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Discussion Starter · #1 ·
A prior thread here: leaking fuel rail cap fix and 2002 4.0 Fuel Rail Leak - Jeep Cherokee Forum

We have occasionally been smelling gas both in the cabin and outside for over a year, so decided to attack the main suspect, the injectors and fuel rail. Van has 285K miles and injectors are OE and untouched as far as I know (bought at 155K miles). Of course, no fuel routes thru the cabin, so fumes must have been sucked in the fresh air duct.
Fuel injectors are fairly standard, with most in U.S. either the EV1 body (short & squat) or the EV6 "pencil" body, which are Bosch designations. The connectors on U.S. vehicles map as "Jetronic" for EV1 and "USCAR" for EV6, so many use the EV names for the connectors though Japanese cars can vary. My 1996 Plymouth has EV1 injectors and my 2002 Chrysler has EV6.

I found an injector rebuild kit for a V-8 on ebay for $10 w/ free shipping. It had filter screens, O-rings, and a tool. All such kits must have Viton O-rings, which are typically brown but blue and black on the OE injectors. As you'll see, you'll need 13 O-rings, so buy a V-8 kit. I didn't use the end caps and disks. I suspect the leak was from the "fuel pulse dampener" cap at the end of the rail, since others have experienced that (links) and the rail appeared unusually clean around it. But as-found bench testing didn't show a leak. Perhaps I had spun the cap a little which sealed it. Indeed, you might try that on-car first since easy once you unbolt the power steering reservoir. I removed the upper intake manifold (plastic) to remove the fuel rail.

I have an injector test bench from prior work. It has a Bosch fuel pump from 1990's Euro cars w/ Jetronic (had spare), but almost any EFI pump will work. I clip to a car battery for power. Last pass, I had used a fuel rail from an early Dodge Magnum V-8 with pressure regulator on the rail. Those disappeared ~1995 with the EPA's "returnless fuel supply" mandate which moved the regulator into the fuel pump assembly in the tank. You can't run an EFI pump dead-headed without regulator. For this pass, I plumbed in a Corvette filter/reg (Wix 33737, popular for EFI conversions) which controls 56 psig by dumping one port back to the tank. Since I had a Magnum wiring harness connected to a switch, I bought adapters for EV1 connector to EV6 injectors ($10 set of 8). I used graduated beakers (99 cent only store) to catch and measure each spray. Problem was the continuous injector spray is forceful enough to give splashing, so I got inconsistent results. Next pass, I'll have tall graduated cylinders. I used gasoline initially, then switched to diesel which gave less splash (narrower spray cone). A lower pressure regulator or electronics to pulse the injectors for less flow would help. You can buy an injector test set for 6 cyl on Amazon for $405.

It is critical the injectors be matched in flow, because there is only one O2 sensor to adjust the average O/F for all cylinders. If the injector flow rates vary, some cylinders will run rich and some lean. As-found readings were the most matched, from 90-95 mL. After cleaning in an ultrasonic bath (hot water and detergent), they varied 42-52 and 39-48 mL flowing gasoline and 102-110 and 103-120 mL flowing diesel. I didn't control the time of spraying, so absolute flow varied between runs. In repeats, the highest and lowest injectors jumped around, meaning my measurements were erratic, likely from splashing. Ideally, you want to know your injectors are matched with 5% max spread. The old filters broke apart in removal, but in what was left of the fine screens I didn't see any debris and could see thru them.

Others had trouble removing the damper cap. I have a set of tubing release tools (photo), but all too tall to slide under, so I resorted to small screwdrivers, bending the fingers back slightly. The O-ring was stuck tight. Looking close, that O-ring showed 2 small cuts, which might have caused the leak. The rubber was still compliant, as were all on the fuel side of the injectors. One of the black lower O-rings, which seal vacuum in the manifold, cracked apart when removing. Those see more heat. The damper uses the same O-ring as the injectors, indeed the port is identical to an injector port. Some have questioned if the damper has any moving parts. I could make out a brown apparent plastic disk, which you might see in the photo. It may have a spring behind it. Those parts are welded shut. Another question is if that damper is needed. I suspect not because nothing like that on my 1996 2.4L fuel rail (also returnless), nor a later returnless Magnum V-8 fuel rail I have. Also, 2003+ fuel rails don't have it, and otherwise look similar. A new 2001-2 fuel rail is $105 on Amazon. You can buy used 2003+ rails from a 3.8L Jeep for $42 on ebay, including 6 injectors (last photo). The supply tube comes out the side instead of the end. It appears that could work in my van, but would have to rework the incoming nylon fuel tube to match.

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When I had this issue at 176K miles, I just replaced the entire fuel rail, with an OEM one, for a little over $100 and replaced all the O rings on the fuel injectors (12). At over 324K miles, no leaks or issues.

Just a note, sometimes it's better to just replace the part, instead of trying to fix it.
 

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Discussion Starter · #3 · (Edited)
I'll apply "just" to swapping the damper cap O-ring since easy. Order the V-8 kit so an extra O-ring for that. Ordering a new rail would have involved waiting for it, paying $105, and perhaps less assurance than a new O-ring, particularly since so many factory ones leak gas for some unknown reason (a tool cut the O-ring?). Drove today and no more gas smell. Not assured since it had been erratic, though became "most times" recently which is why I finally jumped on it.

I wanted to look at the "fuel trim" values to see if injector flowrates had increased (would lower trim%), but can't connect with my ELM327 Bluetooth adapter (doesn't find protocol which works). Strange since it connects to my 1996 Voyager. Can't recall if it ever worked on the 2002. I'll buy another one, and pay a bit more than the current $8 one (blue translucent housing if shopping on ebay). I could read OBDII codes with an older code-reader. It had just tripped codes from when I had the IAC and TPS unplugged to remove the upper intake.
 
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