1986 F150 Posted April 27, 2023 Share Posted April 27, 2023 Okay guys, here's one of many questions I'm sure I'll have down the road: My 1986 F150, is hard to start, and won't idle at all. I have timing spot on at 10* BTDC ( with SPOUT disconnected). To get it to start each time I have to give it a couple shots of starting fluid. As long as I hold pedal down it'll run. Let off and it dies. On a hunch, I pulled off the vacuum line going to the fuel pressure regulator, the hose nipple on the regulator as well as end of the vacuum line was wet with gas. Did I find the culprit, would the pressure regulator cause the problems I described? There are no other vacuum leaks, all ignition parts have been replaced. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted April 27, 2023 Share Posted April 27, 2023 Hi Jeff! I would say definitely A cause, if not THE cause, but you seem to have covered all your bases. The FPR isn't seeing the vacuum it should with the throttle body closed and it's getting raw/rich fuel connected to that vacuum line. Replacing that regulator is a given. Link to comment Share on other sites More sharing options...
1986 F150 Posted April 27, 2023 Author Share Posted April 27, 2023 Hi Jeff! I would say definitely A cause, if not THE cause, but you seem to have covered all your bases. The FPR isn't seeing the vacuum it should with the throttle body closed and it's getting raw/rich fuel connected to that vacuum line. Replacing that regulator is a given. Would also explain it going from 1/2 tank of gas to 1/8th tank of gas only idling it for three 10-15 min periods in last 10 days Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted April 27, 2023 Share Posted April 27, 2023 Hi Jeff! I would say definitely A cause, if not THE cause, but you seem to have covered all your bases. The FPR isn't seeing the vacuum it should with the throttle body closed and it's getting raw/rich fuel connected to that vacuum line. Replacing that regulator is a given. Would also explain it going from 1/2 tank of gas to 1/8th tank of gas only idling it for three 10-15 min periods in last 10 days You seemed to say that it WON'T idle... I'm sure your plugs look like they're covered in Vanta Black but should clean up driving ~50 or so miles with proper mixture. Probably want to replace that vacuum line while you're at it. Not a lot of $ and sitting full of fuel isn't good for most rubber. Link to comment Share on other sites More sharing options...
1986 F150 Posted April 27, 2023 Author Share Posted April 27, 2023 You seemed to say that it WON'T idle... I'm sure your plugs look like they're covered in Vanta Black but should clean up driving ~50 or so miles with proper mixture. Probably want to replace that vacuum line while you're at it. Not a lot of $ and sitting full of fuel isn't good for most rubber. It would idle, but not the best. That bad regulator dumping all that excess fuel wasn't helping matters any. My truck still has the color coded plastic vacuum lines on it. Been thinking of eliminating those in favor of rubber line Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted April 27, 2023 Share Posted April 27, 2023 You seemed to say that it WON'T idle... I'm sure your plugs look like they're covered in Vanta Black but should clean up driving ~50 or so miles with proper mixture. Probably want to replace that vacuum line while you're at it. Not a lot of $ and sitting full of fuel isn't good for most rubber. It would idle, but not the best. That bad regulator dumping all that excess fuel wasn't helping matters any. My truck still has the color coded plastic vacuum lines on it. Been thinking of eliminating those in favor of rubber line If the lines aren't brittle and crumbling to dust I'd say best to leave them alone. Many of us would be envious of functional factory vacuum lines. I think the only one I still have is the one from the cowl splitter to the HVAC controls in the cab. Link to comment Share on other sites More sharing options...
1986 F150 Posted April 28, 2023 Author Share Posted April 28, 2023 If the lines aren't brittle and crumbling to dust I'd say best to leave them alone. Many of us would be envious of functional factory vacuum lines. I think the only one I still have is the one from the cowl splitter to the HVAC controls in the cab. They are all in rather good shape yet, I could at least blow that particular one out with compressed air to get the gas that may be in it out of the line. Link to comment Share on other sites More sharing options...
1986 F150 Posted April 30, 2023 Author Share Posted April 30, 2023 If the lines aren't brittle and crumbling to dust I'd say best to leave them alone. Many of us would be envious of functional factory vacuum lines. I think the only one I still have is the one from the cowl splitter to the HVAC controls in the cab. They are all in rather good shape yet, I could at least blow that particular one out with compressed air to get the gas that may be in it out of the line. Put on a new fuel pressure regulator, Then started it. It fired right off, checked fuel pressure and it is just as the specs say it should be. It idles smooth in park at about 900 rpm. Still, when putting in gear it'll die off. But when restarting now it'll fire right back up, and idle back @ 900 in park. Timing is spot on @ 10*. Could it be, that the computer still hasn't re-learned its memory settings since the battery has been disconnected since 2019? Longest period I've had it idling at any one time is 10-15 min. No vacuum leaks externally. Note: Before I replaced a bad TFI module, it would idle in gear. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted April 30, 2023 Share Posted April 30, 2023 Put on a new fuel pressure regulator, Then started it. It fired right off, checked fuel pressure and it is just as the specs say it should be. It idles smooth in park at about 900 rpm. Still, when putting in gear it'll die off. But when restarting now it'll fire right back up, and idle back @ 900 in park. Timing is spot on @ 10*. Could it be, that the computer still hasn't re-learned its memory settings since the battery has been disconnected since 2019? Longest period I've had it idling at any one time is 10-15 min. No vacuum leaks externally. Note: Before I replaced a bad TFI module, it would idle in gear. That's great news! Congratulations Perhaps the torque converter simply needs some exercise? Four years is a long time. Though I'll admit that I don't know all the in's and outs of the AOD. I would definitely try driving it around the block as is and observe how it behaves. When you change many things at once you can never be sure which changed what. Link to comment Share on other sites More sharing options...
1986 F150 Posted April 30, 2023 Author Share Posted April 30, 2023 That's great news! Congratulations Perhaps the torque converter simply needs some exercise? Four years is a long time. Though I'll admit that I don't know all the in's and outs of the AOD. I would definitely try driving it around the block as is and observe how it behaves. When you change many things at once you can never be sure which changed what. Not really sure myself, I do know the trans was good, as it was being driven daily before it was parked. The fluid was a good red color with no debris in pan. I put new filter and fluid in too. Would idle in gear, before I had to repair the misc issues with the ignition, and the fuel pump relay/pressure regulator. Can't really drive around the block yet, as I have to bleed and inspect the brakes after replacing the master cylinder. I could possibly try at least moving it back and forth. It's certainly possible, the computer does not have a baseline idle speed learned Link to comment Share on other sites More sharing options...
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