General Ford Ranger Discussion General discussion of the Ford Ranger that does not fit in any other sub-forum.

87 2.9 ranger running rough

  #1  
Old 01-17-2019
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87 2.9 ranger running rough

So I can't seem to figure out why its running so bad. I've replaced plugs, wires, cap, roter, fuel filter, o2 sensor, map sensor, idle air control valve, fuel lift pump, fuel pump relay. It seams like its getting to much fuel. I checked the fuel pressure regulator it doesn't seem to have any fuel passing through the diaphragm. When I turn the key on the fuel pump stays on, it doesn't turn off. When it's idling if I pull the fuel pump relay it'll continue to idle really well until I give it gas. I cleaned all the ground wires that I could find. What would cause the fuel pump to stay running with just the ignition turned on? Not sure what else to check for.
 
  #2  
Old 01-18-2019
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1987 Ford Ranger 2.9l

Some one has "hot wired" the fuel pumps, you should have two fuel pumps, one in the gas tank and high pressure pump in the frame rail under drivers seat area, both share 1 power wire coming from the inertia switch located in the cab, passenger side foot well just above carpet level behind glove box on firewall.
Inertia switch is smaller black box with red button on the top.

Normally the power for fuel pumps runs like this:

Battery-------(fusible link)----------fuel pump relay---------------------------inertia switch------------------------------------fuel pumps

Relay is controlled by computer Grounding it

If you pull out the Fuel pump relay from it's GREEN base the engine should stop running

On the relay's green base there should be a Dark Green/yellow stripe wire coming out, that wire runs to the inertia switch, it carries the 12v power for fuel pump
From inertia switch there should be a Pink/black stripe wire and that runs back to the top of the gas tank, powering the fuel pump, this wire will be spliced near the high pressure pump in the frame rail to also power that pump

All the fusible links are connected to the Starter Relay(solenoid) seen in image above, to the left of EGR solenoid
They will be connected to the same post that has the Battery cable on it, this post is the main power distribution for the whole vehicle

So look at the inertia switch to see if someone has added another wire there
And look for the Dark green wire at fuel pump relay and see if its been cut and some one has added another wire there






 
  #3  
Old 01-18-2019
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87 2.9 ranger running rough

So the inertia switch has already been bypassed. When I pull the relay for the fuel fuse pump the pumps do turn off it acts like it's only running from the vacuum if this is possible as soon as I give it any kind of gas it dies instantly. The fuel pump doesn't always run constantly with the key on it's only hit or miss so I really don't think it is hot wired. if there was a ejector that was stuck open would it cause the pump to stay running and not build pressure when the key is on but not running? Thanks for your help RonD.
 
  #4  
Old 01-18-2019
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" When it's idling if I pull the fuel pump relay it'll continue to idle really well.........."

???

So it doesn't do this?

The fuel pumps should only run for 2 seconds with key on, but each time key is turned on they should run for that 2 seconds
If they run longer then most likely there is a computer issue, it grounds the FP relay to turn it on.

On the upper intake on the throttle linkage is the TPS(throttle position sensor), it has 3 wires, unplug that connector and see if you can increase RPMs, TPS is just used for quicker throttle response, engine will run without it.
TPS gets 5volts from computer on upper wire
On the center wire it sends back .69-.99 volts when throttle is closed, under 1volt
Then 4.5volts to 4.9volts at Wide Open throttle(WOT)
So at 1/4 throttle it might sends back 1.5volts
1/2 throttle 2.5volts
ect.....
If its shorted and going to 4.5v when you press a little on the gas pedal then it could flood engine out

Don't replace it, test it
 
  #5  
Old 01-18-2019
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87 2.9 ranger running rough

Yes. It idles really well when i pull the relay, until i give it gas then it dies. Probably three out of five times that I turn the ignition on the fuel pump will run constant the other two it'll turn off after 2 seconds?
 
  #6  
Old 01-18-2019
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Then relay has been by-passed
 
  #7  
Old 01-18-2019
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87 2.9 ranger running rough

You would think that it was bypassed, but that's what I'm trying to say, when I pull the relay the fuel pumps do turn off! it only runs at an idle I don't know if it's because of its getting fuel from vacuum or if it's just fuel thats left in the intake. Like I've said before the fuel pump doesn't always stay on with just ignition on just periodically. What tells the pumps to stay on for 2 seconds is it some sort of a pressure switch that tells the computer. What if there was an injector that was stuck open would that cause the pump to stay on longer not being able to build pressure?
 
  #8  
Old 01-18-2019
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Computer has a timer, 2 seconds and OFF with engine at 0 RPMs, engine above 400RPMs and computer turns on(grounds) fuel pump relay full time.
 
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