Haunted 86/5.0
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From: Mid-Missouri
Haunted 86/5.0
My 86 f150 with the 302 shuts off at different times when you are driving it. once you stop, it starts right up.
Changed the TFI module and it didn't solve anything.
86 5.0EFI - F-150
I'll be driving down the road with no problem. All of a sudden, the tach drops to 0 like it loses it's signal. When I go to restart, I have to cycle the ignition key several times between the off and run position. Usually on the third cycle, it will start and run as if nothing is wrong.
The weird thing is, it only happens in the morning after it has set all night. Won't do it the rest of the day. It seems to happen during the first warm-up cycle as the truck approaches 170 degrees. After that everything is fine.
Doesn't seem to matter which tank I've got selected
Appears to be getting fuel, it restarts and runs fine until the next morning. There has been no other sign that the fuel pressure is running below normal.
When this happens, the rest of the electrical system seems to functioning.
Also, there are no codes other than the EGR, which it has had for 3 yrs now.
Mechanic is puzzled. I'm frustrated.
I'm thinking maybe EEC relay and or fuel pump relay.
Coil and Ignition pick-up test o.k., but that may change due to vibration or heat.
Any ideas.
I'm tired of chasing ghosts like this.
Changed the TFI module and it didn't solve anything.
86 5.0EFI - F-150
I'll be driving down the road with no problem. All of a sudden, the tach drops to 0 like it loses it's signal. When I go to restart, I have to cycle the ignition key several times between the off and run position. Usually on the third cycle, it will start and run as if nothing is wrong.
The weird thing is, it only happens in the morning after it has set all night. Won't do it the rest of the day. It seems to happen during the first warm-up cycle as the truck approaches 170 degrees. After that everything is fine.
Doesn't seem to matter which tank I've got selected
Appears to be getting fuel, it restarts and runs fine until the next morning. There has been no other sign that the fuel pressure is running below normal.
When this happens, the rest of the electrical system seems to functioning.
Also, there are no codes other than the EGR, which it has had for 3 yrs now.
Mechanic is puzzled. I'm frustrated.
I'm thinking maybe EEC relay and or fuel pump relay.
Coil and Ignition pick-up test o.k., but that may change due to vibration or heat.
Any ideas.
I'm tired of chasing ghosts like this.
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Joined: Jun 2004
Posts: 353
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From: Mid-Missouri
Update:
This morning it happened again for about the 6th morning in a row.
This time it seemed to stay running when I let my foot off the accelerator. The tack dropped to 0, I let off and the tack jumped back to 2600 RPM. If I touched the accelerator again, the Tach would drop. Give it a second, and it would recover and drive like normal.
I would have thought this would have set a code. It didn't though. GRRR
This morning it happened again for about the 6th morning in a row.
This time it seemed to stay running when I let my foot off the accelerator. The tack dropped to 0, I let off and the tack jumped back to 2600 RPM. If I touched the accelerator again, the Tach would drop. Give it a second, and it would recover and drive like normal.
I would have thought this would have set a code. It didn't though. GRRR
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Joined: Jun 2004
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From: Mid-Missouri
The pick-up coil is about 1 year old. It also tested o.k. The distributor was rebuilt and the pick-up replaced at that time.
Thing is, it would probably test o.k. unless it was operating under the same conditions as when it fails momentarily. Intermittent problems suck!
Anybody have any idea where the Fuel Pump relay and EEC relays are mounted. One of them appears to be mounted under the hood next to the master cylinder on the firewall. I thought they were suppose to be mounted in the same place. Would the EEC relay be mounted somewhere in the cab near the EEC?
It does almost seem to be an EEC that is getting flaky. I don't really want to replace that unless I have too. I would think the relay would be the more likely culprit. I could be wrong though.
I'm not a big fan of throwing parts at a problem unless I'm reasonably sure.
Thing is, it would probably test o.k. unless it was operating under the same conditions as when it fails momentarily. Intermittent problems suck!
Anybody have any idea where the Fuel Pump relay and EEC relays are mounted. One of them appears to be mounted under the hood next to the master cylinder on the firewall. I thought they were suppose to be mounted in the same place. Would the EEC relay be mounted somewhere in the cab near the EEC?
It does almost seem to be an EEC that is getting flaky. I don't really want to replace that unless I have too. I would think the relay would be the more likely culprit. I could be wrong though.
I'm not a big fan of throwing parts at a problem unless I'm reasonably sure.
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Joined: Jun 2004
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From: Mid-Missouri
Kind of behind the airbox, maybe. The airbox on an 86 f-150/5.0 sits on top of the driver's side valve cover. I only found 1 relay in that area of the firewall and it was located between the master cylinder and the driver's side fender on the firewall.
The bracket is attached to the firewall. On my truck, there is only 1 relay mounted in the bracket. I'm assuming that it is for the fuel pump. I'm going to trace the wiring. A quick glance indicated that some of the wires headed in the direction of the HP fuel pump on the frame rail under the driver's side of the cab.
