Hi thanks for the reply.

1. When the truck is not starting, with the key on verify that you have power on 1 wire at each injector.


2. Next plug the injectors back in and on the back of the distributor disconnect the 4 pin connector. Install the test light to POSITIVE on the battery and then on the disconnected wiring harness, on the PURPLE/WHITE WIRE touch the test light on that terminal momentarily. Each time you pull off and then touch that terminal you should get a spray of fuel out of the injectors.


3. If you do then with your mileage I would replace the distributor. Make sure it includes a new pickup coil and ignition module. What happens is the module goes bad internally and does not pass on the pulses to the ECM or engine computer to fire the injectors, but it still has spark.

Hi thanks for the reply,

First thing, at this point I am trying to get enough information to give you an accurate diagnosis, so be patient with me as I only know about the problem what you have told me and what information we have gathered so far, so resisting the question will more than likely give you a longer wait time as technicians see you have already been helped and will leave the question alone.

The next step is hook the distributor back up and then hook your test light again up to power and then on the wire that does not have power on one of the injectors touch that terminal while cranking it over and see if the test light lights up while cranking it, it should pulse.

If you need clarification or have additional questions just post back here.

If you would rather work with a different tech let me know and I will open the question back up.

Thanks, Aran

If there is NOT a pulse, disconnect the 4 pin distributor connector and use another jumper from battery positive and touch the PURPLE/WHITE WIRE and see if it flashes the test light.

If the test light flashes then, you still need a distributor.

I recommend a whole distributor as even if you replace just the module, the pickup can go bad and also the bushings wear inside, it is just better to replace the whole thing.

Thanks again for your information, help and patience.

Regards, Aran

Thanks for the reply, I added another post in between our last conversation, did you try the powered test light on to the non powered wire of the injector, key on and then touch the purple/white wire with another powered test light and see if the test light on the injector flashes with each wire touch.

If there is NOT a pulse, disconnect the 4 pin distributor connector and use another jumper from battery positive and touch the PURPLE/WHITE WIRE and see if it flashes the test light.

If the test light flashes then, you still need a distributor. It makes sense the fuel pump relay is triggering with the purple/white wire touching as this is the pulse input to the ecm for engine rpm, so it will turn on the pump once it sees this signal, so I believe we are on the right track, I just want to verify the pulse at the injector.

I recommend a whole distributor as even if you replace just the module, the pickup can go bad and also the bushings wear inside, it is just better to replace the whole thing.

Thanks again for your information, help and patience.

Do you need any clarification?

Regards, Aran

Thanks for the reply let me try this and see if this makes a little more sense.

Power up the test light and place it either on the BLUE or the GREEN wire at one of the injectors, it will NOT LIGHT at this time.

Then take a jumper wire from the POSITIVE at the battery, KEY ON, and disconnect the 4 pin connector at the distributor. Momentarily touch the PURPLE/WHITE wire with the jumper wire, each time you touch the PURPLE/WHITE wire, the test light should light.

Is this clear enough?

Is this the test you did?

Thanks, Aran

Wow that is weird, because we know the ECM is getting the signal because it turns the fuel pump relay on as you stated.

So now we have to decide why is the injectors not being fired. There is a tool called a noid light, it may be a better test tool for our injector. They have them at any local parts house, here is a picture of them.

They make specific ones for GM throttle body injections. It is possible that the test light is not being powered on long enough to flash the test light, where as a noid light is very sensitive to electricity.

So as it stands, based on the information we have, we know the ECM is seeing you touch the PURPLE/WHITE wire as the fuel pump relay is triggered. This should also trigger the injector with each tap also. So either the test light is not the right tool to use and we need to try a noid light with the PURPLE/WHITE wire tap or we are going to have to start chasing wiring from the ECM.

Having said that I have never had to find bad wiring from the ECM to the injectors, so my hunch is still the distributor.

Let me know how I can help.

Thanks, Aran

Great, keep me posted.

I know you replaced the cap and rotor, so make sure the new distributor has the module and pickup at least with it.

Thanks, Aran

Hi there thanks for the reply, when we initially spoke you mentioned there being plenty of fuel at the throttle body so that is why I went the direction of the distributor.

So at this point we need to determine what we are missing, either injector pulse from the ECM at the injectors or no fuel delivered from the fuel pump.

1. Honestly these engines will run with very little fuel pressure, if you pour some gas in the throttle body, will it run for a bit?
2. One other thing to check is make sure the injectors keep power on them with truck cranking over, to make sure we are not losing power to the injectors.
3. The spec is 9-13 psi on the fuel pressure.

Hi Doug, thanks for the reply.

I just want to make sure I am completely accurate on what information you have just given me.

When the truck is NOT starting, the injectors ARE spraying fuel?

When the truck is NOT starting, the truck has spark both at the coil and at least one plug?

If you pour gas down the throttle body when it is NOT starting, it will start?

Thanks for staying with me, I am sure we can figure this out.

Thanks, Aran

Hi Doug, thanks for the additional input.

So I assume these tests were done when the truck was not starting is that correct?

If you had spark at #1 then we know the coil is putting out so that is ok.

So to recap, basically if I understand you correctly, when the truck is NOT running you still have spark and fuel is this correct?

I thought before when it was not running we had NO fuel coming out of injectors?

When the truck does run does it run good?

Does the check engine light ever come on when its running?

I will let another tech look this post over tomorrow to see if he has any ideas and then just post back what you find in the morning.

Thanks, Aran40851.0500540509

Thanks for the reply, lets see what the computer is seeing, if the check engine light is on, that means there is a code stored.

CLICK HERE for the procedure to extract codes, I usually use a small paper clip broken in half.

Let me know.

Thanks, Aran

Yes on those just disconnect the battery and that will clear the codes and then after it stalls just leave the on and then jump the terminals and the ses light will flash the codes.

Thanks, Aran

Hi Doug, that code is for the engine coolant temperature sensor. It is over by the thermostat housing. I usually tug on the wires coming directly out of the connector to see if any feel like an elastic, if it does the wire is broken inside of the insulation.

Also disconnect the connector and make sure the terminals in the connector are not spread open so as to not contact the male pins in the sensor itself.

If all that looks ok, it probably is a bad sensor.

Also There should be some grounds on the thermostat housing if I am correct, test all the black wires there and make sure the bolt and nut are tight.

After it died and did not restart did it still have spark and fuel coming out of the injectors when you cranked it over, or what did you find?

I am still just trying to get enough definitive information to give me an accurate direction to go with this.

Thanks, Aran

Wow this has been quite the issue. The only thing that comes to mind is that from all of the cranking the spark plugs could be wet with gasoline and will not fire. You can pull a couple of plugs and see how wet they are, and if they are dripping you need to burn them off with a lighter and then try and start it again.

I apologize that this has been such a pain, usually it is not this bad.

If you do end up taking it to a shop, I would be VERY interested as to what they find.

Thanks for your time and help.

Aran

Glad to hear you got it running, I guess I should have had you verify the install of the new distributor, so for that I guess I too live and learn.

Thanks for being patient.

Aran