Check for spark while cranking. Gotta test for longer than about four seconds.... if you lose spark in that time, then it it probably an ASD event.... search posts by cmckenna for a REALLY good troubleshooting guide.

 

I've been keeping an eye on this thread to see if it has gone anywhere and, so far it hasn't.

The suggestion of placing a moisture trapping membrane (plastic bag) over the CPU is a bad idea. What you are doing is trapping all the moisture inside the bag thus basically trapping it inside the PCM and the connectors. Unless the cowl has a leak that is directly above the PCM connectors, there's no reason to place a plastic bag over it.

Now, here we have yet another NO START thread, one of many as of late. And, in this case, we have popping through the pipe thus, an indicator of a fuel pump on it's way out or, an O2 sensor is going out or another sensor that is faulting.

Now, you can rule out a wire breaking down- this is not how it works.

What needs to be done is to have a few simple tests conducted.

TEST ONE: FUEL PRESSURE VERIFICATION TEST

On the fuel rails, there's what is called a Schrader Valve. Place a fuel pressure gauge here and measure the psi at both KEY <ON> event and while running.

The spec on a 95 may either be:

a. 49 psi ± 5 psi

b. 39 psi ± 5 psi

Here's how it works as a system:

At time of KEY <ON> event, power is applied for ~2-3 seconds to the FUEL PUMP. So during that KEY <ON> event, the FUEL PUMP should pressurize the system instantly if there's no gross leaks or, any leaking fuel injectors.

<IF> pressure reads zero during KEY <ON> event, ether you've got a leaky injector/s thus flooding the chambers with too much fuel thus, flooding it and fouling out the plugs thus, a no start condition OR; the fuel pump is on it's way out.

See if you can hear the fuel pump motor whine while turning the KEY <ON>. Do not start it, just listen for the motor whine of the fuel pump while standing outside the cab reaching through the window OR, have someone else turn the KEY <ON> while you listen with your head down near the fuel tank.

Now, the issue with that popping may be:

a. the fuel pump is NOT putting out to full capacity thus, LEANING out the A/F mix THUS POPPING through the tailpipe due to a lean mix OR,

b. <IF> this popping sound "only" occurs AFTER WARM-UP / CLOSED LOOP MODE, this is an indicator of a failing O2 sensor thus, providing erroneous voltage at the input of the PCM thus, throwing the A/F mix off.

During warm up, only a few sensors are used at which time, it's running on preset values at the PCM. This is called OPEN LOOP MODE. After the timer goes off (apx. 3 minutes) the PCM then goes into CLOSED LOOP MODE if all criteria is met. This being, completion of the timer PLUS- the Engine Coolant Temperature sensor (ECT) voltage meets the programmed parameter value set forth in the program, it will switch over to CLOSED LOOP MODE (It is programmed for a range of 160 - 180°F) on a two-three minute timer.

Start there first and report back. The need to test is very important. IN order to rule things out fast, one must be able to "see" what is really happening with the EFI system and, in order to do that, one must take some simple measurements of one thing at a time thus working through the system one component or system at a time until the root problem has been identified. In this case, the possible root cause may be failing fuel pump but, until we test and verify this, we have no way of knowing.

CM

 

In addition to the above information, if the FUEL PUMP checks out pressure wise, there's something else that just came to mind during mentally mapping out what happens before and after starting the vehicle.

There's three sensors that are commonly referred to as Master Sensors. Those being, MAP, CPS and, the CKPS. The CPS is the CAM position sensor while, the CKPS is for the crankshaft position. All three work together to control the EFI TIMING.

Now, I'd have to reference some documents here but, one of those, (CPS, CKPS) is not read at input during warm-up / OPEN LOOP MODE. EDIT: This is incorrect. It's at the time of KEY <ON> event, that BOTH are not read. I remembered part of that but wasn't sure to where in the starting cycle this occurred prior to posting. I am going to correct that.

Another possibility is that one of the master sensors is faulting thus, throwing the timing out of whack. It will also induce a NO-START condition as well. If either one (CPS, CKPS) is not working - the vehicle will NOT START.

Now, the MAP sensor, being the third Master Sensor, this is also run off the same supply as the former mentioned thus, if this sensor is malfunctioning, it too, will induce the same types of symptoms.

NOTE: Do not buy sensors from 3rd party vendors and / or suppliers. GO WITH OEM on all sensors. OEM sensors from dealers are fully screened for full operation under all environmental conditions. They work vs. working partially to some degree as I have found many times with after-market parts houses.


CM

 

Sorry guys, it's been a while. My computer gave me the blue screen of death and quit working. Took a while to get a new one. I had one of my buddies from Street & Performance go work on the truck a little and he reported back that the fuel pressure and fuel volume are both correct. He took the truck and drove it and told me it does great for 30-45 min then it backpops, barely runs, then dies. It won't restart for an undetermined amount of time once this happens. If it starts and is not run untill it dies then it will restart no trouble indefinately. I am going back home this weekend to work on the truck and spend time with family. I have a new, from Dodge, crank position sensor that I am going to put on. I think this is what the problem is evn though I replaced it already. I will let everyone know if it works. Thanks for the info so far.

 

Just to let everyone know.......the problem is fixed. It was the Crank Position Sensor even though the one in there was new. I'm a believer in using Mopar parts now. Just gotta put a wiper motor, alt, and plenum gasket on so that I can get the truck sold. Thanks everyone.

 

Cmckenna, we should pay you for this stuff!