1992 240SX: Just changed thermostat, now hard to start...coincidence?

[carcrazyguy]

A couple days ago I changed my thermostat and everything went fine. Now my car actually warms up!However, now the car is very difficult to start, especially if it has been sitting a while. It kinda reminds me of a previous RX7 when it would flood as to the way it behaves. It cranks over fine but it is as if there is no fuel (or maybe too much). Anyway, once started, it runs just fine and you could go to the moon at that point without a hitch.I never had the first issue with starting before changing the thermostat either!Any ideas as to why this is?

[elwesso]

I will say that it probably is unlikely, but im also not one that believes in coincidences.....

Does it start fine warm????

[carcrazyguy]

I will say that it probably is unlikely, but im also not one that believes in coincidences.....Does it start fine warm????

You sound like George Noory

There doesn't seem to be any rhyme or reason to when it does this. It did it cold, and it did it warm - for that matter in the Hardees drive in last night! I was SO embarassed. The lady at the window came outside to help. I figured she was going to get in my car and steer as I pushed, but the next thing I knew my car was moving...and she was like 70! She really wanted me out of the line apparently!

Anyway, as I mentioned before, it reminded me of an RX7 flooding. They have issues with this because they run rich by nature (to avoid pinging which will destroy the apex seals immediately). Anyway, the trick with RX7s is to pull the fuel pump fuse, crank the engine (to dry it out) and reinstall it, preferrably while cranking.

Since I was sitting blocking half of the parking lot, I figured it was worth a try. I pulled the fuel pump fuse and started the car...and guess what? It sat there and ran for about 20 seconds with no fuse! I let it run until it dies on its own. Then after reinstalling the fuse, it started back up fine. So I guess my car is flooding it seems?

Anyway, my newest theory is that the injectors are sticking (open somewhat). I have knowledge of this because this problem is another RX7 thing - just one more thing that makes them flood prone in addtion to the richness and low compression that comes with worn apex seals.

So today I filled the tank up half way, yet put a whole bottle of fuel injection cleaner in. I drove about 150 miles today, and never had a starting problem on maybe 4 restarts. I don't want to knock on wood - the problem may come back. Anyway, I will update as a couple more days pass.

[elwesso]

I would leakdown test the injectors.... just take the injectors AND THE RAIL out of the intake manifold. While you have it lifted up so you can see the tips of the injectors, turn the ignition switch on so it primes the fuel pump, and see if any fuel comes out of the injectors. If youre getting and bleed down you could have a bad O-Ring, which would make sense in this case..

ALSO, OHM test your injectors, they should be about 12 ohms, 10-14 being acceptable.......

Pulling the fuel pump fuse and it running is KEY.... its obviously related to fuel pressure... O-rings can seemingly bust on their own, its happened before but not super-common....

Did you ever try mashing the gas to the floor while cranking to see if that makes it start? It sounds like your problem could possibly get worse really fast if the O rings get any worse... If it is indeed an O ring problem and it gets worse, the floodgates will open and the motor probably wont run, and it could POSSIBLY hydrolock!!

[carcrazyguy]

I would leakdown test the injectors.... just take the injectors AND THE RAIL out of the intake manifold. While you have it lifted up so you can see the tips of the injectors, turn the ignition switch on so it primes the fuel pump, and see if any fuel comes out of the injectors. If youre getting and bleed down you could have a bad O-Ring, which would make sense in this case..

ALSO, OHM test your injectors, they should be about 12 ohms, 10-14 being acceptable.......

Pulling the fuel pump fuse and it running is KEY.... its obviously related to fuel pressure... O-rings can seemingly bust on their own, its happened before but not super-common....

Did you ever try mashing the gas to the floor while cranking to see if that makes it start? It sounds like your problem could possibly get worse really fast if the O rings get any worse... If it is indeed an O ring problem and it gets worse, the floodgates will open and the motor probably wont run, and it could POSSIBLY hydrolock!!

Yes, out of frustration, I floored the gas a few times before I suspected flooding. Naturally it didn't help. Well, once it did start that way and surged, but as a rule it just bucked.I will OHM test the injectors and the other tests if it acts up again. I guess I will know tomorrow.

[carcrazyguy]

Well, to update, I drove the car today and still no issues with starting whether hot or cold, so maybe I cleared the injector(s) with the cleaner.Anyway, for what it is worth, I realized that the car had never warmed up all the way until I changed the thermostat. Right after the swap, I was driving the car and it reached full operating temperature for the first time since I've owned it. As soon as it did, the car started to run as if it was running out of gas, but still got me home, barely. The next restart is when the problem began and it continued for a couple days until I ran the cleaner and drove the car a bunch.Maybe it is still just a coincidence, but so far so good!

[carcrazyguy]

I would leakdown test the injectors.... just take the injectors AND THE RAIL out of the intake manifold. While you have it lifted up so you can see the tips of the injectors, turn the ignition switch on so it primes the fuel pump, and see if any fuel comes out of the injectors. If youre getting and bleed down you could have a bad O-Ring, which would make sense in this case..

ALSO, OHM test your injectors, they should be about 12 ohms, 10-14 being acceptable.......

Pulling the fuel pump fuse and it running is KEY.... its obviously related to fuel pressure... O-rings can seemingly bust on their own, its happened before but not super-common....

