wtf is wrong with my dakota! fuel pump on its way out?
#11
06-18-2010, 11:46 PM
If this were my truck I would get a cheap fuel pressure gauge like the one they sell at Harbor Freight, or get one at a parts store and connect it to the fuel test port on the fuel rail, left side of the throttle body. That is the best way to test the fuel pressure. If you have a 3.9 you should have I think 47 to 51 psi of fuel pressure at idle.
The thing to check though is after you turn off the engine, leave the gauge connected to the test port. If the pressure drops below 30 psi within 3 minutes of turning the engine off, your fuel pressure regulator is bad. That's why it takes so many attempts to start the truck, when the truck sits parked for a while or overnight all the fuel bleeds back out of the fuel lines into the tank.
Another way to test the fuel pressure regulator is to leave the key in the run position for about 30 seconds before you start the truck. This will prime the fuel lines. If it starts right up then, you know for sure the regulator is bad. There is a check valve in the regulator that goes bad and causes low or no fuel pressure in the line.
I had the bad fuel pressure regulator problem in my 2001. And it happened right about the same mileage as you have now, I think your odometer in the video was at 120 or 125K. The fuel pressure regulator is an internal part of the fuel pump assembly. You have to replace the whole fuel pump assembly to fix it. I replaced my fuel pump and it has been fine ever since. I got an Airtex pump from Advance, the price was $220 but I had a 20% off coupon so I got it for about $180, and did the job myself in a few hours in my garage. It actually was pretty easy to do.
If you have good fuel pressure, I would check the battery next. Dakota's run like crap when the voltage is too low, even 12 volts can be too low.
Jimmy
The thing to check though is after you turn off the engine, leave the gauge connected to the test port. If the pressure drops below 30 psi within 3 minutes of turning the engine off, your fuel pressure regulator is bad. That's why it takes so many attempts to start the truck, when the truck sits parked for a while or overnight all the fuel bleeds back out of the fuel lines into the tank.
Another way to test the fuel pressure regulator is to leave the key in the run position for about 30 seconds before you start the truck. This will prime the fuel lines. If it starts right up then, you know for sure the regulator is bad. There is a check valve in the regulator that goes bad and causes low or no fuel pressure in the line.
I had the bad fuel pressure regulator problem in my 2001. And it happened right about the same mileage as you have now, I think your odometer in the video was at 120 or 125K. The fuel pressure regulator is an internal part of the fuel pump assembly. You have to replace the whole fuel pump assembly to fix it. I replaced my fuel pump and it has been fine ever since. I got an Airtex pump from Advance, the price was $220 but I had a 20% off coupon so I got it for about $180, and did the job myself in a few hours in my garage. It actually was pretty easy to do.
If you have good fuel pressure, I would check the battery next. Dakota's run like crap when the voltage is too low, even 12 volts can be too low.
Jimmy
#12
06-18-2010, 11:48 PM
Record Breaker
#13
06-19-2010, 09:05 AM
Record Breaker
http://www.harborfreight.com/fuel-in...ter-92699.html
16 bucks at Harbor Freight, if there is one near you. Even cheaper if you can find their 20% off any single item coupon online. The coupon should come up easily in a Google search.
Jimmy
16 bucks at Harbor Freight, if there is one near you. Even cheaper if you can find their 20% off any single item coupon online. The coupon should come up easily in a Google search.
Jimmy
Last edited by 01SilverCC; 06-19-2010 at 09:15 AM.
#14
06-19-2010, 11:04 AM
#15
06-19-2010, 11:31 AM
Record Breaker
You need to relieve the fuel pressure first. Leave the gas cap off and remove the fuel pump relay. Start the truck and let it run, it will start bogging down and run rough. It will eventually cut off altogether. Crank the engine over a couple more times. This will take all the fuel out of the lines. Then install your gauge on the Schrader valve. Reinstall the gas cap and fuel pump relay, and start the truck. It will take a few attempts to start, because there is no fuel in the fuel line at that point. Once you have it running again with the gauge installed, then you can test the fuel pressure.
