'87 TBI No Start.....HELP

[hotrod1442]

Does anyone have a "flow chart" to walk me through troubleshooting a "no start" condition with my '87 1500 w/TBI 5.7?
I have spark, but I'm not getting fuel @ the injectors. I cracked both fuel lines located @ back of the throttle body, and there was no fuel. I replaced the ignition module, thinking that I might not be getting the reference signal to the ECM, still no fuel.
When I turn the key to the run position, I can hear the fuel pump relay click. Should I be able to hear either of the fuel pumps (truck has dual tanks) running at this point? (I don't hear anything)
I should also mention that the truck was running poorly before the "no start" condition began. Sounded like it had an ignition miss.
I just finished changing the plugs, ohm checking the wires, and inspecting the cap and rotor, and was in the process of adjusting the ignition timing, when it suddenly just quit.
I didn't have a chance to check codes.....but the "check engine" light was on. Now, strangely, the CEL does not come on when the key is turned on, or cranked over.
Anyhow......does anyone have a flow chart to help with troubleshooting my problem.

Thanks, Dave Moon

 

[towjoe]

You should be able to hear the pumps run. I know on my fuel injected trucks I can. You check for power through relay?

Jims86 hopefully will stop in after awhile. He's real sharp on the fuel injected trucks

 

[Jims86]

hey there!
So, you were setting the timing, and thebtruck quit, then you walked around to re start, and the check engine light was on, you tried to start it, then the light went out and never came on again?
One thing you can try for now, is check the diagnostic circuit.
You mentioned that you know how to pull codes, so down on the diagnostic plug, see if you have anything occupying port D.
Lets hope you have it.
If so, using a 12v test light, or multimeter, probe pin D with the ground side, and connect the hot to a shunt in the upper region odf the fuse panel, or the center of the cig lighter plug, and turn the key to the on position, where you would normally see the light on the dash, and see if you get a reading.
If no pin D, we will have to get behind the glove box, and pull the computer out and do some direct testing. we will deal with the fuel system testing after we determin if the ecm is fried or not for now.

 

[hotrod1442]

hey there!
So, you were setting the timing, and thebtruck quit, then you walked around to re start, and the check engine light was on, you tried to start it, then the light went out and never came on again?
One thing you can try for now, is check the diagnostic circuit.
You mentioned that you know how to pull codes, so down on the diagnostic plug, see if you have anything occupying port D.
Lets hope you have it.
If so, using a 12v test light, or multimeter, probe pin D with the ground side, and connect the hot to a shunt in the upper region odf the fuse panel, or the center of the cig lighter plug, and turn the key to the on position, where you would normally see the light on the dash, and see if you get a reading.
If no pin D, we will have to get behind the glove box, and pull the computer out and do some direct testing. we will deal with the fuel system testing after we determin if the ecm is fried or not for now.

JIMS86,
No, unfortunately I have nothing going to terminal "D" on my diagnostic plug.

I have the ECM out from behind the glove box ready for troubleshooting. All that I've checked so far is the output from the ECM to the fuel pump relay (pin A1)......I'm only getting an output of 4V for aprox. 2 seconds after the ignition is turned to the "run" position.

I should mention that I picked up a used ECM from the wrecking yard, that is suppose to have tested OK.........if mine proves to be "gibbled"

Thanks, Dave

 

[Jims86]

JIMS86,
No, unfortunately I have nothing going to terminal "D" on my diagnostic plug.

I have the ECM out from behind the glove box ready for troubleshooting. All that I've checked so far is the output from the ECM to the fuel pump relay (pin A1)......I'm only getting an output of 4V for aprox. 2 seconds after the ignition is turned to the "run" position.

I should mention that I picked up a used ECM from the wrecking yard, that is suppose to have tested OK.........if mine proves to be "gibbled"

Thanks, Dave

well, just go ahead and stick that other ecm in, and see if you get the check engine light back. Be sure the chip codes match, or you will have to swap them.
You can also use this diagram and find pin A5 in place of cavity D, and do the same key on test.

