I have had several issues in the past with my truck stalling at low rpms. Most of them were vacuum related. The last one was last year, and it turned out to be a cracked/broken battery cable terminal that caused the alternator to go bad also. I'm just throwing that out there.

 

A somewhat quick recap on my similar problem. Bought the truck 86 F150 302 auto a year ago. Ran great for two months. One day had a similar problem. Would start stone cold, but no fire when cranked warm. Ended up being a bad ground at the drivers side ground point where several wires connect to the last rear intake manifold bolt. Cleaned up as best I could and started cold and hot. No problem until about two months ago when it began to run rough at hot idle (some stalling) and a week ago the truck stopped cranking after a 1 hour drive. Changed a numer of parts; starter solenoid, starter (probably needed it at 133k anyway) and found the ground point again was the problem. Had to remove the air filter box to get to the bolt easier. Removed the bolt and wire wheeled the bolt head, wife connectors, etc. Found the top area of the bolt was painted blue (probably from the factory) where the wires made contact. It's been running great since. Feels like more power. As many have mentioned on here scanning codes is the best indicator of a problem and any of the ground points that become corroded can cause strange faults. Know this is a little long. Just trying to help anyone with the problem I encountered.

 

So many times it turns out to be a simple vacuum leak. It can really throw the
diagnostics off and send ya down the wrong road many times.
It seems there is almost as much vacuum hose on these new newfangled rigs
than electrical wire.

I do like a carb. Even if it burns a little more fuel I can still get her home
and still work on it.

 

I went out to try to test the relay and realized I don't know what I'm supposed to be testing. Which of the 5 pins on the connector is "V power circuit"?

 

Right, most people don't have a breakout box (a device plugged in between the computer & wiring harness that easily lets one use meter probes to test voltages).

But, if you look at an EVTM or wiring diagram, you can easily see that Pin 22 (in this case, for example) is the computer's connection to the device in question. I don't have an 85 or 86 EVTM or wiring diagrams book but I would guess it's the wire running from the computer to the fuel pump relay, and they're basically telling you to check voltages & continuity on the fuel pump circuit wires.

A breakout box makes it easier, but this can still be done by unplugging the harness from the computer and doing an end-to-end check using an ohm meter (testing continuity in this case).

Basically, the error is saying the computer thinks the fuel pump isn't getting the right amounts of power at the right times, and so go check out the wiring & relays and fix as necessary.

I honestly don't know because, again, I don't have those books for those years. This is another time when we need Ralph, I wonder what happened to him. You should have at least one wire running from the computer to the relay, one wire from relay to ground, one wire from a fused power source to the relay, and the other side of that wire (that will get connected together by the relay) will go to the fuel pump.

An EVTM (Electrical and Vacuum Troubleshooting Manual) would be a marvelous investment for you to make, find one on eBay or from any of the various resellers of used automotive literature.

If you can't find a diagram somewhere, then you can unwrap and trace wires by their colors and/or using an ohm meter.

If you want to just go *do* something, you might clean the connections at the relay and maybe even swap it out with another (preferably a known good and working one) then clear the codes and see if the error comes back and/or your engine's running problems have gone away.

 

So I replaced the relay and the truck ran wonderfully for a day and a half. Then, on the way home it stalled out as I was turning into the driveway. I pulled the codes and I still had 10, 11, 87 but a new one popped up 63, for Throttle Position Sensor.

Is this a continuation of my original problem or is this a new problem on top of my other one?

 

Was it a Factory Ford relay? Or a Made In China one?

 

Neither. A BWD one made in India.

 

Well there ya go. The Indians don't like us much either.

Figure out how to test it? Or try another?

Low rev stall sounds like it could be a
vacuum issue. Or a lack of it.

 

I'm not saying it isn't a vacuum problem but the code pulled goes to the TPS saying the voltage is wrong. How is that a problem of a foreign relay?

 

Paul,

How are you pulling these codes? And, there are 3 sets of codes given as results for two different tests. IOW the following are the tests:

KOEO - key on engine off
CM - continuous memory, what the computer remembers about past driving cycles
KOER - key on engine running

Diagnostics for some codes are different depending on from which test the code was from.

I am not even sure what year your truck is, either....

 

I have an 86 f150 with a 302 efi. I'm doing a KOEO test.

 

OK... Are you absolutely certain of the codes you're reporting? The Ford Powertrain and Emissions Diagnostics Manual doesn't list a Code 10 as a possibility.

The KOEO test will give two outputs - one for KOEO, and the latter for CM. Are you counting blinkenlights (or meter sweeps)? Or, are you using a code reader?

What are your results for the KOER test?

 

Hope this helps, it is a wiring schematic for an 86 but it show the fuel pump relay and extra. https://drive.google.com/file/d/0BzI...it?usp=sharing

If yall need i have access to all years ford trucks with how to repairs with some diagrams and wiring schematics!

 

I'm using an Innova 3145 code reader. I shouldn't have included code 10 or 11. From the 3145 reader's manual: