Fuel system prime
08-27-2006, 07:00 PM
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Fuel system prime
I guess this is a moot point now, because the truck started, but I'd like some help so I know what not to do next time. Here's the deal. I changed the fuel filter today. I removed the filter, opened the drain valve, waited for it to empty then closed it, filled the canister with fresh diesel, put in the new filter, tightened the cap. That was the simple part. I then bumped the starter and let the LP run 4-5 times. When I cranked the truck it ran for a few seconds then quit. I then spent the next 2 hours cycling the LP trying to get it to fire. I tried pushing in the schrader valve at the banjo fitting where the fuel line goes into the IP, I also tried opening the drain again for a few seconds. What did I do wrong that it took so long to refire, and what is the proper way to bleed the line between the filter and IP. Any help or tips would be greatly appreciated! Thanks guys!
08-27-2006, 08:54 PM
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Mine usually takes no more than 3 LP cycles and it will start, it will stumble as some air passes through the pump but it usually keeps running . I have changed my fuel filter 5 or 6 times and only twice did it start and die. When it did that I cycled the LP between crankings (I cranked no more than 15 seconds) and it started by attempt #4.
If it still won't start then crack open 3 injector lines. Crank the engine 15 seconds, and let the starter rest at least 1-2 minutes or it can get damaged from excess heat buildup. Do the crank cycles until fuel is seeping from the loosened fittings. Now tighten them. You only need 3 injectors firing to get the engine to start, it will sound very rough. Once it starts let it idle until it smooths out, DO NOT rev the engine to try and make the air purge from the lines faster. This can put unnessesary stress on some of the componets inside the VP44. Once its running check all fittings (fuel filter included) for leaks. After you are certain there are no leaks you are finished.
When you cycle the lift pump the fuel moves from the tank, through the pump, then the fuel filter, then to the VP44. The fuel will then move through some of the VP44 and back to the tank via the return line. The fuel does not go through the the entire pump or the injector lines. The only time fuel goes through the entire pump and injector lines is when the engine is running or when you are cranking the engine.
If it still won't start then crack open 3 injector lines. Crank the engine 15 seconds, and let the starter rest at least 1-2 minutes or it can get damaged from excess heat buildup. Do the crank cycles until fuel is seeping from the loosened fittings. Now tighten them. You only need 3 injectors firing to get the engine to start, it will sound very rough. Once it starts let it idle until it smooths out, DO NOT rev the engine to try and make the air purge from the lines faster. This can put unnessesary stress on some of the componets inside the VP44. Once its running check all fittings (fuel filter included) for leaks. After you are certain there are no leaks you are finished.
When you cycle the lift pump the fuel moves from the tank, through the pump, then the fuel filter, then to the VP44. The fuel will then move through some of the VP44 and back to the tank via the return line. The fuel does not go through the the entire pump or the injector lines. The only time fuel goes through the entire pump and injector lines is when the engine is running or when you are cranking the engine.
08-27-2006, 09:06 PM
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When I changed my filter, I did like you said and filled the canster, primed unitl I had fluid at the test plugs, then cracked the #1 & #3 injectors and let it purge. When it started spitting fuel, it started. I let it run a second then shutdown and tightened the injectors.
08-27-2006, 11:19 PM
#4
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A quick way to get the low pressure side of the fuel system primed is to run a line off the schrader on the VP44 into a container of diesel. The VP44 will draw from this. Once the engine starts, quickly pull the line off the schrader before fuel pressure starts to build.
08-27-2006, 11:43 PM
#5
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Originally Posted by Bart Timothy
A quick way to get the low pressure side of the fuel system primed is to run a line off the schrader on the VP44 into a container of diesel. The VP44 will draw from this. Once the engine starts, quickly pull the line off the schrader before fuel pressure starts to build.
08-28-2006, 07:12 AM
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Jr got it right... If it don't start crack a few injector lines anf bleed the system it should start after that... If you LP pump is weak well that will make thing really tough for the VP44 and getting it started again... We all can't stress how important a fuel pressure gauge is...
08-28-2006, 08:05 AM
#7
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Originally Posted by jrs_dodge_diesel
I don't agree with this. You are possibly opening up the system to more air for one thing. While you are cranking the engine, the ECM puts the LP at half power so it only kicks out 6 PSI. You are also making the VP44 work harder for its fuel supply by splitting the LP output between the VP44 and the bucket.
If the VP has lost prime from the lift pump, the low pressure system will be in a vacuum, and fuel will come in from the container easier than through the lp. An engine with a dead or weak lp WILL start easier with this method if the VP has lost prime.
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08-28-2006, 09:29 AM
#8
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Originally Posted by Bart Timothy
Get seriuos..."making the VP44 work harder".
