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bulldogfan

06 aset hand primer question.

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I have a real head scratcher! I replaced the two fuel filters a week ago. Truck fired up, did the usual stumble than seemed to run okay.

Idle seemed a little rough though the next day. Then, I parked truck with driver side leaning down a bit to unload. Would not fire. Cranked great, but no fire?

This is where I get confused, we dragged truck backwards to other side of road so that now passenger side was leaning downwards a bit. sat for a minute, cranked truck and fired right up!

Been running truck all week, seems fine, except first thing in morning spins over well, but takes just a bit longer to fire. Then today, truck starts good, drove for 3 hours, perfectly, had to park with driver side leaning slightly again,

get in to move and will not fire. Spins over great, but doesn't even attempt to start?  So far, I have opened hood and pumped hand primer. It feels to have little to no resistance. So I replaced hand primer. Still has little to no resistance. Truck is almost full of fuel (single tank).  If truck runs fine, shut off for five mins, get back in and then cranks great, but no fire? Seems electrical? But then why no firmness in hand primer? Help!!

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Gray or red engine?? Do you have a plugged fuel vent try cracking the fuel cap see if that makes the diffrence! So also Gray or red engine?? RED  Injector cup issues if a red engine! MP 7 MP8? If gray faulty fuel supply pump could also be an issue!

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Hello,

 It is a gray engine. And I am thinking fuel supply pump also, but do you think the pump would fail intermittently? And if so, would that cause the hand primer to be pretty spongy? Thanks.

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Posted (edited)

make sure the vents clear anything is possible, fuel return check / drain back valve also can cause this!

Drain back is cheaper than the pump if you going to throw parts I would go there first!

Edited by fjh

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Thanks.  Drain back valve? Is it also called check valve?

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Yes

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Just left mack with$1000 in parts. I will keep updating this post...

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I replaced the transfer pump. Also installed factory fuel filters. Took a while to get all the air to purge. But truck finally fired "rough at first" than smoothed out. Actually seems to idle a lot smoother now too. I bought a new check valve, but don't see where it goes? Is it behind the egr cooler? Thanks.

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Might be one in the fuel filter housing? I've never worked on one this new. 😊

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Dealer sold me a checkvalve. It looks like a hydraulic coupling? Can't seem to locate it. I am sure it's not attached to filter housing.  Going to get my bore scope and look behind the egr cooler. And hope it's not back there! Lol.

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If you are looking for the overflow valve it's in the block above the front of the  head on the air compressor.

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I am now wondering about the fuel line that runs from primary filter to the back of computer? It has swivel fittings, and they have slop in them. Not leaking fuel, but maybe letting air in?

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For future reference... something that I have replaced seems to have fixed issue. Fingers crossed. 

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Sounds like air was getting in

 

The easiest way I have found to find these problems is get a bit of old inner tube and a couple of big flat washers and some air fittings and  put them through the tube 

Next get a big hose clamp and clamp it onto the filler neck of the tank and pressurize the tank a bit and and leaks will show right away 

Sounds like its fixed though, good luck with it

 

Paul 

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6 hours ago, mrsmackpaul said:

Sounds like air was getting in

 

The easiest way I have found to find these problems is get a bit of old inner tube and a couple of big flat washers and some air fittings and  put them through the tube 

Next get a big hose clamp and clamp it onto the filler neck of the tank and pressurize the tank a bit and and leaks will show right away 

Sounds like its fixed though, good luck with it

 

Paul 

Yup agree with Paul  a little Preasure will find a leak where Vacuam not so much! How ever changing  things one a a time is sometimes all you can do!

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Thanks for that! I'll keep it in mind incase the problem comes back. Still curious about the fuel line between primary filter and ecm. Makes sense that I first noticed a hard start and rough idle immediately after service, including changing the centrifuge oil filter. Which you have to move fuel line out of way, to change. 

Ever heard of the swivel fittings going bad on fuel lines?

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