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  View original topic: 91 Carat 2.1 won't start after it's warm.
MattinglyDavid Sun Jun 29, 2008 7:52 pm

Good Evening! I have a 91 Carat that runs great, but recently cranks but will not start right after you shut it off. If it sits for an hour, it starts back up just fine. Good fuel pressure and spark on all 4 is evident while it is trying to start. Any ideas?

MattinglyDavid Tue Jul 01, 2008 5:05 am

Could this be Vapor Lock?

morymob Tue Jul 01, 2008 5:11 am

I had the same happen on my 1st wbx & turned out to be fuel pump. If u turn on ign can u hear pump cycle-if so pump will run at least. mine wouldnt cycle till cooled down.

morymob Tue Jul 01, 2008 5:16 am

If fuel press is ok(?) try a quick shot of start-fluid into intake,if it hits a few times u have an electrical problm operating injectors.

Yellow Rabbit Tue Jul 01, 2008 5:22 am

How is the fuel pressure after you turn off the key? If the check valve is bad in the pump, it will not hold pressure and then it won't start when hot. Cycling the key several times before starting is a temporary work-around.

MattinglyDavid Tue Jul 01, 2008 6:20 am

Thanks for the tips! The pump runs while it's trying to start & there is good pressure after I shut it off in the lines. I'll try shooting some starting fluid into the breather the next time it happens to see if it could be the injectors not opening. If that's the case, could it be the ECU?

Yellow Rabbit Tue Jul 01, 2008 9:50 am

How's your temp 2 sensor?

MattinglyDavid Tue Jul 01, 2008 2:17 pm

Actually, the temp light has been flashing after it warms up, but I thought that was a different problem. The running temp is normal to cool, according to the guage. Can this be linked to the not starting issue?

Yellow Rabbit Wed Jul 02, 2008 3:26 pm

If it is running cool, but the light is flashing, you may be low on coolant. The light will come on if it is really hot or if the level is too low. The level sensor is on the top of the coolant tank. The Temp2 sensor is the blue on on the thermostat housing. It tells the injection system what it needs to know. It is a common failure item and may cause this issue. The sensor is cheap.

dkveuro Wed Jul 02, 2008 9:14 pm

This is generally caused by the fuel system loosing rest pressure too quickly.

If this pressure goes to zero the fuel boils in the fuel rail and you only have vapors in the pressure line when you try to start causing a very lean condition until liquid fuel gets to the injectors.

There is a test port in the fuel rail and until you have verified the rest pressure remains at around 20 psi or so for 20 minutes, you chasing your tail looking for other problems.

The system is kept pressurized by the check valve in the fuel pump and the pressure control valve in the fuel rail after shut down.

Another reason this occurs is due to a leaking injector/s allowing raw gas to fume up the intake......again, this can be confirmed with a pressure test.

MattinglyDavid Thu Jul 03, 2008 10:06 am

Both are great suggestions!
Yellow Rabbit - The coolant level has been good - that's one I check frequently because I had a leak this winter that caused some heartache. It hasn't been low for several months now, but the sensor is easy to get to and replace. I might as well do it, especially before winter comes again! Thanks for the Tip!

dkveuro - I haven't measured the pressure in the fuel line after it has sat for 10 - 20 minutes, but I have loosened the T line cap & gas sprayed out with fairly strong force. I'll get a DPM to measure the actual pressure though, just to be sure it's not vapor lock. Thanks for your tip!

dkveuro Thu Jul 03, 2008 2:26 pm

We have a test in the trade...

Small squirt and wet's your hands= 1 to 4 psi.

Squirts but stays within confines of the engine bay = 5 to 10 psi.

Squirts into your eye and over the floor of the bay = 10 to 20 psi.

Squirts over the guy in the next bay = System okay .

The ECU can become heat sensitive..... the joints on the board fail..dry joint.
You can resolder with a 70 Mag Loop and electronic solder .

With the engine running tap firmly on the ECU.

Also remove and install the ECU plug a few times to clean up the contacts.

Coolant Lamp flashes if coolant low.

Make sure grounds are good. Under the a/c compressor mount. All BROWN wires and a braid.

MattinglyDavid Thu Jul 03, 2008 2:52 pm

dk - I like the unit of measure for the pressure! That's good to know for "on the road" troubleshooting. I have a feeling I may be around 5 - 10 psi based on the description. You've given me a few new things to look for, hopefully I can get to it this weekend.
Thanks & Have a Great 4th of July Holiday!
- David

MattinglyDavid Wed Sep 03, 2008 7:20 pm

DK - It took me a while to get everything taken care of, but I found out it was the pressure regulator. Once I replaced it, the Carat fires up no matter what the condition is.

Thanks for your help!

While I was at it, I replaced all the fuel lines & Injector seals - they were looking a little tired. Running like a champ now!



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