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K5 wont start

sandawgk5

sandawgk5

3/4 ton status
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Oct 28, 2003
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Kitsap County PACNORWEST
I go out to back the K5 out of the Garage cause my bath tub came in and I have to pick it up. I get in turn the key dash does normal all lights buzzers etc. Go to start and all it will do is turn over. Oil pressure comes up when I crank it fuel pump relay is shifting but I have no fuel to the throttle body. It makes me think my fuel pump is dead but I do not want to default to that. Does anyone know if there is a fuse for the fuel pump and where it is I could not find one in the fuse block, but the wiring diagram says it is fused. Also does anyone have any possible ideas of why I would not be getting fuel to the throttle body. Any help would be greatly appreciated. Thanks.
 
It is possible a pickup or ign module failed and on some ECMs that will stop the fuel pump from working and or injector.

You can jump the fuel pump and see if it works.

Do you hear the fuel pump running? You can have a clogged fuel filter or the pulsator inside the tank is loose.
 
I only here the relay clicking under the hood I do not here the pump. It is in the tank so I dont think I could here it I dont recall. If it is a clogged fuel filter it is completely clogged cause the injectors did not drip or anything. How do I check the injectors to see if they are cycling or not will using a multimeter on the terminal damage anything?
 
if you have a high impendence(sp) multimeter which means it has a lot of internal resistance.

You can put it on the two injector wires on top. And see the voltage changing when the injector is turning on and off. (with the vehicle being cranked)

Or you can put the positive wire on the hot wire going to the injector and put the black multimeter wire to chassis ground. And see if the injector is getting power.

The injector works by the computer using a transistor and at the right moment allows the injector to have a ground. Which makes it turn on.


On gm vehicles, if the oil pressure is high enough, the fuel pump will turn on automaticly if the relay fails. But you do hear the relay, and you can possibly rule out the relay.

What you can do is go underneath. Remove the connection before the fuel filter and see if it is putting fuel out. Do this quick because its gonna shoot a lot of gas. Also take a multimeter and backprobe the connections on the fuel pump.

Take the pos meter wire put it on the hot wire on the fuel pump. and put the black cable to ground. See if your getting battery voltage. You will have to do this with someone turning the key to see if it has power. Try it again by putting the black wire to the pump ground. Just to see if the ground is good.
 
Thanks I will have to try this in the AM as I do not have a light in my POS Garage. Damn Condos. If there is no power do you know if it is fused or does it have a fusible link and if so where would it be located. I really hope it is not the fuel pump. If it is I think I will replace with a high pressure high flow cause I intend to convert to MPFI later on.
 
i dont have a wiring diagram in front of me. Hopefully someone can help with that.

Look in your owners manual, and sometimes it will say what fuse position.

You can take your meter and see if that fuse is getting power. Then that would rule out if a fuse link went bad. Or if you had anything on that circuit, it wouldnt be getting any power.


But see if you can get a friend to help crank the engine over while you use your meter.

I dont know what year GM switched fuel filters. But you might need a flare wrench to remove the feed line going to the filter. If it is heavly corroded, i wouldn't touch it. Or have your buddy crank the engine over, while you put your ear near the fuel tank to hear for a wine.

First step is to check the fuse. Then either try removing the fuel line or testing the pump with a meter. What ever seems easier.
 
ECMB is the fuel pump fuse, does the fuel pump run when you turn the key? It should run for a few secs to pressurize the system. You can run a wire from the pos batt terminal, to a little connector hanging off one of the solenoids on the firewall. IIRC, it is a red wire w/ a spade connector on the end. That should force your fuel pump to run, bypassing the fuse box, will tell you if the pump is running.

If the fuse is good & the pump is good, the temp sending unit in the manifold may have crapped out, had one go bad on my 350, kept injectors from firing.
 
Sorry I have been busy at work getting ready to go on leave. I tried the fuel pump and it is running. I pulled the fuel filter and it was clear and fuel in it was clean. I forgot I have the GM Service Manual for fuel and emissions systems which have troubleshooting flow charts for almost every system and situation. I did not know however that the temp sensor had input to the injectors. I will have to test that one. I have a few more steps to go on the flow chart but I dont have an injector tester and it is hard to get the wife to help me ( dont want to get dirty, plus shes busy doing homework all the time). I am afraid that it is the ECM that went tits up, but I dont want to jump to that. It is definately wierd fuel all the way to the TB but not even a drip into the butterflies? I also learned that Washington is not letting me renew my plates so smog station here I come gotta keep fingers crossed. Should not have problems I just get nervous and now this fuel issue makes me worry even more. When I get back from Vegas I will post up with what I find. How do I check the temp sensor.
 
If you are looking to see if the injector is firing when the engine is cranking, you can make a tester quite easily.

Take one of the gauge bulbs (any 12V will work, these just have wires on them already) and bend both wires on it down. Strip the insulation from both ends of two lengths of wire. Wrap one end of each wire around the wire on the bulb, then tape it up, whatever you want to keep the bulb wires from breaking, and you are done.

Pop the injector connector off, plug each wire into the connector, one for each "terminal". (make sure they don't touch each other of course) The nice thing about the light is that you can crank it yourself and see if the injector is being commanded to fire.

Isn't the fuel injector pulse one of the "crank no run" flowchart tests?

ECM temp sensor is easiest to check with a scanner. Cold engine temp should be near ambient air temp, warm engine temp should be near rated thermostat temp. Is this even one of the items mentioned for a crank no run condition?
 
Yes the injector test is in the crank no run flow chart. I scanned and no codes are loaded into the ecm only blinks 12. I do not have a real time "scanner". Trying to convince the wife to buy me one that will do both obd-1 and 2. I will have to check again but I do not recall seeing anything about the temp sensor in the crank no run flow chart.
 
I just checked the temp sensor and by using resistance temp is about 73 which was close to air temp. I checked the TPS volatage also and it is correct and also tracks as it is supposed to. I checked injector firing and they are not getting a signal to fire I have voltage on one side of connector and open of the other lead of the connector. When the ignition is "ON" I have voltage to the connector on the ECM but for some reason the ecm is not telling the diode to ground and fire the injector. The flow chart said to replace the ECM so I did and yet it did not fix the problem. Now I am out 80 bucks and the POS still wont run. Please some body help me. Changing to carb is out of the question cause I live in the Communist state of Kalifornia.
 
Well one of the first tests is to use a scanner to watch and see if the ECM is seeing the distributor reference pulses (RPM) as the engine cranks.

If its not seeing that (manual not in front of me) I *think* the culprit is supposed to be the ignition module. If you've got the flow chart, you should be able to trace that.

If you can't test every part as written in the flow chart, you can't trust it to point you in the right direction. I know checking the ECM for cranking RPM was a test, definitely before replacing ECM.

The only time my troubleshooting test showed bad ECM, I started over at the top and realized I had tested one wrong wire, which skewed me in the wrong direction.
 
Thanks is there any way to test the ignition module other than a scan tool. Will checking the plugs for spark tell me if the ignition module is bad? Just to be sure that is the piece in the distributor that the coil and ecm plug into correct.
 
Thanks Dorian I had an extra ignition module in my spare parts I replaced it and it fired right up. I guess I learned an $80 lesson. Thanks again to all who helped with ideas.
 
Glad it's working. Just as a future reference for you, I believe that a module test has been posted. I've heard that some stores are able to test them too.
 
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