BFRieck Posted February 21, 2012 Share Posted February 21, 2012 Spent the weekend messing with the Series III and have a new item to repair. My Series III is an ex MoD (109 FFR) and therefore has dual fuel tanks - two identical tanks, one under each front seat. Two problems have cropped up - I get a leak at the valve when I switch from the driver's side tank (rhd) to the other side and the fuel gauge shows full (left hand side) even if the tank is only about 60% (the least amount in it during my time to observe it), and it shows slightly less than half full all the time (regardless of how full the tank is - from completely empty to completely full and everywhere in between) when the right hand tank is selected. First question: Is the valve rebuildable? If so, is there a rebuild kit available and, if not, where shall I try to get a replacement valve - I've had no luck from my usual suppliers here in the USA. Second question: Can any of the pros out there diagnose the fuel gauge deal? I didn't have a chance to try to clean all the contacts, etc. My guess is that gauge is fine - the senders are likely to be the culprits - am I on the right track? Thanks. Quote Link to comment Share on other sites More sharing options...
BFRieck Posted February 21, 2012 Author Share Posted February 21, 2012 Well, I've solved part of my own problem. PA Blanchard's website lists the changeover valve as an in-stock item (part numbers: 526783, 526783a, and 526783b - don't know what the difference is, if any). I still don't know if it can be rebuilt. FWIW, it's not in any of the parts manuals being an MoD vehicle item, I guess. Still don't know what what's going on with the fuel gauge, but I assume it's electrical in nature as the fuel changeover valve simply switches from one tank's sender to the other mechanically. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted February 22, 2012 Share Posted February 22, 2012 It is in the optional parts catalogue, I also have one fitted in my ex-mod Lightweight, the parts cat shows it as the attached PDF, and does show some sub-parts, but don't know if it is rebuildable or not: SERIES_opt_parts_cat_part1.pdf Quote Link to comment Share on other sites More sharing options...
BFRieck Posted February 22, 2012 Author Share Posted February 22, 2012 Thanks for the info. It turns out that the part is the same regardless of the (a) or (b) suffix. Also, I have learned that there is a gasket, available from at least one supplier (PA Blanchard - their part number NRC5364), which may repair my leak - at least the people at Blanchard think so. Obviously, the gasket is far less expensive than the entire valve at about $12 but still pretty pricey to my mind. I plan to remove the valve this weekend to see if I can replace the gasket with a homemade one (assuming the gasket material, shape, and my skills are all compatible). I don't see that part shown on the drawing supplied, however. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted February 22, 2012 Share Posted February 22, 2012 I think the gasket may just be a rubber washer, number 606598 on that diagram, but can't find any listing on the interweb for it. This may make it a standard part, fingers crossed Quote Link to comment Share on other sites More sharing options...
BFRieck Posted February 22, 2012 Author Share Posted February 22, 2012 I'm not sure, but I think the gasket in question is different - it appears to have holes in it which may be opened/blocked as the valve handle moves from left tank to right tank and vice-versa. Not sure how to go about getting an image in this message, but here's a link to a picture of the valve and the gasket on Blanchard's website. https://secure.pablanchard.co.uk/photos/Web%20Fuel%20Tap%20Etc.jpg Any ideas what that gasket might be made of? I am hoping I can recover the existing gasket sufficiently intact so as to copy it. Quote Link to comment Share on other sites More sharing options...
Phil Hancock Posted February 22, 2012 Share Posted February 22, 2012 The seals that i have replaced in the past have been cork about 1/8" thick. Quote Link to comment Share on other sites More sharing options...
BFRieck Posted February 23, 2012 Author Share Posted February 23, 2012 Perfect. Just what I needed to know. Quote Link to comment Share on other sites More sharing options...
tacr2man Posted February 23, 2012 Share Posted February 23, 2012 I found the switch over taps to be a total pita over many years, I would suggest that you either just fit a t piece .and an electric pump on each supply or choose which is main tank and then pump from other to that , you will save yourself a lot of agro , and probably fuel as well . You can also get elec operated taps as used on later vehicles that are far more reliable . JMHO Re guages , the tap usually has switchs that operate on a cam that connect whichever tank is selected to the single guage , if guage is misreading usually down to poor connection /corrosion on connectors , or possibly sender units in tank . Quote Link to comment Share on other sites More sharing options...
BFRieck Posted February 23, 2012 Author Share Posted February 23, 2012 Probably good advice. Blanchard has a replacement gasket that they think may fix the problem as I've described it. I ordered one so we'll see. I've learned that Phil Hancock's earlier post accurately described the gasket as cork about 1/8" thick. At my request, Nick at Blanchard was gracious enough to look at the gasket they sell and said it was cork 3-4 mm thick so that tallies. I'm going to attempt to homemake one. It's a bit of a surprise that the factory taps are so problematic - how complicated can that be - particularly when there are no electrics involved (save the gauge stuff which doesn't have anything to do with the tap - it's just a matter of the switch handle contacting the selected side and disconnecting the unselected side). As for the later electric taps that you've found to be more reliable, can you give me a part number or more specific id? I'd like to check out that option. Quote Link to comment Share on other sites More sharing options...
