dennisb Posted March 27, 2021 Share Posted March 27, 2021 85 f150 351 HO with engine bay mounted electric fuel pump seems starved for fuel once at operating temp on long trips, short runs not so much,(Napa fuel pump is new), when this first started happening I was able to rectify it by switching tanks but not anymore, I also do not see the frame mounted vacuum tank switch on my truck all I see is what looks like an inline pump? Any observations would be appreciated. front tank does not register on gage. Thank you. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted March 27, 2021 Share Posted March 27, 2021 Well, there should be no frame or engine bay mounted electric pump. Your '85 would have had in-tank electric pumps with a frame mounted switch valve. Likely there is a suction leak. Electric pumps work much better submerged, and only pushing fuel. Are you looking to return this to factory? Or only cobble it together? Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted March 27, 2021 Share Posted March 27, 2021 Well, there should be no frame or engine bay mounted electric pump. Your '85 would have had in-tank electric pumps with a frame mounted switch valve. Likely there is a suction leak. Electric pumps work much better submerged, and only pushing fuel. Are you looking to return this to factory? Or only cobble it together? On examination, I don't see that Gary has any 351 fuel systems posted from the '85 EVTM. (only 302 & 460) so I can't direct you to a schematic or diagram. Sorry.... Link to comment Share on other sites More sharing options...
dennisb Posted March 27, 2021 Author Share Posted March 27, 2021 Well, there should be no frame or engine bay mounted electric pump. Your '85 would have had in-tank electric pumps with a frame mounted switch valve. Likely there is a suction leak. Electric pumps work much better submerged, and only pushing fuel. Are you looking to return this to factory? Or only cobble it together? Thanks for the quick reply, I'd just as soon keep the new electric pump if it'll do the job? How can I test the tank pumps? Or could the suction problem be coming from elsewhere? Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted March 27, 2021 Share Posted March 27, 2021 Thanks for the quick reply, I'd just as soon keep the new electric pump if it'll do the job? How can I test the tank pumps? Or could the suction problem be coming from elsewhere? If there is even a tiny pinhole the pump will lose prime and 'suck wind' Gary said the lines in his truck were like jello. I will see if I can find a 351 HO diagram for your year. Gary has a massive shelf full of EVTM's, and posts some pages on this site. But if you intend to keep the truck, $15-20 for a copy is a tremendous investment in your sanity. You can find them used on eBay. autocorrect Link to comment Share on other sites More sharing options...
dennisb Posted April 10, 2021 Author Share Posted April 10, 2021 Well, there should be no frame or engine bay mounted electric pump. Your '85 would have had in-tank electric pumps with a frame mounted switch valve. Likely there is a suction leak. Electric pumps work much better submerged, and only pushing fuel. Are you looking to return this to factory? Or only cobble it together? Cobble for now I guess. Thank you. Link to comment Share on other sites More sharing options...
dennisb Posted April 10, 2021 Author Share Posted April 10, 2021 Cobble for now I guess. Thank you. Thank you, where can I purchase? Link to comment Share on other sites More sharing options...
Gary Lewis Posted April 10, 2021 Share Posted April 10, 2021 If there is even a tiny pinhole the pump will lose prime and 'suck wind' Gary said the lines in his truck were like jello. I will see if I can find a 351 HO diagram for your year. Gary has a massive shelf full of EVTM's, and posts some pages on this site. But if you intend to keep the truck, $15-20 for a copy is a tremendous investment in your sanity. You can find them used on eBay. autocorrect Jim - I don't think the 351's had electric pumps. Just mechanical. In the schematic below it says that this is the wiring for "Except 7.5L with dual fuel tanks and electric pumps and 5.0L EFI Engine. All others had mechanical pumps. So Dennis' setup is not stock. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted April 10, 2021 Share Posted April 10, 2021 Jim - I don't think the 351's had electric pumps. Just mechanical. In the schematic below it says that this is the wiring for "Except 7.5L with dual fuel tanks and electric pumps and 5.0L EFI Engine. All others had mechanical pumps. So Dennis' setup is not stock. His first post says HE has an electric pump mounted... I'm not saying it is stock. I'm just trying to figure out how it's wired. But if the fuel lines look like licorice from Halloween three years ago they need replacement. I wonder why someone abandoned the mechanical pump? If the cam eccentric is gone, going back to stock suddenly became a much bigger job. Link to comment Share on other sites More sharing options...
Gary Lewis Posted April 10, 2021 Share Posted April 10, 2021 His first post says HE has an electric pump mounted... I'm not saying it is stock. I'm just trying to figure out how it's wired. But if the fuel lines look like licorice from Halloween three years ago they need replacement. I wonder why someone abandoned the mechanical pump? If the cam eccentric is gone, going back to stock suddenly became a much bigger job. I misunderstood. Thought you were looking for 351HO wiring. Anyway, it is going to be fun unraveling that. Link to comment Share on other sites More sharing options...
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