leaking fuel rail cap fix

83783 Views 67 Replies 22 Participants Last post by atoman, Jan 14, 2017

blknblu

Discussion Starter · May 19, 2012

3

First time posting,
I have a 2001 Chrysler Town Country with 3.8

For several months now, I've detected a strong smell of gas under the hood. After watching it for a couple of days, I noticed gas dripping out of the cap on the fuel rail. I found a post where someone removed the cap and replaced the internal o-ring with an o-ring from the fuel injectors. (Same size) I did the fix, and it has not leaked since I replaced the o-ring. The best part was I did not have to remove the fuel rail. (A new one is pricey) You will need to go to the auto store and ask for fuel injector o-rings for the van. Mine came in a package of 2 for 2.39 from NAPA.

Thse are the steps I took:

1) Relieve gas pressure from fuel injection rail:
Remove the fuel pump relay and start the van, running it until it dies. (The relay is in the fuse box)

2) disconnect the battery (just being cautious)

3) Move power steering reservoir:
Loosen the bolts for the reservoir , lift it slightly and push it to the side.
(There are 2 accessible bolts on the top, and one nut underneath that you just have to loosen)

4) Remove cap:
Gently pry the cap off, use the bracket for the power steering for leverage.

The pic with the blue o-ring is the original. (notice the erosion on it)

5) Prepare cap:
Remove old o-ring
Bend the tangs back on the cap so it will fit tightly when you re-install it.
Lubricate the o-ring with some fresh oil and put it on the cap.

6) Install cap:
Put cap over the hole making sure it is centered.
Gently tap on the end until it slides back in the hole and is seated properly.

7) Check for leaks:
Re-connect the battery.
Put back the fuel pump relay and start van.
Check for leaks.

8) Put everything back together:
Move power steering reservoir back and tighten bolts.

That's it, it is pretty simple to do as long as you are careful.
Not once did the CEL come on.
This cap is not for a test port, it looks more like a pressure relief port.

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Reactions: 5

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kevioll

· #2 · May 20, 2012

It's the fuel pressure regulator. Good tip on just changing the o-ring, a new regulator is about $100

Justin Kerns

· #3 · Dec 8, 2013

I just did this fix myself today. I had a strong gas smell inside and outside the van regardless of full tank, empty tank whatever. No evidence of leaky fuel pump but I could shine a flashlight on the pressure regulator and see that it was dry before starting the van and then as soon as I started it I could see gas around it. Replaced the o-ring per the above instructions and so far it looks dry. I drive 50 miles each way to work every day so I'll find out soon enough if that was my only fuel leak problem!

Thanks for the clear instructions. O'Reilly is my closest store and they had a Dorman variety pack of vitron o-rings (safe for fuel exposure) that cost around $8. There was one in there that was the right size.

Justin

blknblu

Discussion Starter · #4 · Dec 9, 2013

Mine is still holding, glad it worked out.

spacecoast

· #5 · Dec 9, 2013

So....its purpose is to "pop off" in case of too much pressure...and thus starting a massive car fire?

JCamasto

· #6 · Dec 9, 2013

spacecoast said:
So....its purpose is to "pop off" in case of too much pressure...and thus starting a massive car fire?

Yeah, something doesn't make sense... Regardless, prying/flexing the cap tabs back/forth has compromised it, making it more likely for this nightmare scenario. Having seen enough burned vans in the junkyard, I replaced the whole rail - which comes with the cap installed.

-Jim

blknblu

Discussion Starter · #7 · Jan 7, 2014

I found the correct name for this is a fuel pulsation damper or fuel pulse dampener, not meant to be serviced.
Part number is 04591758AA, (You cannot order this) on some of them it has a "do not remove label on them"
It also has 0063 BT 400KPA stamped on it too.

wayneh

· #8 · Jan 7, 2014

Yes it definitely is not a "regulator" in the normal sense, and is not meant to blow off either. Frankly I don't see how it would dampen a pressure pulse either, unless it contains an air bubble in normal operation.

I did my injectors not long ago and stupidly did not also put in the 13th O-ring on this. That was the only 1 of the 13 that was leaking. Murphy's law reigns.

Replacing the O-ring should be part of the procedure to replace the power steering reservoir and vice versa.

blknblu

Discussion Starter · #9 · Jan 7, 2014

once I figured out the proper terminology, google came up with more meaningful results, including people fixing it themselves with a fuel injector o-ring.
At the time I fixed mine, I did not know what the correct term was.

I like to this of it kind of like a water hammer arrester on plumbing pipes.

Road Ripper

· #10 · Jan 8, 2014

It's job is to keep the same volume of fuel inside the fuel rail (to stabilize the pressure) while the fuel injectors are opening and closing. That way the computer can more precisely meter the fuel by adjusting the injector pulse lengths with a known, stable fuel pressure.

