No Codes from EEC-IV

rousech81 · Nov 5, 2007

I have an 89 Ranger 2.3. The truck has run good for all 130 or so thousand miles. the truck recently just quit. It turns over when cranked fine. The timing belt is in tact. The fuel pump does not kick on when the key is turned on. I tracked that back to the fuel pump relay. For some reason, the relay isn't kicking on when the ignition comes on. Thought there might be some issue with sensors so I configured my test light and set everything up to do a KOEO test. No codes come from the EEC, just a constant 7.5 volts. I don't even get an all clear code. I have hooked the fuel pump directly to 12 volts and it is working fine. There is plenty of pressure on the rail but the truck still won't start.
How can I tell if the EEC-IV is shot or should I start trying to trouble shoot sensors? If I start with the sensors, where should I start. I find it odd that the EEC gives me nothing when I hook it up for the self test.

Ranger5.0 · Nov 5, 2007

it sounds like the ecm might have taken a krap. OR its not getting any power. The ecm controls the fuel pump, so if the pumps not working, then the ECM is not powering up, or its toast.

Dave R · Nov 5, 2007

Technically the ECM controls the fuel pump relay's coil ground path.

If the ECM is receiving power, it should prime the fuel system by turning on the pump for about 1 second.

Have you checked to see if you have spark? If not, then check to make sure that the ECM is receiving power on pins 37 and 57 when the key is on and on pin 1 constantly.

rousech81 · Nov 7, 2007

I have checked to make sure that the plugs are firing and they are. I have replaced the ECM relay thinking that might be the issue but it is not as that did not change anything.

On the fuel pump relay, I am not sure how the voltages coming into the plugs should be but there are two large prongs and two small prongs. When you turn on the key, on of the small prongs gets 5 volts and the other one is 0. One of the large prongs has 12 volts at all times and the other one never gets the 12 volts. The other one is the line that goes to the pump.

We have straight wired the pump to work while the engine is cranking but it still won't start. If you spray gas straight into the intake, the engine will run until it burns that little shot of fuel, then turn off. Is it likely that there is something else like the injector timing that would prevent the truck from starting?

I kind of guessed that if there is no response from the ECM when I try to get codes, something must be wrong with it. Is there any way I can have it checked out or should I just start looking for a new one? If a new one is the way to go, any suggestions on where or who might be a reputable source? I have seen some online places to send yours to or just buy one straight out but didn't know how reliable those places were.

Thanks for all the help!! I have been through a couple of issues with my ranger but never anything that stumped me quite like this has!

Ranger5.0 · Nov 7, 2007

DaveR- So, technicaly, the ECM controls the fuel pump then eh lol, i was trying to keep out the details. Maybe we can tell him how it uses a transistor to do so, but that still wont help haha. Im still pointing my finger at the ECM, if you cant get the thing to awknoledge you are doing tests, then its a sign that the ECM is in trouble, not to mention that after the added info you provided, it sounds like its not controling the fuel pump OR even the injectors. When you turn the key on, the ecm wakes up, controls the GROND path for the pump relay, and then on comes the pump. By jumping the pump and hardwiring it in you supplied the fuel system gas, but the injectors still were not instructed by the ecm to alow fuel to flow. This is a pritty vauge piece of info, but without actualy being there with a DMM then i cant realy do much

Dave R · Nov 8, 2007

If you have spark then the computer is functional.

As for why your injectors aren't operating...could be a number of reasons. Including fried injector drivers in the computer.

Just for 'fun' test try running the truck on ether or a splash of gas in the TB.

rousech81 · Nov 12, 2007

O.K. so I took the air intake off again and tried a couple shots of gas straight in and the truck will start and run until that little bit of gas is gone. We tried this two ways, one with the pump straightwired and running the whole time. The truck still won't stay running. We also tried it without the pump running and obviously, the truck died as soon as the gas vapors ran out. Being the inquisitive person that I am, I opened up the ECM just to see what it looked like. Nothing real interesting in there but I did notice that on the board around one of the little things sticking up was rather brown and burnt looking. I am thinking that that may be my culprit right there. The problem then becomes what caused that. If I plug in another ECM, will it just do the same thing or is there a chance that was a fluke occurence?

I know, too many questions without enough information. I really appreciate all the help! Also, any suggestions on the best place to procure a replacement ECM?

No Codes from EEC-IV

rousech81

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Ranger5.0

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Dave R

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rousech81

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