ArdWrknTrk Posted April 18 Share Posted April 18 IMG_2908.png You're not looking at the correct diagram for ,1986, dual tanks, electric pumps, 7.5l ....... These things changed. Go to the pages I pointed out and find the one that represents your truck. Link to comment Share on other sites More sharing options...
viven44 Posted April 18 Share Posted April 18 You're not looking at the correct diagram for ,1986, dual tanks, electric pumps, 7.5l ....... These things changed. Go to the pages I pointed out and find the one that represents your truck. I have deleted my posts as I wanted to make sure I confirm the 86' is the same as the '84 that I have. I may be giving wrong advice here. I did a quick glance and the 86' does look different. First off the tank selector switch on the dash for an 86' is 6 pin and the 84 I have is only 4 pin. If you have the 86' wiring you will definitely want to look into the 86 EVTM that Jim and Bill pointed to. I may be wrong but there may be no tank selector relay on the 86 (and Jim mentioned that as well above and it really does seem that way..) No more multitasking for me and I'm humbled again that not everyone can keep up with Ford's list of changes and revisions Link to comment Share on other sites More sharing options...
Jcomeau85 Posted April 18 Author Share Posted April 18 But the front tank reads correctly and will drive the truck? The problem is either the switch valve, or beyond, from what you've just told me Try jumpering around the valve, and see if the rear tank works. Does the valve also supply power to the rear tank when switched? Link to comment Share on other sites More sharing options...
viven44 Posted April 18 Share Posted April 18 Does the valve also supply power to the rear tank when switched? No.. power to the tanks flow through the in-cab selector switch based on the EVTM. This is a major difference from the 84' wiring that I am used to. As shown in the picture below from the 86' EVTM - When the switch is in the front position, pin 2 on the switch connects internally to pin 1 to supply power to the front tank pump (pin 5 connects to pin 3 which grounds out the rear tank pump) - when the switch is in the rear position, pin 2 on the switch connects to pin 4 to supply power to the rear tank pump (pin 5 connects to pin 6 which grounds out the front tank pump) You should definitely make sure when the in-cab switch is switched between front and rear tanks that you hear the frame mounted selector valve operate. It should be a small "clunk" as Bill described. Have someone sit in the cab and you can be under the truck to see if the selector is actually doing something. You have all the wiring diagrams now. You need to get busy and creative with a jumper wire as Jim said and see where the link is broken. Link to comment Share on other sites More sharing options...
viven44 Posted April 18 Share Posted April 18 You're not looking at the correct diagram for ,1986, dual tanks, electric pumps, 7.5l ....... These things changed. Go to the pages I pointed out and find the one that represents your truck. Thanks for being patient with me. I was completely off-base on this one with knowledge from 84' wiring diagram. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted April 18 Share Posted April 18 Thanks for being patient with me. I was completely off-base on this one with knowledge from 84' wiring diagram. I'm not here to chew anybody's head off. I may come off as gruff because of how autistic I am, but I don't try to hide any of that. I do the best I can, on a phone and about a half hour sleep per night. Please don't feel that I'm targeting you, Vivek! 🙂 Link to comment Share on other sites More sharing options...
Jcomeau85 Posted April 18 Author Share Posted April 18 I'm not here to chew anybody's head off. I may come off as gruff because of how autistic I am, but I don't try to hide any of that. I do the best I can, on a phone and about a half hour sleep per night. Please don't feel that I'm targeting you, Vivek! 🙂 All good. You guys are great!! What’s a way I can test the switch with a volt meter? Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted April 18 Share Posted April 18 All good. You guys are great!! What’s a way I can test the switch with a volt meter? The dash switch, or the switch valve? Link to comment Share on other sites More sharing options...
Jcomeau85 Posted April 18 Author Share Posted April 18 The dash switch, or the switch valve? Sorry. Dash switch Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted April 18 Share Posted April 18 Sorry. Dash switch Okay, give me a minute, because it's hard to Juggle pages and photos into a post from my phone.... 👍 Link to comment Share on other sites More sharing options...
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