91 civic wagon wont start when hot HELP!

PNWagonPNWagon Band Wagon
in Electronics, Fueling & Air Conditioning
so my 91 daily driver is being kind of a pain in the butt. She will start perfectly when shes cold but as soon as i drive and get her up to running temp and shut her off I have to wait half an hour before i can start it again. it also happens when its a hot day i dont even have to drive it and the sun will warm her up and itll just sit and crank over but will not fire up. with summer and hot days coming up this will become a problem so im trying to fix it asap. Ive heard that it could be the relay behind the hood pop lever but im trying to get some legit answers so i can for sure fix it. can anybody let me know what they think is going on?
thanks zach

Comments

  • civtec350civtec350 Wagonist
    a ''no start when hot" problem usually is a sign of the control module on its way out. i have also heard of the coolant temperature sensor causing this issue.
  • geezfoolsgeezfools Wagonist
    I suggested main relay in the build thread
  • AintGotNoSolAintGotNoSol Wagonist
    I had this happen on three of my Hondas in the past. Ignition Control Module (or sometimes called Ignitor), its inside the distributor, beside/behind the coil. When these start to go bad, they'll sometimes work fine when cold, but heating up cases the parts to expand and lose contact apparently. It may still produce a spark, but it will be weak and erratic, enough so that the car won't run, until the unit cools down. On mine, I could pull the spark plug wires and test for spark, and it l=LOOKED like I was getting spark on all cylinders, but it still wouldn't fire. Changed it out, fixed the problem!

    It's a fairly expensive little part, like $75 - $100, so if you can try to borrow one from a friend's running car, I'd try that first!
  • AintGotNoSolAintGotNoSol Wagonist
    As far as the Main Relay being a possible issue, yes those are known to have poor solder joint that crack over time, and the same thing happens, they can lose contact, and heat can be a factor. Listen for the fuel pump to prime for a few seconds when you first turn the key on (without actually engaging the starter.) If the pump doesn't come on at all, then the Main Relay could be the culprit. Usually when those go out, the pump won't prime. USUALLY...

    I'd try to borrow someone's ICM first, (or swap their entire distributor if its the same motor), and see if that does it. If its not anything in the distributor, then pull the main relay out (its held to the driver side kick panel with a ten mm bolt, and its WAAAAAYYYY up there!). You can pop the cover off and look at the solder joints, usually you can see if they're cracked. I pulled my buddy's Main Relay out once and went over all the joints with a solder gun real quick just to melt the joints back together, and put it back in and it worked fine. Just be careful not to actually melt the solder enough to run out of the joints! If you aren't comfortable with trying it, you can just get a new one, lol. But hey, free fixes are the best fixes!
  • geezfoolsgeezfools Wagonist
    listen to that guy ^^^
  • bam-bambam-bam Council Member
    I'll agree with the main relay guys.

    True, the ignitor can have similar symptoms, but you said it happened just from sitting in the sun, not running. To confirm, do what has already been suggested and listen for the fuel pump priming at key-on.
  • quartersquarters Council Member
    it's your main fuel relay.

    just above the hood release handle. next time your car won't start, bash that area with your fist and it should fire right up. go to the wrecker, grab a new one.
  • AintGotNoSolAintGotNoSol Wagonist
    Curious, you get this figured out yet?
  • galexgalex Band Wagon
    I've experienced the same problem off and on until I got tired of thinking it was a BAD case of vapor lock. Finally it wouldn't start at all. After, seeing code 16 on the ecu, (which states a fuel injector problem) I removed both primary and secondary injectors and tested them with the ohm meter. They were fine. Changed fuel filter. No. New plugs. No. So I left the Fuel Supply Section. Finally, I looked in the Relays & Control Unit Locations Diagram, and there it was. the PGM-FI Main Relay. Located in the drivers, side panel under the dash. Basically under the drivers outside air vent. Luckily I had a wrecked spare civic to borrow and BINGO! I've had about 8-12 of these cars in the last 10? years. (when was gas @ $.85/gal.? LOL) I remember filling up Wago for $7-$9p. Sigh...... those days...

    So for all of the previous answers with Main relay, you are correct.... for me anyway.

    Good Luck
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