SW-EM Fuel Tank Notes

The Volvo Fuel Tank configured for use in an Amazon. Notice the arch clearance on left...this is a strong suggestion that the same tank pressings were also used for the 1800, where the vent fitting visible in the 1800 Tank picture, is located there (filler pipe enters Tank below seam).

122 Station Wagon Tank is somewhat unique, and shallow, and it looks like the (side) filler pipe is shorter than on the sedan...this could be the explanation why there is typically a fuel stain under the Fuel Filler of Kombis (and it is important to assure the Fuel Cap has a good seal to prevent this leakage and resulting staining).

The important difference to note in Sedans vs. Kombis: Fuel Cap on the Kombis are unvented to prevent spillage (there is a vent in the filler tube!), unlike the vented Fuel Cap of Sedans.

"Wagons never had locking caps, so I deduce this is an aftermarket one which a PO or you have installed...and knowing it's an aftermarket one, I also deduce that it is vented, which they typically are...and herein lies the rub, this does not play well with the relatively flat Tank and Filler, and is likely cause of your leakage! Factory wagon Fuel Caps were not vented...that is not to say Kombi Tanks were not vented...they were!...but in the filler neck and occurring behind the Cap (which must do its intended function without making a mess). I suggest your leakage is from the vented Cap which you could address. I would suggest rebuilding it, and while you have it apart, you will undoubtedly see the venting provision, which you should defeat before reassembly. Please take and post pix of Cap rebuilding!

Naturally, the sealing of the rubber gasket between Cap and Filler is important and must function well. You may need to adjust or replace with thicker to assure sufficient preload.

Tank venting is routed from Fuel Filler, behind interior panel, not by way of a vented Fuel Cap!

When an OE Filler Cap is not available..."Rustinmotion" pic permission requested.

1800S Tank, with Filler entering the Tank below seam and just above it the Vent connection. Note area for 122 Filler location.

Picture of the inside of a tank from an injected 1800, showing Anti-Slosh Compartment with Fuel Pickup. Second picture shows Fuel Return from Fuel Pressure Regulator of the Bosch D-Jetronic Injection System. One of two big general tank baffles is visible.

Internal Anti-Slosh Compartment is clearly apparent. Fuel return is at front-facing side of Tank, and it feeds into bottom of ASC (Orn), as well as replenishment ASC from main Tank volume. At Green, the Fuel Pickup tube also feeds from the very bottom of ASC, and no prefilter is present (as with the later ES and replacement Tanks). Source of picture: http://www.gas-tank.com/Links2009/Volvo.htm

The following four pictures and info for 1800ES tank were kindly supplied by Jim Perry:

Same Tank bottom view, showing both the central Drain, and the Sump with Prefilter location, and also a good dent which one can suspect as part of the reason Jim replaced the Tank!

Prefilter can be simply pulled from Feedtube, after removal of Sumpplug (Bruce K noted that a 3/8" ratchet extension did not fit the Sumpplug...a sacrificial one had to be ground slightly to make this possible, so it is likely a metric nominally sized Plug...and 3/8" is a bit bigger than 11mm!). Any particles of contamination which have been sucked onto Prefilter fall into the sump when suction from the pump is no longer present, so will be inspectable after removal of Sumpplug.

Note the difference both in the threading and tool necessary for installation/removal in the OE brass Sumpplug, and those of replacement Tanks [china's finest work strikes again!].

For carbureted models, the configurations are fairly simple, with a Pick-up Tube coming in the Tank front side, and making a turn down towards to feed fuel from the Tank bottom. I have tried to collect some internal Tank pictures here, and where I have yet to get a picture, I have included a graphic representation as near to the actual as I could deduce (any individuals who cut open a Tank not shown here, are invited to contribute some pix, thanks!):

Part of a nicely cleaned carbureted Tank, with what looks like a replaced Pick-up Tube.

Injected Fuel Tank Plumbing, 3 Port Fuel Pump (with Prefilter in replacement Tank):

Dan G provided this nice clean picture of his '71 1800E with a replacement Tank*, showing the feed (Green) to the (3 Port) FuPu from the side, FuPu outfllow (Blue) to FuFi and beyond, and the bypass outflow from Pump into "T" fitting (Orn) , joining the Fuel Press Reg Return from engine compartment (which is obscured).

