1994 Explorer randomly died on the highway 5 CEL codes

[Zephr11]

it started briefly and was able to get it parked at a gas station.

I’m having some issues with my 94 explorer, I was driving down the highway and the engine started to miss a bit. Kept driving and the engine completely lost power, was running on 2 cylinders at most. I pulled over and started to look around. Everything was tight and all connections looked good. CEL was on while driving and it appeared when the symptoms showed up so I shorted the pins in the DIAG connector and got codes

*157 R,C Mass Air Flow Sensor below minimum voltage
*158 O,C,R Mass Air Flow Sensor above maximum voltage
*542 O,C Fuel Pump circuit open; PCM to motor
*186 C Injector Pulse-width higher than expected
*181 C Adaptive Fuel rich limit reached at part throttle, right side


after about 30 mins of trying to get it to start again it randomly fired back up and was able to move it again but about 2 miles or so before it started dying out again. I was able to do this about 2-3 times before it completely stopped working.

I think it might be the PCM relay but not too sure, after looking at wiring diagrams the PCM relay also sends power to the injectors, MAF, and also energizes the coil on the fuel pump relay. I don’t have the car near me it’s about 45 mins away and the gas station was nice enough not to tow it away so I want some ideas before I get there! Any advise would be appreciated!

 

[J_C]

Welcome to the forum!

What did you do trying to get it to start? Was it cranking strong but not firing? If you were jump starting it and then a couple miles later it dies again, might just be a dead alternator. Given the codes, it doesn't seem like a dying fuel pump/pressure issue, multiple subsystems at once smells more like low electrical system voltage and this also causing misfires.

It's an older vehicle, could be corrosion on a connector to alternator or battery cable clamp-wire or chassis ground. I know you checked the battery clamps to battery terminals to be sure they were on tight and free of excessive corrosion!

 

[410Fortune]

Check fuel pressure
Low fuel pressure/ weak pump will lose pressure when it gets hot… let it sit for a while and it fires back up… again points to a weak fuel pump. Check fuel pressure especially when it stalls out… 36 psi is required at the rail +/- 4 psi

You will get lots of codes when it’s running on low fuel pressure

Checking the pressure at the rail is a quick way to rule out the fuel system as the issue

 

[Zephr11]

Welcome to the forum!

What did you do trying to get it to start? Was it cranking strong but not firing? If you were jump starting it and then a couple miles later it dies again, might just be a dead alternator. Given the codes, it doesn't seem like a dying fuel pump/pressure issue, multiple subsystems at once smells more like low electrical system voltage and this also causing misfires.

It's an older vehicle, could be corrosion on a connector to alternator or battery cable clamp-wire or chassis ground. I know you checked the battery clamps to battery terminals to be sure they were on tight and free of excessive corrosion!

Solved! Bad Fuel Pump! Was tracing the electrical leads and checking at every stop point and 12v was going into the pump connector and switching to 9v after 2 seconds which is the normal priming procedure. Pump wasn’t making any noise so we removed the tank and took the pump out and tried to prime it dry while it was out of the tank. No noise and no movement. Got a new pump and hooked it up and I heard it turn on and prime. Truck fired right up!
50$ fuel pump/sending unit off of rockauto lasted a year lol.

 

[J_C]

Guess the takeaway from this is don't get too invested in checking codes before you check for fuel pressure. Glad it's sorted out. What brand of pump from RA only lasted a year? IIRC, Bosch is most recommended if they have something for the model year in question.

 

[410Fortune]

Bosch pumps getting hard to find for our trucks not sure if they discontinued or supply chain issues? Not sure