Every once and a while my fuel pressure gauge will drop to and stay around 6 psi. I can ease off the throttle, pop into neutral and let it idle, or even lay into the throttle and the pressure reading stays the same, around 6 psi. It's almost like the gauge is stuck. The first few times it happened it would stay like that for a few minutes then all of a sudden it would go back to normal. Its starting to happen with more frequency now and it takes longer to get back to normal. What I have noticed is that I can put the truck in neutral and kill and restart the engine and the reading immediately goes back to normal. What gives? My pressure gauge reads off the VP44 and I run a needle valve (barely open) with no isolator or check valve to the gauge. The gauge has been replaced and did not solve my problem. Is this normal for a lift pump going south or does it sound like I have some other sort of gremlin? I have less than 10,000 miles on this lift pump by the way. Truck is a 2000, stock.

 

I would say your LP is going south...

 

I'm very new to the Cummins engine but it seems like any fuel, power or just plain burp with our engines is the LP. Is this really true or are we throwing $$$ at a different problem. I mean no disrespect ot Mopar or anyone else but I just find this confusing that one part can actually cause this many problems.

 

I'm not ready to jump at the idea that the fuel pump is bad just yet. If it were bad why would it go back to reading normal pressures (15 psi at idle, 13 psi cruising, and no less than 8 psi WOT) if it were going bad? Could an air bubble be blocking pressure from the gauge every once and a while? Afterall, pressure does bleed off from the system when the truck is shut down, air has to enter the gauge every now and then. If you pull the fuel pressure gauge out from the pod you can watch the fuel drain out from it at shut down. I have an isolator, I'm thinking about installing it before I throw money at a LP. Maybe adding a check valve at the injector pump might help solve the problem?

 

If you want to double check LP.... Do a volume test...

http://dodgeram.info/tsb/2003/14-002-03.htm

This is a for sure way of testing it...

During the testing take notice to unusal noises the LP is making. It should be a steady humm... Not grinding or studdering. My first LP would start and idle with 11-12 PSI and fall to about 5 PSI without warning. The bearing in the pump were failing... (grining noise heard during volume test)

Also do the test at least 5-10 times... The first two PASSED and the other nine FAILED.

The only other thing that pops to mine is check the voltage to the pump...

Check for codes too!

 

Forgot to mention, no codes and the connection for the LP checks out. Thinking about it more this problem seems to creep up more often now that it's hot and I simply start the truck without letting the "wait to start" light go out. Is it possible I'm forcing air into the gauge sytem by not letting the pump run long enough to purge the air before I start the truck?

 

I always let the wait to start light go out. When I was camping a few weeks ago I forgot, new truck etc., and it tried to start but sounded like death wormed over. Even my wife was asking what that sound was. I turned off the key, on again let the wait to start light go off and started just like normal. I'm not sure if it's glow plugs or grid heaters but I'd wait for the light to turn off.

 

Is it an electric pressure gauge? I had the same problem about a month ago and it was my fuel filter. The filter only had about 10k miles on it. After the change the fuel pressure went back up and it stays there.

 

It's a mechanical gauge. I'm replacing the fuel filter today. The thing that really confuses me is why can I kill and restart the engine and everything goes back to normal for a while? And why is the problem occuring with more frequency?

On another topic, how do you determine your "in service" date?

 

Its the LP. Its the internal fuel pressure regulator going bad. This goes bad, but the pump still runs fine (no pressure). Hope this helps. I would go with the FASSII for a "permenant" fix.

 

Would cycling the key "reset" it so that the internal pressure regulator goes back to normal?

I've been thinking about a FASS setup but after seeing one installed on a truck I have my concerns about it hanging down so low, doesn't seem safe. Is the FASSII a better design?

 

Nope. Its all mechanical inside the LP. Not serviceable.

Yes, the FassII uses your existing fuel filter set up. Just the heavy duty pump.

 

Yup....what Geico266 said.....the needle and seat in the internal regulator on the LP can act up and cause erratic pressures and inconsistent performance.....sometimes the needle can even seize in it's bore and then later become unstuck again. This is an early warning that your LP is headed South.....replace it now before it fails completely.

 

Who has the best prices on the FASSII? I haven't seen it advertised but then again I haven't really been looking since the last time my LP went out. Last time it was a gradual drop in pressure.

 

Had the same problem with my truck. Was putting on pump #3 and it would not prime. Found out the connection between the metal tube from the tank and the rubber fuel line to the lift pump was cut short from the factory. Just a pushed together connection. Shoved them back together and put a couple of clamps on it, pressure is fine. Wonder how many pumps were replaced due to this?