Injectors Not Spraying

[fastfredracing]

Originally Posted by E Sully

The ground point for it is the wires connected to the intake runner. Yellow circle in picture, under blower motor. This ground is carried to the chassis through the ground strap on the transmission. The DME supplies 12V to the injector when the engine is running. By switching the ground connection the DME pulses the injectors to deliver the correct amount of fuel.

Behind the pictured ground are three connectors. They are for the speed, reference, and cyl head temp sensors. Did you have these unplugged? Any chance you mixed two of them up? You would not be the first guy this happened to . The speed and ref sensor wires should have markings on them on little tags, make sure they match.

[Srwilliams]

Originally Posted by fastfredracing

Behind the pictured ground are three connectors. They are for the speed, reference, and cyl head temp sensors. Did you have these unplugged? Any chance you mixed two of them up? You would not be the first guy this happened to . The speed and ref sensor wires should have markings on them on little tags, make sure they match.

Fastredracing:

Yep I had them disconnected but I was very meticulous about making sure I did not mix them up. I have always had them tagged when I myself replaced all three sensors a year ago. So, I know they are correct.

P.S> That was the very first thing I checked anyway when I suffered the recent no start

[rusnak]

Originally Posted by bazar01

The above means that all six injectors are fired all at the same time by the DME computer providing the ground path for all 6 injectors provided all 6 injectors have 12V power on one pin of the plug with ignition ON.

To test the injector, you must pull one of the injector plugs, turn ignition ON, (do not start) and probe the pin with a multimeter. One pin should have 12V with ignition switch ON.

If you don't get the 12V power to injector plug to begin with it will not fire even if your DME is good. Then you need to find out why it is not getting 12V to the injector plugs.

But if you have 12V to the injector plug, then you need to test the ground path from the injector plug's other pin. You need to check continuity of the ground wire from the injector plug to the firewall connector and from the firewall connector to the DME.

Good luck.

This is a good post. Also, I would begin to suspect the reference sensor if you fail to get ground pulses and can find no break in the ground wires. Especially if you get 12 v at all of the injectors.

[Srwilliams]

Rusnak:

I know the reference and the the speed sensors are good because I replaced them months ago and never drove the car. But the car was running fine, that is until I decided to dismantle and do powder coating.

Tomorrow I am going to check the injectors and see if I am getting 12 volts like everyone is telling me before I go to the ground aspect. I am still confused on how to check the ground to the injectors, assuming I have 12 volts

[bazar01]

Originally Posted by Srwilliams

Rusnak:

I know the reference and the the speed sensors are good because I replaced them months ago and never drove the car. But the car was running fine, that is until I decided to dismantle and do powder coating.

Tomorrow I am going to check the injectors and see if I am getting 12 volts like everyone is telling me before I go to the ground aspect. I am still confused on how to check the ground to the injectors, assuming I have 12 volts

If you are confused on how to do continuity test on the ground, this diagram might help. It shows the volt meter set up to check presence of 12V with ignition ON and ohm meter set up to check the ground wire from the injector to the ECM with ignition OFF.
If still confused, time to get an automotive electrician help.

[VMAX1]

Lookin at my 87, pull injector connection from injector and it will have a scooped out, half moon, part on one side of the connector. With the scooped out part facing up, the right side should should have 12v+ and the left will be the ground. Take meter, set on volts and put 1 lead in the right side of the injector connector and other lead of meter to a ground, with key, ignition all the way to the right, engine not started. There is a ground on the body behind fuel filter. Try that ground to check for volts. If that works, try the ground on the left intake. To check for ground, set meter to ohms, key off and put one lead in the left side of connector and other to a ground. Use ground behind fuel filter and then the ground on the intake. Provided your ground strap is good from tranny to body. My 87 has 1 ground coming from neg. side of battery to the front fender. Pull the battery and its right there. Ground from battery might be 8 inches long. When I checked the ground, ohms, on injector connection, my meter was around 14k ohms. Hope this helps.

[bazar01]

Originally Posted by VMAX1

Lookin at my 87, pull injector connection from injector and it will have a scooped out, half moon, part on one side of the connector. With the scooped out part facing up, the right side should should have 12v+ and the left will be the ground. Take meter, set on volts and put 1 lead in the right side of the injector connector and other lead of meter to a ground, with key, ignition all the way to the right, engine not started. There is a ground on the body behind fuel filter. Try that ground to check for volts. If that works, try the ground on the left intake. To check for ground, set meter to ohms, key off and put one lead in the left side of connector and other to a ground. Use ground behind fuel filter and then the ground on the intake. Provided your ground strap is good from tranny to body. My 87 has 1 ground coming from neg. side of battery to the front fender. Pull the battery and its right there. Ground from battery might be 8 inches long. When I checked the ground, ohms, on injector connection, my meter was around 14k ohms. Hope this helps.