The bracket is attached to the firewall. On my truck, there is only 1 relay mounted in the bracket. I'm assuming that it is for the fuel pump. I'm going to trace the wiring. A quick glance indicated that some of the wires headed in the direction of the HP fuel pump on the frame rail under the driver's side of the cab.
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From: virginia
someone else posted this but im not sure how acurate it is;
"1986 F-150 5.0 dual tanks, HP up front, The fuel pump relay has (4) wires: Yellow from the battery side of the starter relay to the relay; pink exiting the relay to the inertia switch, then to the high-pressure pumpand to the tank pumpselector switch; red from the EEC relay to the fuel pump relay coil; tan from the relay coil back to the EEC relay"
ill look at the haynes tonight, and take a closer look at my 86 5.0
"1986 F-150 5.0 dual tanks, HP up front, The fuel pump relay has (4) wires: Yellow from the battery side of the starter relay to the relay; pink exiting the relay to the inertia switch, then to the high-pressure pumpand to the tank pumpselector switch; red from the EEC relay to the fuel pump relay coil; tan from the relay coil back to the EEC relay"
ill look at the haynes tonight, and take a closer look at my 86 5.0
Last edited by 99mustang232; Sep 20, 2005 at 04:54 PM.
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Thread Starter
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Senior User
Joined: Jun 2004
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From: Mid-Missouri
It could be the coil or for some reason the EEC may be losing the PIP signal momentarily. That could be a pick-up, tfi, bad ground, short.
Well, last night I replaced the fuel pump relay. and the fuel filter. I was going to replace the EEC relay as well but haven't been able to find it. Cleaned up the EEC ground.
Also replace the TPS with one I had laying on the bench. It seemed to be in better shape than the one on the truck.
After all of this, the truck seemed to be a bit more responsive from a stop.
This morning, I had a similar occurence on the way to work. This time it was more like a brief hiccup and then no problem. The engine continued to run without any problem after that.
Does anybody know where the EEC relay is located? Does this year make and model use a relay. I would assume it does.
Switched tanks this evening to eliminate the chance that it was an intank pump. Also filled up with fresh gas.
Well, last night I replaced the fuel pump relay. and the fuel filter. I was going to replace the EEC relay as well but haven't been able to find it. Cleaned up the EEC ground.
Also replace the TPS with one I had laying on the bench. It seemed to be in better shape than the one on the truck.
After all of this, the truck seemed to be a bit more responsive from a stop.
This morning, I had a similar occurence on the way to work. This time it was more like a brief hiccup and then no problem. The engine continued to run without any problem after that.
Does anybody know where the EEC relay is located? Does this year make and model use a relay. I would assume it does.
Switched tanks this evening to eliminate the chance that it was an intank pump. Also filled up with fresh gas.
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Had this problem once acctually lots of times.. 86 f250 2 wheel 302. Replaced almost everything electrical. Started with modual on distributor went to sensors and relays and so on........Junk modual right from FORD. No warrenty said I did something wrong. Waste of money to fix a wanna be fuel injection. Get in touch can give you a step by step to a 4 barrel. Did a couple and no regrets. (Gas wasn't $1.40 a liter )
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From: Mid-Missouri
Can't convert to a 4 Barrel. We still have MVI in Missouri with a visual inspection of the emissions. It would be very difficult to get most mechanics around here to pass a vehicle with that kind of modification. Doesn't matter if it is kosher or not.
Further update. The situation has changed slightly. Made it all the way to the exit ramp this morning (12 miles of 70 MPH highway from home to work). Let off the gas as I got to the ramp. The tack dropped to zero. I depressed it slightly and it came back to life. Drove the rest of the way to work with no problem (4 miles of surface streets). ????? I'm really confused now.
Further update. The situation has changed slightly. Made it all the way to the exit ramp this morning (12 miles of 70 MPH highway from home to work). Let off the gas as I got to the ramp. The tack dropped to zero. I depressed it slightly and it came back to life. Drove the rest of the way to work with no problem (4 miles of surface streets). ????? I'm really confused now.
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From: Mid-Missouri
I guess that could be a solution. I've just never heard of a fpr acting up only once in a while. If it is sticking open, that would cause a drop in fuel pressure, but it wouldn't explain the tack dropping to zero or would it.
I looked at replacing the FPR some time ago. Just couldn't figure out how to remove all of the screws to take it off. Does the fuel rail have to be removed to get to all of the fasteners? I can't find my Haynes manual right now, or I'd look up the procedure.
Now I just have to find the FPR that I bought a few months ago. I had purchased it to keep on hand. It appeared that the one on there had never been replaced.
I looked at replacing the FPR some time ago. Just couldn't figure out how to remove all of the screws to take it off. Does the fuel rail have to be removed to get to all of the fasteners? I can't find my Haynes manual right now, or I'd look up the procedure.
Now I just have to find the FPR that I bought a few months ago. I had purchased it to keep on hand. It appeared that the one on there had never been replaced.
Last edited by lmadore; Sep 22, 2005 at 10:20 AM.