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leaking fuel rail cap fix

89K views 71 replies 25 participants last post by  FabricGATOR 
#1 ·
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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#2 ·
It's the fuel pressure regulator. Good tip on just changing the o-ring, a new regulator is about $100
 
#3 ·
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
 
#6 ·
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
 
#7 ·
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.
 
#8 ·
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.
 
#9 ·
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.
 
#10 ·
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.
 
#11 ·
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.
 
#14 ·
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."
 
#15 · (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)
 
#54 ·
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...
For those who doesn't understand this physical effect.

Early carbureted vehicles equipped with mechanical fuel pumps didn't had that problem. I don't belive it has to do with frequency either.

The problem is the "Ariete Hammer". More widely known to plumbers as "Water Hammer". Earlier homes didn't had that problem either, until electronically controlled water valves started being used on home appliances, then a pressure dampener needed to be added to the plumbing system to prevent leaks everywhere.

In your vehicles, the injectors are the "electronically controlled valves".
Every time an injector closes, your system pressure will increase due to the "Ariete Hammer" effect. Multiply that by the number of injectors, hope you get the idea. The Ariete Hammer effect is the main reason a cold weld or resine fix on pressurized lines doesn't last long. It may work on a fuel tank because it is not pressurized.

Now that you know about this ariete hammer effect, use this knowledge next time you need to "fix" or repair a pressurized gas component.
 
#17 · (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.
 
#18 ·
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)
 
#19 ·
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
 
#21 ·
It is leaking from the "pulse damper" like it was before. It held tight for almost 2 months but then I smelled gas again and sure enough it's the same thing. It's worsening at a much faster pace than before. I've ordered a new rail assembly and will have it Monday or Tuesday.

I do drive my van a lot - over 100 miles a day for work so from a mileage standpoint it lasted a while. But it definitely isn't a real fix for me anyway. I was careful when bending the prongs back into place and making sure the cap gripped the pipe securely. Maybe it isn't a serviceable part or maybe the o-ring I used was slightly too small or something. It's hard to diagnose it exactly. YMMV.
 
#22 ·
I'd be tempted to try an oversized O-ring if I could find one. I wonder if the cap (hat-shaped thing) or the fuel rail is the culprit, perhaps due to a bit of corrosion? My fuel rail was not pristine and showed some areas of mild surface corrosion.
 
#23 ·
Take a look at my pics in the beginning of the thread. You have no room for an oversize o-ring.
I thing that would help is to to use a brush to clean the cap and carefully wipe where it seats on the fuel rail.
Mine has not leaked since I replaced the o-ring.
Once you put it back together, it helps to give it a little tug and make sure it not loose.
 
#24 ·
I was pretty careful when I re-assembled mine. I bent the tangs just so and it held tight after I put if back on. I couldn't remove it without tools. I don't know why some leak again and some don't. Maybe mine has another problem like a hairline crack or something.

In any event I think it's worth trying to replace the o-ring because it is relatively easy, cheap and fast. It seems to work for some people but not all.

Justin
 
#26 ·
Thanks Guys. My 2002 Grand Caravan 3.3L V6 has been smelling like gas for months now. We have a trip planned for Seaworld in a week so i figured i better fix this. Quick look with a flashlight while the van was running and i found quite a bit of gas leaking under the power steering reservoir. took it off and found this cap your talking about and gas leaking from it. Followed your steps and and replaced it with a doorman vitroline o-ring. seems good as new. I'll repost if i have any issues after Seaworld.
 
#28 · (Edited)
Well I finally did mine today. For months I've had a gas smell that came and went, and was occasionally strong. I had cleaned my fuel injectors and replaced all the O-rings a while back, but didn't do the cap (same O-ring). Of course that's where the leak was, so today I went back in.

I took the opportunity to also replace my power steering reservoir. I've been hearing some funky noises and we'll see if that helps.

My procedure:
• To improve access, I removed the two spark plug wires nearest the reservoir from the distributor cap, and two vacuum fittings from the intake manifold.
• Remove the two easy-to-see 8mm bolts holding the power steering reservoir.
• With a good light, get eyes on the nut below the reservoir that must be loosened slightly (NOT removed).
• Coming from behind with ~5" of extension, get a 10mm socket onto the nut and loosen it.
• Pop the reservoir up and out of the way enough that you can access the fuel rail cap.
• I did not disconnect the battery or drain the fuel system. Perhaps because of my leak, there was no residual pressure.
• It was difficult to pry the cap off. I used a couple of wide flat screwdrivers and as someone mentioned, I used the power steering reservoir mounting bracket for a leverage point. I knew I didn't want to risk permanent damage to the cap's integral spring clips.
• Swapped the O-ring and reinstalled, only to observe a serious leak, maybe 3 drops per second!
• Popped the cap off again and fiddled with the spring clips for a while, trying to find the happy middle where the cap is held tightly but will slip on with moderate pressure. If you bend them too far in, you cannot press the cap back on.
• Finally reinstalled the cap. I was not happy with the way it wobbled and did not seem like a snug fit, so I took a heavy cable tie and wrapped it under the fuel rail and over the cap, and tightened it down.
• So far no leak at all is visible. I'm not sure the cable tie is necessary, or how long it will hold, but time will tell.


Here are the additional steps to complete my power steering reservoir replacement:
• Use pliers to move the two hose clamps, one on the smaller return line and one on the larger supply line.
• It took some effort to loosen both hoses by twisting, without risking damage to them.
• With an empty plastic milk jug handy, pull off the hoses and catch what runs out of the filter and the reservoir. With attention to orientation of the reservoir, little should run out.
• Put the new reservoir in place and attach the large hose and return its clamp to the proper position. At this point you can also tighten the 10mm nut and replace the two 8mm bolts up top that hold the reservoir in place. Replace the spark plug wires onto the distributor.
• Plug the small fitting on the reservoir. I used a small piece of hose with the opposite end held up to the top of the reservoir. This does not need to withstand any pressure, just to prevent the fluid from running out.
• Route the small return hose into the milk jug. A high flow will hit this, so be sure it's secure.
• Add fresh fluid to the reservoir, right up to the top. Turn on the engine and rock the steering back and forth a little. It will only take seconds for the old fluid to be pumped out and chased by the new fluid. You'll feel and hear the loss of power steering as the new fluid is drawn in, emptying the reservoir, and pumped back out into the milk jug.
• Remove the plug from the small fitting and attach the return hose and place its clamp.
• Refill the reservoir and top it off as needed after running the engine and exercising the steering.
• I had bought 2 qts of fluid for the power steering, and most of the 2nd quart is leftover. I could have used more for flushing, but I really don't think it would have done much more. I could not have done the job with just one quart, so you really need to buy two.
 
#29 ·
You certainly have to be carefully getting the cap off. There is a part number for it, but they are not available anywhere.
It is not even listed as a separate part.
They want you to buy the whole fuel rail.
Glad it worked out for you. As far I know, and I will have to check, my power steering reservoir has never been changed.
the van is over 160,000 miles now
 
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