MAF Testing
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MAF Testing
1999 Ranger w/3.0 ff engine. Still can't start without using starting fluid. Cleaned MAF sensor. Does anyone how to check it out electrically? I replaced the fuel filter, I can hear the pump run, When I start it with a shot of ether(starting fluid) it runs good. Checked for looos connections, checked vacuum....all good. My last suspition is the MAF sensor not operating corectly..???
Terry
Terry
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From: SW Va
Well seems to me, if it runs ok after using staring fluid to get it going, then it kinda points to the initial "on time" the fuel pump runs for, to build fuel pressure, when you first try to start it.
SO, you might try switching the ignition key from "off" to "run" (not start) several times, to cycle the fuel pump & build pressure, then go to "start" & see if it'll crank & start itself without the starter fluid.
Seems to me, if the MAF were faulty, you wouldn't find it running ok after starting with the fluid. It should start with the MAF disconnected.
Check for battery voltage to the MAF, at the connector.
If you have battery volage, then back probe the "MAF Signal" & "Signal Return" leads at the MAF connector, it should typically read 0.2-1.5 volts at idle & increase to about 2.0 volts at a rpm you usually turn at say, 60 mph.
Anyway look for the MAF retutrn voltage to rise, as rpm increases.
If voltage doesn't change, measure the MAF's resistance, if it's infinite, the MAF grid or connection to the grid is open & is bad, if it measures something, it's likely ok.
Let us know how it goes.
SO, you might try switching the ignition key from "off" to "run" (not start) several times, to cycle the fuel pump & build pressure, then go to "start" & see if it'll crank & start itself without the starter fluid.
Seems to me, if the MAF were faulty, you wouldn't find it running ok after starting with the fluid. It should start with the MAF disconnected.
Check for battery voltage to the MAF, at the connector.
If you have battery volage, then back probe the "MAF Signal" & "Signal Return" leads at the MAF connector, it should typically read 0.2-1.5 volts at idle & increase to about 2.0 volts at a rpm you usually turn at say, 60 mph.
Anyway look for the MAF retutrn voltage to rise, as rpm increases.
If voltage doesn't change, measure the MAF's resistance, if it's infinite, the MAF grid or connection to the grid is open & is bad, if it measures something, it's likely ok.
Let us know how it goes.
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MAF Testing
Yep you were correct, I disconnected the MAF and it will start still using starting fluid. It ran rough until I plugged it back in and then smoothed out. But yes it does run without it.
I also probed the backside of the MAF connector and got 12v present and 1v.
Still won't start without ether.
Thanks,
Terry
I also probed the backside of the MAF connector and got 12v present and 1v.
Still won't start without ether.
Thanks,
Terry
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fuel pressure
There are valves along the fuel rails for the injection. I depressed the pin in the center of the valve and fuel shot out and hit the hood pad. I assume that the pressure is present.
Terry
Terry
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The Ecm is supposed to give the injectors a pulse when you turn the ignition switch to on (kinda like a shot of ether) you are either not getting that pulse or there is no fuel there when you do get the pulse. This kinda like the old carbs when you would give them a couple pumps before you tried to start them. Actually the ecm is turning on ground for the injectors. First you need to see if you have power the injectors when the key is first turned on second check to see if you can see ground pulse . with an ohm meter on the other side of the injector connector when the key is turned on. Are you getting good spark when cranking if spark is poor while in start mode this can cause it to need a very rich mixture to start which is what you are creating when using ether.
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wow, your right, i didnt think about that. bad spark by poor wires or plugs would definately need for a richer mixture. terrance you do have motorcraft plugs and wires dont you?
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From: Durham, NC
Originally Posted by wtroger
. ...with an ohm meter on the other side of the injector connector when the key is turned on....
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From: SW Va
Ok, so the MAF question is put to bed in your mind.
So what happened when you cycled the ignition switch from "Off to "Run" several times, to cycle the fuel pump & build pressure, before going to "Start" ????
So what happened when you cycled the ignition switch from "Off to "Run" several times, to cycle the fuel pump & build pressure, before going to "Start" ????
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Yea, The MAF looks to me as a non issue. I just went out in the dark to see if had any sparks jumping around. Looks good. If I remember correctly, my son just replaced the wires and plugs in the summer. He also replace the alternator and battery within the last 8 months.
I did try the key on/off action as you described, to build pressure...No change.
In the morning I will check current presents and flow on the injectors. I plan to back probe the injector connector/s with a meter and look for 12v. I'll try it with the key off and then on, and then start the engine ( with ether of course). I'll keep you guys posted.
Thanks, Terry
Does anyone know how much it costs to get an exorcism done?
