Do you guys think my problem could be caused by a bad fuel pressure regulator? Although the fuel pressure seems to be ok, is it weird that it drops off to 0 when the engine is shut off? I heard that it should should in the 30 range for a bit after the engine is shut off.

Pardon the stupid questions, I'm a noob when it comes to anything Dodge


Alex

 

- It is totally normal for the pressure to drop to zero and even rise to 49psi on it's own just sitting parked. Now, in the manual, the spec states that when testing the fuel system, you warm it up to normal operating temp and turn it off. Spec states it should hold 30 lbs for five minutes. If it fails to hold 30psi for five minutes, either a leaky injector is suspect or, the regulator valve on the pump is suspect or, the gas cap is suspect, or, the hose connections at the tank is suspect.

-It is also stated that under certain conditions, if the pressure in the system exceeds the safety threshold for a given temperature, the relief valve will open thus draining the fluid back into the fuel tank. As a result, the fuel pressure will drop faster than the allowed spec thus not meeting the five minute @ 30psi spec as called out in the test procedure.

I don't know if you've solved this issue or if you have enough information but, I'm going to tell you that sputtering is usually a fuel pump related issue. Keep in mind that there's several factors that affect the pump and they are:

-Fuel Pump Relay condition (test and perform OHM test per industry standard test listed in Haynes Manual.

-Voltage at the pump- verify voltage at the pump harness

-Current draw test at pump- verify current draw at pump

-Regulator: perform test after motor has come to full operational temp using a known, good guage in both operational and non-operational modes.

-Fuel pump motor is spent worn: same test as above to confirm

-Fuel pump filter is clogged thus impeding flow. Pressure reads fine when off or initially pressurized but, it drops when in RUN mode.

CM

 

CM,

thanks for the tips. I will be concentrating on the fuel pump when I get back home. So basically, even though it gives good pressure the fuel pump can still be faulty?

Alex

 

As a whole, yes, the pump can be the root cause but, it's not the motor but rather the inlet screen / mesh / sock / filter that may be clogged / restricted.

See, if there's a, NO-FLOW state, pressure will build after a period of time thus masking the root problem which, is LOW FLOW RATE due to restricted filter at the pump inlet.

When there's no flow, and, you turn the key to <ON>, the pump is going to pressurize the line regardless of a restricted filter. The problem shows up during a flow state. When there's a partially clogged filter, during operation, the pump is not able to achieve full output thus causing a drop in pressure over a short period of time. This is why I always recommend to check pressure in both operational and NON-operational modes.

Check the pressure in both modes before doing anything else. This is where you'll start. If the pressure is fine in both operational and NON-operational the pump is not the problem and it's time to look elsewhere.

NOTE: I just had a case of the same thing on a PT Cruiser and, it wasn't the fuel pump but rather a CAN sensor that caused this to happen. So, what you want to do here is get out the guage and test it 100% in both modes of operation along with noting dips, drops, surges or any other anomalies during the test. The results will lead us to making a decision which direction to go from here.

CM

 

Good info. Thanks, CM. I'll be home at some point on Tuesday so I will dedicate the rest of this week to solving the problem.

 

Guys, does anyone know if its possible to remove the fuel pressure regulator from the fuel pump assembly? I have the fuel tank off and I'll be removing the fuel pump later today, I'm just curious if I can pull out the regulator without breaking anything. Thanks

 

I think the whole thing is generally replaced as a unit. Not sure if you can get individual parts for it??

 

In a returnless system, if the regulator fails, the entire pump is to be replaced. In a return system, the parts are field replaceable. If your going to get a new fuel pump, your best bet is to go with Carter fuel pumps. Solid and reliable and, they have an excellent fuel filter as well.

CM

 

Just replaced my pump today with an Airtex, my pressure was good, volume was low, was .2 should have been .5, the problem with mine was after it sat overnight it cranked a time or two before starting. The pump that came out was the oem pump Chrysler logo and manufactured by Airtex, I won mine off ebay for $81.

 

Ok guys I have an update but no good news yet.

I broke down and bought a new pump from Auto Zone (Airtex). I installed the pump and it actually caused the truck to start idling rough and the same problem was still there. So I put in the original pump and now it idles fine at least. Pressure is still good.

Another thing to mention that I've noticed: Once the engine warms up, the truck will sometime backfire when I try to rev it. It happens rarely though.

I was gonna take a look at the TPS and CPS tomorrow. Although I am not getting a check engine light, is there still a possibility that one of these sensors could be faulty?

I'm just baffled at how this truck was running fine and all of a sudden it wont rev above the 1500rpm range. It's just acting like it's not getting enough fuel but everything seems to be ok on the fuel side.

I still have to check some other things that people have mentioned in this thread, but I figured I'll give an update that the fuel pump is not to blame.

Thanks