The fuel pressure regulator is built into the pump assembly, inside the gas tank.

I've started to see some 4th gen vans in the junkyard without this pulsation dampener on the fuel rail. Apparently it has been deleted from the rail by the factory design, and possibly moved somewhere else in the fuel system.

atoman

· #11 · Jan 8, 2014

Road Ripper said:
I've started to see some 4th gen vans in the junkyard without this pulsation dampener on the fuel rail. Apparently it has been deleted from the rail by the factory design, and possibly moved somewhere else in the fuel system.

The fuel rail was re-designed to eliminate the need for this problematic component (the pressure test port was also eliminated) IIRC, the length at the end of the fuel rail was extended providing the volume needed for dampening the pressure pulses.

04anniversaryedition

· #12 · Jan 8, 2014

atoman said:
The fuel rail was re-designed to eliminate the need for this problematic component (the pressure test port was also eliminated) IIRC, the length at the end of the fuel rail was extended providing the volume needed for dampening the pressure pulses.

What year was it redesigned exactly?

atoman

· #13 · Jan 8, 2014

04anniversaryedition said:
What year was it redesigned exactly?

How would I know exactly? probably around '04 when the refresh happened and the new plastic upper intake appeared on the motors..

blknblu

Discussion Starter · #14 · Jan 8, 2014

Here is a thread on the same issue on a Jeep Cherokee which has a similar design:
http://www.cherokeeforum.com/f5/2002-4-0-fuel-rail-leak-33334/

Of interest is this blurb from the Cherokee service manual:
"High pressure fuel from the fuel pump is routed to
the fuel rail. The fuel rail then supplies the necessary
fuel to each individual fuel injector.
The fuel damper is used only to help control fuel
pressure pulsations. These pulsations are the result
of the firing of the fuel injectors. It is not used as a
fuel pressure regulator."

blknblu

Discussion Starter · #15 · Jan 8, 2014 (Edited)

The fuel rail with the damper is for 2001&2002 models only (or fuel pulsation damper or fuel pulse dampener)
The part number is 4861498AC

The part number for the 2003-2007 fuel rail is 4861498AD , I don't think you can put the later one on the earlier models (parts manual shows 2001-2002 fuel rail as distinct)

atoman

· #16 · Jan 8, 2014

IMHO, those fuel pulse dampers were a hasty solution to the problem of leaky fuel rails that goes back at least to mid 90's. The pulsation of liquid fuel caused by injector pulses sometimes caused resonance (hitting a "natural frequency") and caused catastrophic failures and fires...

BillGrissom

· #17 · Jan 8, 2014 (Edited)

A little more info on fuel pressure regulation. Earlier MPFI systems, up to ~2000, generally had a fuel pressure regulator on the injector fuel rail. Those had a return tube back to the fuel tank. The regulator was a simple "back-pressure" design, similar to a spring-loaded poppet that opens progressively as the upstream pressure increases. However, a vacuum hose from the intake was plumbed to it so it controlled the dP between the fuel rail and intake (thus, internally a 2-sided diaphragm that opened a fuel valve). The idea was to control the pressure drop that mattered most - across the injector. An EPA mandate required a change to "return-less" fuel systems, with a single line to the engine, to avoid heating the fuel in the tank and increasing evaporation. Thus, they could only control the pressure right at the outlet of the fuel pump, within the pump assembly (in the tank). In practice, it is simpler, safer, and works almost as well since the computer's equations can account for drops to the fuel rail, the computer already knows the intake pressure (PMAN sensor), and fuel is ultimately controlled by O2 sensor feedback anyway. I wonder if the pulsation damper simply physically replaced the pressure regulator of earlier cars, so they didn't have to redesign the fuel rail and because the regulator diaphragm had acted to damp pulses. Besides the fun of speculating about design choices, the main take-away for me is that it is more important to change your fuel filter in a return-less design since the engine computer assumes a certain pressure drop to the rail, instead of it being controlled as in the past.

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atoman

· #18 · Jan 9, 2014

FWIW, 3rd gen (96-00) used a single fuel line with pressure regulator on the pump..
Also, good luck finding a (traditional, in-line) fuel filter on the later 4th gen vans

(it went the way of dinosaurs with '04? model year)

Justin Kerns

· #19 · Jan 23, 2014

Well my fix did not hold. It has started to leak again and seems to be getting worse. I'm going to have to bite the bullet the replace the whole rail. Oh well you win some you lose some!

Looks like $70-$80 for the part depending on where you get it.

Justin

wayneh

· #20 · Jan 24, 2014

That's unfortunate. I'd be very curious to hear what caused the leak to return, if/when you get a chance to autopsy the situation. Replacing that O-ring is on my to-do list. I won't be happy if the job doesn't hold.

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