Hello. I'm an owner of an 89 F250 5.0L V8. Is it possible that a faulty oil pressure sender can prevent the EEC-IV PCM from letting the car start? Let me give a brief synopsis of my situation. The last time I drove it I noticed some strange errratic behavior of the pressure gage hovering around the low side and bottoming out while idling and then stabilizing later while both driving and idling again. The oil level is ok, the truck runs strong and I doubt the oil pump is bad. Anyway, I let the truck sit for a week and then upon starting, it would turn over but wouldnt start. I did a quick ignition check and discovered no spark at the coil secondary. The primary had full 12+VDC at the run position, but was very weak while in the start position. After a week of more extensive troubleshooting focusing on the notoriously troublesome TFI module, I checked the PIP signal which was ok, but I noticed that the SHOUT circuit from the PCM to the TFI had a very low effectively zero AC voltage (while cranking). So I unhooked the shunt "jumper" on that line and rechecked for spark - this time I got it. The system apparently defaults to a 10 degree distributor advance when it detects the SHOUT circuit open. However the engine still wouldnt start. To make a long story short, before going into a fuel system check, Im now wondering if it is the low oil pressure voltage at the oil pressure sender that is causing the EEC-IV to disable the fuel system and subsequently the SHOUT system, preventing the engine from starting? Any insight would be greatly appreciated.

 

Try a shot of starting fluid and see if it fires.

 

You can also check for trouble codes, to see how go to www.fordfuelinjection.com under getting codes. Its easy and free. You can check for codes even if it wont start. There will be a few codes that you will get because the engine is cold.

 

Oh yeah, I forgot to mention that I got an error code 22. Which is an out of range signal from the MAP sensor. Could that prevent a start?

 

yes, a lean MAP sensor signal will cause the engine not to start, should fire up on starting fluid through if you have spark and all other components for basic engine function.

 

I have an 87 F-150 that had a code 22 and it would only run for 3 seconds with starting fluid. 87 to 89 have the same parts. You should check the voltage to the three Map wires to see if you have a broken wire, also check your vacuum hose. You could get a used Map sensor at a salvage yard or find a store that you can return if it doesn't fix the problem. Orange wire is the VREF wire the black is the signal return, and the Map bp signal. Do a advance search above and you should find the basic voltage levels to each wire. You will need a tachometer and a vacuum gauge really test it. If you replace the Map sensor don't forget to disconnect the battery ground for a few seconds to reset the engine computer.

 

From your symptoms, very good job on the history and symptoms by the way, it sounds like you distributur gear is missing some teeth. Take the cap off the distributor and bump the starter and see if it moves the rotor. If not problem found. I believe that would explain the oil pump as well.

I would take it out to check it, but be carefull that the rotor is pointing at the #1 cylinder wire (front passenger) when you do. That will make it much easier wether you put that one back or replace it.

The computer is basically bypassed from the timing durring starting, until the engine is warm. It uses the the PIP signal directly to fire the coil. If you are not getting any PIP voltage, it could be bad, or the distributor might not be moving.

To answer your oil pressure question, no the computer will not keep the engine from firing without oil pressure. It will keep it from firing without a distributor though.

 

Thanks, The distributor gear looks fine. I pulled that too when I removed the TFI module. I also cranked the engine, and the rotor rotated pretty smoothly..so, no symptom of faulty drive gear. By the way, I also got a new TFI module from the Ford dealer two weekends ago (not a cheap part by the way - $125). I installed the new one but still no start. Luckily the guy at the dealership let me return it. Tonight I tested the fuel pump relay, due to a hint by a previous responder, and i noticed that the output line (brown wire) was getting a couple of millivolts, while the others all had 12VDC. I thought, wow, here is my problem!.. The relay must be sticking! So I went to NAPA and got a new switch, installed it, but still no go!! I tested both relays for continuity later on, and they both seemed fine. I went and returned that too. So now im back to square one. *sigh*

 

Hmm, no gas now?

That's the spout plug. It tells the TFI to use the raw PIP signal instead of computers corrected timing signal. The TFI should be using the raw PIP to start anyway. Did you test the TFI pins 3 and 4 for power during start and run?

It sounds like you might have a computer power problem. That is the common componet between them at startup.

Does the fuel pump click on and whine for 2 seconds when you turn the key to on? If not, you should check the EEC relay.

 

Ok ive tried all the suggestions and found a couple of interesting phenomena. 1) when I disconnect the SPOUT jumper, I get spark - hower still no start. 2) Per a website that I cant post a link to due to the policy of this site I checked the resistance at the harness between pins 46, 40 and 60 ; 46 being the return to several key sensors including the knock sensor (KS). It so happens that I get an open circuit between 46 and both 40 and 60. I checked all the sensors for continuity to pin 46 and they all checked out ok, except the KS, which I cant seem to find! Does anyone know where it is located??? THis sensor may be my problem because apparently it senses combusion timing and relays the information back to the timing advance circuitry in the ECC, and furthmore might explain why my SPOUT circuit isnt working. I also wonder if this is why Im getting error code 22 since the MAP sensor ground goes to pin 46 in the EEC too... Hummm..the plot thickens..

 

Unthickening the plot...

