hard start
12-01-2008, 06:34 PM
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hard start
i just got the lift pump replaced and i replaced my vp44 yesterday and when the truck is warm it takes a little while to start from how it normally did, any ideas, its probably an air leak but there is absolutly no diesel leaks anywhere
12-01-2008, 11:54 PM
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i just went through this. replaced IP and LP then got hard start when it was warm.. mine ended up being a bad injection pump. but i would start with checking all the hose clamps. do you know how much fuel pressure you have? too much can cause hard start
12-02-2008, 11:58 AM
#3
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get a fuel pressure guage and splice it in under the cab.... it proably just a stupid little o-ring somehwere in the injector lines, maybe we lost one when we took 1-3 lines off?? it also could be coming somehwere from your fuel filter? not just the IP LP! i highly doubt its a bad IP!!!!
12-02-2008, 04:20 PM
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12-02-2008, 10:55 PM
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if those guys a the scrap yard gave you one off some other truck besides my brothers then proably yes you do need a new 1...the only reason that 1 is good is cuz is has only 40k on it and is very well taken care of! all others at that yard aint worth 800
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12-02-2008, 11:34 PM
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I know you have a new vp44, but I'd thought I'd share this with you anyways. I just read this a few hours ago. It might help, it might not.
This is on page 5 from here http://www.fassride.com/billcook/FAS...l%20Manual.pdf
Dear Valued Customer,
A small percentage of our customers have experienced hard start issues when placing our pumps on trucks with
the VP44 injection pumps, these pumps are found on 1998.5 – 2002 Dodge Cummins pickups. The hard start issues we
incur are only found on this application. The hard start issue would occur with any fuel pump putting good flow and
pressure to the VP44 after the injection pump has experienced 5psi or less in fuel pressure. A VP44 receiving less than 5psi
in fuel pressure will more than likely be damaged, creating the hard start issue with good fuel flow and pressure. Please
read the following if you experience the hard start issue.
Hard Starts
Usually the FASS only encounters hard starts on the 1998.5 – 2002 Dodge Cummins with the VP44 injection
pump. If this occurs it is usually on a VP44 with high mileage, and/or a VP44 that has been subjected to around
5psi of fuel pressure or less. It is more likely to occur when the weather is warmer/hot.
Explanation of Diaphragm: The diaphragm in the VP44 is designed to move about .5mm with proper fuel pressure
(about 7psi min.). When the VP44 is subject to about 5psi or less the diaphragm can move up to 2mm, an increase
in movement of 4 times more than what it was designed to move. With this type of movement the diaphragm will
eventually develop stress cracks thru out the body of the diaphragm. One job of this diaphragm is to separate low
fuel pressure and high fuel pressure in the housing of the VP44, when the cracks are present this separation does
not occur. This will lead to hard starts even with a stock OEM lift pump!!
Here is a simple test:
Note: Not all failed pumps with broken diaphragms will start with low to no supply fuel. Sometimes the
diaphragm is so broken that charging pressure is not able to build to a level that allows the pump to deliver fuel.
Try starting the vehicle without waiting for the fuel pump to cycle. Meaning when you turn the
key to the on position immediately engage starter.
Or:
Unplug the FASS pump or remove the fuse so the FASS pump does not operate. Note: If the
engine operates without fuel pressure for a period of time the VP44 will be destroyed.
Understanding this condition, start the truck. If the truck starts shut it off immediately!!!! This
test just indicated that the better/increased fuel pressure from the FASS pump is overriding the
defective/thinner diaphragm and/or cracked o-rings surrounding the diaphragm in the VP44.
Here are some solutions:
1. Receive the most current flash from your Dodge Dealer.
2. On our WH-1002 harness, cut the red wire between the FASS relay and engine harness. Splice a
length of the same gauge wire to the red wire coming out of the relay. Relocate this wire to a
fuse that is hot only in the “Run” position. An example is the Power Window or Windshield
Wiper fuse. This will cut power to the FASS when cranking.
3. Repair the VP44. VP44’s were manufactured with a thinner diaphragm which can and will cause
hard starts with hot weather and or higher fuel pressures. Thicker diaphragm’s for the VP44
were released around 2003 for correcting this situation. Remember it doesn’t matter if the VP44
has the thinner or thicker diaphragm, if the VP44 has been subjected to a failing transfer pump
(lower fuel pressure) or a failed transfer pump it will lead to this problem. The damage was done
by the failing or failed lift pump before the FASS was installed.
This is on page 5 from here http://www.fassride.com/billcook/FAS...l%20Manual.pdf
Dear Valued Customer,
A small percentage of our customers have experienced hard start issues when placing our pumps on trucks with
the VP44 injection pumps, these pumps are found on 1998.5 – 2002 Dodge Cummins pickups. The hard start issues we
incur are only found on this application. The hard start issue would occur with any fuel pump putting good flow and
pressure to the VP44 after the injection pump has experienced 5psi or less in fuel pressure. A VP44 receiving less than 5psi
in fuel pressure will more than likely be damaged, creating the hard start issue with good fuel flow and pressure. Please
read the following if you experience the hard start issue.