Good point on the 12V power check.

On the injector plug ground wire, we are looking for zero to 1 ohm to verify good wire continuity from the injector plug to the ECM plug (both plugs removed). If the resistance is very high to infinity, there is a break in the wire or connector somewhere in between.

[Srwilliams]

First I want to sincerely thank everyone for pitching in and trying to assist me, but more importantly thanking all of you for the time you took to educate me on the workings of my car. AGAIN THANK YOU!!!

Well, I took everyone's posts to heart and really studied them before going back out to my car at a local storage unit I am renting. Remember, my initial concerns were that my injectors were not spraying and I did not have 12 volts going to the injectors, although i had plenty of fuel going to the fuel rails. You guys spent a lot of time breaking down in a super elementary fashion ways for me to check if I am getting voltage to the injectors as well as if I am getting proper ground at the injectors. And I mean you guys painstakenly broke things down to the level that even a 11 year old could follow. Well having been properly educated by y'all here is what i found:

1. First, pulled the injector plug as y'all instructed and put a voltage meter on the right prong. Surprisingly, I was getting 12 volts on all of the injectors with car turned on.

2. Went to left prong of each injector and was getting ground signal on each injector with car off.

3. As yall instructed I then moved to test all of my ground points. Found the one behind the fuel filter on the drivers side wall of engine and it was properly grounded, as well as the ground strap on the front of the intake manifold (hope that is what it is called---But trust me I found that strap that you guys posted for me). One poster said on his 87 he had a ground point at the negative side of the battery (8 inches long). On my 87 Carerra, 3.2, I could not find that front ground wire.) Me and a friend mechanic looked all over by the battery---could'nt find.

3. Here is where the problems kick in. Although I was getting 12 volts to the injector, they still were not pulsing. I got noid lights as you guys instructed and I and the mechanic put them on the injectors---no pulsing.

4. Went to check for spark. No spark or fire at the distributor.

5. Checked coil. With engine off, got negative on both wires and postiive on both wires when the engine is on (this may be reversed but you get the idea. Power was going to the coil, as well as ground. But coil was not sending pulse to the distributor to cause arc, fire, or spark (one of them is correct). Everything completely dead at distributor. We pulled a spark plug and put it in the ignition wire that goes either from the coil to the distributor or to the coil and nothing (mechanic did this test so I am ignorant here)

5. Sully sent me a diagram of the readout of the DME. I went to the interior of the car and checked the output of the DME (brain) to the coil (Pins 1&19). The brain was sending out a pulse to the coil as the diagram said it should. HOWEVER, the pulse that is sent by the brain is not being read by the coil and then sent to the distributor (hence no spark).

6. Also, using Sully's diagram I checked the read out of the reference and speed sensors and I was right in the correct readout range.

7. I had Specialized repair my ECU once because it was the board controlling the pulsation of the injectors was malfunctioning. I called them and they asked that i send them back the ECU for them to recheck that board. So, I am feeling pretty good about that being addressed. But what has me stumped is why isn't the pulse being sent out by the brain not being read by the coil and distributed to the distributor to create a spark or fire. there is no fire getting to the plugs. Isn't it interesting that I m not getting a ground pulse in either the injectors or the coil. My voltage side is working well, but everywhere I am supposed to get ground pulse it ain't happening
.

WELL, that is where i am at. I hope you see from the above I took everyone's guidance and instructions to heart and really tried to work my way thru this. So, trust me all of your efforts have been paying off. SO DON"T QUIT ON ME YET!!!!

[rusnak]

the DME sends ground pulses, not 12v pulses. 12v should be there with the key on, as noted by bazar, and vmax. You might try a noid light while cranking since they are very cheap at O'Reily and the like. You can use either an assistant or a remote starter switch to jumper the starter solenoid to kick out the starter gear. The reason to check ground continuity is to eliminate bad connections. I suspect the reference sensor, so you might check continuity there as well. It's time to ohm the reference and speed sensors.

