1G O ring on fuel pump?

[solisjulian]

Hey thanks for viewing just a quick question

what size is the O ring on the fuel pump?

i want to replace it i belive it might be leaking

 

[chrysler kid]

The Toyota “fuel pump grommet” mentioned is the same as the evo fuel pump grommet and can be found on vendor websites for as little as $3

I use them on the 2g cars without issue.

I have tried the o-ring with fuel line under it and always had problems because the o-ring is the pivot point for vibration. The grommet has a larger depth and eliminates any slop or wiggle the pump could have from normal operation vibration. Even when snug the pump still has a slight ability to wiggle

It is my personal preference to always use the grommet. If the o-ring method works for you then by all means keep doing it, but the better solution to me would be using 2 o-rings and then use the fuel hose as the gap spacer on the neck of the pump

Mitsubishi Fuel Tank Grommet - Evo 7/8/9

Genuine OEM Mitsubishi factory replacement fuel tank grommet fits all 4G63 Evo 7/8/9 models. Buy yours at STM!

stmtuned.com

 

[We're on Boost]

If the o-ring method works for you then by all means keep doing it, but the better solution to me would be using 2 o-rings and then use the fuel hose as the gap spacer on the neck of the pump

2 o-rings with some hose for a spacer is probably also a good idea, but I haven't tried it yet.

When I got my car back from ER in 2016, they had it put together with 1 o-ring and some viton hose underneath the o-ring. The viton hose was 1/4" ID x 9/16" OD and it was soft, 60 Shore A, and didn't have any fiber in it, was just rubber. Unfortunately you can't buy that particular size of Viton hose anymore. Can't find nitrile hose that size either. I didn't think to measure the o-ring they had in there.

That worked perfectly and it would probably still be in there, but when I went in for a look in 2022 I just replaced everything including the pump. When I did that, I went back to my old method of using just the 1/4" x 9/16" soft Viton hose but using it full length on the Walbro outlet pipe. So, no o-ring, no cap on the end, and of course it's its own spacer. Molykote 111 lube on the rubber to help slide it in, and it is a tight fit. That all works perfectly too, but as I said that hose you can't buy anymore. I only have a few inches of it left from what I bought in 2009.

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I always use the new rubber foot that comes with the Walbro install kit. That part still fits perfectly on the bottom end of the newest pumps.

What size o-ring did you use when you tried using an o-ring with hose spacer?

 

[chrysler kid]

2 o-rings with some hose for a spacer is probably also a good idea, but I haven't tried it yet.

When I got my car back from ER in 2016, they had it put together with 1 o-ring and some viton hose underneath the o-ring. The viton hose was 1/4" ID x 9/16" OD and it was soft, 60 Shore A, and didn't have any fiber in it, was just rubber. Unfortunately you can't buy that particular size of Viton hose anymore. Can't find nitrile hose that size either. I didn't think to measure the o-ring they had in there.

That worked perfectly and it would probably still be in there, but when I went in for a look in 2022 I just replaced everything including the pump. When I did that, I went back to my old method of using just the 1/4" x 9/16" soft Viton hose but using it full length on the Walbro outlet pipe. So, no o-ring, no cap on the end, and of course it's its own spacer. Molykote 111 lube on the rubber to help slide it in, and it is a tight fit. That all works perfectly too, but as I said that hose you can't buy anymore. I only have a few inches of it left from what I bought in 2009.

You must be logged in to view this image or video.

I always use the new rubber foot that comes with the Walbro install kit. That part still fits perfectly on the bottom end of the newest pumps.

What size o-ring did you use when you tried using an o-ring with hose spacer?

Trying to find the exact size o-ring seems like a shot in the dark. Like even if you order the correct size it could be the wrong thickness

 

[We're on Boost]

It's a little hard to measure an o-ring exactly because they want to flex or ooze away from your caliper or what have you for measuring. But you can measure them very close if you are careful with a dial caliper and match up your measurements with the charts that show what sizes actually exist and are available to the retail customer:

Metric o-rings
Inch o-rings

When you shop for o-rings, you have to know that the inch sizes are only nominal, not actual. I suppose that's why they have a dash number. You would work from info that shows the actual measurements (Cross Section x ID x OD) for each dash number.

The metric sizes are Actual. They are what they say they are in millimeters and they are very accurate. Also the metric sizes come in so many sizes it's incredible, with very small increments from one size to the next.

Either way, inch or metric, the size number you start with is the thickness (CS or Cross Section). Then the ID. Then the OD, or the OD just falls out from ID plus 2xCS.

Usually there is no exact inch equivalent to a specific metric o-ring, and vice-versa. They are just plain different, size wise.

Anyway, the OD of the outlet pipe is bigger on the stock original 1990 AWD fuel pump than it is on the Walbro 255:

0.346" -- OD of stock 1990 AWD pump outlet pipe.
0.318" -- OD of outlet pipe on Walbro GSS 341 (made until a few years ago)
0.312" -- OD of outlet pipe on Walbro GSS 341 G3 (the current model)

So if you have an o-ring that is correct size for the stock original fuel pump, it's going to fit much looser on a Walbro 255, and it will probably leak.

The o-ring that you get in the Walbro installation kit is a metric 3.5mm x 8mm x 15mm, and that is the same as near as I can measure to the original 1990 AWD fuel pump o-ring. So it's correct for the original pump, but not for the Walbro !

So it's no wonder that they leak.

That's why I'm saying, for anybody who wants to use an o-ring (or 2 o-rings), don't use the one that comes in the Walbro kit. Use a 4mm x 7mm x 15mm o-ring. That web page is just one place where you can buy them. It's where I buy o-rings. The minimum QTY is 38 and the minimum order is $10 and o-rings are so cheap that you have to buy a bizarre quantity of them just to meet the minimum order. You can probably find some way to buy them one-at-a time for $2 each or whatever, but know that they really only cost 8 cents each for good industrial quality o-rings! Anyway a website like this is good for figuring it all out and shopping/finding out what exists and is available to the retail customer.