FJ62 having issues turning on at hot start after EFI relay replaced

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luckylandcruiser

Joined
Sep 16, 2025
Threads
7
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19
Location
Connecticut
I had a post like this a few months ago - The truck starts up fine on cold start, then I go to stop in a store for 10 minutes, then the car doesn't want to start, turns over but doesn't start once the engines hot. Then it starts after about 15-30 minutes. People said it was the EFI relay that will overheat and then the truck will not have a hot start or will intermittently. I purchased a new OEM EFI relay to replace but now its still having the same problem. The strange part is, I got the truck to start, drove it home, and to test if it would start right after shutting it off hot, I shut it off then not even 3 minutes later started it again and it started right up. Then I waited 15 minutes, went to start again, and couldn't start but would turn over. What is going on???

Side note: battery is brand new, fuel injectors have been replaced, efi relay replaced, spark plugs replaced
 
I have just battled this issue on out 96 80 Series. Remedy may be similar. Lots of basics like battery connections, relays etc. I ended up replacing my fuel pressure regulator, which may have helped but didn't fully fix. I then used a bike pump (hand held) and found one of the small fittings with a hole to lock into the end. Disconnected the vacuum lines and gave some light pressure. Some have a temp switch so may not completely and buried. I also found a line off the bottom of the charcoal canister. That may have been clogged a little. Never touched that line before. That may have helped the most. Also the 80 has a vacuum line that "engaged vacuum" when the system is hot and trying to start. I think it's connected to the TVV. Mine may be incorrectly. So I capped off that vacuum line from the manifold and at the FPR fitting.
 
Is it throwing a code? I'm guessing not, but it never hurts to ask.

Your issue could be caused by any number of things, including but not limited to:
  • ISC valve
  • Fuel pump switch in AFM
  • Vacuum leak
  • Cold start injector malfunction
  • Wiring/ground issue, including fusible link
Since it seems to be temperature-related, you might want to test the sensors on the thermostat housing: the water temp switch, water temp sensor and the cold start injector time switch. If these do not read within spec, your ECU will not be getting the correct signals. You can get most of these from City Racer I believe, or perhaps the dealer as well.

The Factory Service Manual has diagnostics for each of the systems above: do you have a copy?
 
Heat soak can effect both spark and/or fuel. you'll need to troubleshoot to figure out which. Agree w the items & FSM mentioned above.

Heat soaked coil and/or plug wires can have high resistance leading to spark issues.

A leaky injector, failed fuel pump check valve or regulator can cause loss of pressure in the fuel lines when it sits while heat soaked which then leads to vaporization of the fuel - requiring extended cranking time. Given that you reported the truck started ok within 3 minutes of shutdown but not if you let it sit a little longer - I would start troubleshooting a pressurization/vaporization issue. Easiest to eliminate the guessing would be install a fuel pressure gauge at the cold injector port. Since you've replaced injectors already, my guess is either fuel pump check valve or regulator. The FSM has details on testing those.
 
I just solved the issue in my rig.
Started fine when cold, drive to gas station, fill up, crank crank crank.
Replaced the EFI relay - no change.
Knew it wasn’t my fuel pump pr pump wiring as I had those redone a year or two ago.
Had my tech dig into it and found my fuel rail was going to zero pressure when the condition happened.
Cause - sticking fuel pressure regulator. This explained the intermittent no start condition.
Changed that our and back to normal.
 
luckylandcruiser said:
I had a post like this a few months ago - The truck starts up fine on cold start, then I go to stop in a store for 10 minutes, then the car doesn't want to start, turns over but doesn't start once the engines hot. Then it starts after about 15-30 minutes. People said it was the EFI relay that will overheat and then the truck will not have a hot start or will intermittently. I purchased a new OEM EFI relay to replace but now its still having the same problem. The strange part is, I got the truck to start, drove it home, and to test if it would start right after shutting it off hot, I shut it off then not even 3 minutes later started it again and it started right up. Then I waited 15 minutes, went to start again, and couldn't start but would turn over. What is going on???

Side note: battery is brand new, fuel injectors have been replaced, efi relay replaced, spark plugs replaced
Click to expand...
Did you ever solve this? I have the same exact issue
 
I said this in @jonnyd42 thread about this same thing and really, and I mean really cleaning the cold start injector solved this exact problem for me.

Does it make sense?
No…

It worked for me though.
 
RevISK said:
I said this in @jonnyd42 thread about this same thing and really, and I mean really cleaning the cold start injector solved this exact problem for me.

Does it make sense?
No…

It worked for me though.
Click to expand...
That makes no sense to me, but I will do it!
 
jonnyd42 said:
That makes no sense to me, but I will do it!
Click to expand...
Maybe it gets stuck?
I just know I chased this issue for awhile and a very reputable LC mechanic told me to do this… I don’t listen until I did and it has been fine since.

Best of luck
 
diesellibrarian said:
Is it throwing a code? I'm guessing not, but it never hurts to ask.

Your issue could be caused by any number of things, including but not limited to:
  • ISC valve
  • Fuel pump switch in AFM
  • Vacuum leak
  • Cold start injector malfunction
  • Wiring/ground issue, including fusible link
Since it seems to be temperature-related, you might want to test the sensors on the thermostat housing: the water temp switch, water temp sensor and the cold start injector time switch. If these do not read within spec, your ECU will not be getting the correct signals. You can get most of these from City Racer I believe, or perhaps the dealer as well.

The Factory Service Manual has diagnostics for each of the systems above: do you have a copy?
Click to expand...
Reading this again….good point on water housing temp switch/senders.
While my recent issue was 100% solved by an OEM fuel pressure regulator (aftermarket one was relatively new but wasn’t working correctly), I also experienced some start up trouble due to water housing sensors ealy in my ownership. Engine hot, ECU thought it was cold. Not only did this cause some starting issues, it also caused some high idle/rough idle/rich idle.
Its frustrating for sure but once you solve it, you’ll get your confidence in your rig back.
 
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