Fuel Issues Maybe????? [Archive] - GrandAmGT.com Forum


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02-27-2010, 02:20 PM
okay well i think my fuel pump is going out on me, most of the time the car will just turn over and not start....kinda like what happes when the passlock system is tripped...so im thinking its the fuel pump but when i just turn the key to the on postion i can hear the fuel pump kick on and make a high pitched noise so i know its getting power to it. do you think it is the fuel pump or something else??

02-27-2010, 02:46 PM
oh also i have my check engine light on, i took it to auto zone to read the codes and one was for the map sensor and the other one said fuel issue but didnt say what it was..... so far it has always eventually started sometimes it has take awhille since it keeps tripping the passlock

02-27-2010, 04:44 PM
Your map sensor might be bad and is not telling the fuel pump to do the right thing which is then throwing the other fuel related code. The map sensor is one of the most important things the car needs to run because it controls everything related to the engine.

02-27-2010, 05:51 PM
Your map sensor might be bad and is not telling the fuel pump to do the right thing which is then throwing the other fuel related code. The map sensor is one of the most important things the car needs to run because it controls everything related to the engine.

Actually, not really. The MAF sensor is way more important. That is the sensor the PCM uses for primary fuel and engine load calculations. The MAP sensor is only used for secondary fuel adjustments, ie during throttle transitions and for calculating barometric pressure for air density, and it is used for referencing the VE table. It also is used for controlling EGR system function. It has nothing to do with controlling the fuel pump.

To the OP, could you post the actual codes that were in the PCM? Because there is no actual DTC code for fuel pressure. In fact the engine doesn't even have a fuel pressure sensor and you can not scan for fuel pressure with a scan tool. With a Tech2 you can check the status of the fuel pump (on or off) and the electrical circuit, and you can check the status of the fuel tank pressure as part of the EVAP system. That is it.

What you need to do to check if you are actually getting pressure is have someone hook a fuel pressure gauge to the test port on the end of your fuel rail. It is possible that the fuel pump is getting weak and the pressure is low, or the fuel filter could be clogged. Has it been changed recently? Also do you run your tank down a lot? When you run it low a lot the pump tends to get hot and it will weaken over time, and any crap in the bottom of your tank can also get sucked into the filter bag on the end of the pump and hurt the pumps performance.

02-27-2010, 09:41 PM
i went to look for the test port on the end of the fuel rail and could not find it all i found was a vaccum line at the end... i might be blind and just missing it but didnt see anything like the test ports ive seen in the past any ideas or could someone post a photo where it should be... i have the 4cyl motor

I will also check the codes again and post what they say, I was just goin off what the Auto Zone guy told me, but ill get the actual code

02-28-2010, 09:28 AM
Ah, didn't know you had the 4cyl. That is kinda important. But anyway, that vacuum line goes to the top of the fuel pressure regulator. The fuel return line comes out the bottom of the regulator and goes back to the tank. Somewhere before the regulator, either on the rail itself or on the supply line going to it, there should be a black plastic cap that is screwed on over the test port. I'm not as familiar with that engine though so I can't tell ya exactly where it's at.

03-01-2010, 02:37 PM
okay got my codes read today here is what they are...... there were 3 of them

1/3 - P0108 - High Pressure Map Sensor

2/3 - P1025 - insfuncant coolant temp

3/3 - P0108 - Map Sensor (again dont know why it came up twice)

so im going to replace the map sensor wednesday and I hope that it takes care of the problem

03-02-2010, 06:33 AM
An easy trick to know if your fuel pump is going is to beat on the bottom of the gas tank with your fist while someone else cranks. If starts or tries to start while hitting the tank then the fuel pump is bad for sure. I know sounds dumb but works great. hopefully that will help you.

03-03-2010, 08:47 AM
i just noticed that i have a vaccum hose that i has broken off, i think its the one comming from the map sensor going to replace that b4 i do the sensor, im guessing that is what is causing the rough idle and possiably whats causing it not to start...

as far as the fuel pump is concerned the car starts most of the time the few times it didnt start it seemed like it wasnt getting fuel maybe it was just too much air due to the failing map sensor

03-03-2010, 11:06 AM
okay so i cut off the broken part of the bad hose, (it still needs to be replace weather cracked badly) and reattached it to the map sensor the car idels alot better but still a bit rough, strange thing now is that i can turn on/off my ETS wich i wasnt able to before. the SES light is still on i will rescan codes tonite to see if its throwing the map sensor still or just the low coolant temp....where is the coolant temp sensor located at? if its not throwing the map code i will just replace the coolant sensor tomorrow.....so far the car is starting up just fine

03-03-2010, 04:42 PM
The SES light won't turn off immediately just because you fixed the problem. Most of the codes require you to drive the car through several complete cycles (driving, turn off and cool down, and cold start again) without detecting the problem before the computer will turn off the SES light on it's own, and it will still store that code in the PCM for a long time unless it's cleared.

I'd check the codes again and drive it a few times before replacing the coolant temp sensor, just to make sure. The code can be set from a low constant coolant temp, or it can be set just from not warming up fast enough within a certain time frame. It could have been due to your vacuum leak issue and rough running, and not actually a problem with the coolant temp sensor. Better to make sure before spending the money on a new one. If you do end up needing to replace it, the sensor is threaded into the coolant neck on the lower intake manifold behind the thermostat. You'll see it below the throttle body facing the front of the engine bay. :thumbs:

03-03-2010, 07:21 PM
all lights are off and car is running good for now thanks for the help