2G Vapor lock - help

[Proud Owner]

So I seem to be having all the classic signs of vapor lock on my 2g Eclipse. It cold starts just fine but once its fully warmed up if I shut it off and then try to start it RIGHT AWAY it starts, but if I let it sit about 3-4 minutes it cranks and cranks but won't fire at all. if you let it sit for 15 mins or more then it starts just fine.

I have a Haltech ECU and checked prime pulse table which looks fine, changing values in there higher, lower etc doesn't help at all.

My coolant temp sensor is working perfectly. Fuel pump runs great (its kinda loud so its obviously working) didn't check fuel pressure though but the car runs great so I'm assuming that's not the problem.

During normal operation, my engine warms up to 200F nice and quick at which point the fans start cycling and keep it steady between 190 and 197 (data logged). when I shut the car off it starts to heatsoak up to 223 and that's where you can't start it for crap then it slowly creeps back down and under 195 it will usually start again.

First of all I don't quite understand how vaporlock can happen in a recirculating system. wouldn't the fuel pump just push the vapor back into the tank and fresh cool fuel into the rail? If so would I maybe have a blocked return line? Also the evap system has been deleted, maybe they didn't do that right? Anything I can check? Has anyone else struggled with this and found a better fuel maybe or another solution? I understand the boiling point of gas can very dramatically from one company to another so maybe I keep getting cheap gas? Or should I have my cooling fans kick in sooner to keep the car maybe around 180F instead of closer to 200F ?

Thanks for any and all help!

 

[DSM1G90]

You mentioned a perfectly good temp sensor, but they can still fool your ECU. I had the same issue until I replaced my "good temp sensor" and problems were solved.

Do this trick though: next time this happens, take the intake tube off the throttle housing and zap some starter fluid in there, then try a hot restart.

If the motor catches immediately, it's definitely "vapor lock." This is when you need to find a way to insulate the fuel line coming up to the fuel rail so the line doesn't get so warm.

But, if that doesn't do anything, your plugs are all but wet with fuel and it could be the ECU, or that 'perfectly good temp sensor' (and we can throw in the power transistor in this loop which can cause tonnage of misfiring) messing around with the ignition.

Good luck in your find. - DSM

 

[SrKegler]

If you find out it's vapor locking, try putting a few metal type clothes pins on the line before the fuel rail. Just curious if a bad fuel pressure regulator wouldn't contribute to the problem.

 

[Proud Owner]

thanks guys. yeah reason I said "its a perfectly good temp sensor" is that I have a haltech ECU that shows the actual degrees read by the sensor not just a crappy dash needle that effectively shows cold or not cold . when its 90 outside and the car is parked in the detached garage and hasn't been run all day the haltech shows 90 almost on the dot. but yeah you're right, I didn't calibrate it by sticking it in a glass of water with a thermometer which I will do if I keep having problems. I was figuring on doing the starter fluid test too so thank you, I'll definitely do that. tonight I swapped the 195 degree thermostat for a 180 and cut the thermofan turn on temp from 200 to 185. will see on my next run if temps are cooler, especially the heat soak after shutoff. if so I"ll see if it helps hot starting. still interested to see if anyone has better luck with better fuel like Sunoco Vpower etc. which claims about a 360F boiling point from what I found.

 

[Proud Owner]

ok, a few things. first off I tested my temp sensor by removing it and placing it in a glass of water along with a thermometer. everything from ice water up to boiling water showed that I do indeed have a VERY accurate sensor so that's good. the new 180 degree thermostat helps a bit but after a good heatsoak it rises up to 203 where it still refuses to start. only when it dips down to about 195 will it (begrudgingly) start.
one MAJOR thing I noticed tonight is that I actually DONT have a circulating system! there's no return line to the tank from the fuel rail. After some reading, I see they did this on the non turbo 420a's after 1995. so my question is, is this my main problem. if so why isnt it a problem with all stock setups? and what should I do to help fix it? is it worth trying to swap out a circulating system? or is something else simply wrong?
thanks for any help guys!

 

[DSM1G90]

We, as a family, used to have a 1987 Dodge Aries with the 2.2L. Got it for 600 bucks with lotsa miles on it. I had to put a new cam and lifters in it since one cam follower chewed up the lobe real bad.

Ran great after that, but on hot day talk about hard starts after stopping for a few minutes ! This vehicle had the older single point injector system where they took a carb body and adapted it for usage with an injector.

As with the carb systems: fuel line going in and no return to the tank. Fuel line was terribly close to the EXH manifold and I knew right off that I was fighting vapor lock real bad.

Went to Home Depot (or similar if closer) and got some pipe insulation - the fibreglass variety - and wrapped up that fuel line with this stuff.

Doing that trick got rid of my vapor lock completely.

It's just something that DODGE seems to miss is the how the fuel lines run and they love to run the lines close to something hot.

-DSM