If the VP has lost prime from the lift pump, the low pressure system will be in a vacuum, and fuel will come in from the container easier than through the lp. An engine with a dead or weak lp WILL start easier with this method if the VP has lost prime.
If the VP has lost prime from the lift pump, the low pressure system will be in a vacuum, and fuel will come in from the container easier than through the lp. An engine with a dead or weak lp WILL start easier with this method if the VP has lost prime.
08-28-2006, 06:51 PM
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Thanks for the tips guys, I just need some clarification. I guess I have a foggy understanding of what is going on here. I thought that the IP maintained pressure between itself and the injectors, and that the only place that needed to be bled was between the LP and IP, and between the tank and LP. Can the pressure generated by the LP force fuel/air out through the IP and injectors by just bumping the starter with the injectors loosened, or do you have to actually crank the truck?
08-29-2006, 09:17 AM
#10
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The fuel goes through 3 pumps/plungers and 3 different pressure regions before it reaches the injectors.
The first region is from the lift pump to the high pressure pump inside the VP44. This is the region which everyone is so concerned about pressures, and when it looses prime the others, obviously, quit working. Usually when a lift pump or fuel filter is changed, this is the only region which needs primed. If it looses prime it will go into a vacuum, which is created from the suction of the high pressure vane pump, and when it does, it can be primed from the outside schrader valve on the VP44. This is an unconventional way of doing it, but it does work. Opening the schrader valve to the outside air without having a pressure guage, or a line with fuel in it, attached, when this region has lost prime and is in vacuum, only puts more air into the system and compounds the engine starting problem.
The second pressure region is the high pressure chamber which feeds plungers. This is the region were the 0216 code comes from. If it can't get enough fuel to create the pressures needed, or it has some kind of leak, the 0126 timng code will be thrown (the code can also be thrown from a timing piston siezure - the piston is in this area). There's no way to directly prime this region, and get the air out, short of actually running the engine. Fuel (and air) will go though the high pressure chamber if the plungers are pushing fuel out the injectors, or enough pressure is created to crack its check valve.
The third pressure region is from the plungers to the injectors (it's basically consists of the injector lines and the dristributer assembly). If air gets here, the line fitting at the injector can be cracked to let it out. The engine has to be cranked to do this.
The lift pump, by itself, cannot push fuel through the high pressure pump and plungers to the injectors. The internal high pressure vane pump, by itself, isn't able to push fuel past the plungers.
When you change out a fuel filter, bump the starter a few times, letting the lift pump run until it quits, before actually cranking the engine. This will make sure the first pressure area is primed and that minimal air will get into the high pressure chamber and injector lines.
The first region is from the lift pump to the high pressure pump inside the VP44. This is the region which everyone is so concerned about pressures, and when it looses prime the others, obviously, quit working. Usually when a lift pump or fuel filter is changed, this is the only region which needs primed. If it looses prime it will go into a vacuum, which is created from the suction of the high pressure vane pump, and when it does, it can be primed from the outside schrader valve on the VP44. This is an unconventional way of doing it, but it does work. Opening the schrader valve to the outside air without having a pressure guage, or a line with fuel in it, attached, when this region has lost prime and is in vacuum, only puts more air into the system and compounds the engine starting problem.
The second pressure region is the high pressure chamber which feeds plungers. This is the region were the 0216 code comes from. If it can't get enough fuel to create the pressures needed, or it has some kind of leak, the 0126 timng code will be thrown (the code can also be thrown from a timing piston siezure - the piston is in this area). There's no way to directly prime this region, and get the air out, short of actually running the engine. Fuel (and air) will go though the high pressure chamber if the plungers are pushing fuel out the injectors, or enough pressure is created to crack its check valve.
The third pressure region is from the plungers to the injectors (it's basically consists of the injector lines and the dristributer assembly). If air gets here, the line fitting at the injector can be cracked to let it out. The engine has to be cranked to do this.
The lift pump, by itself, cannot push fuel through the high pressure pump and plungers to the injectors. The internal high pressure vane pump, by itself, isn't able to push fuel past the plungers.
When you change out a fuel filter, bump the starter a few times, letting the lift pump run until it quits, before actually cranking the engine. This will make sure the first pressure area is primed and that minimal air will get into the high pressure chamber and injector lines.
08-29-2006, 11:02 AM
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Like mentioned, you probably have a bad lift pump. I had a hard time getting mine primed the first time I changed my filter, I also found out I had a dead lift pump.
Another way is just use a little ether. Cycle your grid heater first, then spray a couple of shots into the intake tube and crank it over. You can't loose that much fuel to make it that hard to pick fuel back up.
