F150 problems.. Figure out the problem i paypal you $10
08-04-2009, 12:02 AM
#21
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You have a vacuum problem in your tank. There is enough pressure in the tank to allow you to run normally for a short time, but after a while, the vacuum forms by having the fuel leave the tank and no incoming air to offset and compensate.
You need to make sure your return vent is not clogged.
Chris
You need to make sure your return vent is not clogged.
Chris
08-04-2009, 01:50 AM
#23
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Agreed with the 190 t-stat, lets not have the PCM going back into open loop on us. I don't understand the 20-25 PSI pressure at running speeds. To be honest, can't remember ever having to check pressure while driving. At running speeds we know vaccuum is less and is controlling the regulator, check for possible vac leak. Is there anyone you could swap the PCM with for a test? And finally are there any codes to assist us, or are we working blind? A nasty but intrigueing problem, a couple of other older (more experienced) guys here, lets see what they cough up.
Take off the fuel cap and run the truck to see if it happens...if your getting a fuel system vapor lock the pumps wont be able to suck fuel from the tank. if the vent hose from the tank is plugged it can't get air into the tank to allow the fuel to be pulled. it'll run right while there is air in the tank till you suck it all out.... does it do the same with both tanks...
Sounds like you're going through what I did with a Torino I used to own. Checked or changed just about everything without any improvement. Finally on a lark, I changed out the flex fuel lines, problem gone. I couldn't find anything 'proof positive' but I found some flaking and decomposition in the sections I cut apart. I think it may have been a combination of heat and pressure was pushing junk to the point the line was partially closed off. replacing those sections of line worked for me.
Good luck in your search.
Paul
Good luck in your search.
Paul
You have a vacuum problem in your tank. There is enough pressure in the tank to allow you to run normally for a short time, but after a while, the vacuum forms by having the fuel leave the tank and no incoming air to offset and compensate.
You need to make sure your return vent is not clogged.
Chris
You need to make sure your return vent is not clogged.
Chris
08-07-2009, 09:03 PM
#25
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ok at this point i am so frustrated with this truck i just want to push it off a ****ing hill and go buy a chevy.. heres what happened. like suggested i jumped around the switch valve for the tanks.. it ran great for 20 minutes and then basicly did what it did before (stops running).. having to go somewhere i park the truck in a safe parking lot and have someone pick me up to deal with this **** later.. well i come back 4 hours later and get in the truck and it will not hold a idle.. off idle it runs great but below 1000 rpm its jumping between 250rpms and 750rpms and black smoke is coming out of the exhaust.. how i jumped the valve was basicly straight from the front tank to the fuel filter..
so it goes, front tank, fuel filter, boost pump, fuel rail..
this is really pissing me off
so it goes, front tank, fuel filter, boost pump, fuel rail..
this is really pissing me off
08-07-2009, 10:19 PM
#27
wbstaz
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Could also be blocked vent from the tank(s), try taking the tank cap off when it plays up, obviously you cannot run like that by just see if it makes a difference!! As you say try anything!!
Good luck let us know what the eventual cause is thanks Billabong.
Good luck let us know what the eventual cause is thanks Billabong.
08-07-2009, 10:27 PM
#28
wbstaz
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I think I have it!! Had this same trouble with a Volvo once, cracked circuit board in the computer system, as it warms up the crack opens causing all this trouble, also look for any pressure points on cables etc. that should not be there!!! Sometimes an ignition problem can be exactly like a fuel problem, certainly on early EFI.
Good luck, let us know blah blah Billabong
Good luck, let us know blah blah Billabong
08-07-2009, 10:37 PM
#29
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the truck is FOR SURE running out of fuel...
it has a full tank and it is running itself out of fuel..
somewhere between the tank and the cylinder there is a malfunction that does not allow the truck to get the proper amount of gas...
it has a full tank and it is running itself out of fuel..
somewhere between the tank and the cylinder there is a malfunction that does not allow the truck to get the proper amount of gas...
08-08-2009, 10:40 AM
#30
Hook'em Horns
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ok so i have thrown a bunch of money at this problem and still cant figure it out.. both my father and I are mechanics (he has been a truck mechanic for 30+ years).. here is what we have so far.. a 1985 ford f150 with a 5.0l v8 fuel injected (dual tanks), it is a 4spd 4x4.. The problem is as follows. the truck will start and run fine but after about 20 minutes of continuous driving (takes less the hotter it is outside).. it will stumble and act as if it is running out of fuel (inside the truck it feels as if someone is popping the clutch over and over again).. i hooked up a fuel pressure regulator to look at the fuel pressure when this is going on and the needle will show anywhere from 35-40 psi when it is running fine and <20-25 when it is stumbling and jerking the car around (running out of fuel).. now when this happens i usually pull over, as i do not want to cause a accident, and if i try to restart it it will idle very rough (barely idle) or wont run at all.. so far i have changed both in tank pumps, cleaned tanks, blew out the lines with air, changed boost pump on the fuel rail, changed both fuel filters, changed the fuel presure regulator, the line from the boost pump to the fuel rail, changed the ignition control module, spark plugs, spark plug wires, cap, alternator (for other reasons), exhaust (its same as stock, but all new).. i honestly dont know what else it can be.. it is obviously running out of fuel.. of course there is gas in the tank etc..any help would be appreciated
