likely, the leak is on the inlet side of the pump. If you reused your stock dorman fitting for suction, that is the most likely location. I would double check everything on the suction side of the pump.

Dave
Correct me if Im wrong Dave, because I haven't been in the fuel tank in a while, but doesn't the return fuel return to the tank BELOW the level of the diesel in the tank. The return line inside the tank rides in the little floating canister thing (can think of it name right now:doh:). If thats right, then the return system doesn't vent to open air, and an airleak could cause loss of prime..?
 

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Rollin Coal,

If the connector tube o rings don't do anything, please explain to me why they are there. Im not being a smart @SS I just really want to know why a tube that seals on both ends by a tapered press fit (like a compression coupling), would need that little oring at all??
the only reason ive heard that makes any sense is to keep the connector tube centered for assembly
 

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Has anyone actually looked at how the return fuel moves through the head?? If your gonna pull the tube, replace the orings. Its cheap insurance. Duke, my hard start issue was from the injector oring, although some on here have said that they cant cause hard starts either. Sure cleared up my hard starts, which were happening on every start once it got really bad.

I'm gonna stick to my belief that an air leak in the return side will cause hard starts......
:doh: :doh: i forgot about that.
 

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Correct me if Im wrong Dave, because I haven't been in the fuel tank in a while, but doesn't the return fuel return to the tank BELOW the level of the diesel in the tank. The return line inside the tank rides in the little floating canister thing (can think of it name right now:doh:). If thats right, then the return system doesn't vent to open air, and an airleak could cause loss of prime..?
It varies by module and year. Some modules have a return tube about halfway down the tank. Usually, these returns are outside of the bucket. And in the case of the DS1 it returns at the top of the tank.

Dave
 

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The o-ring prevents low pressure returned fuel from the injector from leaking out of the head and directs that fluid to the back of the head and it's return.

Dave
Thats what I thought, Thanks Dave. Oh yeah, Could you explain DS1 to me?
 

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Thats what I thought, Thanks Dave. Oh yeah, Could you explain DS1 to me?
It's short for DrawStraw 1. It has a 1/2" suction tube with 1 or 2 return fuel ports based on the customers needs. These return fuel ports are basically at the top of the module.

Dave
 

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ok, I was talking stock since thats what the OP has.
 

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bama called me last night....cool guy :thumbsup: hey bud if you need anything else just call. how did the stuff you changed last night go. any difference?????
 
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