mp470 Posted August 20, 2017 Share Posted August 20, 2017 Hi all, Took the truck out for a short drive yesterday, came back home to grab something to take it for a longer one. Shut it off, went inside, came back to start it, nothing. No accessories, lights as if there was no battery at all. Battery is brand new. Disconnected it for a while, starts up like a dream again. After a few starts and off cycles, turn the key, hear a click and then back to square one. Something else to note. Ever since I test drove it, it sometimes shuts off when pulling over to park - never at a red light though. It doesn't stall, just electrically shuts down but the oil and battery light remain on as in accessory mode. Now, while it's on and running, i jiggled wires around, positive to and from starter relay (also relatively new), negative (bit of exposed wiring near the terminal), computer wires. Couldn't recreate the issue. The battery terminals are pretty shot and i will be replacing them tomorrow. It all really seems like an intermittently bad ground but I can't be sure. I haven't yet checked what the battery ground looks like at the other end (where does it go?). Any suggestions would be appreciated. Thanks, Mike Link to comment Share on other sites More sharing options...
Gary Lewis Posted August 20, 2017 Share Posted August 20, 2017 Mike - I don't remember what engine you have, but it would help if you would put details about your truck in a signature so we do't have to try to remember. Anyway, on most 8-cylinder engines the ground goes to the block and from there to the frame. But, if you still have oil and battery lights when the engine stalls and don't have anything when you turn the key, it sounds like these are two different situations. Yes? Or, if it is an intermittent connection perhaps the engine dies and then the power comes back, illuminating those lights. Link to comment Share on other sites More sharing options...
85lebaront2 Posted August 20, 2017 Share Posted August 20, 2017 Since you say computer wires, I assume you either have a feedback carburetor or one of the 5.0L EFI models. On the 5.0 and possibly the FBC engines the entire system grounds at the battery with a pigtail plug/socket assembly that looks very much like a power window motor connection. Since it is very close to the battery and is not a sealed weatherproof connection, it will corrode, giving a high resistance to ground which drives the electronics crazy. I would start there. If you have the EFI engine, the 1985.5 and 1986 models are extremely sensitive to TPS (Throttle Position Sensor) voltage at closed throttle. These engines have a voltage specification for idle setting and there was a Ford IAC (Idle Air Control) bypass kit Ford had as a TSB (Technical Service Bulletin) solution. The issue arises that at a very small amount over 1.0 volts, I believe around 1.1 volts, the EGR (Exhaust Gas Recirculation valve)vacuum solenoid is activated. Since these early controls use a vacuum and vent solenoid pair to control the EGR, if the vacuum is activated, the RPM will drop, the EVP (Exhaust gas recirculation Valve Position sensor) tells the EEC "too much, vent", the feedback loop starts and the two solenoid valves near the battery start chattering like a squirrel. Link to comment Share on other sites More sharing options...
mp470 Posted August 20, 2017 Author Share Posted August 20, 2017 Mike - I don't remember what engine you have, but it would help if you would put details about your truck in a signature so we do't have to try to remember. Anyway, on most 8-cylinder engines the ground goes to the block and from there to the frame. But, if you still have oil and battery lights when the engine stalls and don't have anything when you turn the key, it sounds like these are two different situations. Yes? Or, if it is an intermittent connection perhaps the engine dies and then the power comes back, illuminating those lights. Sorry guys, I set my signature but it's not displaying for some reason. It is indeed a 5.0 EFI. Thanks for the tips so far. Link to comment Share on other sites More sharing options...
mp470 Posted August 20, 2017 Author Share Posted August 20, 2017 Mike - I don't remember what engine you have, but it would help if you would put details about your truck in a signature so we do't have to try to remember. Anyway, on most 8-cylinder engines the ground goes to the block and from there to the frame. But, if you still have oil and battery lights when the engine stalls and don't have anything when you turn the key, it sounds like these are two different situations. Yes? Or, if it is an intermittent connection perhaps the engine dies and then the power comes back, illuminating those lights. When it 'stalls' out while parking, it always starts right back up but when I turn the key and nothing happens at all, it's usually parked for a bit and stays like that until i unhook the battery for a while. Link to comment Share on other sites More sharing options...
85lebaront2 Posted August 21, 2017 Share Posted August 21, 2017 When it 'stalls' out while parking, it always starts right back up but when I turn the key and nothing happens at all, it's usually parked for a bit and stays like that until i unhook the battery for a while. When you unhook the battery, are you taking off the negative cable? If so go back to my first reply on the ground for the entire EFI system. I think you will find the problem right there. Link to comment Share on other sites More sharing options...
mp470 Posted August 21, 2017 Author Share Posted August 21, 2017 When you unhook the battery, are you taking off the negative cable? If so go back to my first reply on the ground for the entire EFI system. I think you will find the problem right there. I hope you're right. I know what you mean, the small wire with the 1 pin connector on it spliced into the battery negative lug. I always unhook the negative first for a bit, but so far I've also been removing the positive, mostly to check the connection to the starter relay and clean up the lug itself. Link to comment Share on other sites More sharing options...
85lebaront2 Posted August 21, 2017 Share Posted August 21, 2017 I hope you're right. I know what you mean, the small wire with the 1 pin connector on it spliced into the battery negative lug. I always unhook the negative first for a bit, but so far I've also been removing the positive, mostly to check the connection to the starter relay and clean up the lug itself. Suggestion, from my son's problems with his 86 F-150, bypass that connector by splicing (soldered) a long enough lead to allow a direct ground to the battery. A good body to battery ground while you are at it will help also. These trucks had a lot of ground issues which were corrected on later models. Link to comment Share on other sites More sharing options...
mp470 Posted August 22, 2017 Author Share Posted August 22, 2017 Suggestion, from my son's problems with his 86 F-150, bypass that connector by splicing (soldered) a long enough lead to allow a direct ground to the battery. A good body to battery ground while you are at it will help also. These trucks had a lot of ground issues which were corrected on later models. Well i didn't end up bypassing the connector but re-did the battery terminals after cutting out enough of the negative cable where corrosion was evident. Hasn't stalled out since. I did however notice something else. The oil pressure light is still flashing when coming to a stop in gear. When in park / neutral, it doesn't flash. I just changed the oil with the proper amount and filter. Is the oil pressure sensor / switch capable of signalling the engine to shut off? The light flashes now but no stall. Drives down the road perfectly at all speeds but the engine does seem to bog down some at idle after a few minutes. Almost seems like a misfire. Link to comment Share on other sites More sharing options...
85lebaront2 Posted August 22, 2017 Share Posted August 22, 2017 Well i didn't end up bypassing the connector but re-did the battery terminals after cutting out enough of the negative cable where corrosion was evident. Hasn't stalled out since. I did however notice something else. The oil pressure light is still flashing when coming to a stop in gear. When in park / neutral, it doesn't flash. I just changed the oil with the proper amount and filter. Is the oil pressure sensor / switch capable of signalling the engine to shut off? The light flashes now but no stall. Drives down the road perfectly at all speeds but the engine does seem to bog down some at idle after a few minutes. Almost seems like a misfire. No, low oil pressure will not shut it down, only one I know of is the 460 with hot fuel handling package. They have electric in-tank low pressure pumps controlled with a switch from the oil pressure fitting on the back of the engine. On the low idle, possible misfire, can you hear the EGR relays chattering when it does this? I will have to find my idle set procedure for the 1985.5 and 1986 EFI systems. Link to comment Share on other sites More sharing options...
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