My '89 F150 4.9L 5speed just dies, and sometimes doesn't live again, usually when I try to shift from 1st to 2nd, but sometimes it doesn't start at all. Once it runs, it runs perfectly, then dies suddenly. I scanned the codes and I get 2, code 32, which is EVP voltage below closed limit, so I'm going to replace that sensor, but also get code 67, which is: Neutral/drive switch open or A/C on, or Clutch switch circuit failure, or MLP sensor our of range. Sounds a little vague, I think the clutch switch is working because I can't start the truck without the clutch pushed in but then the starter engages fine, the A/C isn't on and doesn't trigger the failure mode. I pulled off the 2 dual pin connectors on the driver side of the tranny and inspected them, but the book doesn't say exactly how to test those switches, what should I be doing next? Are there any common failure areas I should be looking at?

Thanks,
Cameron

 

The Code 67 just means you did not hold the clutch to the floor during the test.
The 32 may also be an open wire from the EVP sensor to the computer or bad plug at the EVP sensor.

You may want to look at the Ignition Switch and its plug also. The Ignition switch is located down by the floor on top of the column.

The Neutral/drive switch and its circuit will not kill the engine as you drive or stop it from starting if it is cranking.

 

the EVP didn't change resistance between 5K and 100ohm as manifold vacuum varied, so I can assume it probably is bad, so I'll replace it.

Am I just looking for clean contacts/voltage on the ignition switch, or is that somehow tied in via something complex through the computer?

 

You will not see it change unless you use a hand vacuum pump on the EGR valve.
Just because the engine vacuum changes the vacuum to the EGR valve will not change unless the EGR solenoid valve is energized by the computer grounding the green wire of the solenoid. And this will only happen with a warm engine and at hi-way speed.

The Ignition switch has no wires to the computer, only to the EEC Power relay and the Ignition System as far as the engine is concerned.

You would be looking for maybe a burnt plug or the switch itself coming apart.

 

The strange thing is I know I have good spark and the fuel system is okay too (good tested flow, pump cycles prior to startup, manual override produces steady stream of high pressure fuel, though I'm going to check the fuel pressure using the schrader valve and a tire guage, the high pressure pump and filter have been replaced, and it's got dual tanks and works the same on both tanks, so the low pressure circuit must be good), even in its non-start condition, if the ignition switch were intermittent and didn't have a computer interface, why wouldn't the truck run? When it decides to run, it runs perfect.

The method I'm using to test the codes uses the wiring test harness in the engine compartment, are you supposed to have another guy in the truck with the clutch depressed when you use the voltmeter sweeps to check the codes?

Thanks for the tips on all of this, they are VERY appreciated

 

I am not sure I understand what you are asking.
The intermittent ignition switch would turn the power off to the Ignition System. Power to the coil and the TFI module. The Ignition system is independent of the computer other than the computer monitors the spark, counts the PIP pulses and if the SPOUT shorting bar is in then the computer can change the timing and that it. You can unplug the computer and crank the engine and it will have spark and if you spray starting fluid in it and it will run.
There is not much difference in the Ignition system with the computer and the ignition system before the computer other than a different looking Ignition Control Module (ICM) and it uses a switch in the distributor rather then the pickup coil that the old system used.
You should be able to ground the wire, set in the seat and turn on the Ignition switch hold the clutch in and count the codes. Or set the meter in front of the windshield.

 

It looks like I'd have to unbolt and lower the steering column to get to that switch right? It's tucked up in there pretty tightly if I'm looking at the right animal. The book says there's only 1 wire coming out of it and it goes to both the ignition coil, which I know is working and producing spark, and to the EEC power relay, are you saying it's possible to be having intermittent power to the EEC power relay which causes it to not run but still generate spark? I'm a little fuzzy on this. It also powers the fuel pump relay, and I have the fuel pump running steady if I remove a fuel line and just turn leave the ignition switch on.

