'93 4.0 OHV won't start after rebuild

Splash93 · May 5, 2016

I just rebuilt the engine, put it in the truck, and now it will not start. I have 35 psi of fuel pressure. The engine turns over, but will not fire. If I spray brake cleaner into the intake manifold, it fires right up then dies. I have replaced the spark plugs, wires, fuel pump/level unit, fuel pressure regulator. What am I missing?

RonD · May 5, 2016

Welcome to TRS

If it fires up by adding fuel manually then spark and compression are good, fuel injectors are not working, assuming you have fuel pressure.
The Computer(ECM, PCM) runs the fuel injectors

1994 and earlier 4.0l uses an EDIS-6 module to run the spark.
Crank position(CKP) sensor connects to EDIS directly, and Coil Pack connects to EDIS directly.
That's the spark system, self contained, but computer does assist with spark advance.

The EDIS module also sends the spark timing signal(PIP, SAW) to the computer so it can time the injectors with the spark.

If computer doesn't get this signal then it doesn't even know you are cranking the engine.
And if computer is not powered on the same thing would happen, spark works, fuel doesn't.

When you turn on the key the CEL(check engine light) should come on, that means computer is powering up.

Splash93 · May 5, 2016

Thanks RonD, the check engine light does not come on when I turn on the key, only the little red battery light. The battery is fully charged. The engine was running prior to the rebuild. How do I test/check the computer?

Splash93 · May 5, 2016

I just pulled the instrument cluster and checked all the bulbs. Bad contacts. Now all bulbs work and the "Check Engine" light comes on with the key. Light goes off when cranking the engine over then comes back on when key is in acc position.

RonD · May 5, 2016

Does it start when you add fuel manually or just fire or backfire?

Coil pack wires
3 4
2 6
1 5
Front

the 5, 6, 4 side gets me every time.

The computer power comes from the EEC relay(EEC Fuse) and that also powers the Fuel injectors and fuel pump relay.
Fuel injectors get 12volts when key is turned on, computer controls injector ground, so Grounds the injector to open it.

You can test if a fuel injector has 12volts with key on, the Red wire.

You should hear the EEC relay in the engine fuse box "click" when key is turned on then the Fuel pump relay right next to it will also "click" ON, then "click" OFF after 2 seconds.

You should hear the fuel pump run for those 2 seconds, each time key is turned on.

jeremysdad · May 6, 2016

564...that could explain my random miss.

German joke? Cause ford is passenger front:1234 Driver front: 5678.

Easy as pi.

Splash93 · May 9, 2016

Still working on the engine not starting. The engine will start and run when brake cleaner is sprayed into the intake. Coil pack wires are correct, 123, 564. I checked the throttle position sensor and got correct voltage up to 4.67 dc. I checked the Crank Position sensor and got AC voltage and the crankshaft only has one missing tooth. I put noid lights on all injectors and got a flashing light. I checked the resistance of all injectors and all were within spec. with no significant variation between injector readings. The ECC relay clicks when I turn on the key. The fuel pump relay clicks when I turn on the key and I can hear it running for 2 seconds. I have 35 psi at the scharader valve. I don't know where to go from here.

RonD · May 9, 2016

If engine fires when fuel is added manually the CKP sensor is working and in a '93 4.0l the EDIS module is working, so spark is working.

Since adding fuel manually causes firing then either injectors are not passing fuel into intake or the fuel they are passing in doesn't ignite(bad gas)

You are getting pulses via NOID light so we would assume injectors are opening from that.
Pull out #1 spark plug and see if it is wet after cranking engine, without adding fuel manually.
If it is dry then injectors are not passing fuel into the intake.
If it is wet, put a match to the spark plug tip, see if it can burn, if not you got bad gas in the system.

If spark plugs are dry after cranking then injectors can not pass fuel.
Try this test, hook up fuel pressure gauge, turn on key.
Say pressure shows 35psi.
Crank engine a few times, pressure should drop down each time you crank the engine because fuel would be flowing out of the injectors, and fuel pump is off.
If pressure stays at 35psi then injectors are not opening, or all are plugged(long shot).

But easiest is just to pull a plug and see, wet or dry

Splash93 · May 12, 2016

Checked the spark plugs, and they are all dry. I rechecked the resistance of the injectors and they are within spec. I connected the noid light and got no light. Checked voltage of red wires and got 12 volts. I do not know why the noid lights worked earlier and now do not. Could the PCM be bad. How do I check.

RonD · May 12, 2016

PCM can be bad but doesn't really happen much even on older ones.

If you want to pull it out and pop the top off you can usually see damage on the circuit board.
Blacken or discolored areas.

Picture and Pin Out diagram here: http://www.auto-diagnostics.info/ford_eec_iv

Look at Pin 56, that's the input for PIP signal that comes from the EDIS module.

58 and 59 are the Grounds for the fuel injectors

CKP sensor--------EDIS-----(PIP signal)---------PCM---------fuel injectors

Without a PIP signal the computer doesn't even know you are cranking the engine, so wouldn't Ground the injectors.
There are also 3 Ground points for the PCM plus the case ground, none of these are shared inside the PCM, so if the injector "ground pin" was bad then PCM would be grounding the injectors but there is no ground to pass on.

Check Ground pins with ohm meter

If computer connector was off and you were to test pin 56 while cranking you should see a voltage change if not then wire is bad.

Pins 58 and 59 should show 12volts when key is on, just a pass thru from the 12volts at the injectors.

Cars+PCs=Awesome · May 13, 2016

Speaking from my experience with electronics, and computers, this is sounding like the PCM is either bad, or corrupted. You can check this simply by finding a salvage yard that has one you can borrow, either simply offering partial payment, or if they'll be generous enough to let you borrow it free. Do as was recommended, and check the board for damaged circuitry, or a burning plastic smell to it.

But attempt to double check the fuses... Never hurts.

Andy D · May 13, 2016

Check the fuel line end to end especially in the engine. 23 yr old engine wiring is very tender. Sounds to me something couldn't take being taken apart. Check all your connections? when was the truck last driven?

Splash93 · May 15, 2016

OK, I got the noid light working, I forgot to reconnect the crankshaft position sensor. I pulled the PCM and popped the lid. It looks brand new inside, no sign of damage or wear. I checked all the electrical connections on the PCM and got ground at the appropriate pins and voltage at the injector pins. I also checked the PIP pin and there was a voltage drop.

After reconnecting the CKP sensor, I got the engine to run, but it ran very poorly. It seemed like it had no power. The only way to keep it running was to remove the intake tube from the air cleaner to the manifold and hold the throttle half open. As soon as I release the throttle the engine dies. Moving the throttle while the engine is running does not cause the engine to rev up or down.

I checked the codes from the PCM using the Check engine light and got a 327 = EGR (EVP,PFE,DPFE) circuit below minimum voltage and a 157 = Mass Air Flow (MAF) sensor below minimum voltage.

RonD · May 15, 2016

Good that it started but reads like it has low compression, or spark timing is way far off.

Did rebuild include new timing chain?
Just test one cylinder, should see above 130psi if other spark plugs are in
150+ with no spark plugs in, faster crank speed.

Use a timing light to check spark advance, but that's a long shot, you should see 20+ deg advance at 1,500rpm
The CKP sensor or tone wheel would have to be out of position to change spark timing.

Could be fuel pressure but I would expect good idle and stalling when revved

And double check firing order on coil pack and at spark plugs
3 4
2 6
1 5
front of coil

564 gets me every time
I also reverse 4 or 5 at plugs, or 5 and 6

'93 4.0 OHV won't start after rebuild

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