Hard starting

Tiny
BILL411
  • MEMBER
  • 2000 PONTIAC GRAND PRIX
  • 3.8L
  • V6
  • 2WD
  • AUTOMATIC
  • 155,000 MILES
Car cranks for a long time with no start. I turn the key off and crank some more and no start. I finally get a start on the third try. Next time I want to start the car I turn it on, then off, then on, then off, then on and then I try to crank it over and it starts right up. This tells me it is not getting enough fuel when it only gets one pulse to the injectors. It needs three pulses (key on, key off) to start. Does this mean the injectors are partially clogged? I should mention the car runs great once it starts. I have 50 psi at the fuel port (gauge attached) so fuel pressure is not a problem and it does not leak down. If it is the initial pulse not providing enough fuel, how do I fix this? Currently, I put Seafoam in a quarter tank of fuel. That has not made a difference yet. What do you think?
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Thursday, May 11th, 2017 AT 11:12 AM

12 Replies

Tiny
HMAC300
  • EXPERT
Scan for codes and see if security light is on if it is reset security if it is a VIN 1 your pressure is low if it is a VIN K it is in range. VIN 1 should be 52-59 psi so it kind of sounds like it is a bad fuel pump.
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Thursday, May 11th, 2017 AT 12:16 PM
Tiny
BILL411
  • MEMBER
Security light is not on. CEL is not on. There are no codes. I found on other sites that the normal range is between 40 PSI and 60 PSI, which indicates the fuel pump is okay. When I hook up the fuel pressure gauge and turn the key on the pressure is right there. It is not like the pressure takes time to build up. Bam, it is right there. The pressure regulator is good. The problem is the initial pulse being too little to start the car. As I said. I turn the key on and off three times and the car starts okay. Once started it has plenty of power. A bad fuel pump would not have the guts this car has. Thanks, but I believe the fuel pump is okay.
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Thursday, May 11th, 2017 AT 2:18 PM
Tiny
KEN
  • ADMIN
Hello,

Sometimes tests can fool you. Here is what I want you to do. Next time the engine will not start (on the first time) spray a little choke cleaner in the intake to see if it starts, this will determine fuel delivery or something else like ignition.

Please run this test and get back to us so we can continue helping you.

Cheers, Ken
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Thursday, May 11th, 2017 AT 5:36 PM
Tiny
BILL411
  • MEMBER
I will try that tomorrow. I have read elsewhere that people have solved it by trying a different MAP sensor. Sounds unlikely but I am going to check the voltages on the MAP tomorrow. I also read that the engine temp sensor data affects the length of the initial injector pulse, which seems to be the problem. Pulse too short.
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Thursday, May 11th, 2017 AT 7:16 PM
Tiny
BILL411
  • MEMBER
Today I took off the MAF sensor and inserted a tube past the throttle butterfly and squirted gas in. I put the MAF back in and it fired right up. So, it is the lack of a fuel pulse or sufficient one on start up keeping it from starting. I did check the voltages on the MAP and they are normal.4.96v key on.1.12v at idle. I took the engine temp connector apart and ohmed it out. I got around 1000 ohms between the yellow and black wires. That seems about right as the engine was not quite warmed up yet. Besides, the dashboard temp indicator works. I can actually start it after just turning the key on twice.I think the residual fumes from the gas I squirted in are causing this. Well, I still think the problem is due to the initial fuel pulse being insufficient to start it on the first try. What do you think?
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Friday, May 12th, 2017 AT 9:13 AM
Tiny
KEN
  • ADMIN
Yep it makes sense that the multiple cycles of the key helps it. I think you should ohm out each of the injectors to see if one stands out, then disconnect that one and try to start it. Its like the injector drivers in the PCM are getting over loaded which explains the key cycles helping it.
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Friday, May 12th, 2017 AT 1:05 PM
Tiny
BILL411
  • MEMBER
I will try that tomorrow.
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Friday, May 12th, 2017 AT 2:14 PM
Tiny
BILL411
  • MEMBER
I had some time so I checked the injectors. They all read about 12ohms. I give up. I can live with turning the key a few times to get it started. I want to thank you and HMAC300 for responding.
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Friday, May 12th, 2017 AT 5:01 PM
Tiny
KEN
  • ADMIN
The next thing it could be is the PCM itself.
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Friday, May 12th, 2017 AT 7:36 PM
Tiny
BILL411
  • MEMBER
Here is an update. I took the GP for a 60 mile ride and then the car started like it used to. I just touch the key and boom it starts. This lasted for a few days and now it's back to turn the key on, turn the key off three times to get it to start. I am now convinced it is either a bad ground or a flakey connection somewhere. I don't know where all the ground connections are. The starter works fine so I am assuming it is a small ground somewhere possibly related to the PCM. Does anyone know where all the ground points are?
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Friday, June 9th, 2017 AT 2:54 PM
Tiny
HMAC300
  • EXPERT
Most pcm's ground on engine so get the one on stud behind engine on trans and any other one on engine they will be easy to spot also get the one on battery to body it may go under battery and be corroded it will be a smaller wire. Leading form negative cable.
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Friday, June 9th, 2017 AT 3:01 PM
Tiny
BILL411
  • MEMBER
Thanks. I will check those tomorrow.
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Friday, June 9th, 2017 AT 6:24 PM

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