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Hard start

dodgedieselnewbie
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dodgedieselnewbie

dodgedieselnewbie

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Hey guys...  My truck has been giving me a hard time starting. It started happening last year and only did it when I was parked nose uphill. I remember reading something about this one time a few years back... but never heard what the cause was. This year.. a few months ago.. it's been starting hard on level ground. I have to hold the key on for 10-15 secs til it fires up. Almost like leaving it unplugged on cold days of winter. This only happens the first start of the day and only if I let it sit for more than 24 hours. Where do I start? No pun intended.... Thanks

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IBMobile

IBMobile

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Your loosing prime, the fuel is draining back to the tank.  You have a fuel fitting that not tight or an O-ring that is old and falling apart.  Check all of your fuel lines and fittings.  The fuel return line fitting at the back of the head has given problems.  A few people have had the O-rings go bad.   

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  • 2 weeks later...
dripley

dripley

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Did you replace you return lines also? The tee or the connection on the back head can both cause the problem. 

 

Also did you have the problem prior to replacing the fuel lines? Anything that lets air into the fuel system can cause it. A slow cranking starter can cause it too.

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KATOOM

KATOOM

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Leaks can be very difficult to spot.  You have to feel all the fittings for diesel residue since diesel doesnt act like gasoline.  And a leak doesnt have to mean fuel escaping the fuel line either but rather it can be air entering.

 

The most common places for leaks are ANY fitting you've messed with.  Its surprising how hard it is to get some fittings to seal tight.  The other places are the single banjo on the back of the head (towards the drivers side) and the T fitting just below it.  The T fitting doesnt use banjo fittings but rubber ends.  The torque for banjo fittings is 18 ft lbs.

 

The other non-visible thing that can leak is the o-rings on the injector crossover tubes in the head.  They can dry out and leak.  Its definitely worth shelling out the few bucks for new o-rings when replacing injectors.

Edited by KATOOM
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xtreme95cummins

xtreme95cummins

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On 9/3/2019 at 8:55 PM, dripley said:

Did you replace you return lines also? The tee or the connection on the back head can both cause the problem. 

 

Also did you have the problem prior to replacing the fuel lines? Anything that lets air into the fuel system can cause it. A slow cranking starter can cause it too.

I replaced the starter. The fuel pressure gauge shows slowly building pressure to 10-12 psi while cranking. When running its at 14 psi and drops to 12 psi at wide open. It starts right up once its been runnig. Even if it sits for a few hours, it will crank for a few and fire up.. But if it sits overnight or longer, its really hard to get started. 

On 9/5/2019 at 10:37 PM, KATOOM said:

Leaks can be very difficult to spot.  You have to feel all the fittings for diesel residue since diesel doesnt act like gasoline.  And a leak doesnt have to mean fuel escaping the fuel line either but rather it can be air entering.

 

The most common places for leaks are ANY fitting you've messed with.  Its surprising how hard it is to get some fittings to seal tight.  The other places are the single banjo on the back of the head (towards the drivers side) and the T fitting just below it.  The T fitting doesnt use banjo fittings but rubber ends.  The torque for banjo fittings is 18 ft lbs.

 

The other non-visible thing that can leak is the o-rings on the injector crossover tubes in the head.  They can dry out and leak.  Its definitely worth shelling out the few bucks for new o-rings when replacing injectors.

I havmt checked the fittings on the back of the head.. Im just learning about those.. Ill be replacing the entire steering linkage this weekend so Ill check the fittings on the head. Thanks for the info. 

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dripley

dripley

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6 hours ago, xtreme95cummins said:

I replaced the starter. The fuel pressure gauge shows slowly building pressure to 10-12 psi while cranking. When running its at 14 psi and drops to 12 psi at wide open. It starts right up once its been runnig. Even if it sits for a few hours, it will crank for a few and fire up.. But if it sits overnight or longer, its really hard to get started. 