[dshepp806]

I would think that the actual signal from the DME (to fire the injectors) really needs to be looked at with an O-scope.....I like to look at the slopes/waveform to check true firing integrity.

Aside, couldn't your coil (or coil wire) be bad? Or did I miss something? (your mention: """5. Sully sent me a diagram of the readout of the DME. I went to the interior of the car and checked the output of the DME (brain) to the coil (Pins 1&19). The brain was sending out a pulse to the coil as the diagram said it should. HOWEVER, the pulse that is sent by the brain is not being read by the coil and then sent to the distributor (hence no spark). """". I assume that means the coil has no output..


Best to your efforts!

Doyle

[Srwilliams]

Originally Posted by rusnak

the DME sends ground pulses, not 12v pulses. 12v should be there with the key on, as noted by bazar, and vmax. You might try a noid light while cranking since they are very cheap at O'Reily and the like. You can use either an assistant or a remote starter switch to jumper the starter solenoid to kick out the starter gear. The reason to check ground continuity is to eliminate bad connections. I suspect the reference sensor, so you might check continuity there as well. It's time to ohm the reference and speed sensors.

Rusnak:

In my long diatribe and I apologize about that I said we used a noid light after I saw that I had 12 volts to the injectors. the noid light was let me know there was no pulse at the injectors.

Also, when you say it is time to ohm the reference and speed sensors, isn't that what i did when I located the pins at the DME harness and made sure I was within the appropriate readout provided in the charts in this thread. Did I not check the ohms by doing that

[Srwilliams]

Originally Posted by dshepp806

I would think that the actual signal from the DME (to fire the injectors) really needs to be looked at with an O-scope.....I like to look at the slopes/waveform to check true firing integrity.

Aside, couldn't your coil (or coil wire) be bad? Or did I miss something? (your mention: """5. Sully sent me a diagram of the readout of the DME. I went to the interior of the car and checked the output of the DME (brain) to the coil (Pins 1&19). The brain was sending out a pulse to the coil as the diagram said it should. HOWEVER, the pulse that is sent by the brain is not being read by the coil and then sent to the distributor (hence no spark). """". I assume that means the coil has no output..


Best to your efforts!

Doyle

Doyle:

You read correct. the pulse is going to the coil, but there is no output of the pulse from there. There are two wires to the coil. When the car is off they both read negative and when the car is on they both read positive (or vice versa). Doesn't the fact that these wires are reading positive and alternatively negative mean that they are good. What do you mean by a possible bad coil wire---could you direct me?

[dshepp806]

No apologies necc'y there, I would think, in making use of the noid light. Having 12 volts, it's just like you (and Rusnak) stated: it is a ground-fired circuit topology. Ground continuity through each connection (back to the DME) is quite important.

Best,

Doyle

[dshepp806]

Originally Posted by Srwilliams

Doyle:

You read correct. the pulse is going to the coil, but there is no output of the pulse from there. There are two wires to the coil. When the car is off they both read negative and when the car is on they both read positive (or vice versa). Doesn't the fact that these wires are reading positive and alternatively negative mean that they are good. What do you mean by a possible bad coil wire---could you direct me?

I assume by your comment: """""5. Sully sent me a diagram of the readout of the DME. I went to the interior of the car and checked the output of the DME (brain) to the coil (Pins 1&19). The brain was sending out a pulse to the coil as the diagram said it should. HOWEVER, the pulse that is sent by the brain is not being read by the coil and then sent to the distributor (hence no spark).""""" that you mean the coil input signal is seen at the primary, yet the secondary has no output (that is, the coil output signal is not there (AT the coil output, that is). One could test the coil's output (and it's associated cable connection TO the distributor) through simple spark testing of the feed wire to Distributor from the coil. Of course, one has to gauge the spark "qualities" (as to health), but you get the drift, I'm sure.

As well, there exists some resistance measurements/specs within the Bentley that will give you a static resistive read of both primary and secondary coil condition. Of course, sometimes, when heat is expended, things change: still, a good check.

Best!

Doyle

[rusnak]

Originally Posted by Srwilliams

Rusnak:

In my long diatribe and I apologize about that I said we used a noid light after I saw that I had 12 volts to the injectors. the noid light was let me know there was no pulse at the injectors.

Also, when you say it is time to ohm the reference and speed sensors, isn't that what i did when I located the pins at the DME harness and made sure I was within the appropriate readout provided in the charts in this thread. Did I not check the ohms by doing that

Sorry, I missed that. Did you also say that you filed any powercoat off of the DME ground at the intake manifold? You might have a defective DME, but the timing of the failure would suggest not.

