fuel problem?
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New User
Joined: Sep 2012
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fuel problem?
1991, F-250, automatic, 150,000 miles, two tanks. Used mostly for towing an RV plus some pleasure. Not in daily use. A month ago I parked it and a few days later cranked it up and found it wouldn't run over thirty MPH. There was some high pitched backfire in the engine compartment and the trans. wouldn't shift. I parked it and the next day it wouldn't start. When I turned the key on the fuel pumps (either tank) ran continuously. Towed to a garage (I am not a Mechanic). They have replaced the fuel pressure control, checked all pressures and it still won't run right. The problem is intermittent. My tranny man said the trans was good. My mechanics don't know what to do. I need help this is a cherry truck I bought from the original owner in 1998.
Lead Driver
Joined: Sep 2006
Posts: 7,907
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First, your in the wrong board for 91 5L AOD truck.
But here is some place to start.
Remove the drive belt and test crank for noise and ease of cranking.
If all is ok...
Remove the #1 plug and remove the coil wire.
Then either bar the motor over or tuche the starter to get the cranlk pully lined up with the pointer when the #1 cylinder is up on compression and piston is at top dead center..
Then remove the distributor cap and see if the rotor is pointing to the #1 plug wire post or very close.
If yes, put all back togather.
If no, either the distributor gear pin has sheared or the timeng chain has jumped time.
Good luck.
But here is some place to start.
Remove the drive belt and test crank for noise and ease of cranking.
If all is ok...
Remove the #1 plug and remove the coil wire.
Then either bar the motor over or tuche the starter to get the cranlk pully lined up with the pointer when the #1 cylinder is up on compression and piston is at top dead center..
Then remove the distributor cap and see if the rotor is pointing to the #1 plug wire post or very close.
If yes, put all back togather.
If no, either the distributor gear pin has sheared or the timeng chain has jumped time.
Good luck.
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Thanks for your reply. I have moved my request to the proper forum didn't scroll down far enough to see it. I had a 74 F-350 with a slipped timing chain and it wouldn't start or run until it was changed. The problem on my 91 is intermittant. Sometimes it will start and run, sometimes not. Sometimes the fuel pumps race on when you turn the key on and sometimes they act normally. Sometimes it will run OK but mostly not. This is driving my mechanic nuts. Nothing is showing up on the computer except a bad readout on the air pump (new last year). Will a slipping chain cause these symtons?
More Turbo
Joined: Aug 2011
Posts: 544
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If there is slack in the chain that is just on the border of where the ecm can correct the ignition timing enough it can show up as intermittent.
Pull the distributor cap and take the front pulley to TDC.Then turn it back the other way and watch how many degrees of rotation it takes to start the rotor to turn again.
Any more than 5 or 6 degrees is a fail and it should be replaced along with the timing gears.
EDIT If it is as much as 10 Deg. I would think that might be the problem
Pull the distributor cap and take the front pulley to TDC.Then turn it back the other way and watch how many degrees of rotation it takes to start the rotor to turn again.
Any more than 5 or 6 degrees is a fail and it should be replaced along with the timing gears.
EDIT If it is as much as 10 Deg. I would think that might be the problem
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