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Old 08-19-2010, 10:47 PM   #1
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Default Hard hot start, stalls at idle

Been helping a friend figure out a problem with his car. It would hard start when hot. such as drive to a store, go inside, then come out and restart. It would also stall at idle. It died in the shop here, it'* died coming off the interstate. It would just shut off like a switch was flipped. Really thought it was a electrical problem. Swapped out a few items, TPS, cleaned the throttle body, IAC. Nothing worked. On a whim I said check the fuel pressure. He had about 42 PSI. So he pulled the vacuum line, it jumped up to 55 psi. Fuel was squirting out of the FPR. Turns out the FPR was the problem. He replaced it and the problem went away. Posting this to help the next person with the same symptoms.
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Old 08-20-2010, 11:46 AM   #2
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Old 03-15-2011, 11:36 AM   #3
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Quote:
Originally Posted by Danthurs View Post
Been helping a friend figure out a problem with his car. It would hard start when hot. such as drive to a store, go inside, then come out and restart. It would also stall at idle. It died in the shop here, it'* died coming off the interstate. It would just shut off like a switch was flipped. Really thought it was a electrical problem. Swapped out a few items, TPS, cleaned the throttle body, IAC. Nothing worked. On a whim I said check the fuel pressure. He had about 42 PSI. So he pulled the vacuum line, it jumped up to 55 psi. Fuel was squirting out of the FPR. Turns out the FPR was the problem. He replaced it and the problem went away. Posting this to help the next person with the same symptoms.

What kind of car was this on? eng?

I havent tryed this yet, but its on the list!

Denny
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Old 03-15-2011, 12:04 PM   #4
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I don't remember posting this. Someone must have pulled it from another thread. Oh well. It was a 2000 Grand Prix. But it will work on any car with a FPR.
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Old 03-15-2011, 05:54 PM   #5
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I don't remember posting this. Someone must have pulled it from another thread. Oh well. It was a 2000 Grand Prix. But it will work on any car with a FPR.

My 95 Olds Cutlass , 3.1, 64K has been on the sick list sence OCT 2010, It would drop dead just like you stated above, sometimes it would not start, come back later and it would.

I did the pressure test today I get about 40 psi KOEO.
With eng running I get a steady 32-33 psi.
With eng running and pulling vac line it jumps to about 45 psi for maybe 5-6 seconds then drops to zero and dies. (key still in on position)

This is what bothers me:
When I turn key to off then to ON again PSI stays at Zero psi, There is NO fuel squirting from the FPR! If I wait afew minutes and turn key to ON again psi will build to 40 psi.

Whats going on here??
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Old 03-15-2011, 06:35 PM   #6
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Wow, someone other then me actually used KOEO and knows what it means.

Well, if fuel pressure is dropping to zero I would suspect the fuel pump. A bad filter will still have some pressure. And the FPR has no control over what the actual fuel pressure is, it simply controls it after the fuel pump has built up pressure by opening and closing a valve. The full PSI is still in the fuel line behind the FPR.
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Old 03-15-2011, 10:14 PM   #7
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[QUOTE=

Well, if fuel pressure is dropping to zero I would suspect the fuel pump. .[/QUOTE]


Lets talk about this:

If my thinking is right, removing the vacume line from the FPR would produce the same conditions as if the engine was not running,(NO VACUME) and the valve would be closed, that being the case a fuel preasure guage would drop towards zero as fuel is consumed.

Its my understanding that the computer will give 1 prime shot of fuel per key cycle! After this is where I get lost! The computer at some point will have to comand the fuel pump to operate, the fuel pump has a relay and that is connected to the computer.

Can anyone comment on this procedure? How does it all work?
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Old 03-16-2011, 01:09 AM   #8
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Old 03-16-2011, 08:58 AM   #9
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As I said, I don't see zero pressure being a result of a bad FPR. Can you hear the pump running?
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Old 03-16-2011, 10:37 AM   #10
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I never hear the pump, I do have a AMP draw meter that plugs into the fuse bay that should confirm if it working. If i find nothing there I will go to the FP relay with a meter.

I tryed doing that test again last night, after removing the VAC hose psi went to 45, but this time the eng kept running. The only difference between the tests was that the eng was totally warmed up in the first test, the second test was cold start.
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