Lost wont start, lots of info in here..
05-23-2018, 01:09 AM
#1
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Lost wont start, lots of info in here..
1992 F150 4.9 Auto 2wd 136K
Ran great one day and next it was hard to start and unbelievably rough idle and stalled like its missing on multiple cylinders next day its fine again and put a few miles on it than few days later back to rough running and I cant figure it out. It will run in carb clean sprayed in it all day so I believe its a fuel issue.
Check fuel pressure on rail and its 48 or so while cranking and remained there when it did start (while running rough). It did blean down rather quickly when cranking stopped.
Replaced Wires and plugs. No change. Tested spark on all CYC and they all fire.
Pulled cyc 1 fuel injector plug and put on noid light and get nothing when KOEO or while cranking but same noid light on cyc 2 gets lit with KOEO and flashed on cranking.
So I checked wiring diagram and seems red wire has power to all injectors and 1,3,5 get ground signal from ECU on tan wire and 2,4,6 get ground signal from ECU on white wire. Checked all harnesses and all look on so ran wire from ECU tan to injector wire tan and tried it and same result. No light on cyc 1.
Thoughts?
Ran great one day and next it was hard to start and unbelievably rough idle and stalled like its missing on multiple cylinders next day its fine again and put a few miles on it than few days later back to rough running and I cant figure it out. It will run in carb clean sprayed in it all day so I believe its a fuel issue.
Check fuel pressure on rail and its 48 or so while cranking and remained there when it did start (while running rough). It did blean down rather quickly when cranking stopped.
Replaced Wires and plugs. No change. Tested spark on all CYC and they all fire.
Pulled cyc 1 fuel injector plug and put on noid light and get nothing when KOEO or while cranking but same noid light on cyc 2 gets lit with KOEO and flashed on cranking.
So I checked wiring diagram and seems red wire has power to all injectors and 1,3,5 get ground signal from ECU on tan wire and 2,4,6 get ground signal from ECU on white wire. Checked all harnesses and all look on so ran wire from ECU tan to injector wire tan and tried it and same result. No light on cyc 1.
Thoughts?
05-23-2018, 11:20 AM
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We need a LOT more info about the truck. Click this, read the caption, and put EVERYTHING into your signature:
(phone app link)
Pull the EEC & look inside:
(phone app link)
(phone app link)
Pull the EEC & look inside:
(phone app link)
05-23-2018, 11:24 AM
#3
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Done.
We need a LOT more info about the truck. Click this, read the caption, and put EVERYTHING into your signature:
(phone app link)
Pull the EEC & look inside:
(phone app link)
(phone app link)
Pull the EEC & look inside:
(phone app link)
05-23-2018, 11:33 AM
#4
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No, there's still no signature at the end of your post. Make sure it's set to automatic in your profile settings.
05-23-2018, 11:34 AM
#5
Senior Member
1992 F150 4.9 Auto 2wd 136K
Ran great one day and next it was hard to start and unbelievably rough idle and stalled like its missing on multiple cylinders next day its fine again and put a few miles on it than few days later back to rough running and I cant figure it out. It will run in carb clean sprayed in it all day so I believe its a fuel issue.
Check fuel pressure on rail and its 48 or so while cranking and remained there when it did start (while running rough). It did blean down rather quickly when cranking stopped.
Replaced Wires and plugs. No change. Tested spark on all CYC and they all fire.
Pulled cyc 1 fuel injector plug and put on noid light and get nothing when KOEO or while cranking but same noid light on cyc 2 gets lit with KOEO and flashed on cranking.
So I checked wiring diagram and seems red wire has power to all injectors and 1,3,5 get ground signal from ECU on tan wire and 2,4,6 get ground signal from ECU on white wire. Checked all harnesses and all look on so ran wire from ECU tan to injector wire tan and tried it and same result. No light on cyc 1.
Thoughts?
Ran great one day and next it was hard to start and unbelievably rough idle and stalled like its missing on multiple cylinders next day its fine again and put a few miles on it than few days later back to rough running and I cant figure it out. It will run in carb clean sprayed in it all day so I believe its a fuel issue.
Check fuel pressure on rail and its 48 or so while cranking and remained there when it did start (while running rough). It did blean down rather quickly when cranking stopped.
Replaced Wires and plugs. No change. Tested spark on all CYC and they all fire.
Pulled cyc 1 fuel injector plug and put on noid light and get nothing when KOEO or while cranking but same noid light on cyc 2 gets lit with KOEO and flashed on cranking.
So I checked wiring diagram and seems red wire has power to all injectors and 1,3,5 get ground signal from ECU on tan wire and 2,4,6 get ground signal from ECU on white wire. Checked all harnesses and all look on so ran wire from ECU tan to injector wire tan and tried it and same result. No light on cyc 1.
Thoughts?
When you turn the key to on, you should hear the fuel pump prime for about 2 seconds before you actually start it. At that moment you should be seeing 45-60 psi on the rail (the closer to 60 the better). It should hold that pressure for awhile - if it is bleeding down right away, then you have a problem, like an injector stuck open or something similar.
05-23-2018, 12:31 PM
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If my memory serves the 92 4.9 is going to need 45-60 psi to run well, so when you say it bleeds down quickly after cranking, do you mean the pressure drops below 48? Will it do the same thing on both tanks (assuming it has 2)?
When you turn the key to on, you should hear the fuel pump prime for about 2 seconds before you actually start it. At that moment you should be seeing 45-60 psi on the rail (the closer to 60 the better). It should hold that pressure for awhile - if it is bleeding down right away, then you have a problem, like an injector stuck open or something similar.
When you turn the key to on, you should hear the fuel pump prime for about 2 seconds before you actually start it. At that moment you should be seeing 45-60 psi on the rail (the closer to 60 the better). It should hold that pressure for awhile - if it is bleeding down right away, then you have a problem, like an injector stuck open or something similar.
The thing that still gets me is the noid light. We assume 1.3.5 and 2.4.6 all wired together Why with noid in cyc 1 I get no light with key on or it turning over and in cyc 2 with key on it gets dim light that flashed when cranking. Should these 1 and 2 cyc not be the same on the light?