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[hotrod1442]

Jim,
-Do I need to be concerned about any possible bad sensors/inputs to the ECM harming the replacement ECM?
-If I'm reading this right, I should have 0 volts @ pin A5 w/key switch "ON"?

Thanks, Dave

 

[Jims86]

Jim,
-Do I need to be concerned about any possible bad sensors/inputs to the ECM harming the replacement ECM?
-If I'm reading this right, I should have 0 volts @ pin A5 w/key switch "ON"?

Thanks, Dave

We're not testing a5 for voltage, you want to use a5 for the ground side of whatever test equipment you are using which will be connected to a constant 12v source. you want to do this with the ecm plugged in, so go from the side of the plugs that the wires are going into with the probe, which will make contact with the pin its self.
A test light is best, or an analog volt meter. You can use a Digital volt meter, but it will only show that the circuit is working, you can pull codes with the light, or analog meter.
If you see power on the meter with the key on while the ground is on a5, and pos. to 12v, the ecm is good, and its trying to activate the check engine light.
Before doing all of the above though, check all the fuses...gauge/idle, ECM, ECM B are the important ones. A bad sensor wont toast an ecm, but if you find any of those fuses blown, you will want to investigate the wires coming from the sensors, and around the wire harness to make sure nothing is broken or chaffing
You can still get spark with a bad ecm, because the ignition module is powered from a branch off of the coil, which is getting its power from the ignition switch.

 

[hotrod1442]

Jim,
First off, let me say thanks, I REALLY appreciate you taking the time to help walk me through this issue. I like to be as self sufficient as possible (fixing my own stuff, as opposed to farming the job out) but I'm a little challenged when it comes to electrical systems troubleshooting, so again thanks for your help!

So to continue on, I;
-re-checked all the fuses in fuse block (pulled out, ohm tested, & visually inspected "Gauge/Idle", "ECM", & "ECM B" fuses) all were good.
-checked A5 as you indicated, and got confirmation that CEL output is OK.....so I need to check bulb/wiring to CEL
-checked for any stored codes....just got the 12. I did however have the ECM unplug @ some points during my troubleshooting, would this have cleared any existing codes?

Thanks, Dave

 

[89Suburban]

Yes, that would have cleared the codes. Subscribed.

 

[Jims86]

Jim,
First off, let me say thanks, I REALLY appreciate you taking the time to help walk me through this issue. I like to be as self sufficient as possible (fixing my own stuff, as opposed to farming the job out) but I'm a little challenged when it comes to electrical systems troubleshooting, so again thanks for your help!

So to continue on, I;
-re-checked all the fuses in fuse block (pulled out, ohm tested, & visually inspected "Gauge/Idle", "ECM", & "ECM B" fuses) all were good.
-checked A5 as you indicated, and got confirmation that CEL output is OK.....so I need to check bulb/wiring to CEL
-checked for any stored codes....just got the 12. I did however have the ECM unplug @ some points during my troubleshooting, would this have cleared any existing codes?

Thanks, Dave

Your welcome!
As 89s said, yes. disconnecting the battery will clear codes, but thats ok, we need to get the truck running again, which we can do, regardless of any kind. of sensor fault.
Should check the bulb in the dash....but you can do that later, we know that circuit is working.

Here we go with the fuel issue...
Make sure there is fuel in the tank(s)... It happens!

Locate the red wire hanging off the bottom of the fuel pump relay(it may have a grey plug on it) and use a piece of wire long enough to reach from the battery positive terminal to the red wire, use a clothes pin or alligator clip to hold the wire onto the batt terminal, and a piece of tape to hold it into the red wire.
then go pull the filler cap(s) off, and hopefully its quiet. listen down the filler tube(s) and hopefully you hear the pumps.
Make sure you cycle the tank selector switch if you have dual tanks to listen for both pumps.
Let us know what you find, and we will go from there.

