HELP! cutting out under light throttle
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From: Curwensville,PA
HELP! cutting out under light throttle
hi guys i have a 91 300 6 and i have been fighting a cutting out issue for about 2 months. my truck idles fine but cruising in OD in cuts out like crazy, it is very intermittent sometimes it runs fine but when it cuts out it does it bad. I've ruled out bad fuel, fuel filter. i took it to a garage and they said they couldn't find anything but said these trucks were known for a wire corroding and intermittently shutting off the fuel pump?
has anyone heard of this or have any suggestion?
im getting really frustrated and have about had it with this truck
has anyone heard of this or have any suggestion?
im getting really frustrated and have about had it with this truck
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Joined: Sep 2008
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Do you have an in-tank fuel pump? I wonder if it's the same type as my truck uses.
I had a situation which sounds similar to yours...when I start the truck it was fine but I wasn't able to go above 20 MPH. It was obvious it was a problem with a lack of fuel but other than that, I wasn't sure what it was. I took it to a garage and they bought a $5000 piece of equipment to help diagnose the problem. They had the truck for a week and only charged me $15 for a part they replaced - but they never found the problem.
After I got the truck home I pulled the fuel pump out of the tank. Inside the fuel pump was a small, dime-sized diaphragm that had a crack in it. That was the cause of my problem. Can't replace the diaphragm alone, I had to break the pump to get to it. But I already had fixed my problem with a new pump by the time I was ready to dig into the old pump and then I found the diaphragm.
I had a situation which sounds similar to yours...when I start the truck it was fine but I wasn't able to go above 20 MPH. It was obvious it was a problem with a lack of fuel but other than that, I wasn't sure what it was. I took it to a garage and they bought a $5000 piece of equipment to help diagnose the problem. They had the truck for a week and only charged me $15 for a part they replaced - but they never found the problem.
After I got the truck home I pulled the fuel pump out of the tank. Inside the fuel pump was a small, dime-sized diaphragm that had a crack in it. That was the cause of my problem. Can't replace the diaphragm alone, I had to break the pump to get to it. But I already had fixed my problem with a new pump by the time I was ready to dig into the old pump and then I found the diaphragm.
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From: Curwensville,PA
thanks for the reply's guys! Krisverde mine is more of a cut out than a misfire, i think i would prefer a misfire at this point lol when it cuts out you can see the rpms go way up and down.
RIKIL i will have to look into that and mine seems to be the same way it seems like a lack of fuel. i think mine does have the in tank pump
RIKIL i will have to look into that and mine seems to be the same way it seems like a lack of fuel. i think mine does have the in tank pump
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thanks for the reply's guys! Krisverde mine is more of a cut out than a misfire, i think i would prefer a misfire at this point lol when it cuts out you can see the rpms go way up and down.
RIKIL i will have to look into that and mine seems to be the same way it seems like a lack of fuel. i think mine does have the in tank pump
RIKIL i will have to look into that and mine seems to be the same way it seems like a lack of fuel. i think mine does have the in tank pump
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From: Curwensville,PA
i have not tested that how do you test the fuel pressure regulator?
and yea i have tried on a few occasions but got pretty confused as i have seen 3 digit and 2 digit codes online. But i should probably try running them again
and yea i have tried on a few occasions but got pretty confused as i have seen 3 digit and 2 digit codes online. But i should probably try running them again
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If the answer to either of the first two questions is yes, then replace the FPR and see if your problem goes away. If the answer to the last question is no, put the vacuum line back on the FPR and get ready to take out the fuel pump. FYI - not sure about your setup but for me it's easiest to get the pump out by raising the bed of the truck (just remove 6 nuts) as opposed to dropping the tank.
As for the codes, I don't think your year will produce a 3 digit code. My 92 only produces 2 digit codes. I want to say the 3 digit codes are from ODBII systems (yours and mine are ODBI) but don't quote me on that.
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From: Lynnwood Wa.
I had an f350 with a 460 that would cut in and out and sometimes it would just die on me. Very unpredictable. I know I know its a different year and a different engine. I went thru the whole ignition system top to bottom plugs wires cap rotor and coil still nothing. I changed the distributor out and bam all back to normal.
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I had an f350 with a 460 that would cut in and out and sometimes it would just die on me. Very unpredictable. I know I know its a different year and a different engine. I went thru the whole ignition system top to bottom plugs wires cap rotor and coil still nothing. I changed the distributor out and bam all back to normal.
Cargo Master
Joined: Nov 2013
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From: South Central,MO
My 90 did this and after 2 months of fighting it looking for the problem, turned out to be a bad coil wire. The metal end that goes in the coil was burnt off! Might not be your problem, but something that's easy to check.
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From: Curwensville,PA
(UPDATE) i did the fuel pressure regulator test. i removed the vacuum hose from the top of the regulator i did not see or smell fuel i started the truck and still no fuel. i then drove the truck with the line disconnected, NO cutting out!, so what does this mean???
Cargo Master
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From: South Central,MO
Well even though the regulator is not leaking it may still be bad. Next step is to get a gauge and see what kind of pressure you have both with and without vacuum. Could be a weak pump and boosted pressure with removed hose will make it run, but just barely!
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From: Curwensville,PA
ok i will test the fuel pressure next. i am leaning to the second thing you said about the weak pump and the boosted pressure makes it run. it did not cutout but something about it didn't feel quite right it also seems to be using a ton of gas.