1993 Ford Ranger 4.0L 6 cyl intermittent won't start-low/no fuel pressure?


#1

My 1993 Ford Ranger XLT w 170,000 miles has been having an issue with not starting. It cranks fine. At first (for the last year), the fuel pump didn’t sound right or didn’t come on at all; when normal, you hear it for three seconds or so after turning key on. I have replaced fuel pump/relay/filter. Now, in the last week, it also will not idle after initial start, and I have to rapidly pump the accelerator lest it dies again. This whole process can take ten minutes or more to get the stars in proper alignment. This morning, I had to give up and drive my other beater into town. In addition to the parts I mentioned, I also replaced the ignition switch thinking not correct voltage to pump. I finally traced wires and do indeed have 12 volts to the pump (under the bed, after the inertia switch and all harness plugs). It has a new windshield, new tires, cold old R-12 A/C, and it’s paid for. So if there are any ideas, I just hate to give up my old clunker. Help?


#2

Possibly a bad throttle position sensor.


#3

Insightful, I can definitely try that. I should add, if and when it does start, I can drive the 7 miles into town, a few slow curves and stop signs, with no issues whatsoever. It’s only those first few seconds after it starts that I’m having to play with the gas pedal. Then, the tach levels off, I hear a slight difference in the engine (sorry, can’t describe-usually too flustered), and it’s happy. I have started it right back up after turning off-does ok. But sitting for 8 hours or overnight; trouble.


#4

I’ve owned a few Rangers and they all had the same problem from time to time. Jump the inertia switch and see if the problem goes away. They can be very intermittent.


#5

One more clue with the no fuel pump part of my problem; Under normal conditions, when you turn the key to on (not start), you hear the fuel pump run for 3-5 seconds, then the relay clicks off. It will start fine after that (still have the gas peddle pumping to do to keep it running). At times, when I turn the key on, the fuel pump does not sound normal, and the relay never clicks off. I finally noticed that under these conditions, the ‘check engine’ and ‘brake’ lights are dim, leading me to assume there is low voltage to them and the pump and maybe more. I have replaced the ignition switch thinking it might have bad contacts, but no luck.
I have a Ford electrical manual, but it has no mention of those ‘status/warning’ lights or where they are powered from. If I knew that, it might go a long ways toward troubleshooting.


#6

If I remember correctly, on my old Rangers there was a fuel pressure regulator located above the drivers side valve cover near the firewall.

This could be why you have zero to low fuel pressure.

Yosemite


#7

@OldcarsRbest

How about measuring fuel pressure . . . I believe the fuel rail has a test port

Report back with the pressures, and we’ll try to tell you if they’re good or not

Does the truck still have the original fuel pump?


#8

db4690, I replaced the fuel pump last winter, along with the filter and relay. I am really leaning toward an electrical supply problem; once it starts, I have driven it 80 miles with no hiccups whatsoever in speed/power. It’s just getting it started, dagnabit!


#9

The computer turns the fuel pump on by grounding the relay at pin 22. A digital test light properly connected to BAT and Ground and back probed into the pin 22 connection should be off when the key is on and the computer is turning the fuel pump on. With the test light connected and the key turned on the light should be off while the pump primes for several seconds and then the light should come on and remain on while the key remains in the on position. When cranking the light should again go out as long as the key is held in the start position or the engine starts. I recall having computers that intermittantly failed to turn on the fuel pump relay and one that would intermittantly turn the fuel pump on with the key off, mysteriously running the battery dead.