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Hello Everyone,
I have a 1986 4 runner and ever since I've got it, its had long crank issues (like 20+ seconds of turning over before it would start), and 3 separate times where it just would just crank until the battery died without the running. (I suspect that the long crank is due to insufficient voltage from the STA circuit, but this has not been verified with a test yet, and is no the point of this post)
when I first got it the previous owner knew it had starting issues, and the solution was to smack around the COR while cranking the engine. this worked for a while until one day it didn't I tested the relay and it would close with 12 volts applied to it, but would only let through about .3 volts.
The relay got replaced with a O'Reilly's replacement part and it started again, but still only after turning it over for 20 seconds or more. This worked for a few months and then one day it just wouldn't start again, found the 15a EFI relay under the dash on the left side was blown. replaced the fuse and it would start again (Still with and extended crank). This worked for a few more months, and then it sat for a while after I busted the radiator. Yesterday I replaced the radiator and it would turn over but not start.
I disconnected the fuel pump and tested for voltage at the harness side while cranking, and only got .5 volts reaching the pump. This was very similar to the first time the COR went out so I unplugged the COR to test it and found the FP pin and the plastic around it to be burnt/discolored. I jumped the FP and +B slots and the car fired up instantly, (no long crank!!!) and idled perfectly for a few minutes before I pulled the wire.
What could cause the FP pin to be burnt?? I did some generic research about fuel pump relays and saw people saying that high current draw from a fuel pump that is going out could cause this.
What do y'all think? Is my FP pin in the COR burnt from a fuel pump that is going out or is it from something else??? picture of burnt FP pin on COR
Put a DC ammeter in series with a FP to battery+ jumper in the diagnostic port and see what amps your pump is pulling.
A good pump draws about 4 amps, a little more, or a little less.
I changed out a pump once that was still functioning but drew more than 7 amps.
High current, and/or loose connections can sure make things hot.
The COR is supposed to close with the start signal, and once the engine is pulling air the FC pin in the VAF grounds and keeps the COR closed. What happens if the COR doesn't close on STA? I've never tested this, but it wouldn't surprise me that a long crank would eventually close the FC pin, then starting the pump and after a few more cranks it could start. This doesn't explain the burning on the pin (I would start with millball's advice; easy to do and a good diagnostic). Then I'd use my ammeter to close each half of the COR (battery to B+, ground to FC) to assure myself that the pump runs each way. Then I'd test the STA supply (you don't have a starting relay in your year, but I'm told that if you don't depress the clutch the starter won't turn but the pump should run).
What could cause the FP pin to be burnt?? I did some generic research about fuel pump relays and saw people saying that high current draw from a fuel pump that is going out could cause this.
What do y'all think? Is my FP pin in the COR burnt from a fuel pump that is going out or is it from something else???
the photo isn't good enough to see any actual burn marks, but it does show that the pin in question doesn't have any score marks on it, that are clearly evident on the other pins.
if both sides of the pin don't have those long marks, i'd question how tightly clamped that pin connection is... aka, is the female end too loose, does it need to be crimped down a bit.
in other words, if any connection is weak it could jump a spark and cause burn marks.
you can confirm it's a fuel issue by pulling a vacuum hose on the plenum and giving it a very short squirt of starting fluid or even carb cleaner... if it fires for a second, it's a fuel problem, but that's something that you'd do when the engine is cold, and we don't know when this issue is happening.
Put a DC ammeter in series with a FP to battery+ jumper in the diagnostic port and see what amps your pump is pulling.
A good pump draws about 4 amps, a little more, or a little less.
I changed out a pump once that was still functioning but drew more than 7 amps.
High current, and/or loose connections can sure make things hot.
I don't have a DC ammeter, only a multimeter with an "amp clamp" that reads AC amps. so I wasn't able to get a accurate reading. seems like its time to invest in a DC ammeter!!
However I did test try closing up the female pins on the harness side like CSV suggested, and figured id try the relay again. It tested good, according to the testing procedure on 4crawler. and it worked!!
started right up and took it for a drive with no issues. For the time being closing up all the pins on the female side of the harness seemed to do the trick.
This seemed like too easy of a fix to me, some in sure this problem will come up again, if it does ill update this form with what I find in case anyone else has a similar issue.
Thanks to everyone who replied and shared their knowledge with me!!!
04-04-2024, 06:36 PM
