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not firing but have prime?


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Okay, so I have been having trouble with the truck recently. If I let it sit longer than a day, I have to cycle the lift pump to prime to get the truck to fire. Takes a couple tries before it will fire too.

If I drive it daily, no problem. I've posted recently about this sort of problem.

Today, I primed by cycling the lift pump doing a bump start. Cranked and tried to pop off once. Every time after, no go.

So I primed 3 times no go. Then I cracked the injector lines and primed multiple times, no go. I've done everything I think of to try to get it to fire. I have fuel supply to the injection pump, but anything after the pump, dry.

Scan gauge show no codes. Is my injection pump giving up the ghost?

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I'll have to try some things when I get home. I was reading that there is a check valve on the injection pump that could get stuck?

I had a wait to start light, could it be an ecm issue at all?

Edited by hex0rz
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Okay, so i spent about an hour or more tonight after work to get the truck running. I tried cranking and no go. Bump started a few times no go. Battery was almost dead so I hooked a charger up.

Then I cracked the injector lines. Cranked more until I got fuel. Tightened up the lines. Cranked, still no go. Then I cracked them again. Got fuel, at number 1. Tightened it up, then cranked again. Finally fired over.

Ran rough until I tightened the other two, obviously.

So everything must be in working order, except the leak that's causing me to lose prime?

Checked the over flow valve and it was functioning.

With such a drastic loss in prime, could there be any tell tale secrets?

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Okay, so i spent about an hour or more tonight after work to get the truck running. I tried cranking and no go. Bump started a few times no go. Battery was almost dead so I hooked a charger up.

Then I cracked the injector lines. Cranked more until I got fuel. Tightened up the lines. Cranked, still no go. Then I cracked them again. Got fuel, at number 1. Tightened it up, then cranked again. Finally fired over.

Ran rough until I tightened the other two, obviously.

So everything must be in working order, except the leak that's causing me to lose prime?

Checked the over flow valve and it was functioning.

With such a drastic loss in prime, could there be any tell tale secrets?

  YOU SHOULD SEE THE LOSS IN PRIME ON YOUR FUEL PRESSURE GAUGE... when you first bump the starter to cycle the lift pump, does the fuel pressure come up 

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With such a drastic loss in prime, could there be any tell tale secrets?

 

The secret is that loss of prime typically don't leave a wet spot. If the air leak is in a pressure spot it will leak fuel while running. So typically the leak is in a suction spot of the fuel system.

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What return lines do you have on it? Stock or???? Could be leaking at one of those connections. If not there then check the banjo at the back of the head, or the T where the return lines connect to go back to the tank.

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When I bump the starter initially, iirc, the pressure comes up immediately.

It must be on the suction side of things. I have never seen this truck make a single wet spot of anything amazingly.

Stock return lines, yes. Except for the AD return line on the AD filter block..

I know this is on the pressure side, but the fuel supply line to the vp44, right before it goes to the vp44, I have cracking in the line. It's not wet that I can tell, but I thought maybe it could be the culprit. I was meaning to try and tale it with some electrical tape to see...

Edited by hex0rz
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When I bump the starter initially, iirc, the pressure comes up immediately.

It must be on the suction side of things. I have never seen this truck make a single wet spot of anything amazingly.

Stock return lines, yes. Except for the AD return line on the AD filter block..

I know this is on the pressure side, but the fuel supply line to the vp44, right before it goes to the vp44, I have cracking in the line. It's not wet that I can tell, but I thought maybe it could be the culprit. I was meaning to try and tale it with some electrical tape to see...

It would be leaking and wouldn't effect Running unless it was bad enough to be losing a good amount and effected Fuel psi in which you would have no trouble seeing

IF YOU have air getting in the system it has to be on the suction side from lift pump to tank, no exceptions. as I said above you should see it in your fuel psi either fluctuating or dropping off dramatically to near nothing

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What return lines do you have on it? Stock or???? Could be leaking at one of those connections. If not there then check the banjo at the back of the head, or the T where the return lines connect to go back to the tank.

What return lines do you have on it? Stock or???? Could be leaking at one of those connections. If not there then check the banjo at the back of the head, or the T where the return lines connect to go back to the tank.

I dont think a leak on return side past the return banjo would cause his issues would it, I Could be wrong..

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Yes, it can suck air into the system and cause it to hard start. I've never heard of it to this degree though.

OH" OK,,,,, You mean like a VENTURI SUCTION PUMP TYPE of method where the ​Fluid speed & velocity motion traveling by an open port create suction in the said port..

    Now I'm on the same page

Edited by rburks
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My return tee o rings and the sealing washer on the back of the head were all leaking and it did cause hard starts for me. Not to the degree Hex is seeing however. Sometimes it would only take one cycle with the lift pump and sometimes more, just depended on how long it sat. I never had to open the injectors to get it started. All I could figure is that air got in and let the fuel back to the tank and took some of the fuel out of the high pressure lines. I do know when I replaced the leaky parts the problem went away.

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I Still don't see it, I MEAN I'LL give you that Air "could" meaning its Possible be sucked into the return, BUT ITS in the return, SO WHAT. its going back to the tank so

as long as theres plenty of fuel to keep pick up tube/draw straw submerged it should not matter unless its capable of vacuum pulling fuel out of the injector line to head which i would think there is some kind of valve in VP to keep this from happening

 

     wHere am i wrong???

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