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4.0L OHV & SOHC V6 Tech General discussion of 4.0L OHV and SOHC V6 Ford Ranger engines.

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Old 05-20-2010
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Fuel Pump/Delivery Problem

Tuesday I changed the brake pads on my truck. After I was done I took her for a spin to ensure the brakes worked fine (which they did). On the way back to my house the truck died and I couldn't get it started. After pushing it a block home and got it in the driveway I started trying to diagnose the problem.

Here's what I found:
-I have spark.
-No codes
-All the dash, lights, radio works.
-The fuel pump turns on and then stops after 1-2 seconds (priming). It even does this when I pulled the fuel line before the filter.
-When I spray ether in the throttle body the truck starts and then dies after the ether burns off (which pretty much means I have a fuel problem).

Here is the work I have done to the truck:
-I replaced the fuel pump and filter less than a year ago when the pump went out.
-I replaced the IAC about 20,000 miles ago when it went out.
-The starter and battery were replaced <1 year ago.

Here are my questions:
-Why would the fuel pump turn on and then off immediately? Even after I pulled the line? I would think I would get a constant flow since the pressure isn't building up.
-Would the relay do this?

Today:
-I am going to check fuel pressure

Any other ideas?

2000 Ranger
2 wheel drive
4.0
5-Speed

Thanks in advance

Last edited by barndoor; 05-21-2010 at 10:09 AM.
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Old 05-20-2010
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Even with the line pulled it should only prime for a second or two before cutting off if the engine doesn't start.

I went through this with my Mustang recently (different problem but still had the troubleshooting list to go through) and we left everything hooked up, but attached a hose to the fuel schrader valve (after pulling the valve core out so it will stay open). Fired it up and while it was running were were able to conduct an output test. For the Mustang (5.0L) it was supposed to be at 16oz for a 15 second run. Which it did handily.

I don't know if the Ranger has a similar schrader valve on the rail but I assume it does. Thats just how we did it.
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Old 05-20-2010
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may have to check pressure at the fuel rail.
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Old 05-20-2010
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Thanks guys

Sixt9coug- It does have the same valve

fourliter dan- I am checking the pressure today after work.

I know this sounds weird, but does anyone think it has anything to do with the brake job I did or do you just think it is a coincidence?

I also checked the inertia switch to ensure it wasn't tripped and it wasn't.

Last edited by barndoor; 05-20-2010 at 05:20 PM. Reason: spelling
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Old 05-20-2010
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there is a fuel cut off switch in the cab. look at the firewall under the glovebox. there is a red pushbutton. push it to reset it, then see if it will start.
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Old 05-20-2010
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nevermind the above, looks like you did that.
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Old 05-20-2010
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Quote:
Originally Posted by Sixt9coug View Post
Even with the line pulled it should only prime for a second or two before cutting off if the engine doesn't start.
.
The only reason I think it should run continually is because when i replaced my fuel pump and filter almost a year ago I forgot to put the line from the pump to the filter and it pumped gas while I was turning the motor over. The strong smell of gas was what alerted me to the leak.

But in this case as I am cranking the engine over it only pumps gas for a couple seconds. Even if I continue to crank.

Is there a way to jump the terminals where the fuel pump relay goes to make the pump run? I read this in the Hayes manual when I was working on my bronco, but didn't see it in the ranger manual.

Thanks
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Old 05-20-2010
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you must wait at least 5 seconds before you crank over the engine
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Old 05-20-2010
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okay when you pulled the line off how much gas came out alot or alittle if allittle u got a bad filter or pump try changing the filter on the rail
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Old 05-20-2010
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Quote:
Originally Posted by barndoor View Post
The only reason I think it should run continually is because when i replaced my fuel pump and filter almost a year ago I forgot to put the line from the pump to the filter and it pumped gas while I was turning the motor over. The strong smell of gas was what alerted me to the leak.

But in this case as I am cranking the engine over it only pumps gas for a couple seconds. Even if I continue to crank.

Is there a way to jump the terminals where the fuel pump relay goes to make the pump run? I read this in the Hayes manual when I was working on my bronco, but didn't see it in the ranger manual.

Thanks
The fuel pump is controlled by the fuel pump relay which is actuated by the PCM.

When the ignition is first turned on, the PCM should command the pump on for about 1 second to pressurize the system.
When the PCM recognizes engine rotation, it should turn the pump on continuously.

What year is it?
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Old 05-21-2010
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rwenzing- It is a 2000 4.0 manual trans.

last night I couldn't hear the fuel pump turn on at all and I wasn't getting any pressure at the fuel rail. I dropped the tank and bench tested the pump which worked fine. I hooked the pump up to the wiring harness outside of the tank and the pump turned on for a second with the key turned to "on" (which it suppose to do).

I also swapped relays and determined the relay isn't at fault.

I guess today when I get home I will put the tank back in and try it again. I am trying to determine if there is pressure at the rail in the "on" position.

Any other ideas?
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Old 05-21-2010
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it is possible that it is the PCM

continuous voltage is not reaching the fuel pump when you crank the engine
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Old 05-21-2010
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How can I diagnose this?

Also, not sure if it matters, but with the key "on" I get 12 volts at the harness for 1 second and then it drops to around 6 Volts which i assume is the relay doing it's thing.

When I get home today I will verify the pump is not pumping while I am cranking the engine over.

Thanks
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Old 05-21-2010
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Quote:
Originally Posted by barndoor View Post
Also, not sure if it matters, but with the key "on" I get 12 volts at the harness for 1 second and then it drops to around 6 Volts which i assume is the relay doing it's thing.
Fuel Pump Monitor (OBDII):

When the fuel pump is commanded on by the PCM via the FP relay, the PCM monitors the voltage on the wire from the FP relay to the Inertia Switch to make sure that the relay is working. Should be near normal battery voltage

When the pump circuit is commanded off via the relay, the PCM supplies a voltage to that same wire to check continuity through the Inertia Switch and then through the fuel pump to ground. This is probably the open circuit 6V you are seeing. When the circuit is complete, the voltage will be pulled down much lower than 6V by the path through the pump to ground. The voltage level is used by the PCM to make a judgment about the integrity of the circuit.

I don't have the exact thresholds but it could be something like this:
Low voltage within a calibrated range => circuit OK
Voltage hgher than calibrated range up to 6 volts => open circuit
Zero or near zero volts => short to ground

.
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Old 05-22-2010
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**Update**

-No pressure at the rail.
-I pulled the line that connects to the rail and no fuel comes out even while cranking.
-I cleared all the lines to ensure they weren't blocked
-I hooked the fuel pressure gauge directly to the fuel pump and it pumps fuel (very little), but no pressure....

I tested the volts at the harness to the fuel pump and i get 10.5 v while cranking.

Is 10.5v enough to run the pump to operate properly?

Even though the fuel pump is only 7 months old I am taking it back to get replace.

Thanks
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Old 05-22-2010
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10.5 is enough to operate the pump.
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Old 05-22-2010
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i would replace that line from the filter to fuel rail
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Old 05-22-2010
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I cleared all lines with a compressor.

Turns out the fuel pump was bad (again).....

They accepted the exchange and the truck is running.

What a waste of time this was for me.... That'll teach me to buy motorcraft parts next time instead of the parts made in China

Thnx to all for the suggestions and help
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  #19  
Old 05-23-2010
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i just hot wire it
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