People will say ether is no good at all, bull. Cycle your plugs/grid first and go at it. Been using ether on the two dozen diesels we have since the begining of time.
Another way is just use a little ether. Cycle your grid heater first, then spray a couple of shots into the intake tube and crank it over. You can't loose that much fuel to make it that hard to pick fuel back up.
People will say ether is no good at all, bull. Cycle your plugs/grid first and go at it. Been using ether on the two dozen diesels we have since the begining of time.
08-29-2006, 02:42 PM
#12
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Originally Posted by RJF
Like mentioned, you probably have a bad lift pump. I had a hard time getting mine primed the first time I changed my filter, I also found out I had a dead lift pump.
Another way is just use a little ether. Cycle your grid heater first, then spray a couple of shots into the intake tube and crank it over. You can't loose that much fuel to make it that hard to pick fuel back up.
People will say ether is no good at all, bull. Cycle your plugs/grid first and go at it. Been using ether on the two dozen diesels we have since the begining of time.
Another way is just use a little ether. Cycle your grid heater first, then spray a couple of shots into the intake tube and crank it over. You can't loose that much fuel to make it that hard to pick fuel back up.
People will say ether is no good at all, bull. Cycle your plugs/grid first and go at it. Been using ether on the two dozen diesels we have since the begining of time.
08-29-2006, 05:06 PM
#13
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Fuel Filter Change The Easy Way? At least it works for me!
Had experienced BAD problems in the past like the initial post to where I never wanted to do my own fuel filter changes again.
NOW on my 99 all I do when I change my fuel filter is:
1.) Drain the canister and remove the old filter.
2.) Put the new filter in bone dry and bolt the assembly back on.
3.) Then I un-bolt the small brass fitting on top of the fuel filter housing that goes to the injector pump side - not ALL the way though - J U S T enough to bleed air.
4. ) I then tap the starter. As the LP fills the canister it is expells the air out of that brass fitting. You'll know when most of the air is gone cause it starts to spew diesel. Since this fitting is on the VP-44 side the fuel should be filtered.
5.) If I can get around the driver door quick enough I'll start to tighten that little brass fitting back up before too much diesel spews all over the place.
6.) After that I just crank her up and and listen to her PURR.
This has worked flawlessly for me the last 5 changes (I change my fuel filter every other oil change which amounts to every 10K miles highway driving).
Since I started using this method I've NEVER experienced that old crank, kitten purr, sputter, engine die, knot in gut and couple of Hail Mary's syndrome since.
If this is hurting my truck someone please let me know. Otherwise it sure beats jacking with injector lines, recharging batteries and and saying the Rosary.
NOW on my 99 all I do when I change my fuel filter is:
1.) Drain the canister and remove the old filter.
2.) Put the new filter in bone dry and bolt the assembly back on.
3.) Then I un-bolt the small brass fitting on top of the fuel filter housing that goes to the injector pump side - not ALL the way though - J U S T enough to bleed air.
4. ) I then tap the starter. As the LP fills the canister it is expells the air out of that brass fitting. You'll know when most of the air is gone cause it starts to spew diesel. Since this fitting is on the VP-44 side the fuel should be filtered.
5.) If I can get around the driver door quick enough I'll start to tighten that little brass fitting back up before too much diesel spews all over the place.
6.) After that I just crank her up and and listen to her PURR.
This has worked flawlessly for me the last 5 changes (I change my fuel filter every other oil change which amounts to every 10K miles highway driving).
Since I started using this method I've NEVER experienced that old crank, kitten purr, sputter, engine die, knot in gut and couple of Hail Mary's syndrome since.
If this is hurting my truck someone please let me know. Otherwise it sure beats jacking with injector lines, recharging batteries and and saying the Rosary.
08-29-2006, 07:16 PM
#14
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Steve. that sounds good. You aren't pushing air through the lines when you purge since it goes out the filter lid. What you are accomplishing is keeping air from even entering the line to the VP44. All the air stays in the canister until you purge it.
I can't do the same on my 01. When I purge the air has to go through the main lines and out the return line. Usually this doesn't disturb the fuel in the rest of the VP44 and my truck usually starts right up, maybe a slight stutter from any remaining air, and she keeps going.
I can't do the same on my 01. When I purge the air has to go through the main lines and out the return line. Usually this doesn't disturb the fuel in the rest of the VP44 and my truck usually starts right up, maybe a slight stutter from any remaining air, and she keeps going.
08-29-2006, 08:36 PM
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I like the idea about loosening the brass screw, but as was just said, the 01's dont have that setup... Could we just leave the plastic cap loose enough to let air escape and close it before the mess gets to bad?