Starting issues

[Lalean75]

I have a '91 Geo tracker 1.6 liter duel overhead cam 4x4 automatic
When we got it we were told that it vapor locked sometimes when it got hot. It has only stalled/stumbled (as it didn't completely die) when it was hot out once. However recently with the temps outside now in the 50's and 60's we have had trouble with it not starting wait anywhere from 5 min to an hour or so and it will start. Then today I had to drive it further than usual and the only indication there might be a problem I was doing 35 and felt a sudden drop in speed though my foot was still on the accelerator I let of then gave it a little gas it would pick back up. It did that 3 times in succession.
When I got to where I was going I shut it off waited and started it, worked fine. Went to my appointment for 1 1/2 hours came out and it wouldn't start. Later my husband went to go try and start it (4hours later) and it still wouldn't start he used starter fluid in the throttle body(?) and it started right up and drove fine the rest of the day. The check engine light hasn't come on and it is supposed to have a new fuel pump (can't confirm this though)
Any thoughts what could be causing this my husband thinks it might be the computer, but we've had other cars send us on wild goose chases before and don't want that again (our mechanic doesn't mind but we do)

[tracka96]

Have you put a fuel filter on it since you've had it? If not, I'd try that first since it's probably due anyhow. Tracka96

[Lalean75]

We had normal RPM's on start up and haven't had a problem with it idling cold and warm at the right rpm's, just the issue once in awhile where it acts like it's "out of gas" and won't start. We'll change the fuel filter, because I have no idea when that was last done.

[Lalean75]

Ok an update we replaced the ECU just over a week and a half ago as I'd had it die on me 3 more times, and wow it seemed to run great it was shifting smoother not dying etc until today it sat all day until I got off work and got to try starting first off it just wouldn't start it would crank but nothing I checked the oil (assumed my hubby had done this as he kept saying it was due for and oil change) and it was out added 2 qt's and used starter fluid and it would try to start (this has worked in the past within 2 or 3 tries. So my friends that were assisting and my dad all thought it was the gold looking "fuel filter" on the side of the carburator we pulled the fuel line off both ends and had fuel going to it but not out of it so I assumed get a new fuel filter cause it's clogged.
When I couldn't get it off I hit it hard with a wrench and on a whim tried to start it and it started right up. I drove to the parts store to get a "fuel filter" where I find out it's the fuel pressure regulator (much more costly) So I call my hubby who is currently across the country his concern is alot of money has already been put into trying to solve this problem by us and the previous owner. what is the likelyhood it really is the fuel pressure regulator how cani go about proving it or did I just do that
I know the basics when it comes to cars so I can usually follow directions to test or fix something.
Sorry it was such a long follow up.

[captchee]

yep everything JT said .
i would add that if you are truble shooting by changing parts , use WY parts first .
your fPR wont cost youy but a couple bucks . yes you can get a bad one but most times they are ok .
most place will let you put it on right there in the yard . pressure regulators can get lacquered up and not work properly .
What they do is control the line pressure to keep it into tolerances for the injectors .
When they go bad , you can get to high a pressure or to low a pressure where the ejectors just dribble instead of squirt. This depends on if the regulator is mechanical or electric .
With electric regulators , the will close completely when the engine isn’t running .
When you turn the key , , it tells the ecm when the line pressure reaches its proper level .
, it opens and the ecm fires the injectors .
If it sticks then the ECM thinks the pressure is correct and opens the injectors but no fuel is able to get to the engine .

When the engine is running the regulator controls the line pressure for the injectors. IE keeping the line pressure proper .
If it sticks then you lose power either from flooding or to lean as the injectors don’t get the fuel they need .

To often folks just start replacing parts and guessing about a problem .
You will always save money by diagnosing the problem first .
One short fall I find to often with today’s mechanics is that they don’t know how to diagnose and engine that has a basic ecm or none at all . Basically they get lost, the don’t seem to understand how to backwards diagnose without the ECM telling them where to start .

What I would recommend is again getting a regulator from a WY and trying it . But in the main time go down and get you a cheep inline fuel pressure gage and place it , just before the regulator . This little gage will tell you a lot and very quickly .. Get one that will read 0-30Lbs .
The cheep 10 dollar ones that go to 15lb are for carb set ups . While they will work for a short time the will break fairly quickly even with a TBI .
So if after changing the regulator you still find your having this problem . Look at the gage while trying to start the engine .
JT can tell you what the line pressure should be . but with most GM TBI it must be at leas 12.5lbs -18 .
The engine will run with more but not less .
If its less then the minimum line pressure you know you have either a plugged filter . Kinked fuel line or the fuel pump is going .
If the pressure is within its parameters then you know that the problem isn’t in fuel supply prior to the TBI and thus has to be either the regulator or , the injectors themselves “ possible ground fault or clogged , or just bad .

[captchee]

I never recommend a used sensor, but if you must you must. ( tail chaser if ever there was one. in spades for people guessing and no instrumentation)

thats all well and good TJ when folks fully understand what your saying , how things work and that there are diffrences .
to often when they dont they result to buying parts and guessing .

so if thats the case and things are going over your head and your going to just start replacing parts , use good used parts .
if you get lucky and fix the problem then be smart and replace that part with a new one .
as said above , its much easyer and cheeper to learn how to diagnose then guess

[Lalean75]

Ok I haven't the foggest how to tell if it's a 16 or 8 valves (something I should probably learn huh?) So I'm waiting on my hubby to call me! I'd rather spend time learning to diagnose problems and do that than throw money I don't have at this (as that was done by the previous owner who gave up and just gave us this car)
I've tried the key on off trick sometimes it works sometimes it doesn't but I can hear the click of the fuel pump. Usually the temp outside has been around 60 degree F when this happens we have yet to have any really hot days, and It seems to do this more often within 5 miles of starting. As soon as I have the # of valves I will let you know and will start looking over some of the things you both have recomended.

[Lalean75]

ok 16 valve

[Lalean75]

ok 91 2dr. 4x4 automatic A/C and power steering. Only words on top of the engine are "Electronic Fuel Injection"
I added a photo of the engine in the attachment maybe that will help

[jtgh]

that is an 8-valve single cam engine. TBI , throttle body injection.

recommend checking fuel pressure after changing fuel filter.

then test ECT sensor. << far too easyh to test with ohmeter cold and hot.
200 ohms hot, and 2k cold , see my sensor page for exact values.

checking ECT is so easy, 10 min job. test cold with ohmeter , write down ohms.
then completely warm up engine now measure it again.
do not break the connector by yanking it, all conn. on this car have locks,
just depress the lock lever and wiggle gently.
if it dont come off assume you are doing something wrong.



read capchees posts , he is the man.
my 91 GEo tracker manual must be corrupted some how.


Here is my ohm chart, yellow is factory data, white is new in the box sensor tests I did for my new custom ECU.
temp-sensors