car only starts sometimes

My friend has a 1999 ford ranger with a 4 cyl. About a month ago i went to help him with his truck not starting.It kept turning over but just wasnt firing. we kept cranking it and he even pumped the gas to see if it was getting fuel. Next We shot starting fluid into the throttle body and it fired right up.
For the next week it ran fine and then all of a sudden it wouldnt start again. A week later he went to start it and it fired up again with starting fluid. It then died again a week later. It doesnt die while driving or anything, only when you try to start it, it wont start.
Is this a fuel pump problem? Im going to help him replace it but he wants to make sure that that is acually the problem before he spends the money on it.

Thanks

You should find a fuel pressure gauge and attach it to the fuel injector rail. If the fuel pressure is low, first would be to replace the fuel filter if that hasn't been replaced recently. Next would be to suspect the fuel pump once you confirm it is getting full battery voltage for the 2 seconds after the key is turned to the Run position.

-Rod

thank you for the response. Do you use a vacuum/fuel pressure gauge or is there a different tool to use? and you said use it on the fuel rail?

Ford usually uses a schrader valve on the fuel rail. Looks like a valve stem cap. The guage should hook right up to it. Fuel pressure gauges are usually dedicated to fuel pressure only.

ok. Thanks. I know i have a vacuum gauge that says it does fuel pressure as well but if its a valve it doesnt seem like it would work for that.

Thanks again

oh. one more thing, what should the fuel pressure be at?

thanx

Do you use a vacuum/fuel pressure gauge

That type of gauge is not for fuel injected cars because of the higher pressures in those systems.

Not exactly sure on a ranger without looking but id say it should be 45-50psi regulated and 50-60 unregulated. If the gauge has a bleed hose, you should be able to get it to fill a 20oz soda bottle in about 20-30 seconds without any affect on the way the engine runs. Pressure should hold for quite a while before dropping off any more than 5psi.

The service manual states 64 +/- 8 psi KOER and KOEO for the non-flex fuel engines.

-Rod

thank you guys. ill be helping him out tomorrow and hopefully get it figured out.

ok. just did the test on it and it only gets about an ounce in about 30 seconds when i bleed out the fuel and it makes the pressure go right to 0. Im assuming that it is for sure the fuel pump. It runs at 64lbs while running and runs that constantly. when i rev the engine the fuel pressure doesnt respond at all.
Just want to make sure that you guys can confirm that it is the fuel pump.
Thanks in advance for the help.
david

I'd start by changing the fuel filter. Did you try a KOEO fuel pressure check? With the engine and key off, connect the fuel pressure gauge. Turn the key to the Run position and see what the pressure goes to. Verify that the fuel pressure jumps to spec range and remains there for at least several seconds. If it doesn't get to spec pressure or drops quickly there is a problem. Low pressure with a new fuel filter would suggest a weak fuel pump, pressure that drops quickly would suggest a leak or stuck fuel injector.

-Rod

i did replace the fuel filter and ran again and had the same results. I loaned the tool and i belive when i turned the key to on it held the pressure the whole time and after the car was off.

thanx

Has your friend noticed a trend such as it starts fine when the tank is full of fuel, but as the level gets to 1/4 or so it has more trouble starting reliably? Unfortunately you're really going to want to also make pressure measurements when the truck won't start to see what you get then. Your measurements so far don't point to fuel pump, but it doesn't sound like you were probably having any trouble currently either.

-Rod

he didnt say anything about fuel levels but at the same time too, i know he doesnt pay attention to those details. I know when I went to start it, it was a half of a tank of gas and on a level surface. Thats a good point though that i should try it when its not working right. I got it started and drove it to my house and has been fine since.
What does it sound like to you if not the fuel pump?

I went over to start it this morning and it fired right up. Within about 5 seconds it died. I started it back up and ran for about 3 seconds. started it up again and it went for about 1 second. After that it wouldnt start anymore. each time it died it stumbled to a halt. Does that info help?
Thanx again shorod for all the help

To properly diagnose it you'd want to confirm battery voltage to the fuel pump when the key is first turned to Run (or at least battery voltage from the inertia cutoff switch) and check fuel pressure while acting up. If I were just going to shotgun something though, I'd probably start with the fuel pump. It's a lot of work though if you're not sure it's the problem.

-Rod

I went over to start it this morning and it fired right up. Within about 5 seconds it died. I started it back up and ran for about 3 seconds. started it up again and it went for about 1 second. After that it wouldnt start anymore.

It's exactly what happened when my fuel pump failed in my Windstar.

Instead of checking fuel pressure, try the current test. Remove the big fuel pump's fuse (20 amps) under hood, and connect an ampere-meter at the place of the fuse. Ask someone to turn key to run. If you read a steady current (like 7-8 amps) the pump is bad. Especially if you don't hear it priming.

ok. I went out today to start checking stuff again and do another fuel pressure check since it wouldnt start, and now the fuel pump isnt turning on. After i relized that, i checked the fuel pressure which of course was at 0. I then sprayed starter fluid in the intake again, and it wont run anymore sincwe the fuel pump isnt working. Im going to do a voltage test tomorrow but im not completly sure exactly how to do it and what the amps should be. Do I test the plug going into the fuel pump while the key is on? \
Where would i buy a ampere-meter? ive never used one before and how acurate of a test is that?

thanks

The digital multimeter includes voltmeter, ampere-meter and ohm-meter in a single tool. The whole tool cost just 15-20$ at any tools/electro store.
To use the ampere-meter, select 10A DC range (the line and dotted lines symbol for DC).
Then plugs the red wire to 10A plug and black to the COM. It's very accurate.

Remove the big fuel pump fuse under-hood, and connect ampere-meter lead to the contact where the fuse goes. And turn key to ON.

I found ampere-meter more practical to test pump than voltmeter. Cause if you read current, it means that you don't have bad contacts but the pump propellers are broken.
And you don't need to remove the gas tank or anything, since it's the same current everywhere.

If you have a steady 7-8amps and no prime, the pump propellers are broken. No need further test.

If you read 0 amp, it worths to test voltage at many place to see where is the breakdown. Maybe a bad contact, or a bad realy... You can just swap relays to test it.

If you see zero current draw, I'd switch to voltage and confirm battery voltage to the pump from the inertia fuel pump cutoff switch. From my experience the failure mode of the fuel pump is not so often the impeller but instead an open circuit in the fuel pump, likely worn brushes (similar to why starter motors fail). If the brushes stop making contact with the commutator there will be no current draw (open circuit) but that doesn't mean that voltage is not making it to the pump. If the pump is still running but the impeller were broken, you should be able to hear the pump running when the key is turned on and therefore you shouldn't need a current meter to tell you that. If the pump is seized up though and not an open circuit, you will get significant current draw and not hear the pump run. Personally I'd start with the voltage check at the inertia cutoff switch and fuel pressure. If you have voltage and no pressure, I'd say it's probably a 90% chance the pump is the cause.

-Rod

thanks guys. i went and tested the interia switch and it read 6 volts. we went ahead and replaced the pump and fired right up and ran. thanx for all the help on me tryoing to figure it out.

david