Spark + Fuel + air = NO START??

[surphrat420]

OK bear with me..
This explorer is a 94 4x4 4.0 auto, its my backup truck
i only ride it around every 4 or 5 months, well used to, it doesnt fire up anymore. used to run fine never a single starting problem, one day after giving the battery a recharge it never started back up. The situation goes like this. new batt , key on, and i hear the fuel pump whirl for 3 sec. all dash indicates full power and function. the engine will crank and crank but never fire up, UNLESS i spray some gas into the TB. THis leads me to my problem NO fuel. So i purged the fuel via the purge valve (tire valve on fuel rail), well it squirt me in the eye, I dont have pressure gauge so I opened the valve and connected a container to the open relife valve and turned the key on and off and it filled up about 1/2 soda can in two key cycles. That seems like a good amount of gas? well I broke down the Top end removing the upper intake plenum and fuel rail itself to remove and clean the injectors, then i connected each injector to a 12v source to listen for a click, they all tested ok( as well as all checking for around 16 ohms). they were cleaned and every think was blown dry and reasembled. i get some votage on my digital multimeter at the injector harness plugs when i crank the engine( some voltaghe means the same result i usually get by tapping the leads onto a 12v source quickly removing them). This is driving me crazy, could all the injectors be very cloged?? all at once?? the presure regulator seemed to be stuck closed when the rail was off i pulled a 25psi vac on the vac line and i could not blow through the valve ( im not sure if that is how the regulator works anyways) could this be my problem? ANyways , ive tried every thing in the chiltons book with no luck , i ve tried alot more than i can write here, any one have any suggestions? Does a fuel pump go bad and only pump1/2 output , or do they usually just quit?

I guess next step might be getting a fuel pressure kit

thanks in advance

 

[i8u]

Take a fuel sample to be anaylized at you nearest dealor. The there may not be enough violitility in the fuel to burn.

 

[jgilbs]

i agree with i8u. gasoline i volitile and it has a shelf life. after a certain amount of time, the compounds in the gas will break down to form a more stable compund. i would try siphoning out all the gas and replacing it with fresh gas. next time you store your truck, add some gasoline stabilizer (available at most auto parts stores) to your gas to help prevent it from breaking down.

 

[surphrat420]

yes im familliar with the gas stabalizer i actually have a bottle in my garage for my boat alot good it does in the bottle. hehee.

well i tested the gas by purging some into a bottle and using that to spray into the TB to get it started and it runs! this makes me think the gas might not be bad yet?

I also poured a bottle of octane boost into the trank and shook it up. the tank in FULLLLLLLL s oi hate to dump the gas and i dont have 15 gallons worth of containers.

 

[unclemeat]

How about the fuel filter?

 

[surphrat420]

Oh yeah i just changed the fuel filter and it is installed in the right direction i double checked, can i check the fuel rail pressure with one of those foot bicycle pumps with a gauge on it?

 

[surphrat420]

Ok i just bought a 40 dollar fuel pressure tester and did the test of the shrader valve.

it jump right to 25psi when key is on and 2 sec later it almost to 40psi but still no starting after cranking?

I next left the tester on and connected vaccum pump to the fuel relief valve and DID NOT see a drop in pressure after appling almost 30 Mg/in vac. Will the fuel relief , not reliving (stuck closed) keep the truck from starting?

i doubt ALL 6 injectors went bad, Maybe the computer isnt sending a signal to the injectors? but all at once? is there a master connector for all 6 injectors?

Anyone have this problem and FIXED it??

 

[Billy177]

try resetting the computer you can also get an injector tester and test them

 

[surphrat420]

fuel injector tester?
the NOID light? is that what your refering too?
i took out all the injectors and fired 12v to them and heard them all click.

Im looking up how to reset the computer ill try that ,


All this today after dumping 6 gallons of gas until the tank was empty , and refueling about 4 gallons.

 

[wilson_nick]

you should be able to just disconnect the battery for a couple of mins to reset the computer. then once you finally get it started let it idle for a couple mins so it can reprogram itself.

 

[surphrat420]

ok now that im covered in gas ill quit for the night...
It still wont start ive determined its definatly getting 30-40 psi at the fuel rail

and since i dont belive all 6 injectors go bad at once i think it has to be the signal going to the injectors.

Does anyone know of a good method of testing the injectors without having to take off the upper air plenum again? or how to check for signal (what ever voltage the injectors need to fire) at a connector other than the one directly attached to the injector?

