It's been awhile, but I've been busy. I know I had a lot of questions before about this check engine light that will not stay off on my '99 Dakota. I may have found the problem though, just seeking some more input before I make a 200 dollar purchase that may or may not fix the truck.

Problem has been, and still is, a cylinder 6 misfire (I have the 318). I have changed plugs, wires, distributor cap and rotor, and the downstream O2 sensor. However, the problem has gotten worse. Here are my symptoms:

-Rough ride on highway, assuming the fault lies in the misfire.
-Starting from a dead stop, it often has no power, and I have to mash the gas in order for it to go. Something I never had a problem with before this "check engine scenario".
-Friday the 21st I stopped, was back in it not ten minutes later, and it cranked and cranked but would not fire. I let it sit for about half an hour and it started right up, then while I was driving the streets of town to see what other signs I could get (going 20mph) I slowed down to yield, and it died, then it started right back up. Thursday it would not start, but I had to be at work so did not mess with it..after work it fired right up. Then a repeat of the friday ordeal this past friday (I hope that makes sense). Fuel was around 1/4 tank the last two times..I wasn't paying enough attention the first time to know if I had filled up or not.

Everyone I talk to says it seems like a fuel pump...there is no in line filter on this truck, and I just found out today that the only time a pressure checker will actually tell me is when it is not starting...not something I have, and who knows when it could happen again...so the question is, should I buy a checker gauge and just wait it out to see what happens, or do I have enough evidence to buy a new pump and install it?

 

New update today. I cranked it over thismorning, and it took awhile for it to fire..but when it did fire, it was only for a split second...then by the time I got my foot down on the accelerator it had died..I finally got it started, and it was the same as before...then thisafternoon I kept the truck running, and when I got back in it and went to go, I noticed a serious lack of power..she almost died on me. I am pretty convinced it is a fuel pump, but that is just using the opinions of others and some logic/common sense. Like I said, I just don't want to make the investment if I really do not need it.

 

You can buy this fuel pressure test gauge set at Harbor Freight Tools for $19.99, it is on sale right now:

http://www.harborfreight.com/fuel-in...ter-92699.html

You can probably find other brands of fuel tester gauges at most parts stores or maybe Sears. I like Harbor Freight because the quality of most of the hand tools and diagnostic tools they sell is pretty good, or at least good enough for what I use it for, yet the prices are cheap.

i don't know the fuel pressure specs on a 318, but it is probably listed online or is in the Haynes Book for your truck. I have an 01 with a V6 and I believe the fuel pressure specs are different between the two trucks. If the truck will run and idle you can test the fuel pressure pretty easily. That is going to be the best way to check the fuel pump.

What is the mileage on the truck? I have read most OEM Dodge fuel pumps usually quit around 120,000 to 125,000 miles.

Jimmy

 

Yeah, I thought about getting a gauge just to keep in there until the problem is resolved...but I dunno, it seems pretty clear..and if that's not it, I have no clue what it could be.

I have 166K miles on it, and thank you for your input.

 

my fuel pump died at 125,xxx. 45-50psi at idle is normal. if it drops below 30psi i think after 5min its also a sign its bad.

 

I think pressure is like 44-55 psi and if it drops below 30psi in under 5 min then you have a problem. Call a garage and ask them if they can check the pressure real quick most good garages wont charge you anything since it takes 2 min to do.

 

I talked to the local mechanic, he claimed it wouldn't be an accurate test unless the truck wasn't starting..but im thinking of buying one or renting one from AZ before I spend the money on a fuel pump.

 

We just had to pull it in the shed with the tractor, and had to pull the (not exactly what it is called, sorry for my illeteracy) part between the air filter and the top of the engine (where the carb would be on an older truck)...got it started and the coil is sparking like crazy...potential cause of the starting problems? With all the rain we have had in the past two days, dad thinks so..but we cant be sure...

 

Then maybe it could be a problem with either the throttle position sensor or the manifold absolute pressure sensor. The part that you removed is called the throttle body, and both the TPS and MAP are mounted to the throttle body. Maybe in the process of removing the TB you jiggled something loose or somehow made either one or both sensors work again so the truck started.

I would say grab a volt meter and a Haynes Book and check the TPS and the MAP sensor. The TPS is on the driver's side of the throttle body, as you look at the engine with the TB installed on the manifold. To check the TPS you check for voltage on the center wire at the TPS's wire harness connector. With the engine off and ignition key in the on/run position, the center wire should have about half a volt on it. As you slowly and evenly open the throttle plate by hand, the center wire voltage should slowly and steadily increase until you have the throttle plate held wide open. With the throttle plate held wide open, the voltage on the center wire should be between 4.5 to 5.0 volts. Anything less or any oddball erratic voltage as the throttle plate is opened means the TPS is bad.

Checking the MAP sensor is a different process. With the ignition on, the center wire on its wire harness connector should read between 4 and 5 volts. Start the engine, let it idle and the center wire should steadily decrease to about 1.5 to 2 volts. Anything less than 1.5 or any erratic voltage fluctuations on the center wire would indicate a bad MAP sensor. There is also a vacuum hose on the bottom of the front side of the MAP sensor. Be sure it is in good shape and is connected to the sensor.

Both the MAP and IAC operate on 5 volts. Each sensor has a 3 pin electrical connector. You should have about 5 volts on each one when you measure the voltage across the two outside terminals on each sensor's electrical plug. Anything less means you either have a bad ground for the sensor or there is a problem with the PCM, it is not providing the 5 volt power input to the sensor. This is probably not the problem though, otherwise the truck would not run at all.

This would also be a good time to clean the Idle Air Control valve. It is mounted on the back side of the throttle body between the TB and firewall. Remove the IAC and clean the black crusty junk off the pintle end with a shop rag soaked in carb/tb cleaner and spray the valve and its bore with carb/throttle body cleaner. Clean the IAC orifice on the TB too, and lube the IAC's O-ring with a little clean motor oil when you reinstall the IAC. Do not handle the IAC roughly or drop it, otherwise you will be buying a new one. The IAC regulates the flow of air into the intake when the truck is at idle or is slowing down from speed to idle. A bad IAC can definitely cause a rough idle and/or stalling out condition.

Maybe one of these things is the problem. It is still a good idea to check the fuel pressure, if only just to rule out the possibility of a bad fuel pump.

Jimmy

 

Will do all of that, getting the new Ignition Coil tomorrow, when i go to install it I will check that out, appreciate it! And I should have known that was the throttle body...i just dont have a good technical terminology, yaknow?