 

[hotrod1442]

Jim,
Today, I was trying to use logic, and some of the wiring schematics that I got online, to try a couple of checks/tests ....I checked, as you indicated, to see if I could start either of the pumps using the red wire coming off the Fuel Pump relay.....neither started.

I also checked the Tan w/White stripe wire coming off the relay for voltage......I got 12V for about 1 sec. after key was turned to "run" position.

I then decided to get under the truck and check to see if I could start the pumps by applying 12V to each @ the weatherpak connector on each side. I made a bit of a mistake in testing.........I didn't have a diagram indicating what color wire was what, so after looking at both sides (one side was a pink w/blk & a gray, the other was a pink w/white & a tan) I assumed incorrectly that the pink w/striped wires on each side would be the pump + leads.......I have since come to find that I applyed 12V to the sending units on each side hopefully this didn't take them out! Anyway, when I retested the correct GREY wire on the pass. side, the pump started. When I moved over to test the drivers side it got a little confusing........the weatherpak connector on the drivers side has a pink w/white stripe & a tan on one side of the connector, but coming out the other side is only the pink w/white stripe, the tan is terminated???? I couldn't see the top side of the tank, and it was getting dark out so I packed it in for the night.
What is the procedure for troubleshooting the Fuel Tank Selection Valve?

Thanks, Dave

 

[Jims86]

Jim,
Today, I was trying to use logic, and some of the wiring schematics that I got online, to try a couple of checks/tests ....I checked, as you indicated, to see if I could start either of the pumps using the red wire coming off the Fuel Pump relay.....neither started.

I also checked the Tan w/White stripe wire coming off the relay for voltage......I got 12V for about 1 sec. after key was turned to "run" position.

I then decided to get under the truck and check to see if I could start the pumps by applying 12V to each @ the weatherpak connector on each side. I made a bit of a mistake in testing.........I didn't have a diagram indicating what color wire was what, so after looking at both sides (one side was a pink w/blk & a gray, the other was a pink w/white & a tan) I assumed incorrectly that the pink w/striped wires on each side would be the pump + leads.......I have since come to find that I applyed 12V to the sending units on each side hopefully this didn't take them out! Anyway, when I retested the correct GREY wire on the pass. side, the pump started. When I moved over to test the drivers side it got a little confusing........the weatherpak connector on the drivers side has a pink w/white stripe & a tan on one side of the connector, but coming out the other side is only the pink w/white stripe, the tan is terminated???? I couldn't see the top side of the tank, and it was getting dark out so I packed it in for the night.
What is the procedure for troubleshooting the Fuel Tank Selection Valve?

Thanks, Dave

Gray wire is for the right pump, tan wire is for the left pump.
Energize the red wire at the relay again.
Pull the selector and look for the tan/white wire from the relay, check it for power, and then select the pump wire to test, and see if you get power to either of them.
That tan wire shouldnt be terminated, per the diagram.

You must be registered for see images attach

 

[hotrod1442]

Jim, I can't seem to enlarge that schematic......I'm having a hard time trying to make it out.......eye sight isn't as good as it could be

Dave

 

[Jims86]

i cant make it bigger....anyone else able to?

 

[hotrod1442]

OK, I energized the red wire @ relay. I've got 12V @ the tan w/white stripe wire @ selector switch, but no voltage @ either fuel pump wires (tan or gray)
Figured the switch must be bad, so I check continuity between blk to gray, and tan to tan w/stripe with switch toggled to feed left pump. Then checked blk. to tan, and gray to tan w/stripe with switch toggled to feed right tank...switch seemed to check OK.

I figured the next thing to try would be to use jumper wires to replace the switch......so I jumped tan w/stripe to tan, and black to gray.......I was surprised to see no voltage @ tan wire.....jumped it to the opposite way, and had no voltage @ gray wire. Just for the hell of it, I removed the jumpers and verified that I still had 12V @ tan w/stripe wire. I found that as soon as I connected tan w/stripe to tan, voltage @ tan w/stripe was lost???

I'm a little confused by this....what am I missing/doing wrong?

Dave