How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Virtual Wrench Your Own Question
Virtual Wrench
Virtual Wrench, Chevy Mechanic
Category: Chevy
Satisfied Customers: 14620
Experience:  35 years Master Mechanic
2617050
Type Your Chevy Question Here...
Virtual Wrench is online now
A new question is answered every 9 seconds

Having problem with 91 Lumina stalling and not wanting to

Customer Question

Having problem with 91 Lumina stalling and not wanting to start hot. From cold if you start it up and drive it, it will stall once to get up to temperature and not want to start until you let it cool off. But if you start it up cold let sit in the driveway idle as long as I let. So far the longest I've let it sit and idle in the driveway is about 35 minutes. Then if you turn it off in the driveway and come back after about 10 minutes or more it won't want to start until it cools down. It is vin code T the 3.1 multi, I have done new spark plugs, spark plug wires,temperature sensor, crank sensor, ignition module, MAT and MAP sensors; also new fuel pump and filter. Also I checked the fuel rails when it does not want to crank over there is 35-40 PSI in the rails.
Submitted: 1 year ago.
Category: Chevy
Expert:  Tim's Auto Repair replied 1 year ago.

Hi, My name is ***** ***** for the delay.

I will do my best to assist you

you replaced the crank sensor on the side of the engne block?

Customer: replied 1 year ago.
I did, I'm sorry I thought I had listed that as one of the number of parts that I've already replaced
Expert:  Tim's Auto Repair replied 1 year ago.

you did list..i am just making sure

Expert:  Tim's Auto Repair replied 1 year ago.

other than the ignition module and the crank sensor,there isnt much to break down with heat like this other than the ecm[computer] itself

Expert:  Tim's Auto Repair replied 1 year ago.

the crank sensor made no change?

Customer: replied 1 year ago.
No it did not
Expert:  Tim's Auto Repair replied 1 year ago.

sorry,my internet went down

Expert:  Tim's Auto Repair replied 1 year ago.

you problem sounds as if you have a bad crank sensor...but

Expert:  Tim's Auto Repair replied 1 year ago.

sense you have replaced it and the ignition module..i would think your problem is the ecm[computer]

Expert:  Tim's Auto Repair replied 1 year ago.

there isnt anything else left

Expert:  Tim's Auto Repair replied 1 year ago.

you may want to try one more crank sensor,it is possible to get a bad new one

Customer: replied 1 year ago.
I'll try replacing the sensor again and then ecm to see if that solves the problem
Expert:  Tim's Auto Repair replied 1 year ago.

ok

let me know how it gos

thanks

Customer: replied 1 year ago.
Replaced new CPS with another new one and ECM checks out fine.Problem continues/ is still unresolved
Expert:  Tim's Auto Repair replied 1 year ago.

ok,,,stand by,i will opt out,maybe one of the other guys has a better idea of what is going on

Expert:  Virtual Wrench replied 1 year ago.

Hello,

different expert here.

That fuel pressure is too low. It has to be at least 45 psi to run right.

When it wont start, give it a shot of starting fluid and if it starts with that, this will be a fuel supply issue.

Let me know

Customer: replied 1 year ago.
I have tried the starting fluid trick, sometimes it start briefly, some times it will not.
It has a new fuel pump and filter in it. Why will it start initially and then stop running when it warms up, if it is fuel pressure related, shouldn't refuse to start it all or not be able to run in my driveway continuously?
Expert:  Virtual Wrench replied 1 year ago.

Thanks, ***** ***** only start briefly with the starting fluid.

When the pump is cool it can make more pressure and when the little pump motor gets hot it slows down and cant make enough pressure. It only takes a few PSI to low, and the injectors cant open unless it has at least 45 psi. So you need to concentrate on that area. Check the wiring at the pump and make sure it has 12 volts and a GOOD ground when it wont start. A lot of times that connector where the pump plugs into gets a bit corroded and doesnt let enough power go thru it, OR the ground wire has a bad connection where it comes out of the harness and goes to ground.

Customer: replied 1 year ago.
I will check on all those again. I did check all those things when I put in a new fuel pump and fuel filter. Are you offering are suggesting that I might have a bad brand-new feel pump? . Like I said the starting fluid trick does not work all the time maybe 50% .
Expert:  Virtual Wrench replied 1 year ago.

Hi,

Yes, it is VERY common to get a bad pump right out of the box. especially if you bought it from autozone, advance, orilleys, etc...you really need to get one from the dealer. I know they are more money but well worth it because you dont have to keep changing it!

You cant really go off the starting fluid only does it 50% of the time because there is no way to accuratly measure how much gets sprayed. BUT 40 PSI is not enough so thats why i keep going back to the source.

LJ

Customer: replied 1 year ago.
far all the connections and everything tested properly. I have just drop the tank and going to be putting in a brand-new feel pumped to see if that solves the issue. I surely hope so, because I called and spoke with mechanics at two of the local Chevrolet dealerships and they both told me that 35 to 40psi while running was the range for this car at idle
Expert:  Virtual Wrench replied 1 year ago.

Hi, my specs as i am looking at them right now and not going off the top of my head is 40 is the lowest on the range of 40-47

Regardless that is low on the scale and will drop lower with engine speed because the pump always turns at the same speed.

You have tried to see it it hits on starting fluid havent you? Thats when it wont start. That right there will tell you if its fuel or ignition related

Customer: replied 1 year ago.
New fuel pump installed
Problem still NOT solved
Engine starts from cold runs fine. Will not restart if turned off and left to wait for 10 minutes or more
Expert:  Virtual Wrench replied 1 year ago.

Are you checking for spark at the plugs when it wont start?