Hard Starts
Usually the FASS only encounters hard starts on the 1998.5 – 2002 Dodge Cummins with the VP44 injection
pump. If this occurs it is usually on a VP44 with high mileage, and/or a VP44 that has been subjected to around
5psi of fuel pressure or less. It is more likely to occur when the weather is warmer/hot.
Explanation of Diaphragm: The diaphragm in the VP44 is designed to move about .5mm with proper fuel pressure
(about 7psi min.). When the VP44 is subject to about 5psi or less the diaphragm can move up to 2mm, an increase
in movement of 4 times more than what it was designed to move. With this type of movement the diaphragm will
eventually develop stress cracks thru out the body of the diaphragm. One job of this diaphragm is to separate low
fuel pressure and high fuel pressure in the housing of the VP44, when the cracks are present this separation does
not occur. This will lead to hard starts even with a stock OEM lift pump!!
Here is a simple test:
Note: Not all failed pumps with broken diaphragms will start with low to no supply fuel. Sometimes the
diaphragm is so broken that charging pressure is not able to build to a level that allows the pump to deliver fuel.
Try starting the vehicle without waiting for the fuel pump to cycle. Meaning when you turn the
key to the on position immediately engage starter.
Or:
Unplug the FASS pump or remove the fuse so the FASS pump does not operate. Note: If the
engine operates without fuel pressure for a period of time the VP44 will be destroyed.
Understanding this condition, start the truck. If the truck starts shut it off immediately!!!! This
test just indicated that the better/increased fuel pressure from the FASS pump is overriding the
defective/thinner diaphragm and/or cracked o-rings surrounding the diaphragm in the VP44.
Here are some solutions:
1. Receive the most current flash from your Dodge Dealer.
2. On our WH-1002 harness, cut the red wire between the FASS relay and engine harness. Splice a
length of the same gauge wire to the red wire coming out of the relay. Relocate this wire to a
fuse that is hot only in the “Run” position. An example is the Power Window or Windshield
Wiper fuse. This will cut power to the FASS when cranking.
3. Repair the VP44. VP44’s were manufactured with a thinner diaphragm which can and will cause
hard starts with hot weather and or higher fuel pressures. Thicker diaphragm’s for the VP44
were released around 2003 for correcting this situation. Remember it doesn’t matter if the VP44
has the thinner or thicker diaphragm, if the VP44 has been subjected to a failing transfer pump
(lower fuel pressure) or a failed transfer pump it will lead to this problem. The damage was done
by the failing or failed lift pump before the FASS was installed.
12-03-2008, 06:39 PM
#11
Registered User
How long should it last? That is a really loaded question. But if you keep feeding it good fuel pressure and proper lubrication (not straight ULSD) it "should" last a good while.
Keep an eye on your FP gauge.
Keep an eye on your FP gauge.
12-03-2008, 06:53 PM
#12
Registered User
91.5beater, it is possible that the rebuilt VP44 is faulty but before giving up on the pump try the low fuel pressure start from the post above.
Cummins developed the ECM software to limit starting fuel pressure to be around 7 psi. I think they knew about hard starts with too high a pressure and tried to fix the problem by lowering it.
The VP44 has a built-in rotary vane pump that pressurizes the internal side of this diaphragm to about 350 psi this pressure is engine RPM dependent. It is unlikely that changing from 5 psi to a minimum of 7 psi on the inlet (lift pump) side of this diaphragm is going to prevent a crack. It is far more likely that your VP44 is one that will not tolerate high pressure on a hot start (or possibly a bad rebuild).
Cummins recognized a hot start problem that was caused by too much fuel pressure and in the 2000 model year issued an ECM re-flash to limit the key-on lift pump run time to less than 1 second.
With all due respect to FASS, a newly rebuilt injection pump should not have a problem with the diaphragm. This diaphragm can crack over a period of time, usually more than 100K. In my opinion FASS got it wrong with their explanation of cracks in the diaphragm due to low lift pump pressure.
There are many generator applications using the VP44 where the fuel is gravity fed to the injection pump. My guess is the fuel pressure is less than 2 psi.
Cummins developed the ECM software to limit starting fuel pressure to be around 7 psi. I think they knew about hard starts with too high a pressure and tried to fix the problem by lowering it.
The VP44 has a built-in rotary vane pump that pressurizes the internal side of this diaphragm to about 350 psi this pressure is engine RPM dependent. It is unlikely that changing from 5 psi to a minimum of 7 psi on the inlet (lift pump) side of this diaphragm is going to prevent a crack. It is far more likely that your VP44 is one that will not tolerate high pressure on a hot start (or possibly a bad rebuild).
Cummins recognized a hot start problem that was caused by too much fuel pressure and in the 2000 model year issued an ECM re-flash to limit the key-on lift pump run time to less than 1 second.
With all due respect to FASS, a newly rebuilt injection pump should not have a problem with the diaphragm. This diaphragm can crack over a period of time, usually more than 100K. In my opinion FASS got it wrong with their explanation of cracks in the diaphragm due to low lift pump pressure.
There are many generator applications using the VP44 where the fuel is gravity fed to the injection pump. My guess is the fuel pressure is less than 2 psi.
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