Hard Start After Fuel Pump Replacement

[resh...@sbcglobal.net]

I have a 1999 Chrysler T&C Limited w 3.8L engine. It has just under 140K miles and has served our family well in the 15+ years we have owned it. It was starting and running great up until a week ago when it died without warning while traveling at about 50MPH. There were no warning lights and no diagnostic codes. I pulled it off the roadway and it would start, then die immeidately. Eventually after 5 or 6 such starts, it failed to start any more. A check of the fuel rail showed no pressure and a check of the fuel pump showed it was getting power. In additon, the car would not start at all, but I found that it would start and run as long as I pounded on the fuel tank with my hand. The conclusion was that the fuel pump was defective, so I drained and dropped the tank and then replaced the integrated pickup/pump/regulator/gauge float unit.

After replacing the fuel pump and the fuel line filter, the vehicle took a while to crank over, but eventually started and ran well. I put a fuel gauge on the schrader valve on the front top fuel line and it read 50 PSI while it was running which I believe is the proper pressure specification.

Now that I have explained the background, here is the current issue and why I am asking for advice here in this group. The vehicle continues to be extemely difficult to start (cranks for about 30 seconds., then catches and runs great) when it sits for even very short periods of time. My understanding is that the fuel rail is supposed to stay pressurized between starts, but when I check it it shows 0 PSI. So why is it behaving this way? Is the new integrated pump assmebly or the fuel filter I installed somehow defective? (If so, exactly how does it work sicne there are two lines running from the filter to the fuel pump assembly? Any theories?)

By the way, there are no fuel leaks anywhere. All of the pressure clip fittings seem to be good. Also the ASD relay and fuel pump relays are working correctly as well. I am certain that I got the large O-ring on the retaining ring installed correctly and tightened down securely. I also believe that I correctly re-connected the fuel tank connections (2 evaporative emissions lines and the filler tube).

Lastly, here is the procedure I have come up with to make the car start properly till I can get this fixerd permananently. I cycle the ignition key from off to the on (no start) position about 10X. I can hear the fuel pump run for about 1/2 second each time and eventually can determine the fuel line is actually pressurized from the slight change in how it sounds. I thne turn the key to start and it fires right up like it should normally.

My theory is that the replacement fuel pump assembly is defective in that the back flow valve (assuming it has one) is not working correctly. Any thoughts on what I could also check or a specific diagnoistic procedure that might identify the culprit here? I hate to think about draining and dropping the tank again unless I can confirm that is the problem. Thanks in advance for your thoughts.

Bob

[Rob]

put your gauge on the Schrader valve, and then turn key on one time and
leave for about 30 seconds. while it is still on, and you're getting proper
pressure, turn key off and watch the gauge. if the pressure drops, your
fuel pressure regulator on the fuel rail is possibly bad. if it has a
vacuum line on it, check for cracks and splits.


if you find none of this then you might have a bad valve in the pump. But
more than likely is as simple as a leak at the regulator vacuum hose.


<resh...@sbcglobal.net> wrote in message
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[resh...@sbcglobal.net]

Here is some aditional diagnostic information obtained this morning. After the vehicle has been running, when the ignition key is turned to the off position, the measured fuel pressure drops as follows:

Running: 50 PSI
5 seconds: 30 PSI
10 seconds: 20 PSI
15 seconds: 15 PSI
30 seconds: 10 PSI
45 seconds: 5 PSI
60 seconds: 3 PSI
90 seconds: 1 PSI
120 seconds: 0 PSI

The bottom line here is that the new pump (and the fuel gauge sender which are integrated into the replaced assembly) appears to be working as designed, but the fuel line quickly loses its pressure (it should stay at or very near 50PSI) immediately upon fuel pump shut down. Since there are no fuel leaks, the only place the fuel can be going is either into the engine cylinders via faulty fuel injectors, or back into the fuel tank. I believe that in my case if this was due to a leaking fuel injector(s), then I would have observed this prior to replacing the fuel pump. Additionally, I would think that it would take several hours (vs. seconds) to fully depressurize the fuel rail and the engine would shake/shudder upon starting due to the amount of raw gasoline that would have been leaked into the combustion chambers. What I see is that once I fully pressurize the fuel system by cycling the ignition key on and off about 10-15 times (not actually starting the vehicle, just letting the fuel pump run each time for the fraction of a second before it stops) the engine starts instantly and runs smoothly. This is why I am of the opinion that the most likely cause here is a defective backflow valve or regulator in the fuel pump assembly.

Does anybody know exactly how the fuel pump assembly is supposed to work? Am I correct in assuming that it should not allow the fuel to drain back into the tank? Thanks in advance. Where is this vacuum line going to the fuel rail? Does it attach to the tank itself since that is all that I had removed and all was working fine with the old pump.

Thanks for your thoughts.

Bob

[Rob]

your regulator might be on the pump

https://www.rockauto.com/catalog/moreinfo.php?pk=945620&cc=1353877

https://www.rockauto.com/catalog/moreinfo.php?pk=977711&cc=1353877

note the little shiny vacuum pot.. did you reuse your old one? if not then
the new one is most likely bad. surprised its not on the fuel rail but it
differs from year to year.






<resh...@sbcglobal.net> wrote in message
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[resh...@sbcglobal.net]

Thanks Rob. I replaced the entire module. Like you, I suspect the regulator on he new pump module is defective.

[Rob]

its odd on this model since many of the regulators are on the fuel rail. it
sucks to have to pull the pump again.


<resh...@sbcglobal.net> wrote in message
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[resh...@sbcglobal.net]

I am re-posting a reply I received on the Minivan forum from dmccrea:

Is your fuel pump an Airtex?



On another Dodge Caravan related forum, it was shared with me by several members with similar symptoms that their problem was their fuel pump they had recently replaced. They had used Airtex fuel pumps and Airtex as of late has had quality issues. They replaced their Airtex pumps with an alternate pump manufacturer and their problems were solved. I am going back to vender who sold me the Airtex fuel pump back in December (they no longer sell Airtex) and get a Delphi under the same warrantee.

Anyone have any comments on this statement regarding Airtex fuel pumps? I do believe this is the manufacturer of the reppacement I had used and seems to support what I am seeing.

Bob

[MoPar Man]

resh...@sbcglobal.net wrote:

> I have a 1999 Chrysler T&C Limited w 3.8L engine.

Why didn't you mention that in the subject line?

[resh...@sbcglobal.net]

This is my last post to this thread. I wanted to let everyoine know that as suspected, the replacement fuel pump module I purchased was indeed defective. I convinced the Internet supplier from whom I had purchased it, to send me a replacement pump. I installed it and now all is well again on the family minivan!

The new pump generates 51 PSI when running. When I shut down the engine, the pressure dropped immediately to 45 PSI. An hour after the engine was shut down, it still read 44 PSI. This seems to be working as intended. While it was a PITA to drain and drop the tank twice, I was much faster the second time around and I am glad it fixed the problem!

Thanks to all for their feedback and assistance.

Bob

[Rob]

yeah holding 44 sounds great, and when you turn the key on now makes it
pressure back up to the 50s.


Great to here its working


<resh...@sbcglobal.net> wrote in message
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