I did try the key on/off action as you described, to build pressure...No change.
In the morning I will check current presents and flow on the injectors. I plan to back probe the injector connector/s with a meter and look for 12v. I'll try it with the key off and then on, and then start the engine ( with ether of course). I'll keep you guys posted.
Thanks, Terry
Does anyone know how much it costs to get an exorcism done?
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From: SW Va
OK good troubleshooting, so it sounds like the fuel pump is doing it's thing, after I re-read your above post about fuel squirting out of the rail test valve & hitting the hood.
Seems to me the injectors likely have a pulse, or it wouldn't continue to run, after you've given it a shot of ether.
You could check them with a noid light.
If you don't have one, you could probably make loan of one, from a "loan-a-tool" autoparts store.
SO, what would cause the air/fuel mixture to go dead lean, such that it won't start without help.
Maybe the IAC or throttle plate are out of whack!!!! Maybe something like the throttle plate stuck open too much from deposits, such that it passing too much air at start up.
Or maybe the IAC is acting out & bypassing too much air & leaning the idle mixture out too much, at start up.
Or a vacuum leak thats upsetting things.
Just some more things to ponder.
Keep us posted, it's getting interesting!!!!
Seems to me the injectors likely have a pulse, or it wouldn't continue to run, after you've given it a shot of ether.
You could check them with a noid light.
If you don't have one, you could probably make loan of one, from a "loan-a-tool" autoparts store.
SO, what would cause the air/fuel mixture to go dead lean, such that it won't start without help.
Maybe the IAC or throttle plate are out of whack!!!! Maybe something like the throttle plate stuck open too much from deposits, such that it passing too much air at start up.
Or maybe the IAC is acting out & bypassing too much air & leaning the idle mixture out too much, at start up.
Or a vacuum leak thats upsetting things.
Just some more things to ponder.
Keep us posted, it's getting interesting!!!!
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No you do not want to put the ohm meter across the leads on the injector. Just put it from ground to the ground side of the injector and turn the key on and do not try to start see if you see a pulse. this is only when you turn the key to the on position If you do not see a pulse then it is time to look at the ECM for issues if there is a pulse then look for the pulse in start mode. There are different circuits involved when the key is in start verses run position. You still probably need to check fuel pressure to see exactly what you have and when you have it. When you start it on ether does it fire immediately or do crank for awhile if the latter is true you may want ot look at the ignition module it may not be working right in start mode. I have seen engines that you could turn over and they wouldn't start until you let the key come back to run mode while they where still spinning then they would catch and run. On the old point systems this was usually caused by a bad starter. On late models we have seen this when the start side of the module is bad.
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From: Durham, NC
Originally Posted by wtroger
No you do not want to put the ohm meter across the leads on the injector. Just put it from ground to the ground side of the injector and turn the key on and do not try to start see if you see a pulse. this is only when you turn the key to the on position If you do not see a pulse then it is time to look at the ECM for issues if there is a pulse then look for the pulse in start mode..
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From: SW Va
Bob has a very good point here.
With the multimeter set on the "Ohms" scale & one lead on ground & the other on either side of the injector, which has battery voltage on it all the time the ignition switch is in the "run" or "start" position, the ohm meter then becomes the path to ground & it doesn't really like that at all, when set to "OHMS"!!!!!
In other words, you'd be trying to use it as a volt meter, with it set on the OHMS scale & it really really won't like that at all, as Bob points out!!!!!
SO, just set the multimeter to the 20 VDC range & verify you have 12 volts dc to the injectors, then cycle the switch & watch for a dip in the voltmeters reading, as the computer grounds the injector, IF the computer is pulsing the injector!!!!!
If you don't see the volt meter reading dip, then the pulse isn't there, or the meters response is too slow to detect it.
Also the reason I suggested using a noid light to check the injectors pulse.
Just some more thoughts on the subject.
With the multimeter set on the "Ohms" scale & one lead on ground & the other on either side of the injector, which has battery voltage on it all the time the ignition switch is in the "run" or "start" position, the ohm meter then becomes the path to ground & it doesn't really like that at all, when set to "OHMS"!!!!!
In other words, you'd be trying to use it as a volt meter, with it set on the OHMS scale & it really really won't like that at all, as Bob points out!!!!!
SO, just set the multimeter to the 20 VDC range & verify you have 12 volts dc to the injectors, then cycle the switch & watch for a dip in the voltmeters reading, as the computer grounds the injector, IF the computer is pulsing the injector!!!!!
If you don't see the volt meter reading dip, then the pulse isn't there, or the meters response is too slow to detect it.
Also the reason I suggested using a noid light to check the injectors pulse.
Just some more thoughts on the subject.