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89 Ranger No Self Test Output/No Codes

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Old 09-09-2005, 12:10 AM
Shade_Tree_Ed Shade_Tree_Ed is offline
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89 Ranger No Self Test Output/No Codes

Here we go gang, my first post. My name is Ed. I turned wrenches for about 17 or 18 years til about 93 so I know a little about this so here it is.

1989 Ranger / 2.3 EFI / DIS 8 spark plug setup / No self test output to malfunction indicator light circuit 17 during key on engine off self test / Fuel pump continues to run with KOEO / Timing and injector pulse acting fixed / No PIP crank signal because MIL stays on during cranking / MIL stays on while KOEO, KOER also cranking / 1500watt inverter installed for 120 volt AC output for key machine, others...

That being said I believe I need to replace the ECA because somehow I feel my processor received a voltage spike from my charging system do to the inverter or the regulator or a lose battery cable that I found. I think the processor software (RAM) is no longer functioning and the ECA is in 'Hardware Limited Operation Strategy' or HLOS mode which my processor does have.

I'm basing this on an 'assumption' that the fuel pump relay timer no longer works in Hardware Limited Operation Strategy on an 89 EEC-4. Does anyone know if the ground circuit for the fuel pump relay coil stays grounded allowing the fuel pump to run while the key is on letting the driver limp home during HLOS?

One other minor thing I found bothersome after running all resistance and most importantly, voltage checks at the breakout box for the rest of the system, then in order going through the quick test, then pinpoint test specificly QA which is the PT for 'No Codes'
is pinpoint test QA5.

My 13 year old Motor Manual says QA5 states the resistance between test pin 17 (STO/MIL) at the processor and ground should be over 10,000 ohms and if it isn't, I should fix the short in the MIL circuit and check it out again to see if it works. The resistance at the MIL bulb to ground is 35 ohms. The bulb is 6 ohms. This leaves 29 ohms between ground and the feed circuit to the MIL bulb from the ignition hot side.

Now I know how Ford can be about wanting us to think about what the engineers are really trying to tell us when talking about shorts and grounds. Afterall the light comes on and if it were shorted at the feed side it wouldn't work. I think what they are trying to tell me is the 36 ohms at the MIL is no big deal and this didn't cause my processor to blow its' top. Remember the processor does use grounded switching and this being the case the grounded switching shouldn't be concerned with a 36 ohm circuit where the voltage is normal. I'm a little rusty and my book is a little old.. Does this seem reasonable?

I appreciate the help. I'm really wondering about the FP question because if the pump circuit does stay on with the KOEO in HLOS, that tells me the voltage spike fried the RAM and I need the new ECA. The other with QA5 is most likely no big deal.

What do you think?

Ed
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Old 09-09-2005, 01:33 AM
Dave257 Dave257 is offline
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"My 13 year old Motor Manual says QA5 states the resistance between test pin 17 (STO/MIL) at the processor and ground should be over 10,000 ohms and if it isn't, I should fix the short in the MIL circuit and check it out again to see if it works. The resistance at the MIL bulb to ground is 35 ohms. The bulb is 6 ohms. This leaves 29 ohms between ground and the feed circuit to the MIL bulb from the ignition hot side.

Now I know how Ford can be about wanting us to think about what the engineers are really trying to tell us when talking about shorts and grounds. Afterall the light comes on and if it were shorted at the feed side it wouldn't work. I think what they are trying to tell me is the 36 ohms at the MIL is no big deal and this didn't cause my processor to blow its' top. Remember the processor does use grounded switching and this being the case the grounded switching shouldn't be concerned with a 36 ohm circuit where the voltage is normal. I'm a little rusty and my book is a little old.. Does this seem reasonable?"
---------
The ground povided by the processor to turn on the MLI light is done with a solidstate device not a relay. So with the light off it should measure about 10,000 ohms to ground not open. Between pin 17 and B+ 35 ohms seems about right. Now when you measure the resistance on the processor pin to ground you can try reversing the probes. Solidstate devices are polarity sensetive and it may be that you are reading the processor pin 17 to ground the wrong way. It will make a difference in the reading the way it is measured. If it measures 29 ohms both ways then I would say it is bad.

As far a the fuel pump I don't have info on that year.. but (and take this with a grain of salt) It would seem to put a lot of work on the pressure regulator to run the pump all the time the key was on, but they may handle it that way.