[Srwilliams]

"One could test the coil's output (and it's associated cable connection TO the distributor) through simple spark testing of the feed wire to Distributor from the coil. Of course, one has to gauge the spark "qualities" (as to health), but you get the drift, I'm sure."

Doyle:
In my earlier listed points I mentioned that me and the mechanic did the test you reference above.

Rustac:

DId not have to scape powder coat off of the ground point on the intake manifold because there was no coating there. I had good ground there

[bazar01]

Originally Posted by Srwilliams

Doyle:

You read correct. the pulse is going to the coil, but there is no output of the pulse from there. There are two wires to the coil. When the car is off they both read negative and when the car is on they both read positive (or vice versa). Doesn't the fact that these wires are reading positive and alternatively negative mean that they are good. What do you mean by a possible bad coil wire---could you direct me?

Yes there are 2 wires to the ignition coil. First wire is the 12V power feed when ignition is ON. Second wire should also read 12V or less due to voltage drop from primary winding of the coil with ignition ON. When you crank the car, if the ECM is good, you will see the pulse on the second wire as 12V and 0V but your voltmeter may or may not be able to display this change depending on the model of your voltmeter. But a scope or graphing type meter will.

I suspect you have a loose speed or reference sensor connector or might have been accidentally switched when you put the intake back together since both the injectors and spark ignition circuit do not work.

[Srwilliams]

Originally Posted by bazar01

Yes there are 2 wires to the ignition coil. First wire is the 12V power feed when ignition is ON. Second wire should also read 12V or less due to voltage drop from primary winding of the coil with ignition ON. When you crank the car, if the ECM is good, you will see the pulse on the second wire as 12V and 0V but your voltmeter may or may not be able to display this change depending on the model of your voltmeter. But a scope or graphing type meter will.

I suspect you have a loose speed or reference sensor connector or might have been accidentally switched when you put the intake back together since both the injectors and spark ignition circuit do not work.

Bazaar:

You are correct. When I turned the engine on both wires to the coil read 12 volts.

We connected and reconnected the speed and reference sensors and so they are not loose. Also, I switched the sensors around just to make sure I had not crossed them up. But I know that did not happen because I have the ires labeled so as to prevent this. But, your surmise is on point because I too feel this way given that i am not getting a ground pulse both at the the injectors and spark ignition circuit. this is really perplexing me becuase i have pulse going into the coil from the brain

[bazar01]

Originally Posted by Srwilliams

Bazaar:

You are correct. When I turned the engine on both wires to the coil read 12 volts.

We connected and reconnected the speed and reference sensors and so they are not loose. Also, I switched the sensors around just to make sure I had not crossed them up. But I know that did not happen because I have the ires labeled so as to prevent this. But, your surmise is on point because I too feel this way given that i am not getting a ground pulse both at the the injectors and spark ignition circuit. this is really perplexing me becuase i have pulse going into the coil from the brain

You are doing great. Having 12V at the coil and injectors are good. If you label the connectors, I believe you did not get them mixed up.

12V feed to ignition coil comes from the ignition switch if I am not mistaken. You confirmed 12V was present.
12V to injectors are fed from the DME relay. You confirmed this too.
12V to ECM is also fed from DME relay. You need to test if ECM is getting power at terminals 18 and 35. If it is not, DME relay is suspect. Do you have a new DME relay?

[Srwilliams]

Originally Posted by bazar01

You are doing great. Having 12V at the coil and injectors are good. If you label the connectors, I believe you did not get them mixed up.

12V feed to ignition coil comes from the ignition switch if I am not mistaken. You confirmed 12V was present.
12V to injectors are fed from the DME relay. You confirmed this too.
12V to ECM is also fed from DME relay. You need to test if ECM is getting power at terminals 18 and 35. If it is not, DME relay is suspect. Do you have a new DME relay?

Bazaar:

You know I never checked the DME relay because since the car was running great before I powder coated I assume that the DME relay was good. But I am a little confused. I thought the relay next to the DME (brain) was the fuel relay and if it was no good your fuel pump would not have power to work. Since my fuel pump is powered and spraying its butt off I assumed that the relay was good. If that relay was not good my fuel pump would not engage, correct? Could that DME relay prevent the spark that I am missing. Here, I am trying to educate myself