Did you ever try mashing the gas to the floor while cranking to see if that makes it start? It sounds like your problem could possibly get worse really fast if the O rings get any worse... If it is indeed an O ring problem and it gets worse, the floodgates will open and the motor probably wont run, and it could POSSIBLY hydrolock!!

Guess what...the starting issue is back. Sometimes it fires up fine, and others it will not start for anything...until I pull the fuel pump fuse that is. It does it the worst on a totally cold start...where the car has sat overnight. The other problem starts are when the car has been driven some, shut off, and then restarted in, say 45 minutes. Any other situation is fine. I noticed the idle sits at 1200 even when warm, so this could likely signal stuck injectors, right? I tried to turn it down some with the adjustment screw, but it was already all the way down. If I remember correctly, my last 240, a SOHC had one sole stuck injector with similar symptoms, yet not as extreme. I am guessing all 4 on this car.

I took the fuel pump cover off today to see if there was junk in the tank but it looked ok. The reason I suspected this is because the car had sat for over a year when I bought it...which is likely why the injectors may be sticking open. Anyway, I plan to do the first thing you mentioned tomorrow. My question is about the ohm checking. Where do I measure it and do I simply use the two wires going to the injectors or one and a true ground, etc?

[carcrazyguy]

I would leakdown test the injectors.... just take the injectors AND THE RAIL out of the intake manifold. While you have it lifted up so you can see the tips of the injectors, turn the ignition switch on so it primes the fuel pump, and see if any fuel comes out of the injectors. If youre getting and bleed down you could have a bad O-Ring, which would make sense in this case..

ALSO, OHM test your injectors, they should be about 12 ohms, 10-14 being acceptable.......

Pulling the fuel pump fuse and it running is KEY.... its obviously related to fuel pressure... O-rings can seemingly bust on their own, its happened before but not super-common....

Did you ever try mashing the gas to the floor while cranking to see if that makes it start? It sounds like your problem could possibly get worse really fast if the O rings get any worse... If it is indeed an O ring problem and it gets worse, the floodgates will open and the motor probably wont run, and it could POSSIBLY hydrolock!!

For the first time this morning, I could not get the car to start at all - as it has gradually gotten worse. It also may have to do with the fact that this morning had probably the coldest temperature we will ever see here...around 20 I guess.Anyway, I ohm tested the injectors, and 3 of them were 10.8 with one at 10.9.Although this is in the range you mention, it is at the bottom of the range. What does that mean versus it being at the top of it or more toward the middle?

[elwesso]

That is fine... I woudl take the fuel rail out with the injectors still in there and see if fuel is leaking pas the injectors. if you want an easier way, you could hook up a fuel pressure gauge just past the fuel filter.... if the injectors are leaking it shoudl give nice pressure (somewhere between 35-40ish) and as soon as the fuel pump turns off it shoudl start falling off...

[boriquaS13]

Just a thought have you checked your coolant temp sensor? And also pull the vacuum line off your fuel pressure regulator see if gas is just dumpingstraight into the intake. I've run across it many times anyway good luck.

[carcrazyguy]

Just a thought have you checked your coolant temp sensor? And also pull the vacuum line off your fuel pressure regulator see if gas is just dumpingstraight into the intake. I've run across it many times anyway good luck.

I looked for the regulator today, but wasn't sure which thing it was (it wasn't as obvious as on other cars I've owned). Regardless, I can look at the FSM and find it.My question is how will I know if it is dumping. What precisely happens or do I look for when I pull the vacuum line off? Is the coolant temp sensor OK if the dash gauge is working fine? Or is one sensor for the gauge and the other what you are referring to (there are two similar looking sensors right beside each other). What would the coolant sensor have to do with starting anyway (I would like to actually understand what is going on rather than just fix it).

Quote »That is fine... I woudl take the fuel rail out with the injectors still in there and see if fuel is leaking pas the injectors. if you want an easier way, you could hook up a fuel pressure gauge just past the fuel filter.... if the injectors are leaking it shoudl give nice pressure (somewhere between 35-40ish) and as soon as the fuel pump turns off it shoudl start falling off...[/quote]I was going to do that today, but it was so cold (to me anyway) that I had no coordination. I barely got the plastic harness plugs off and got the ohm readings.I will give it a go tomorrow. Is using the gauge really that much easier? If so I can borrow one, most likely.

[boriquaS13]

If you pull the vacuum line off the fuel pressure regulator and there is fuelcoming out then the diaphram is bad and it needs replacing. There shouldbe 2 sensors one for the gauge one for the computer. If the temp sensoris reading lets say -40 degreas and its 35 degreas out side then the computer will compensate too muck ie to much fuel and give you an overly rich condition, extended crank fuel fouled cylinders and so on anyway hope 2 help you get thia problem fixed keep posting..

[carcrazyguy]

Thanks, I will also check the regualtor. Is there a measurement for the sensor that will diagnose it?

[carcrazyguy]

Just an update...after I checked the resistance a week ago I never had another starting issue. The car starts and runs just fine now - I drove it every day since then with lots of starting from short errands (easily 6-10 times a day) so I am fairly confident all is OK now. I must have had a loose connector or something? Anyway, as happy as I have been about the car running right, it had to spite me and the digital speedometer quit lighting up Sunday. So I am not sure what I will do...I realize this is a simple fix, but since I currently have no spare time and no garage I may just turn this car over to someone else.Regardless, thanks for the help so far.