I havmt checked the fittings on the back of the head.. Im just learning about those.. Ill be replacing the entire steering linkage this weekend so Ill check the fittings on the head. Thanks for the info. 

Lower pressure while cranking is normal. the ECM is doing that. You are most likely loosing the prime in the fuel system. By that I mean air is getting in some where. The return line from the back of the head and the VP is a major culprit. Those two lines join together at a tee back behind the fuel filter canister. I would check those line first. 

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xtreme95cummins

xtreme95cummins

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23 hours ago, dripley said:

Lower pressure while cranking is normal. the ECM is doing that. You are most likely loosing the prime in the fuel system. By that I mean air is getting in some where. The return line from the back of the head and the VP is a major culprit. Those two lines join together at a tee back behind the fuel filter canister. I would check those line first. 

OK I'll look into those.. I checked the banjo behind the head, it was tight.. I'll just replace those return lines.. I've replaced the lines from the tank to lift pump and from lp to vp44.. 

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dripley

dripley

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1 minute ago, xtreme95cummins said:

OK I'll look into those.. I checked the banjo behind the head, it was tight.. I'll just replace those return lines.. I've replaced the lines from the tank to lift pump and from lp to vp44.. 

No need to replace the lines. There are two sealing washer on the back of the head that might need replacing. The bolt might be tight bur the washers get hard with time and loose their sealing ability. The tee down stream of the head joins with the return from the VP. The lines dont go bad but the orings in the tee do. I still have all my OEreturn lines but have had to replace the washers and o rings. 481k on the return lines.

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xtreme95cummins

xtreme95cummins

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1 minute ago, dripley said:

No need to replace the lines. There are two sealing washer on the back of the head that might need replacing. The bolt might be tight bur the washers get hard with time and loose their sealing ability. The tee down stream of the head joins with the return from the VP. The lines dont go bad but the orings in the tee do. I still have all my OEreturn lines but have had to replace the washers and o rings. 481k on the return lines.

OK good. I'll check the washers and rings. I hope that's the problem.. The truck runs great once it starts. Just can't figure why it's so hard to start when it's sits.. 

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dripley

dripley

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6 minutes ago, xtreme95cummins said:

OK good. I'll check the washers and rings. I hope that's the problem.. The truck runs great once it starts. Just can't figure why it's so hard to start when it's sits.. 

It is just loosing prime in the fuel system. Air is getting in some where and causing the hard start. Try parking nose down one night and see if it cures it. That gets the fuel tank above the air leak.

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KATOOM

KATOOM

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2 minutes ago, xtreme95cummins said:

OK good. I'll check the washers and rings. I hope that's the problem.. The truck runs great once it starts. Just can't figure why it's so hard to start when it's sits.. 

 

Its because the fuel is running out of the lines.  The fuel system must retain a "prime" whereby the fuel stays in the lines when the engine is off.  Also, there is NO pressure in the fuel lines/system when the engine is off.  Anyone who says so is mistaken.

 

Think of the fuel lines like a straw in a cup of water.  Put your finger over the top and pull the straw out and the water remains in the straw.  Thats a "prime".  But put a hole in the straw and the water will run back into the glass.  The size of the hole is dependent on how fast the water runs out of the straw.

 

This is whats happening with your hard starting.  When the engine is off, somewhere the fuel lines lost their seal and the fuel is allowed to run back to the fuel tank.  When you go to start the engine the fuel lines/system must re-prime before the engine will start.  The larger the leak the shorter the truck has to sit before it hard starts.

 

This is also why you can typically find out if this is the problem by parking with the nose pointed downhill, because the fuel tank is then in line with or higher than the engine and the fuel has a harder time running out of the lines.

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JAG1

JAG1

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Thanks Dripley, I don't know how folks started calling them O rings since they are really sealing washers. I have saved a few of those when redoing my fuel systems to three different trucks. I don't think they are designed to use a second time, but being a little bit of distance from town I think I may have reused them successfully only a couple times on easy reach areas is all.

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