I tried to little avail to test the fuel pressure at the pressure test schrader valve, I really didn't have the right setup, so I have to just assume it's working okay, it did spray a lot of gas out when I depressed the valve stem.

 

I was thinking more along the line of losing power to the Ignition system and the EEC Power relay of course would lose power at the same time.
Have tested for spark when it does not start?
How do you know it is producing spark when it quits?
If the engine quits all of sudden it means most of the time you have lost spark.

It sounds like you are trying to say the engine quits and you still have fuel and spark.
I do not by it.

 

now I can't seem to get the truck to run at all, no matter what I've tried and it has bright blue spark on all the plugs and fuel and pressure at least to the injector rail. If I spray ether down the manifold, it runs, otherwise it won't. It used to be intermittent, now it just won't hardly ever run.

 

Does not sound good for the computer.
Does the fuel pumps run all the time the key is on?
If so it is the computer.

 

On a normal startup sequence, once you turn the ignition to the "on" position the fuel pumps engage for about a second, like you'd expect, presumably while building pressure, unless you have a fuel line unhooked where they'll run indefinitely, or if you use the diagnostic jumper that keeps them running. I guess the computer is storing codes normally, i.e. I replaced the O2 sensor and it cleared that code, etc. so I'm not really sure how I would test the computer, or how tied to the exact VIN a replacement would be from a junkyard or someplace besides $$$Ford, though I'm used to Mercedes so it might not be that painful...I hope I can't see really any way to force the injectors to inject, and this might cause more problems than it solves...anyone know of a good computer source?

Thanks for all your help, no matter how this turns out, you've been really wonderful and helpful! It's a good old truck and it really doesn't need a burial, I'm hoping to get years more service out of it, it's basically in really sound condition compared to most of them this year, I'd like to keep it a couple decades

Thanks,
Cameron

 

Make sure you test this fuel pressure with a fuel pressure gauge before you condemned the computer because if it is not at least 42 PSI it will not try to start.
Normal fuel pressure with the use of the diagnostic jumper or the vacuum line off the FPR is about 60 PSI.
Normal Fuel Pressure at idle is about 45 PSI and at WOT about 58 PSI.

I do not know where everybody gets this idea about the pressure building up and the pumps stop. It has nothing to do with pressure, it is a one second timer in the Computer that times out and turns off the fuel pumps if it does not see a PIP pulse in the one second time frame.


The Computer also needs this PIP pulse from the distributor before it will fire an injector.


You can match the Ford Drawing number off the computer with one from a salvage yard or use it at an auto parts store. If you find one with the same program code (some call it a catch code) it will work also. The same computer can be found in Ford trucks + or – a year or two.
More on the program code:
Ford Fuel Injection EEC Program Codes


To test fire an injector you can use a 9 Volt radio battery and listen to it click.

If you post the calibration number off the drivers door post and I can tell you what the Ford Drawing number is (the number on the computer) and also the Ford Part number (this number is not on the computer).

 

I measured the fuel pressure after I found a high pressure test gauge and hookup to the schrader valve, it produces 55psi while cranking the engine (though it never started) so I guess that's okay.

I replaced the EVP sensor too, just in case.

I also pulled the computer out to get the numbers to search for a replacement, and when I put it back in to test the fuel pressure and see if it cleared the EVP code, it still wouldn't start, but now it has the codes 12 and 21, then I cycled power and it threw 2 different codes, 21 and 24, then I cycled power again and it only threw 1 code, 24, then I cycled power again and the check engine light never went out, so my next step is to replace the computer, nothing else makes sense. I'll let you know if that fixes it, but I can't see how it could be anything else.

 

it was the computer It runs perfect now. What a nice running old truck, I think she'll be around for years, a very pleasant truck to drive, very easy to live with. Thanks again for all the help subford, you're a real life-saver, couldn't have done it without you !!

Now I have to put a paint job on her, the years haven't been kind to the paint...big patches just peeled of over time, but we'll fix that soon...if I can find the paint code