BFRieck Posted February 27, 2012 Author Share Posted February 27, 2012 Well, I wished I had never ordered the replacement gasket from Blanchard as I was able to make one in about an hour without too much trouble. Turns out the one I had was bad but good enough to make a pattern. I made a new one out of 1/8" cork sheet from a hardware store. It appears to be the same material as the original; works fine, no leaks, etc. Couldn't get the gauges sorted, though. It may be the senders. Apparently, the gauge is pegged "full" when there's no connection. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted February 27, 2012 Share Posted February 27, 2012 Half good news then I seem to remember that to show full on the gauge you needed to short to earth, in which case I would be looking at the wire going from the switch to the sender for chafing/piching etc, there's a lot of panels with sharp edges found here for it to catch on. Quote Link to comment Share on other sites More sharing options...
Snagger Posted February 27, 2012 Share Posted February 27, 2012 I have two of these valves on my 109, and rebuilt them with new gaskets prior to installation. I have had no trouble at all from the valves since the vehicle was rebuilt. People complain about many "standard" LR maladies, but these are more often than not down to extreme age and lack of maintenance- Remember that the vehicles that these valves are fitted to are at least 28 years old, and more typically around 40. To expect the cork gasket to still be intact at that age is simply unrealistic. I did initially rebuild my valves using rubberised gasket material before finding the correct cork gaskets at Blanchards, and they seemed to work well enough (no leaks). I did apply a smear of grease to the gaskets during assembly to make sure they didn't tear as the valve was rotated. The fuel sender units are almost certainly the cause of your gauge issues, though a full indication on an empty tank could come from an internally short circuiting switch and the half indication could come from a switch with corroded contacts (internal or external). The correct switches are shockingly expensive, but by drilling out their mounting holes in the valve cradle, you can fit brake light switches which are about 1/4 of the cost and have much bigger contacts (as they're designed to handle higher currents). As well as saving money, it also means that you are thus carrying spares should the switch on you brake pedal box fail (an additional benefit that paid off for me once). Quote Link to comment Share on other sites More sharing options...
BFRieck Posted February 28, 2012 Author Share Posted February 28, 2012 I assume Blanchard does stocks the proper cork gasket (don't know for sure as mine has not yet arrived). However, for us yanks they are pretty expensive what with the exchange rate and shipping - a single gasket came to nearly $20 fob Texas. By contrast the one I made cost $0 for the material - I needed so little the hardware store gave me a scrap of 1/8" cork sheet and about an hour of work including removal and disassembly of the valve, using a cad program to draw the gasket, transferring the drawing to the cork, cutting out the gasket with a Stanley 99 utility knife and a leather punch, installing the gasket, and reassembling and re-fitting the valve. Installing the gasket from Blanchard would have saved about half that time. Of course, as my wife reminds me - at my billing rate doing it myself cost a lot more than buying the gasket - to which I reply that what I do for money is not nearly as much fun as fiddling with the LR so I rightfully regard any labor devoted to the LR as money well spent. I did not put any lubricant on the gasket which I might have had I thought of it, but the way the gasket is captured and the fact that the brass surfaces which slide on the gasket are pretty smooth pretty much rules out any tearing of the gasket. I tend to agree with the theory that the left hand tank gauge wiring is shorting because it reads the same (pegged to full) whether attached to the sender or not. Cleaning up the contacts on the right hand tank (both the contacts on the selector switch and the contacts on the tank sender unit itself) did not change the "nearly half full" reading reagardless of tank volume. Is there any way to tell if the tank mounted sender unit is functioning short of having a known functioning gauge and getting a proper reading? Quote Link to comment Share on other sites More sharing options...
Snagger Posted February 28, 2012 Share Posted February 28, 2012 Bypass the switch - disconnect the wiring from all the switches (after applying some markings and noting down what goes where) and connect the earth from the gauge directly to one of the tank's senders (the gauge earths via the "sender" units). Turn the ignition on and move that sender's float by hand (if you have a MoD under-seat fill type tank, just remove the cap and the extendable neck and you should be able to reach in directly; with civilian tanks you'd need to remove the sender unit to manipulate it). Then repeat with the other tank. You could also use a multimeter to test the switches by removing the wiring from them and then testing the resistance with the switch open and closed, remembering also to test the resistance between the terminals and the casing in each condition to search for a short on the side that always reads full. (I'd suspect a chafed wire between the switches and that tank's sender, though. Quote Link to comment Share on other sites More sharing options...
BFRieck Posted February 28, 2012 Author Share Posted February 28, 2012 Thanks, I'll try that this weekend when I'm once again LR'ing. Mine are the twin ExMoD under-the-seat tanks so getting at the fuel sender devices is a reach-in affair. Quote Link to comment Share on other sites More sharing options...
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