 

[ipozestu]

From what I have read it seems that your fuel system is ###tioning normally. Although I don't think that the injectors ever recieve a 12v DC signal. Correct me if I'm worng. Most signal driven sensors and solenoids only ulitize a 0-5V DC. You may have caused some damage to your injectors in this case. You should only measure the Ohms across a solenoid. The Hayes/Chilton manuals have acceptable parameters for the injectors. You say that it starts when you put gas in the TB. There may be a chance that the IAC/MAS could have problems. I guess what I am saying is the problem may not be fuel rather air. When you open the TB to put fuel you are also letting in air. It may benefit you to test the IAC solenoid as well. This should be open at start up. I'll keep an eye on this thread to see if any new clues become apparent.

 

[i8u]

Originally posted by ipozestu
From what I have read it seems that your fuel system is ###tioning normally. Although I don't think that the injectors ever recieve a 12v DC signal. Correct me if I'm worng. Most signal driven sensors and solenoids only ulitize a 0-5V DC. You may have caused some damage to your injectors in this case. You should only measure the Ohms across a solenoid. The Hayes/Chilton manuals have acceptable parameters for the injectors. You say that it starts when you put gas in the TB. There may be a chance that the IAC/MAS could have problems. I guess what I am saying is the problem may not be fuel rather air. When you open the TB to put fuel you are also letting in air. It may benefit you to test the IAC solenoid as well. This should be open at start up. I'll keep an eye on this thread to see if any new clues become apparent.

Agreed. Try cranking it and push the gas pedal down to the floor and hold it once the engine is cranking. If the engine turns over suspect the IAC. Go tap on it. Try normally cranking it. What did you find?

 

[surphrat420]

well heres the new report:

I took a look at the IAC.... the solinoid is mesurring @ about 11ohms well within spec. I removed the valve from the intake and jumped 12v to it , it definetly makes a click noise and i can see the valve push in and out. i Next messured the connector that plugs the IAC it messured around 11.95v just a little lower than the 12.5 comming right off the batt. So i reasembled everything.

Heres the good part, i know the IAC was working cause i could hear it click back and forth when testing it, BUT if I connect the plug back to it (with the key in the on position) I dont get any click?? even thought the plug is giving 11.94v?? is this strange or what??

 

[MattPersman]

unplug your IAC to see if it starts with out it. then try unplugging other stuff 1 thing at a time, it could be your TPS. what does it read KOEO? 4.8 or 5 volts or something, if so then its telling the PCM that its at WOT aka clear flood mode and won't start, seen it happen before on a different vehicle. kicks ya in the butt to try to figure that one out.

does it stay running once you inject fuel into the TB? or does it die after thats used up?

 

[MattPersman]

I was thinking a little more about this, but a defective crank shaft position sensor (CKP) will also make it not start with fuel, ignition and base engine ok

so I would look at the TPS, easy to read with key on engine off and then if thats not it, I would put a new CKP on see if that works

 

[Billy177]

have you measured the fuel pressure on the test port while someone cranks if that checks out okay unplug the iac maf and 02sensors and try and start it i would also look into the comuter. maby ford could test it or something

also if you have a scanner that would be a great help


also try hookinga timing light to the number one plug even though it rins with fuel something may be screwing with the timing such as the iat or something

 

[MattPersman]

you can unplug the IAT and it would run, he claims fuel, spark and air, really that could only be an input sensor telling it not to fire the injectors, broken timing chain, or CKP off the top of my head

to test the CKP from Autozone.com same as alldata

Using a DVOM set to the DC scale to monitor less than 5 volts, measure the voltage between the sensor Cylinder Identification (CID) terminal and ground by backprobing the sensor connector. If the connector cannot be backprobed, fabricate or purchase a test harness. The sensor is okay if the voltage reading varies more than 0.1 volt with the engine running at varying RPM.

kinda hard to test if it isn't running, for 30 bucks its worth trying if you exhausted your other options

if there is 35-45 psi at the rail KOEO and it holds then you got fuel there at least the pump is pressurizing and fuel is available, now if the injectors are not firing that is another story but if there is pressure then its good. if there is no pressure then it would be the pump, inertia switch, regulator, block inlet line or filter, etc.

claims there is spark, you either have that or don't. if your plugs are firing then yep you got spark. could be very weak have to use an ignition testor

whats your cranking vacuum? does it crank really fast?

 

[Billy177]

it can not be a broken timing chain because it runs when he pours fuel down the throttle body. also if you unplug the iac it will read -88f with this timing it would make it hard to start. this might sound dumb but have you checked all of your fuses

 

[savant]

I just recently bought a 1991 EB, and had this exact same problem. I had good fuel pressure, replaced the fuel filter, plugs, wires and whatnot.

It turns out, I pulled off my throttle position sensor, left it off, and the vehicle started without problems. Try pulling off your TPS, wiggle it some, and start the vehicle. I put mine back on and have not had problems since.

Hope that works for you.