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I have done alot of searching on the forum for lift pump diagnosis. My truck has been randomly hard to start recently. Sometimes it will take many, many cranks to get it started - mainly in the morning. So I decided to diagnose the lift pump. I know that pressure is not a very good means to measure lift pump output so I went with a volumetric output. I opened the fuel filter drain and drained out the fuel until it was empty and then turned on the key with a gallon jug below the drain hose to collect what was pumped into the feul filter. It went for a couple of minutes and after about a pint or so stopped filling the container and stopped completely flowing. So I guess I have 2 questions.

1) IS this a reliable method of determining lift pump flow?

2) Any reason why it would flow out for about 30 seconds and then completely stop?

Thanks in advance!

Chris
 

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When you turn the key to the run position and the truck is not running the lift pump will only run for 30 sec. If it ran for the full time I would get a pressure gauge. Hard starting does not mean the LP is bad, it could be a number of things.
 

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Things to check:
1. Minimum cranking speed of 150 rpm. The computer will not open the injectors untill 150 rpm are reached.
2. Fuel check valve. If the pump has to reprime the the injector pump, cylinder head or any volume gap in the system its going to take a lot of cranking to achieve this.
3. Fuel pressure and volume to the injector pump.
4. Injection pressure
5. Fuel injector return rate. This is a detailed and time consuming procedure that requires some special tools but it can be done if you are willing. Indicates a worn injector(s) or restriction in the fuel return system.
6. Check fault codes, they are there for a reason. Even if the check engine light isnt illuminated there may still be codes recorded in memory indicating a problem.
7. Vehicle security system.
 

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what year of Ram?
if 03>04 does it have the OEM filter housing mounted lift pump in engine bay or dealer upgrade replacement pump in tank?

measure low pressure fuel system delivery at the steel line into the CP3 injection pump.
remove banjo
put end of line into min. 1/2 gal. container
turn key on and bump starter but don't start. kicks lift pump on for max 30secs and ECM then shuts it off. turn key off after 10 seconds.
needs to pump minimum of 1/2 qt in 10 secs or if you have a milliliter gauge 510ml. to meet specs.

the OEM 03 04 lift pumps are known road toads that will leave you walking

any codes? do the key on 3 times trick
more than likely low rail pressure from loose injector hold downs, loose connector tubes, injectors leaking nozzles or bypass valve, popped rail overpressure relief valve.

any white smoke or raw diesel odor in exhaust?
any increase in motor oil level or smell of diesel in oil?

get it started
measure:
cold idle rail pressure
hot idle rail pressure
hot 2000 rpm cruise control flat freeway run
WOT
 

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Discussion Starter #5
what year of Ram?
if 03>04 does it have the OEM filter housing mounted lift pump in engine bay or dealer upgrade replacement pump in tank?

measure low pressure fuel system delivery at the steel line into the CP3 injection pump.
remove banjo
put end of line into min. 1/2 gal. container
turn key on and bump starter but don't start. kicks lift pump on for max 30secs and ECM then shuts it off. turn key off after 10 seconds.
needs to pump minimum of 1/2 qt in 10 secs or if you have a milliliter gauge 510ml. to meet specs.

the OEM 03 04 lift pumps are known road toads that will leave you walking

any codes? do the key on 3 times trick
more than likely low rail pressure from loose injector hold downs, loose connector tubes, injectors leaking nozzles or bypass valve, popped rail overpressure relief valve.

any white smoke or raw diesel odor in exhaust?
any increase in motor oil level or smell of diesel in oil?

get it started
measure:
cold idle rail pressure
hot idle rail pressure
hot 2000 rpm cruise control flat freeway run
WOT
Sorry. I thought my signature would show up. IT is a 2006 Ram
No codes at all
There is no smell of diesel in the oil or doesn't seem that there is an increase in oil level.
There is a lot of white smoke after it finally cranks over and starts but there doesn't seem to be excessive white smoke anyother time.
I plan on getting an EDGE CTS Insight gage system here very soon so that will allow me to monitor rail pressure.

Is there any difference in the way I measured low pressure fuel output by just checking ouput from the drain of the fuel filter housing after fully draining it than the way you are telling me?

How do i check for injector leakby?

Thanks!
 
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