* Notice that this arrangement is with a replacement Tank. These Tanks are all configured with an internal Prefilter, so the external FuFi is plumbed post-pump...since there is no Prefilter in the original E Tank, the FuFi would need to be located before Pump.

Versions of Tanks for Injected Models, internal Tank configurations got more complicated, with the addition of the Fuel Return Line from the Fuel Pressure Regulator, an Anti-Slosh Compartment and on the last models a Prefilter with Sump. Versions 1-3 known to the author are shown here (if the reader can help with internal pictures of various configurations of OE Tanks, please e-mail!):

Version 3. Pic of a cleaned the '73 ES (Version 3) Sump with Plug removed, so that angle-cut Pickup Tube with shoulder-stop for the Prefilter and soldered-in brass Sump fitting are all nicely discernable. Picture by Bruce K. and reposted with his kind permission.

PLACEHOLDER FOR INTERNAL PICTURES OF ES TANK WITH INTERNAL PREFILTER AND PLUMBING

PLACEHOLDER FOR 3 Port vs 2 Port Volvo/Bosch Fuel Pumps (also non-Volvo replacement Pumps) and their variations in plumbing...it can get complicated!

A replacement Tank (which apparently all have the side-located feed, plus front-located return necessary for FI) has the feed plugged, and some custom plumbing feeding from the return (which apparently also works), supported by a less than impressive wire, which looks like it came off a bundle of asparagus from the grocery store...hmmm! David Smith picture used with his kind permission.

PO (aka Mr. Goodenoughwrench) strikes again! I spy late Trailing arms with Poly bushings, and a 3/4" IPD rear anti-sway bar!

Fuel Tanks for non fuel-injected vintage Volvo cars are, and must be(!), vented to atmosphere. Failure to have this condition, by for instance, replacement of an incorrect Fuel Filler Cap can/will cause problems...

Here, an example of the important requirement for an atmospherically vented Fuel Tank for a carbureted 1800:

Replacement Rubber Seal installed as one might reasonably believe it should be...but this is wrong...read on!

My response to a question of

about "loud woosh sound" when opening 1800 Fuel Filler Door:

"These cars had no evap recovery/control systems, and the 1800 Fueltank (just as the 122) should be vented to atmosphere...wooshing sound is escaping of pressure due to temp rise and resulting evaporation...and the ENTIRE fuel sys before FuPu is subjected to that pressure! (Edit: CORRECTION: ...entire fuel Sys...not only before FuPu, but also downstream since both Checkvalves in Fuel Pump would allow flow in that direction), so you might experience some (undesirable) leakage in the plumbing or engine compartment!

Conversely, when driving, you might experience fuel starvation issues when a vacuum is created in Tank because it can't draw make-up air through that Cap and Seal...so I'm with Mike...I'd simply enlarge that central securing hole (or add some slits) so it doesn't seal quite as good. " This was not the remedy for this issue...read on!

[The above info is all correct, and this issue was caused by owner reasonably following Volvo's Exploded Assembly Diagram...but the solution was even simpler: What is shown in the Exploded Assembly Diagram is slightly deceiving, and maybe of an earlier design (or just plain wrong). Part 27 is the metal cup behind the The Rubber Seal (35). It is secured to the folding Fuel Compartment Door by way of the central pin/washer/cotter pin, and should be installed with convex down!]

Although one might mistake Item 27 for the Rubber Seal, [IT IS NOT!] ...it is the metal cup which supports the Seal (Item 35), and unfortunately, the way Item 35 is originally shown in the diagram, it looks like only a flat circular gasket and not with a cup-form (pointing down!) as seen in the Correct Assembly shown below. I have added what I believe to be a better representation of the Seal in the highlighted area at 35A.

With the Rubber Seal (35) installed as shown below, the central hole is unblocked which allows breathing of the Tank and no pressure or vacuum build-up or wooshing effect.

Correct Assembly: The Washer (29) and Split Pin (30) are to secured the Cap, lower (27), with cup up, and the Gasket (35, Cupped Rubber Seal) must be glued to Cap with cup down. Of course, since the central hole is not used to retain Seal when mounted like this...it is free to allow venting to take place through the hole and past the Pin to Cup mount, and pressure/vacuum in the Tank is prevented!

Correctly installed Rubber Tank seal (35). Glued in place with convex (and venting hole) down.

