QuestionQUESTION: I have a 1998 dodge ram 1500 truck with a 5.2L engine. My truck ran great until earlier this year when she started having serious issues. After filling the tank and pulling out of the gas station she lost all power, started coughing, sputtering and shut off. We managed to limp her the few miles to the house (never going more than 10-15mph) and started troubleshooting.
After replacing the fuel pump (which had burnt diodes), cleaning the tank and adding fresh gas. She made it a few hundred feet, bogged down and died.
Then we replaced the spark plugs, wires, air filter, catalytic converter, o2 sensors, ... anything we could think of that might cause a loss of spark, fuel or air. After replacing all that she ran great for a few more days then did it again.
Now there is pressurized air in the fuel rail. We bled the air out and she went about 75ft before she bogged down, started randomly misfiring her cylinders and died. We did that about three times trying to get the problem diagnosed and each time we had to bleed a bunch of air out of the fuel rail.
I don't have any fuel leaks or anywhere i could think of that much air getting in in less that 3min of running time.
So checked all the injectors, plenum gasket, cam position sensor, crank sensor, coil, distributor, evaporation canister,evap canister purge solenoid and hoses. Still no change.
I am hoping its not the PCM.... any thoughts? The truck is mostly new at this point lol.
ANSWER: Hi Carly,
I don't have a manual for trucks in the 90's so will have to work from other experiences. I wonder whether the fuel pressure regulator might be involved with the air in the fuel rail problem. So check the pressure in the system with a gauge and also look over the return lines.
The initial issue having started with a fill-up of course points to the fuel evaporation collection system at the fuel tank (which has been an issue in the mini-vans) but you seem to have gone thru that possibility. The problem seemed to be liquid fuel getting recycled through the evaporation canister and then flooding the intake manifold.
Have you tried to get fault code readout using the ignition key: "on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time? Then watch the odometer window to see if the mileage is replaced by a 4-digit number preceded by a P. Let me know if you get such. This method of getting the fault codes was available in the cars of the later '90's.
Please read the PS (below) and respond to it.
Thanks,
Roland
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QUESTION: Not getting any fault code readout at all, just the mileage.
The fuel pressure regulator comes on the fuel pump assembly that we just replaced. I don't believe that is the problem because there is great fuel pressure as long as it is running good. When she starts malfunctioning then there is suddenly about five seconds of air blasting out of the fuel rail before we get a spurt of fuel.
Yesterday we completely blocked off the evap systems at the hoses under the hood so we could see how she did without it. Better, we made it further today before ending up on the side of the road.
Thanks for the help, I look forward to getting her fixed :)
Also, I do have the book... just didn't help much.
ANSWER: Hi Carly,
Your question title: 'Drives great until warm' raises the possibility that the coolant temp sensor is not accurate, i.e. the resistance is not dropping as the engine warms. It should be around 4,000 ohms when cold, and drop down to around 1,000 ohms when warmed up.
I would suggest that you get a fault code readout using a plug-in fault code reader. Some of the nationwide auto parts stores will do that for free (e.g. Autozone), or an independent shop will charge around $40. Let me know any code numbers that you receive.
Thanks for the rating and kind remarks. Consider doing the rating again and also whether I deserve a nomination for 'volunteer of the month'.
Thanks for doing that.
Roland
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QUESTION: Thank you, I will test the sensor in the morning.
Been doing the code readout practically every time we replace a part, it's been pretty consistent lol. Today it was (again, even after resets) misfire on 1, misfire on 2, misfire on 3, misfire on 5, multiple misfire and running lean on right bank. The only code that has really changed was the lean on right bank, it had been rich on right bank. Then we replaced the upstream o2 sensor again.
Thanks for your time!
AnswerHi Carly,
The apparent 'air' (empty of gas situation) you notice in the fuel line when the engine has died causes me to wonder if there is a fuel injector(s) that is (are) leaking badly. Have you checked the spark plugs immediately after the engine goes faulty to see if there is any cylinder that is awash in fuel? You could remove all the plugs and then crank the engine over and watch for a gush of fuel to be blown out of the spark plug holes. Another possibility would be if the harness for the injector wires was partially melted and the fuel injector driver wires were shorting to ground, which would produce the same result.
Unfortunately the listed causes of "misfiring" codes are very numerous so there is no 'magic bullet' that will come from that list of possibilities.
The only other item I can suggest at this point would be the exhaust gas recirculation valve which may be gummed up and if it stick slightly ajar it can cause lean out the mixture in all the cylinders. So take a look at that valve and see if its stem is moving freely and closing to a dead-stop via the internal spring-action. It has a vacuum hose on the top of it, and between the top and valve body there is a flange which is where you will find the valve stem with a circumferential slot into which you then insert the tip of a screwdriver to move the stem back and forth. If it is gummed up then spray some WD-40 on the stem where it enters the body of the valve and move the stem so as to free-up the action.
Thanks for the rating and nomination.
Roland
