hard starting after fuel pump change

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  #1  
Old 03-27-09, 12:50 PM
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hard starting after fuel pump change

fuel pump was changed at the dealer week and a half ago. Ever since then the car takes longer to start when cold. It used to start right up, but now takes 2 to 3 times as long.

car (99 continental 70k 4.6L v8)

Testing info:
If I prime it a few times first, by turning the key to "on" so the fuel pump kicks on for a second, then back off. It starts easier.

I have a cheap fuel pressure guage. When The key is turned on, the fuel pressure rises to about 31 psi. When starting, it appears to bounce around between 20 and 40 psi.


What could the problem be?

Thanks
 
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Old 03-27-09, 01:04 PM
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If your gauge is partially correct, you have plenty of pressure. What is your pressure when idling? Try turning your switch on and pausing for 10 seconds prior to cranking. Is it fuel injected? Are your injectors tight? Are all your fuel hoses tight. It seems there may be an introduction of air somewhere, not sure. But try the pause thingy first.
 
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Old 03-27-09, 02:05 PM
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was your pressure test done on a cold start? after cycling the key to the on position once what does the pressure go to and does it hold steady or does it bleed off quickly?
suspect ther may be something wrong with the pump they installed and you may have to return it to the dealer.
 

Last edited by bejay; 03-27-09 at 02:22 PM.
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Old 03-27-09, 02:17 PM
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Did they replace the filter at the same time?
 
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Old 03-27-09, 04:52 PM
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Suspect The Pressure regulator has gone south......

When the car is parked at night, the fuel "Bleeds" back to the tank, leaving the rail empty. The extended time your experiencing is the time it takes to prime the empty rail.

#2....Bounces between 20 and 40????? Way too much of a variation......

#3....Running a pump without "BackPressure" can easily explain why your original pump failed, and will definitely make "Short order " of the new one if it isnt attended to.
 
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Old 03-27-09, 04:59 PM
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What about the built in check valve going south?
 
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Old 03-27-09, 05:08 PM
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What about the built in check valve going south?........

Would explain the hard start, but not the pressure variation.

Additionally, The Check valve would cause an issue consistently, not just cold, or after sitting.
 
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Old 03-30-09, 09:29 PM
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Thanks for the responses

My dad has almost the same car as my mom('98 vs '99) so when I looked at hers, I looked at his too. His pressure was bouncing like hers was, and the running pressure was about the same. Both cars tested cold.

I'm not sure about the actual numbers, the guage I bought wouldn't work properly yesterday, so I dont trust my previous numbers, I just know that the readings on the car are relativly the same as on my dad's car.

Towguy - I changed the fuel filter as a "just in case" before it was taken into the dealer. (old filter had about 7k miles on it) I'm not sure if they changed it again when the replaced the pump.

chandler- I tried turning it to "on" and pausing for 10 sec. Still had same starting issue.

On the old pump I got back from the dealer, there is just one outlet and four wires, no return.

Original problem :
-The car would start missing over about 2500rpm and could not run at all above 4000rpm. no codes
-took it to dealer for diognastic, said it was a cracked pcv hose and the MAF senser needed cleaning.
-doubted diagnosis I had cleaned the MAF sensor 2 months ago, and a vacuum leak from the pcv hose causes different symptoms (tested with my dad's car).
-Pcv hose was fine, but I replaced the hose and valve anyway, and switched MAF sensor with my dad's car. No improvement.
-Took it back to dealer, they looked at it again, and did a fuel pressure test this time, said it was dropping as low as 12psi at higher rpms. They changed it ($600), but have had starting problem ever since.

Sorry for the long post. Hopefully this info will help.


Thanks
 
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