Common weakness of the 122 sedan Fuel Tank. Soldered joint at Filler Neck to Tank. The solder fractures due to weight of the fuel filler pistol being hung onto the filler. This is less of an issue in other models, where the filler is better supported in the body. A leak-test with water verifies the fractured solder joint at Filler Neck root.

" Leakage as shown in Pieter's video is absolutely typical...and due to cumulative fatigue of years flexing the joint from hanging the fuel-filling pistol onto the fuel filler...that is only a solder joint, and it gets stressed and shows once again, that solder just isn't mechanically strong and up to the task long-term... My Tank had a cracked solder joint there also (although I was not particularly rough with hanging the fuel filler on there!)...I resoldered it, but noting the long-term weakness, added strengthening gussets (see below) to significantly improve the mechanical support of the filler-neck.

If you cannot solder (for which tank must be COMPLETELY empty and vented, or baked in the sun until no more strong fuel smell confirms non-flammability!), OR you don't want to remove Tank, you can temporarily seal fuel leaks with fuel compatible (silicon) RTV (like Dow-Corning 730 Fluorosilicon formulation, NOT 732 general purpose [which is not hydrocarbon compatible!]) ...until it can be repaired right...but again, I highly recommend installing strengthening gussets to support filler neck or this condition can easily return! There's not a lot of room, but enough...see below for a sketch of what I installed last time my Tank was out. "

Gussets support Filler Neck to seam, here. The fuel filler protrudes through inner bulkhead, then outer body. No supporting rubber surround is present yet in this excerpt of the R. Watson photo.

Locking Cap partially disassembled, showing what certainly looks like a possible vent.
Picture credit: Rainer of the Volvoniacs Forum.

Internal Tank cleaning of rust...strapping the tank to a cement mixer, with a few of handfuls of course stones for abrasive.

When using tank sealers, like POR15 subsequently, its critical to follow the sealer manufacturer's instructions to the letter...take no short-cuts, make no "judgment calls"!

Maybe unique, "rustic", and noisy, so should definitely be done "behind the barn", but a very effective way of prepping the Tank interior for sealing.

Update: Notes on a conversation with Joseph Moyer, long-time owner/operator of Moyer Fuel Tank Renu (http://www.gas-tank.com ). They bake out each Tank and prep by blasting, to give their baked-on internal plastic coating the best adhesion possible, and their work is guaranteed for life. They are located near Pittsburgh PA. Mr. Moyer tells me that the Fuel Filler behind the license plate of seventies GMs was similarly susceptible to fractures on the soldered-on filler pipe (soldering is apparently the typical manner in which fittings and pipes were connected to steel fuel tanks in the past. He has also reinforced such weaknesses with gussets [I guess great minds do think alike!...just saying!]

Knowing the internal condition of my 1800ES Tank, I intend to use their service when the ES gets next recommissioned...instead of changing to a new, but chinashit replacement Tank, guaranteed to last from 11 'til noon!...and he tells me the mounting holes of chinashit tanks often don't line up!...more of china's finest work! Watch this space for results of the experience!

He stocks OE Tanks and just replaces them now..."they're all going on 50 years old now..." ...he's got a valid point there, but not if the chinese, in their neverending quest to cheapen things up, get it wrong...like here: china gets it wrong...again!

External material sources are attributed. Thanks again to all contributors of pictures and information! Otherwise, this article is Copyright � 2020-2023. Ronald Kwas. The terms Volvo, and name of any other companies or individuals included here are used for reference only. I have no affiliation with any of these companies other than to try to keep their products working for me, help other enthusiasts do the same, and also present my highly opinionated results of the use of their products here [like the fact that china got it wrong again!]. The information presented comes from my own experience and carefully considered opinion, and can be used (or not!), or ridiculed and laughed at, or worshipped, at the readers discretion. As with any recipe, your results may vary, and you are, and will always be, in charge of your own knuckles and future!

You are welcome to use the information here in good health, and for your own non-commercial purposes, but if you reprint or otherwise republish this article, you must give credit to the author or link back to the SwEm site as the source. If you don�t, you�re just a lazy, scum sucking plagiarist, and the Boston Globe wants you! As always, if you can supply corrections, or additional objective information or experience, I will always consider it, and consider working it into the next revision of this article...along with likely the odd metaphor and probably wise-a** comment.