Fuel Line O-rings

[WahooSteeler]

In the process of swapping in 746 injectors on my 88 Renix 4.0L. Are the o-rings on the fuel return line and on the pressure regulator the same size? I thought the return line was larger, yet the o-rings I pulled out look identical in size and match up with the replacement 5/16s I bought. The pack also came with a pair of 3/8.

 

On a different note, I pulled out the o-ring and the spacer from the return line and I don't see or feel a bottom o-ring. I have scraped inside with a pick and I am almost certain there is not a 2nd one in there. There should be, correct?  

[Drahcir495]

There should be two tiny o-rings and a spacer that goes in between them. I found out the hard way after several attempts. I have the part number for the kit if you need me to find that for you.

[WahooSteeler]

47 minutes ago, Drahcir495 said:

There should be two tiny o-rings and a spacer that goes in between them. I found out the hard way after several attempts. I have the part number for the kit if you need me to find that for you.

 

Yeah, confirmed all that. I have new o-rings and saved the spacers. I am still searching for confirmation if the supply line and return line take the same size o-rings. Just came across an old post on here that said the supply line takes 3/8 o-rings and return line off the regulator takes 5/16. Logically that at least makes sense when you buy a replacement pack like Dorman 800-013 it comes with a pair of each size. I'd like to see another post somewhere confirming this, amazed that with all the threads on various Jeep forums about injector swaps and o-ring replacement for fuel line leaks there is never any clarification of what size goes to what line. 

[Drahcir495]

Same thing with my search. Finally found a small bit of info buried in a  thread somewhere?? Maybe NAXJA? I only changed the leaking in line, so not sure about the return line?? I thought they were the same 

[88mancheman]

I couldn’t tell you exact sizing but I can confirm that the supply side o ring is slightly smaller than the return o rings, when I did the 746 swap a few weeks back I went and bought the below part # from my local parts store as the return side didn’t seem to have anything existing in it still it was kinda held together with magic lol but when I did that I tried out of curiosity to see if the supply side was the same and it appeared it be a tad bit smaller

 

The return line measures 5/16 so I’m assuming the supply side o right was 1/4 hopefully this helped a bit

 

 

 

[WahooSteeler]

I've read about 20 threads across here, NAXJA, cherokeeforum, and jeepforum and nobody clarifies this. What makes it harder is visually they look identical because they are only 1/16 difference in diameter. That said, the one post I've found that specifies says 3/8 is the supply line and 5/16 is the return line which makes sense the supply line would be slightly bigger. 

 

 

 

[WahooSteeler]

7 minutes ago, 88mancheman said:

I couldn’t tell you exact sizing but I can confirm that the supply side o ring is slightly smaller than the return o rings, when I did the 746 swap a few weeks back I went and bought the below part # from my local parts store as the return side didn’t seem to have anything existing in it still it was kinda held together with magic lol but when I did that I tried out of curiosity to see if the supply side was the same and it appeared it be a tad bit smaller

 

The return line measures 5/16 so I’m assuming the supply side o right was 1/4 hopefully this helped a bit

 

 

 

 

Well no surprise, this just adds to the confusion being the opposite of what RockFrog posted in the thread I linked in my last comment. I don't think the supply is 1/4, I haven't seen that size mentioned in any of the threads I've read. That said, I put 3/8 on my supply line tonight and could not get the hose to push over the new o-rings and click in place on the disconnect. I expected the new o-rings to be tight, but I put some real effort in to pushing it on with no luck. I have the 3/8 on my return line also but have not attempted to connect it back to the pressure regulator yet. So tomorrow I will try the 5/16 ones on the supply and report back along with which size seems correct on the return side.  

[fiatslug87]

All three places where the o-rings and spacers are used in the 4.0L are the same size. The difference is between RENIX and HO, HO are larger. For RENIX the original PN for the repair package was 83502745, same for the 2.5L engine, #25 below.

[WahooSteeler]

1 hour ago, fiatslug87 said:

All three places where the o-rings and spacers are used in the 4.0L are the same size. The difference is between RENIX and HO, HO are larger. For RENIX the original PN for the repair package was 83502745, same for the 2.5L engine, #25 below.

 

Ha! Slug, I just went through my PDF parts manual and was about to post the exact same page! Stuff like this would keep me up all night, I have to have the answer knowing it is out there! So HO's must be the 3/8, but that is irrelevant to me and my 88 Renix LOL. Looking forward to buttoning up the job tomorrow and going for a drive with the Bosch 746s installed. 

[88mancheman]

All three places where the o-rings and spacers are used in the 4.0L are the same size. The difference is between RENIX and HO, HO are larger. For RENIX the original PN for the repair package was 83502745, same for the 2.5L engine, #25 below.

does that mean the supply line should have a oring-spacer-oring aswell? When I did my swap I only recall there being 1 oring inside the regulator

[eaglescout526]

1 hour ago, fiatslug87 said:

For RENIX the original PN for the repair package was 83502745, same for the 2.5L engine, #25 below

I have a few of those repair kits. There’s plenty from Chrysler. They come in handy. Now if only I could find the right flare nut to repair my original supply line. 

[fiatslug87]

8 hours ago, 88mancheman said:

does that mean the supply line should have a oring-spacer-oring aswell? When I did my swap I only recall there being 1 oring inside the regulator

Yes, supply line to the fuel rail is o-ring/spacer/o-ring. The regulator has a single o-ring where it attaches to the fuel rail (I think same size as injector o- rings) but o-ring/spacer/o-ring going out to the return.

[JustEmptyEveryPocket]

11 hours ago, WahooSteeler said:

That said, I put 3/8 on my supply line tonight and could not get the hose to push over the new o-rings and click in place on the disconnect. I expected the new o-rings to be tight, but I put some real effort in to pushing it on with no luck.

When I swapped in my new injectors I had the same issue. My final solution was to lightly clamp on a small trigger clamp and use a dead-blow hammer to hit the clamp, thereby forcing the connector together. Was the only way I could think of to get it the last 1/2" and click in place. Be it right or wrong my truck has been leak free for 2 years now. 

[WahooSteeler]

As confirmed with Slug last night, all fuel line connectors use 5/16 o-rings. After swapping that size on the supply line in place of the 3/8 ones I still couldn't quite get it to click in place by hand, but it took almost no effort using channel locks on the metal collar of the supply line and the back of the fuel rail. I haven't driven it yet but have idled it and revved it for about 20 mins with no leaks anywhere so far. 

[WahooSteeler]

Been on a couple of test drives this afternoon/evening and happy to report still no leaks and definitely a noticeable difference with the 746 injectors. Seems to fire faster and no doubt it's smoother at idle and normal acceleration. Very happy with this upgrade, cost to benefit ratio is hard to beat. 

[cruiser54]

A little trick for future reference:

You only need to disconnect the rail at the fuel pressure regulator. It will move out far enough to facilitate the installation of injectors.