Someone with a little more info on that year will come along and have a better understanding then I do.
good luck.
Dave

Last edited by Dave257; 09-09-2005 at 01:43 AM.
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Old 09-09-2005, 02:03 AM
irishguyincc irishguyincc is offline
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I have an '87 Ranger with the 2.3 and my fuel pumps run constantly in KOEO. I have bypassed my inertia switch due to the plug there being bad, but I don't think that in itself would cause the pumps to run constantly. On these trucks they probably just do, though it doesn't seem right.
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Old 09-09-2005, 12:45 PM
Shade_Tree_Ed Shade_Tree_Ed is offline
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Irishguyincc;
This old trucks' fuel pump cut off after 2 seconds with the KOEO before all this happened. It uses the processor to switch on and off the ground circuit at the low side (coil side) of the fuel pump relay, and the other side of the coil powers up with the key. The circuit now stays grounded and the timer for the fuel pump is in the processor so I know for a fact my processor is fried because the wire going from pin 22 (FP cut-off circuit) at the processor to the self test connector and to the relay isn't shorted to ground with the processor disconnected.

The 87 2.3 with EEC4 and single fuel tank is the same. You did say you have fuel pumps so I take it you have duel tanks. I dont have a wiring diagram for a truck with duel tanks but if the system was dealer installed it would be the same unless someone didn't go by the book. If it's aftermarket I dont know. I'd disconnect the processor and fuel pump relay, (the green one under the fuse block) and see if the tan/light green wire which is circuit 97 if I remember right is shorted to ground. The best place to check the wire is at the self test output connector, the terminal on the right end of the connector with two T/LT.GR wires coming from it.

Dave257;
That STO/MIL circuit on my truck just doesn't jive with my book and this is what is holding me back from buying another processor. I know I need one but I dont want to blow a new one if I'm wrong about the STO/MIL circuit. I know these books aren't perfect even Motor makes mistakes but this one, if it exist and my truck STO/MIL circuit is OK, is a big one and one I thought should be brought up for discussion so it can save someone from tearing out their dash trying to find a 35 ohm short that may not be a problem at all. Maybe my MIL is shorted on the other hand.

The best way I can describe the problem with pinpoint test QA5 that I'm having is it is saying if there is a resistance between ground and test pin 17(STO/MIL) at the processor connector 'with the processor disconnected' and 'with the key off' of less than 10,000 ohms then a short exist between the STO/MIL circuit and ground and the processor may work after finding the short.

IMHO QA5 doesn't take into account the resistance at B+ located at the hot side of the MIL bulb to ground. If you test the resistance at pin 17 to ground with the bulb installed and the processor disconnected you get 35 ohms on my truck because the same circuit that feeds the hot side of the MIL bulb also feeds the guages and everything else in the instrument cluster and the guages are nothing more than resisters to ground and I think this is where the resistance is coming from.

If I pull the MIL bulb out then pin 17 is open to ground 'with the processor disconnected' between the processor and the bulb.

Grounding of the STO/MIL circuit is what turns the bulb on. Because the bulb is staying on and no codes are being outputed QA5 is saying the STO circuit is shorted causing this. On the surface this seems right. I seem to think after looking at the back of the instrument cluster and seeing that the hot side of the MIL bulb also goes to the guages and everywhere else, this may not be a problem. I think the RAM test failed during processor start up. Afterall the fuel pump timer is fried and the pump is staying on IMO.

However, if I'm wrong and the STO/MIL circuit is grounded by a 35 ohm dash short and if it is possible this is causing the processor to run in HLOS mode, (hardware only) and this is causing the fuel pump to run all the time, then this is something I need to know more about.
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Old 09-09-2005, 03:32 PM
Dave257 Dave257 is offline
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I chcked the autozone site and their wiring diagram dosen't show the dash wiring and so I can't see whats happing. I am travelling and don't have anything with me so I can't be more detalied. Sorry I can't be more helpfull, someone will come along with more help. Anyone??
Dave
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Old 09-09-2005, 03:52 PM
Shade_Tree_Ed Shade_Tree_Ed is offline
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I think I found the answer to the STO/MIL circuit. I looked in a 94 Crown Victoria service manual and it showed me a wiring diagram of the instrument cluster. It should be the same.

It seems the Motor Manual pinpoint test QA5 is wrong. The 36 ohm resistance is normal with the MIL bulb installed. That circuit also feeds all four guages and a few lights. Problem solved.

I'll go down and get a processor and post back here in a day or two to let everyone know if that solved the problem. I think it will.

I just hope no one else runs that pinpoint test on their truck only to find after taking their hole dash apart there was nothing wrong. That's sure the way it's wrote at least in my 4th Edition Truck Engine Tune Up and Electronics Manual.

Ed
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Old 09-09-2005, 10:22 PM
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Welcome to FTE, Ed!

Glad you found the cause of your problem. A few things that someone might consider when they run into a related problem can be found here:

The CEL Comes On But I Can't Pull Any Codes - Why Not?

Just an FYI.
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Old 09-17-2005, 08:00 PM
Shade_Tree_Ed Shade_Tree_Ed is offline
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I just wanted to bump this up to let everyone know I replaced the processor and the truck is fine now.

The give away was the FP running all the time. I installed a rebuilt Cardone unit. I get better mileage now too.

Have a good one.

Ed
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