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Old 09-25-2015, 08:12 AM
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Join Date: Dec 2011
Posts: 423

when the car loses injector pulse, spark is still present...correct?

here are 2 possible fixes from identifix for no injector pulse

1. Check the Throttle Position (TP) sensor input voltage on the Light Green/White (LG/W) wire at the TP sensor. The closed throttle voltage should indicate about 0.5 volts.

2. If the TP sensor voltage is high, disconnect it and check for the engine to start. If the engine starts, replace the TP sensor.

3. If the TP sensor checks to be OK, check the Black/Red (BK/R) wire at PCM pin 3B to verify it indicates battery voltage as the engine is cranking.
1. Unplug the mass air flow sensor and see if then there is injector pulse if there is look for a shorted mass air flow sensor.

2. Check the Engine Control Module (ECM) powers and ground. If there are any questionable powers or grounds, add redundant ground wires and recheck. Also check the main relays on the firewall that supply power to the ECM.

3. Check for a tachometer signal on the Yellow/Blue wire in the large ECM connector. If the ECM has good power and ground and a good tachometer reference signal, it should have injector pulse.
Old 09-26-2015, 01:22 PM
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Join Date: Sep 2015
Posts: 9

Yes, the sparkplugs are always getting spark, but, now, I'm not sure the injectors are shutting down! I followed your instructions:

1. I checked the Throttle Position (TP) sensor input voltage on the Light Green/White (LG/W) wire at the TP sensor with the closed throttle and the voltage was 0.54 volts.

2. Because I got the approximate reading we were expecting, I did not disconnect the TP sensor.

3. I checked the Black/Red (BK/R) wire at PCM pin 3B and verified voltage (approx. 9 volts) as the engine was cranking.

Here's the 'kicker':
1. I unplugged the vane air flow meter and listened to the injectors with a stethoscope and monitored my timing light which was on a spark plug wire. The injectors didn't sound like they had shut off; in fact, I could hear a hissing sound in each of the injectors after the engine died, as though they were still spraying fuel into the engine until the ignition was turned off. I had replaced the vane air flow meter with a used one a few months ago, thinking the one I had was bad, but no change.

I, then, plugged the vane air flow meter back in, with exactly the same results: injectors clicking and hissing after the engine had died, while the spark plugs were receiving spark the whole time. Now, I am confused!

2. I checked the Engine Control Module (ECM) powers and ground and they seem to be ok. I also checked the main relays on the firewall that supply power to the ECM and they are supplying power. In fact, early in the process, I replaced them just to be sure they weren't weak and causing a problem.

3. The tachometer is working for the short time the engine is running and the engine is receiving spark, so I'm assuming, according to the wiring diagram, that the Yellow/Blue wire in the large ECM connector wire has a pulsing electrical current.

I think we may be getting closer to finding the problem. If we have spark and fuel all we're missing is the air, right?

Last edited by Gene C; 09-26-2015 at 01:26 PM.
Old 09-26-2015, 03:13 PM
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Join Date: Jun 2010
Posts: 9,140

To confirm that the injectors are being kept open you might pull one of the plugs off any one of the injectors and determine which wire is constant with power then the other should be the ground supplied by the ECM when the injectors are to be fired. If the ground from the ECM is holding the injectors open you should be able to confirm it with your meter + lead connected to the positive battery post and your ground lead connected to the injector grounded wire coming from the ECM. 9 volts is really not enough to permit everything to function . Either the battery is weak or something is pulling that voltage down. I think Use common sense offered a good suggestion on confirming you do have the correct fuel pressure. Just a thought, they won't inject fuel if getting air ! Did you install all the timing components from your engine or are you using the parts from the installed engine. Will the engine continue to run if you sprayed carb cleaner into the intake? If so, possible fuel delivery problem.
Old 09-27-2015, 06:23 PM
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Posts: 9

