Kind of long, but this is the info I received directly from Cummins.
Wed, 04 Jan 2006 12:47:24 -0500 (EST)
From: -- email address removed -- Add to Address Book Add Mobile Alert
Subject: Re: RQST00000402246
Summary: 65216 VP-44 Fuel Supply Pressure Requirement
Solution:
Thanks for your Email message.
You may need to add an additive if your fuel is in question. Lubricity and
water problems are the two big factors. For more information, contact Fleet-tech
Customer Assistance at 1-800-22FILTER(1-800-223-4583) fax 1-800-999-8664 or visit
us at
www.fleetguard.com
When the transfer/lift pump fails fuel flow may or may not stop flowing to the
VP44 pump. It all has to do with the position the pump fails in. If you had a
gauge that could read positive or negative pressures on the outlet side of your
fuel filter you could see when there was a problem. At that point you could
stop and fix the problem with your truck. At that point the problem may be a
filter, plugged inlet line, transfer/lift pump or something simple.
Information about pressure:
Concerning lift pump pressures for ISB 24 valve engine, in the Ram application,
the following information is from the Cummins ISB Troubleshooting and Repair
manual, Bulletin number 3666193. This information applies to engines having the
Bosch VP-44 injection pump (not the high-pressure common rail found on 2003 or
later models).
The lift pump pressure is only one parameter pertaining to fuel system
operation/diagnostics, and as long as you have positive pressure to the VP-44 at
adequate flow, your engine should run fine. "Adequate" means normal performance,
starting and smoke levels. Any issues with the engine running outside of the
below listed pressures being in their respective proper ranges should be addressed.
The numbers in the manual are:
Idle speed:
700-1000 rpm
Maximum fuel inlet restriction to lift pump:
6 in Hg
Maximum Fuel Pressure at Fuel Filter Outlet (engine cranking): 4 - 8 psi
Minimum Fuel Pressure at Fuel Filter Inlet (engine running): 8 - 17
psi
Fuel Drain Line Maximum Restriction:
10 psi
Fuel Inlet Maximum Temperature:
165 deg. F
Engine Minimum Cranking Speed:
150 rpm
Excessive smoke can be a symptom of improper injection timing, which MAY be
caused by insufficient fuel to the VP-44. Variable pressure within the pump
rotates the cam ring that affects/effects injection timing changes; insufficient
fuel delivery to the pump will affect the pumps ability to establish the correct
timing per operational condition. Normally this is a blue-ish white smoke.
Black smoke is indicative of over-fueling (relative to the amount of air).
The fuel flow test (005-011) states to run the engine at high-idle (running on
governor with no load) speed; the outlet side of the filter should read 10 psi
minimum. To be thorough, one needs to check at high-idle as well as idle and
measure at the correct places. Under high-idle conditions the pressure drop
across the filter is to be 5 psi maximum.
The manual further states, not to operate the fuel system with suction
restriction of more than 3 psi but Bosch prefers that there is no negative pressure on
the VP-44. We are not aware of any durability validation tests at "outside of
acceptable operation" parameters or that negative pressure might cause VP-44
failures due to the lack of sufficient fuel for pump lubrication. Unlike the
P7100, the VP-44 is lubricated by the fuel which circulates through it. Bosch may
be able to advise the effects of low lift pump pressure on the VP-44 injection
pump.
The output of the fuel lift pump is checked via test (005-045-012) by measuring
the output pressure, using a pressure gauge at the fuel filter head tap. For
long injection pump life, the Bosch VP-44 pump requires clean No. 2 diesel fuel,
with no water or foreign debris. Owners should be very careful during fuel
filter maintenance or replacing the lift pump, to ensure that no debris gets into
the injection pump side of the filter.
Always use the lift pump to fill the filter. This can be done by bumping the
starter with the key switch but not starting the engine. The lift pump will run
for 25 seconds. Turn key off and repeat two more times then filter should be
full.
We thank you for your interest in Cummins products. Please let us know if you
need assistance in locating the nearest Cummins-authorized Dealer or Distributor
Service Provider. For assistance in locating a Service Provider, feel free to
use Cummins North America Dealer Locator, which can be found on Cummins website:
http://wsl.cummins.com/ServiceLocator/jsp/controller.jsp?action=servicelocator
Please let us know if you have other questions and if away from your computer
or have a time-critical request that needs more urgent attention, feel free to
call us toll-free (from North America) at 1-800-DIESELS (343-7357).
Email direct: -- email address removed --
Regards,
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Customer Assistance Center
Cummins, Inc.
Columbus, Indiana, USA
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