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Loosing prime with no leaks?

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Old 12-11-2006, 12:55 PM   #1  
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Loosing prime with no leaks?

I have been having the hard start problem do to air getting into the vp44. I have checked and found no leaks! I put in a check valve and it solved the problem for now.

It has to be leaking from the pump, so how long do you think this thing will last?

Any other ideas?

Thanks Bob
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Old 12-11-2006, 05:37 PM   #3  
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I've got the same problem and I plan on replaceing the orings on my injector tubes very soon. Also are you talking about the check valve on the return side of the VP44?
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Old 12-11-2006, 05:50 PM   #4  
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The check valve I am talking about is a valve in the supply line so the fuel can not drain back to the tank. The check valve in the return line checks out ok.

If the cross tube o-rings were leaking, would there be any indication? And where do you get the o-rings from? I am going to check my service manual to see them right now. I did replace the injectors last March, but used the same cross tube o-rings.

What do you think would be a more common problem? VP-44 or cross tube o-ring? Just wondering on what is more common.

Thanks Bob
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Old 12-11-2006, 06:28 PM   #5  
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On an 01 in Connecticut, I would sure have a look at the fuel fittings at the top of the tank. The top of the fuel sending unit is notorious for rusting out, and this is hard to see. It helps to have the truck on a lift if at all possible.
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Old 12-11-2006, 06:55 PM   #6  
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I checked the top of the tank and all the fittings are plastic, the bed dumps so it is easy to check.

Also, there is no diesel in the oil, I would think that a leaking injector or tube would leak into the oil, or be visible? If I park it will loose prime in about 30 min, so it has to be a good size leak?

I don't want to take out all the injectors and or tubes for nothing? Wouldn't I have some symptom other then hard starting?

Also I have checked the old posts and I can not find anyone who have actually fixed the hard start via finding a leaking injector or cross tube?

HELP THIS IS DRIVING ME CRAZY!

Bob
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Old 12-11-2006, 08:11 PM   #7  
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I'm not sure if you have the same setup, But I had a leak develop around my fuel heater at the top of my ff canister. At first there was no fuel leaking out, but just enough air getting in to float a bubble up to my vp. In lieu of replacing the parts, I have been using vice grips on the rubber portion of my fuel line. Same result, it keeps the fuel from backflowing and let's me start the truck. What kind of check valve did you use? Anyhow, it only takes a minute leak to lose prime..
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Old 12-11-2006, 09:43 PM   #8  
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I just used a standard one way check valve from MSC. I located it by my fuel pump at my tank. I ordered a Draw Straw, so now I am going to put a plastic valve at the bottom of the draw straw in the tank. This valve will have a lower crack pressure, less then 1psi. My bed dumps so getting to the tank is very easy.

I have no visible leaks and no smell of diesel, so unless I get a better idea, I am going to stay with the check valve deal, plus it could be leaking back through the IP, and for that there is no fix, other then replacment. If I do replace the IP, I would keep the check valve in place, unless there was a reason not to?

Thanks Bob
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Old 12-24-2006, 05:36 PM   #9  
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I was just wondering if you ever got that thing straightened out?
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Old 12-24-2006, 08:42 PM   #10  
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I went through everything but could not find a leak, but I know there is one somewhere? So here is what I did. I put a 3/4(big) check valve on the pick up tube in the tank, think of it as a foot valve. Then I put a 1/2(not so big) check valve on the return line at the tank. The thought goes like this, both have a crack psi of less then 1psi, so when I shut down, the valves will close and seal the system, now the leak will weap and show its' sorry self, then I can fix it! Well I do see a small, I mean small weap spot at the conection under my fuel canister, I have not yet fixed it. The truck starts fine every day and sits for 24hr periods and starts fine, like it used to. The fuel psi holds at 12psi wot so I may keep all the valves in place, why take them out? I will fix the leak next week.

Bob
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Old 12-24-2006, 10:14 PM   #11  
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Well at least it will crank on the first try. I still have to bump the starter unless its facing down a little slope and then it will crank right up. Where did you pick up these check valves at? I broke my output shaft the other day and won't have my truck back till next week sometime. When I get it back I'm gonna mess with the check valve at the VP44. I installed the draw straw but that didn't do anything for my hard start. Also how do you test the check the check valve on the VP44 where the return line starts?
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Old 12-25-2006, 10:28 AM   #12  
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I got the check valves from MSC. The one in the tank is big, so as to have as little resistance as possible.

To check the valve in the vp just pull it out and make sure it is seated, but be advised, mine has a bleeder hole in it, so it will bleed through unless you plug it with your finger for test. I don't see how this could lead to a leak down any way, the bleeder is allways open, it is designed to open more at 14psi so as to bleed off more pressure.

My truck has been parked up hill for the last three days without start, I went out this morrning and it started right up! The check valves will not fix your leak, but it sure does remedy the start problem.

As I also mentioned in my last post, I can now see a very small leak(wet spot) that I will fix next week. I have had such great luck with the check valves that I think I am going to leave them in place.

Bob
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Old 04-17-2007, 02:54 PM   #13  
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I am having the same problem with my 02. Bob, where in the return fuel line did you install the check valve? My check valve is ordered and on the way.
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Old 04-17-2007, 06:15 PM   #14  
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I have easy access to the fuel tank, so I put the valve there, but any where near there would be fine, maybe on the frame rail buy the tank. Also, since I did this I have had no more trouble. It also has not hurt my fuel pressure.

So I have a BIG check valve in the tank on the bottom of the draw straw, and one on the return, make sure you have them in the correct direction!

Hope that helps

Bob
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Old 04-17-2007, 07:37 PM   #15  
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I think I might try this cause I'm tired of mine losing prime except when it's facing down hill. You got any part numbers for those check valves?

http://www1.mscdirect.com/CGI/NNSRIT...MT4NO=21256030

Would that work? I've got 3/8" line on the truck now so I'm thinking as long as it maintains that I'm not gonna lose any flow. It's a brass fitting with Viton seals so it'll hold up to diesel or biodiesel.
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