In answer to 'Use Common Sense, I did replace the fuel pump and I verified the fuel pressure in the rail, again today, and it meets specifications: 30-40psi.
Primem, I will double check the 9 volt reading I got in the Black/Red (BK/R) wire at PCM pin 3B. I see that, according to the schematics, I should be reading closer to 12 volts.
Hanky, I followed your instructions to see if the PCM is supplying ground to the injectors after the engine dies (leaving the ignition in the on position). The PCM is NOT grounding the injectors, so the "hissing" sound I'm hearing must be fuel leaving the fuel rail through the pressure regulator. The fuel pressure does not hold after the engine dies; it loses all pressure in the rail within a minute. In answer to your questions: The engine was a complete engine, except for the distributor and other ignition components. I've replaced all ignition components, including the distributor which includes the crankshaft positioning sensor, etc. Also, when we checked a few months ago, the engine would continues to run when we sprayed ether into the intake.. haven't tried carb cleaner, but I'm sure we would get the same result.

Last edited by Gene C; 09-27-2015 at 06:46 PM.
Old 09-28-2015, 03:51 AM
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Join Date: Jan 2007
Location: Yorkshire, NY
Posts: 2,167

I just read this in your last post "Also, when we checked a few months ago, the engine would continues to run when we sprayed ether into the intake".

I may be barking up a tree, but here's something that happened to me with my 1988 Ranger (short version). Was driving down the road and the engine just died. Got it home and started what I call "Chasing Ducks". Engine would fire and die immediately, but would run if I fed it a fuel source thru the intake. After a few days of banging my head against the wall, I started chasing grounds. Found that the small ground lead disconnected from the battery (Ford used fuse like twist locks back then). This ground lead went to a junction splice that fed 5 other grounds. 1 of the grounds went to the ECU for the injectors. The loss of this ground was causing the injectors NOT to fire. As soon as I reconnected the ground, the engine fired right up.

Might want to verify all grounds are connected and have good contact.
Old 09-28-2015, 05:19 PM
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Posts: 9

'Use Common Sense', I will take your advice. I do feel like I'm "chasing ducks"!
I really believe you're on the right track because so many have told me to check the ground wires.
All those I've checked have been good, but I never thought of following the ground battery cable.
I'll keep everyone on this 'thread' informed.
Old 09-28-2015, 05:57 PM
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Join Date: Jun 2010
Posts: 9,140

Gene if you try the test I suggested in the earlier post you can verify if the injectors are getting the ground to fire.
There is something going on that is causing the fuel pressure to drop so quickly after shutting down the engine. If the press reg is defective that should be corrected first.
I hesitate to suggest the use of ether/starting fluid because I have seen it take off the tops of pistons and even blow holes in them. I suggest carb cleaner because it is similar to gasoline. Have you pulled one of the plugs to see if it is wet or dry? It could provide a clue to which direction you might pursue. You have a lot of people watching your progress and waiting to see what you finally found as the problem. We all will learn something from this.
Old 09-28-2015, 08:04 PM
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Join Date: Jun 2010
Posts: 9,140

Does the fuel pump still continue to run when you stop cranking the engine as you stated in an earlier post? If it does we need to look into that further.
Old 10-03-2015, 08:36 AM
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To recap:
1) The fuel pump does not begin running until the ignition switch is in the start position and continues to run in the 'on' position after the engine quits running.
2) I found that the reason the fuel pressure was dropping after the engine stopped was because a fitting on my pressure gauge was leaking. With the leak fixed the fuel pressure holds after the engine stops.
3) Several months ago, I replaced the fuel pressure regulator.
4) All ground wires check out.
5) No voltage in the Black/Red (BK/R) wire at PCM pin 3B while starting the engine. I ran a wire from the ignition to the PCM Bk/R wire (to supply battery voltage on 'start') but no change.
6) I found that the fuel pump switch in the 'used replacement' vane air flow meter was not working, so I've reinstalled the original vane air flow meter.
7) I just now replaced the ignition switch with no change.
8) The injectors are getting ground to fire.
9) I lost spark to engine for a short while, again, but it's back now. That's happened once before. For some unknown reason the engine turns over but I lose spark. Then as quick as I lost the spark it returns and the engine runs for about a second and dies.

I am going to go back over step by step instructions in all of your previous replies to see if I might have missed something.

Last edited by Gene C; 10-13-2015 at 09:07 PM. Reason: Found defective replacement part, installed ignition switch and performed more tests.
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