Jimmy
Jimmy
#16
06-19-2010, 11:41 AM
#17
06-19-2010, 12:16 PM
#18
06-19-2010, 01:36 PM
Record Breaker
Hard to say. Modern vehicles don't vapor lock but I guess it's always a possibility. I would check the battery and alternator next. You need at least 12 volts across the battery terminals with the engine off and 13.5 on up to 14.5 volts with the engine idling. 13.5 is at the low end of acceptable. Dakota's are real funny about low voltage.
If the battery and alternator are OK you can check the Idle Air Control valve. It's on the back side of the throttle body. Remove it and clean the black crusty crud off the end of it. Handle it gently and don't drop it or you will need a new one. A bad or dirty IAC will definitely cause a rough idle.
Check the voltage outputs on the Throttle Position Sensor and the Manifold Absolute Pressure sensor. I doubt the MAP sensor is causing this problem though. The Haynes Book tells how to check the sensors. It's probably on here in more than a few places too. At the MAP sensor you should have somewhere between 4 to 5 volts on the center wire with the ignition on but engine not running. Start the engine, let it idle and the center wire voltage should drop slowly and stay right at 1.5 to 2 volts. Anything less than 1.5 and the MAP needs to be replaced. The TPS center wire should read between .35 and .90 volts with the ignition key on but engine not running, and it should slowly increase to about 4.5 volts as you manually open the throttle by hand. Anything less and the TPS is bad. Some say .75 volts with the throttle at rest is best for throttle response. There is a mod for that on here somewhere.
Other than that I don't know. When was your last tune-up? Maybe there is a plug wire or something lying too close to the exhaust manifold or maybe there is a bad plug? Are the catalytic convertors OK? Have you ever replaced the O2 sensors? Both of those can easily make the truck hard to start and hard to keep idling. You could have a bad Crankshaft Position Sensor but if that were the case the truck would probably not start at all.
Someone else here will probably have better ideas than I do.
Jimmy
If the battery and alternator are OK you can check the Idle Air Control valve. It's on the back side of the throttle body. Remove it and clean the black crusty crud off the end of it. Handle it gently and don't drop it or you will need a new one. A bad or dirty IAC will definitely cause a rough idle.
Check the voltage outputs on the Throttle Position Sensor and the Manifold Absolute Pressure sensor. I doubt the MAP sensor is causing this problem though. The Haynes Book tells how to check the sensors. It's probably on here in more than a few places too. At the MAP sensor you should have somewhere between 4 to 5 volts on the center wire with the ignition on but engine not running. Start the engine, let it idle and the center wire voltage should drop slowly and stay right at 1.5 to 2 volts. Anything less than 1.5 and the MAP needs to be replaced. The TPS center wire should read between .35 and .90 volts with the ignition key on but engine not running, and it should slowly increase to about 4.5 volts as you manually open the throttle by hand. Anything less and the TPS is bad. Some say .75 volts with the throttle at rest is best for throttle response. There is a mod for that on here somewhere.
Other than that I don't know. When was your last tune-up? Maybe there is a plug wire or something lying too close to the exhaust manifold or maybe there is a bad plug? Are the catalytic convertors OK? Have you ever replaced the O2 sensors? Both of those can easily make the truck hard to start and hard to keep idling. You could have a bad Crankshaft Position Sensor but if that were the case the truck would probably not start at all.
Someone else here will probably have better ideas than I do.
Jimmy
#19
06-19-2010, 02:28 PM
#20
06-19-2010, 03:07 PM
Record Breaker
Loss of power and MPG taking a nose dive are sure signs the MAP sensor could be bad. When I replaced mine, Autozone had the best price. It was about $66.00. I did mine at about 85,000 miles just for maintenance but it helped improve my truck's power and MPG. There is a post on here somewhere about a year ago called "Power Loss and MPG solved" or something like that. If you can find it with the search function there is a lot of good info in it about the MAP sensor.
Jimmy
Jimmy