1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Vapor lock? And, if so, what is the cure?

Old Jun 19, 2010 | 09:04 AM
  #1  
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NY Vapor lock? And, if so, what is the cure?

After 3+ years and 12,000 miles, I'm suddenly faced with a real problem. Isolated it to extreme heat and extreme traffic situations only (happened twice), but the engine is still operating within normal temperatures.

Car, as I come to a stop, while idling, will sputter out and die. Will not re-start. 10 - 15 minutes later, presumably after it cools, it re-starts, and if I can get it up to speed (out of traffic) it will not act up again. While it is not re-starting, I am getting a spark and it's not an electrical problem.

I changed my fuel filter, which was pretty badly clogged, and thought that was the problem, but then 3 weeks later it happened again, just as above. Air cleaner is good, and I am thinking perhaps a tune-up is in order (plugs, cap, rotor, wires), though it has only been 11,000 miles since the last change.

I assume the fuel pump is working properly, since the car will start up and continue fine once it cools. Also, I've been on the highway, maintaining 75 MPH for over an hour at a time, and that's never a problem.

Could there be anything else I should be looking at?

Thanks for your thoughts.

Pete
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Old Jun 19, 2010 | 09:56 AM
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Any chance the fuel filter has gotten dirty again? This can happen if you are getting rust in the tank, sometimes you can go through several filters before it gets straightened out.

I had something similar with my white 84 GSL during the first few months after I got it on the road. It would not restart when hot (after getting gas, after a stop at Home Depot, etc). I never did figure out what caused the problem (loosening the gas cap didn't help) but after awhile it just went away and didn't return for the next three years of driving.
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Old Jun 19, 2010 | 09:57 AM
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Could be flooding just a little causing fuel to build up when not being used eg at idle

to eliminate this as the problem just run it for a while at idle and check the float bowls, the fuel level shouldn't move.
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Old Jun 19, 2010 | 11:38 AM
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https://www.rx7club.com/1st-generation-specific-1979-1985-18/hose-question-750125/
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Old Jun 19, 2010 | 04:14 PM
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+1 on the rusted gas tank. mine was totally rusted. my fuel filter kept getting clogged up. each time i changed it, it bled red. i would have to floor the pedal and let the engine crank for like 5 sec for it to start. once it started, i didnt have any problems keeping it on. in the end, i had to get my tank refirbed. had it sand blasted and recoated inside and out. i also had my injectors cleaned also (GSL-SE). only then did the problem go away. now it starts up every time and runs perfect. 1st gens came with iron gas tanks and at the ripe age of 25, its safe to assume that you probably have lots of rust in there. i hope this helps...

Originally Posted by ray green
Any chance the fuel filter has gotten dirty again? This can happen if you are getting rust in the tank, sometimes you can go through several filters before it gets straightened out.

I had something similar with my white 84 GSL during the first few months after I got it on the road. It would not restart when hot (after getting gas, after a stop at Home Depot, etc). I never did figure out what caused the problem (loosening the gas cap didn't help) but after awhile it just went away and didn't return for the next three years of driving.
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Old Jun 30, 2010 | 05:08 PM
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Thanks for the replies, everyone. I did not realize anyone had replied, my spam filter must have kept these from me.

Anyway, I ended up changing the air filter, spark plugs, cap, rotor, and wires. The plugs were in terrible shape, not to mention being Autolite 2526's. (I know, I know). I never changed them when I bought the car 3 years ago (12,000 miles ago), since the car has always run so smoothly and the paperwork indicated it had just been tuned up weeks before I purchased it.

Anyway, it now runs a little better, needless to say. But, unless it ever stalls out again, I will not be sure if anything I changed was related to the problem. It has not been as hot lately, and I've avoided taking the car on the highway (out of my area) in case it does stall out.

Questions:

Could a fuel filter be acting-up sporadicly like this?

The #12 lead from the ignition wire to the cap had severe green copper-oxidation at the cap side. Could that "less than ideal" situation have been related to this?

That hose indicated in the link above is not faulty on my engine, any other hoses to look at?

Thanks!!
Pete
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Old Jun 30, 2010 | 06:00 PM
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I'd change that fuel filter right away.

Clean the copper corrosion, maybe get a new cap and you'll be fine.

And if you have a vacuum leak you are screwed. Starter fluid is your friend.
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Old Jun 30, 2010 | 06:29 PM
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Thanks Ray. Yeah, I changed the filter a couple weeks ago, and a couple days ago I changed the cap, rotor, wires, and plugs. Does seem to run a little smoother, but cannot tell if the stalling is gone. I guess I'll have to just wait and see.
Thanks for the suggestions.
Pete
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Old Jun 30, 2010 | 08:38 PM
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I just found today that damn vacuum leak that was costing me gas mileage for the last 1000 miles. Spray it with starter fluid, if you hear something weird, bingo.
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Old Jul 4, 2010 | 11:50 PM
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It could also be fuel boiling in the float bowl as you suggested causing vapor lock. Only cure is ceramic coat the header or wrap it or just a heat shield might work. This used to happen to me seldomly when sitting in nonmoving traffic on 100* days.
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Old Mar 20, 2011 | 09:19 AM
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The warm weather is back and so is my problem. Gonna change the fuel pump, I think.
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Old Mar 20, 2011 | 09:54 AM
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May be a good idea to check you return line for a clog. Try using compressed air through the return line. Take off fuel filler cap and hear for bubbling in the tank to make sure is is clear. Also may be a good idea to check to make sure your return line restrictor (gray metal thing on return soft line) is on the correct way. If you get an aftermarket pump make sure to get a regulator that is good, and by good I mean NOT one of those dial ones.
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Old Apr 21, 2011 | 10:37 AM
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I changed the fuel pump 2 weeks ago, but of course the warm weather went away. Hopefully, I'll get a few good hot days soon and I'll be able to report back whether this did the trick for me.
Pete
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Old Apr 21, 2011 | 12:21 PM
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I had this same issue a year or so back. It was the ignition, specifically, my SA
ignition decided it wasn't going to work anymore once it got hot. Exact same
symptoms. I completely gutted and redesigned a new ignition system based on
GM HEI ignitors and Ford TFI coils and dropped the trailing plugs altogther. See
the link in my sig.

If your not that adventurous, you should probably try checking the ignitors via
the FSM test and seeing if one or both are bad. If you can do it when its hot
and failing you may even see an ignitor fail. I know you said you had spark but
the issue is how good was your spark. It could also be the coils from being
forced to fire really poor quality plugs for so long.

You replaced the fuel pump and filter so I suspect its not a fuel issue and it
appears to be heat related. Ignition parts usually fail under heat stress. That goes
for ignitors and coils.
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Old Jun 6, 2011 | 07:21 AM
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For anyone following this thread or for anyone new finding it with this problem, it is 100% official. The new fuel pump cured my problem. I have had it out and tested it a dozen times on different hot days with various short and long trips and it has not stalled once. I can safely say the problem is solved.

Pete
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Old Jun 6, 2011 | 11:28 AM
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Glad to hear you got her sorted. Thanks for posting the results.
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