1980 - 1986 Bullnose F100, F150 & Larger F-Series TrucksDiscuss the Early Eighties Bullnose Ford Truck
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Had truck in shop 3 times in last week. Cuts out when it warms up. Have replaced fuel pump twice,fuel cutoff relay,distributor,ICM module.Cap/rotor,wires,plugs recently.
Mech has checked Map sensor,etc.,ignition switch. Says it is losing voltage to fuel pump?
Happens after about 30 minutes of driving
Seen something like it on this board but never gave answer or way to check for it. Also have friend with same motor in a 87 Mustang that does same thing. Common problem?
[font size="1" color="#FF0000"]LAST EDITED ON 07-Oct-01 AT 08:08 PM (EST)[/font][p]Drive it with a fuel pressure guage tempoarily hooked up and taped to the windshield. You need to decide if it's ignition or fuel problem. Are you getting any error codes from the computer?
I've been having the same problem with my '86 F150 302 EFI. Cuts out sometimes after 20 - 30 minutes of driving. It's been tuned up, new EGR valve. I have a new ignition module on my seat - I dont't think this is will fix it. When it's dead there's still spark to the plugs so I believe it's not a problem with the ignition.
When it's dead what I've noticed is that when I turn the key (without starting the engine) the fuel pump relay doesn't engage. I've checked the relay it seems to work fine.
I have temporallily bypassed the ECM signals into the fuel pump relay. The switch will allow me to run with the ECM in line to the relay and if the truck dies I can switch the pump 'on' with the ECM out. I made this mod this morning.
I don't know what's wrong. I'm hoping the bypass swicth will keep me from being stuck on the side of the road until I can get some good advice. It's been in the shop twice.
I'd like to know how the ECM functions - under what conditions would the ECM cut off the fuel pumps?
Bojunk, code 31 is an egr code, and if the egr is screwed up, it can make the engine stall when you come up to a stop light. It shouldn't affect running down the highway too much.
griffofk, My fuel injection book says the PIP signal is the primary input for the control of the fuel pump relay. The fuel pump relay receives power from the keyswitch in the "start" position, but after the key is released, the computer must receive a PIP signal to send power to the relay to keep the pump running. The PIP signal is generated inside the dist. It's a train of pulses that are sent to the TFI module on the side of the dist, and they are also sent to the computer for fuel pump control and injector synchronization.
Sounds like if I continue to have problems cutting out even with the fuel pump relay bypassed I should trouble shoot the PIP signal. Which I guess takes me through distributor, ignition module, computer?
How to Tune and Modify Ford Fuel Injection. I picked it up in the bookstore. I like these kind of 3rd party books because the guy actually talks and explains things, unlike the factory manuals which are good, but never give an explanation of the theory behind what's going on.
[font size="1" color="#FF0000"]LAST EDITED ON 10-Oct-01 AT 07:00 AM (EST)[/font][p]Got truck out of shop for 4th time today, changed ICM (2nd time)runs smoother but still stumbles (hasn't died yet). Can hear motor surging when it idles. The weather here (Arizona) has cooled alot so I cant really compare to when problem first appeared, although I dont think it is fixed. Friend with 87 Mustang got new computer drove around all day and had no problems. Think I will try O2 sensor next?, before I try new computer. My dad owned truck before me and says thats only thing he never replaced and it seems like it is cycling (surging) between rich lean rich lean.
Thanks for the reply to my string. It sounds like we are having the same problem. My truck also surges when idling, and it seems to be cycling between rich and lean also. Try unplugging your air temp sensor. That made my idle smooth right out, and the mixture seems to be good, but the truck has a slight loss of power and will still load up at times. If your truck does the same, then we probably are experiencing the same fault. The only thing I haven't done is replace the computer, which I am going to do next pay day. I'll let you know how it turns out
I had the same problem with an 84 F150. Replaced the ICM 3 times, didn't fix it. Turned out to be the Hall Effect sensor in the dist. This is the sensor that takes the place of the points. Replaced mine and never had a problem after that.
Sr. Automated Test Engineer
If the Hall Effect Sensor is the same as the Stator Assembly, then I have replced it, and it didn't fix the problem. However, when I replaced the stator assembly, it did get rid of the cut-out problem I was having at 2500-3500 rpms.
[font size="1" color="#FF0000"]LAST EDITED ON 11-Oct-01 AT 06:45 AM (EST)[/font][p]I put a new distributor in first, it came with new stator (pickup) coil. This is what I thought the problem was at first,thats what led me to take it to the shop. I thought I had messed up the timing when I did it. I have made it the 15 miles to work and back twice now but still surging. What happened when you replaced O2 sensor? Unfortunately my buddy who replaced the computer got laid off today. We are in the aviation biz. damn shame smartest 19 year old I have ever met. Sharp kid Might still be able to get a hold of him though to see if it fixed his problem
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