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3.9/5.2/5.9 Magnum Fuel Line Leak Question

395 Views 9 Replies 5 Participants Last post by  Dave Z
Hi All

I have a fuel line leak at the fuel rail connector (all original parts with quick-connect intact) that slowly leaks. There must be some sort of o ring or other seal in the quick connector but I can't find a part reference for this. I checked Dorman's website as was recommended but there is no available fuel line repair kit for my application - 1993 Dodge Ram 150 5.2L. I'm looking for a simple repair as opposed to finding NOS lines or having new lines made. The connector for this first gen Magnum fuel system has the connector at the rear (not the side) of the fuel rail.

Presumably there are (were) millions of people out there with these types of connectors that at some point developed leaks at this connection point. I saw through searching everything out there on the web that there are other types of leaks on the rails (balance tube, injectors, etc. which is not the problem that I have. Please let me know what anyone's experiences are with this.

Thanks for any help!
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While looking, keep in mind 1992 (3.9 and 5.2 only) and 1993 fuel rails are different than the later ones. 1994 started the returnless fuel injection system on the Magnum engines.
 

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You may not find any reference to the quick-connect supply & return hose fitting o-rings as they are serviced with the hose assembly only. Not serviced separately.
These parts are discontinued by Mopar, but you may find 'generic' fuel hose, fitting & clamp repair kits from HELP! or Dorman at the auto parts store.
The supply line is 5/16" (Mopar #52020170). The return line is 1/4" (Mopar #52020171).

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EFI hose is bulk. Sold by the foot.
 
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I had a leak at the return hose at the other end below, at the quick-connect by the frame. It was cracked away from the braided stainless steel portion of the line. I found a NOS line on eBay.

Unfortunately, when I tried to disconnect at the fuel rail, I found that the Dakota parts book had labeled the return and supply lines reversed (they are both 5/16" lines at the fuel rail, but the ports are different sizes, and not obvious). So I ruined the supply quick-connect at the fuel rail, which was the inboard one.

I finally fixed it with one of the quick-connects above, and in order to get my hands in there and make the line reach, had to snip the top rubber portion of the hose above the bellhousing, and use a double-barbed fitting to connect the remaining fuel hose with a short portion of FI hose to the quick-connect. I double-clamped everything with FI clamps, and all is well.
 

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Just as a note to those less careful than Bob Lincoln, the fuel pressures are quite high, so any connection has to be really good... and for anyone else looking in, you always have to use fuel line, not a non-fuel-rated hose...
 

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Discussion Starter · #6 ·
While looking, keep in mind 1992 (3.9 and 5.2 only) and 1993 fuel rails are different than the later ones. 1994 started the returnless fuel injection system on the Magnum engines.
Thanks for the extra info. I didn't know that the difference between the returnless (connector on the side) and the "non-returnless" (connector at the rear) was for these reasons - not a JTEC person :)
 

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If you splice with hose, use only fuel injection rated hose that's SAE rated at 100R06, or 30R09, or higher. These are rated to handle the 55 psi typical pressure, and have burst ratings as high as 400 psi. Hose rated only 30R06 or 30R07 has much lower ratings that should only be trusted for carbureted vehicles, despite what any clerk may tell you.
 
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Discussion Starter · #9 ·
IIRC the turbo era fuel pressures were the ones that were high and the pressures dropped over time.

Thanks to everyone for the wealth of information. It goes to show the depth of knowledge and experience that members have on this archetypal site. I couldn't find this information after many hours of searching!
 
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