hard start when hot
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Elder User
Joined: Mar 2004
Posts: 759
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From: mohave valley, arizona
hard start when hot
im having a really hard time starting hot, 110 here. started perfect when it was cold outside. i know this is a common problem on these old trucks. where should i be looking. thanks. added note is that it seems to start up a lot better when hot with the pressure regulator disconnected.
Cargo Master
Joined: Jul 2009
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From: Des Moines
Well first off it would be useful if you told us the year/engine of the vehicle you're talking about.
Second, hard hot starts can indicate ignition coil going bad. But if it started easier with the fuel pressure regulator [I'm assuming that's what you meant] unhooked that could be the problem too, or at least part of it.
Ford Fuel Injection » How To Run a Self-Test Go to that page and use the procedure outlined to pull diagnostic codes- those can help point us in the right direction.
Second, hard hot starts can indicate ignition coil going bad. But if it started easier with the fuel pressure regulator [I'm assuming that's what you meant] unhooked that could be the problem too, or at least part of it.
Ford Fuel Injection » How To Run a Self-Test Go to that page and use the procedure outlined to pull diagnostic codes- those can help point us in the right direction.
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Elder User
Joined: Mar 2004
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From: mohave valley, arizona
sorry about that. its a 90 with the 4.9. its starting perfect now. it only does it when it gets above 105 outside. once it starts then its perfect. idles perfect and runs perfect.
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Elder User
Joined: Mar 2004
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From: mohave valley, arizona
ok i finally read the codes. im getting a 51 with key on and engine not running. the book says = ECT sensor out of range indicated/circuit open. not sure what that ECT is. running im getting a 77 = operator error during dynamic response test/wide open throttle not sensed.
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Elder User
Joined: Mar 2004
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From: mohave valley, arizona
well i checked the ECT and the readings were off. i had a old one that i took out when i was just swapping parts, it checked out good so i installed it. it was cold and the reading were good and when installed, and engine at operating temp. it checked good. ill see when the outside temp hit 105 today.
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Elder User
Joined: Mar 2004
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From: mohave valley, arizona
well seems like im back to square one. temps outside are 115 and it starts really hard, it starts like its flooded then clears up and runs perfect and runs perfect. it has to have something to do with the temps outside. under 100 and its fine. maybe the pip is acting up. although id think it would be pretty hot mounted on the distributor. im at a loss.
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Elder User
Joined: Mar 2004
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From: mohave valley, arizona
well i went outside, 117 degrees, and this time i opened the front gas cap to relieve pressure then screwed it back on. my truck started right up, no problems at all. im thinking that pressure must be building up inside the tank with the temps being so high. how do the tanks release pressure ?
FTE Chapter Leader
Joined: May 2009
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From: Eastern Ky
Vapor Purge Valve seems to be stopped up....Its the little plastic unit on the main top of the gas tank, has a hose ran to the charcoal canister IIRC.....Or in my case, routed over and down....Same deal...Check into that.....
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Elder User
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From: mohave valley, arizona
i checked the hose that comes out of the tanks to the canister and it seems fine, then from the canister to the manifold and it seems fine. would i be able to find that Vapor Purge Valve on the tank without dropping the tank.
FTE Chapter Leader
Joined: May 2009
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From: Eastern Ky
Yeah....On the side tank, check on the highest point, on the top...And IIRC, its on the rear half.....Just to narrow it down...
Rear tank, its in the center....and 6" or so forwards of the sending unit....Its a 1 way valve type deal..>Basically, to just relieve pressure and prevent vapor lock....
Also, be CAREFUL....The plastic barb is brittle, and will snap of if you simply grab it and yank......If it comes out, and has a issue going back in, rub a lil bit of vaseline on the seal....It'll simply fall into place then....
Best way I have found to remove them, is a side-to-side twisting action, while gently pulling up....
Rear tank, its in the center....and 6" or so forwards of the sending unit....Its a 1 way valve type deal..>Basically, to just relieve pressure and prevent vapor lock....
Also, be CAREFUL....The plastic barb is brittle, and will snap of if you simply grab it and yank......If it comes out, and has a issue going back in, rub a lil bit of vaseline on the seal....It'll simply fall into place then....
Best way I have found to remove them, is a side-to-side twisting action, while gently pulling up....
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Elder User
Joined: Mar 2004
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From: mohave valley, arizona
ill check them out. hard to think there both bad. and why only when its 105 or hotter outside. i think thats the clue, it only does it when temps are above 105. the only think i can see being affected by that is the gas expansion and something inside my truck, maybe the computer. no matter, its something that outside temps is causing, not the engine being hot but outside temps. anything under the hood is going to get hot weather its hot outside or not. at least by replacing the coolant sensor got rid of the code 51. im tempted to replace the ignition module, only because it has 170,000 miles on it and is original, but then id just be swapping out parts. as far as i know the original module might last forever. i think, and might be wrong, that they either work or dont work. besides it would get hot when i drive the truck so 105 or 110 outside temps wouldnt even get it to the temp it would get to while driving it.
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Elder User
Joined: Mar 2004
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From: mohave valley, arizona
well i looked underneath my truck and can see a good size vent line coming from each tank, they Y together and then it connects to a hard line and goes to a plastic box on the passenger side inner fender. from there a line goes up and then Y,s both lines connect to the valve body. i didnt find any electric valve that would open and let vapors go to the intake, also i didnt see any kind of valve on the tanks, ofcourse i cant see on top of them. but even today, with temps hitting 120, i went outside and my truck starts perfect. im thinking now that this problem ive always had. as soon as the outside temp would get above 90 my truck would start funny, has temps got hotter my truck would stat harder. guess these vapor release valves have been bad for years and with high temps, and the tanks being pressurized higher and higher, that must of created to much pressure for starting, forcing to much gas. not positive but it seems to be starting perfectly now. but getting back to these vapor release valves, are they on top of the tank, where i cant get to them ?
FTE Chapter Leader
Joined: May 2009
Posts: 8,843
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From: Eastern Ky
You should be able to get to the side tank's....And have enough room to run your hand between the bed floor and top of the tank...
The rear one...I dunno....Its smack in the centr of the tank, and the tank is flush with everything else...So it'll require dropping it porbably...
The rear one...I dunno....Its smack in the centr of the tank, and the tank is flush with everything else...So it'll require dropping it porbably...