First, 40 and 60 are main power grounds back to the battery,
second, pin 46 is an internal computer ground for Power steering switch, TPS, EGR position, MAP sensor, ECT sensor, ACT sensor, and KS sensor (I personally have never seen a knock sensor on a 5.0, but the professional component wiring diagram book for Motor says it is in the cylinder block, rear of engine. I don't think we need to go there, because your internal ground of pin 46 is not connecting to internal ground pin 40 or 60. Problem inside ECM, Note: #1 failure, computer
Next is the Spout connector issue, looking in my Target Training Systems manual at the theory of the Hall Effect Signal information, it is noted on this page, I will type it word for word: A special NO-START condition must be covered, The EEC Processor will cause a no-start if the SPOUT driver is bad, The fastest way to test this is to open the SPOUT/TIMING connector. If the engine starts with the connector open and dies when the connector is reconnected, the SPOUT signal is grounded or the EEC processor is bad. The SPOUT signal on pin 36 will follow the changes in the PIP signal. A bad computer will not follow PIP change, but the injection may still work. Since you can unhook your SPOUT connector and get spark, and you connect it back up and you loose spark, it is saying to me the driver is grounded internally in the EEC.
Noted: failure #2, computer
Try for #3,
MAP code 22, Target Training Systems again say code 22 engine off: MAP frequency out of 140 to 160 hz range.
running or memory, MAP ferquency is out of the normal operating range with the engine running. Typical MAP sensor frequency is 108hz @ 18" of manifold vacuum. Now since you have not given this information, this makes it difficult to clarify your code 22, but MAP is a main fuel control to the EEC system. You could externally ground pin 46, if you wanted to invest in instrumentaion to note if your MAP system was functioning correctly before you replaced the EEC, but other than that, I believe another EEC is in line here for your special no-start. Plus the SPOUT can give you spark but still no-start on the sence your complete input system is not giving any input for the computer to do computations with. #3 failure, computer
If it was in my shop for repairs, I would get another computer. Check all of your powers and grounds from the computer back to the battery, 5 volt reference from the TPS, Fix what it missing. You noted 40 and 46 are not connected, you have no power over this, it is in the EEC. Broken Wire

 

Pin 46 is SIGRTN. If you probe the harness with the computer disconnected, you will not find (and should not find) continuity between 46 and 40 or 60.

As Broken Wire mentions above, with the computer connected, 46 should be a fairly low resistance to 40 or 60 -- less than 10 ohms.

The oil pressure sender and knock sensor should have no impact whatever on ability to start the vehicle. The computer does not care if there is oil pressure or not, and will cheerfully operate the engine until it siezes up. The knock sensor is probably ignored during crank. It is definitely ignored if you pull the SPOUT jumper.

The strange behavior of the oil pressure guage, the no-start, and problems with SPOUT could all be linked to bad grounds. Check the ECM ground connection at the firewall, check the battery post, check the chassis ground at the radiator support, check the connection to the block.

The weak SPOUT output, low voltage at the coil, and the no-start could also be caused by poor voltage to the PCM (and the rest of the system) during crank. The voltage will drop to 11 volts +/- but should not drop further than that. Check the PCM relay. Check your battery + cables. Just because the engine cranks OK does not mean the voltage/grounds are good enough.

If the PIP line does not make it back to the computer, the computer will not supply SPOUT and it will not fire the injectors, and the engine will not start. If you have an LED test light, you can check SPOUT/PIP for a flashing signal during crank. (I find AC volts too misleading). Probe one of the injectors and see if it is firing during crank. If the injectors don't fire, the computer is bad or it is not getting PIP. (And it definitely won't start). Probe the FP wire during crank. It should go to ground if the computer is seeing PIP. (If you are lazy, or stranded at the side of the road, you can listen for the whine of the fuel pump for about 1/2 second just as the starter spins down when you release the key. If PIP isn't working, the pump won't be running. If PIP is working, the pump should be running during crank, and stops just after the starter.)

 

Does anyone know what the eec-iv pcm p/n code stands for? Specifically the last three digits. My eec is p/n <!--StartFragment --> e8tf-12a650-g2a, and im wondering if I could use an e8tf-12a650-f2a?

 

I checked my books, they are just noting that both come from an 88-89 Bronco and F series trucks, If you want my opinion, I would put it in and try it, it should (note: should) not hurt anything if it does something strange, but (FA) is a previous version of (GA). Another item that really makes no difference but to clarify, pin 46 is a ground return, not signal return, signals are feedback circuits back to the computer off of the 5 volt reference, pin 46 is the connection area for all of the PCM input devices setup by using a common ground. Make sure you check the black plug together wires behind the area of the battery, I believe there is 2 of them there, these are the main grounds for the PCM. Broken wire

 

Thanks broken wire. So if I understand you correctly, If I pull the pcm out of the harness, and check continuity between pins 46 and 40 (and 20 and 60), I should get a closed circuit <5 ohms. I did this and I got an internal open. In my previous post, in which you replied to, I had checked pin 46 on the harness to ground and this should definately be an open, which it is. I also measured pins 20, 40 and 60 on the harness to the battery terminal and I got <5ohms, which is apparently to spec.
These pcms arent cheap, but im going to test one from a friend of mine which is out of an 88 F150 with the same engine and tranny. If this finally causes a start then im going to look for a rebuilt one with the same p/n as mine. This problem has gone on for way to long!