Crank no start no rpm 96 5.7

[Thatbluek1500]

I have a 1996 k1500 5.7 I have been experiencing a crank no start situation also no rpms while cranking. since the no start I have replaced the crank sensor and also the distributor and timed it. Before this problem I had another no start changed a lot of parts including ignition coil and ignition control module. Also replaced all plugs and wires along with spyder injectors and fuel regulator. Before that I replaced all the fuel lines and fuel pump. I have checked all the crank sensor wiring and cam sensor wiring all has checked out good I’m at a loss here and I’m looking for some assistance. Any help is appreciated.

 

[Schurkey]

No rpm shown on the scan tool, or no RPM shown on the dash tach?

If scan tool, probable faulty crank sensor, or crank sensor wire harness back to the ECM.

If dash gauge, check all ignition fuses/fusible links. Potential ignition switch failure. Several other possibilities, but check the fuses first.

 

[Thatbluek1500]

I checked fuses, and the crank sensor is new. And I also checked all the wiring for the crank sensor all checked out.

 

[evilunclegrimace]

I checked fuses, and the crank sensor is new. And I also checked all the wiring for the crank sensor all checked out.

New does not always mean good, bad parts slip through the quality control process all the time.
See if you can substitute a known good part from a running truck or install your new part in a running truck and see if the problem persists. Also find some one with a scanner and check the data stream for problems.

 

[Thatbluek1500]

I have a scanner as I am a ford technician, scanner shows no rpms. Scanner also shows no codes no problems

 

[Schurkey]

I have a scanner as I am a ford technician, scanner shows no rpms.

The computer gets it's RPM signal from the crank sensor.

If the sensor, reluctor, wire harness is not at fault...maybe you have a faulty computer.

Consider connecting an oscilloscope to the crank sensor wire harness at the computer end. Look at the sensor signal waveform. Find out if the sensor/harness is transmitting signal that the computer isn't processing, or if the sensor/harness has failed.

There HAS to be an RPM signal that the computer recognizes, or the fuel pump doesn't run after the "prime" cycle completes, and there's no command from the computer to fire the injectors or the ignition coil(s).

OR the scan tool isn't properly communicating to the computer. WHAT scan tool is this? Has it worked on other GM OBD-2 vehicles, particularly GMT400s? OTOH, if the computer was getting an RPM signal and just not displaying on the scan tool, the engine would probably run.

Scanner also shows no codes no problems

So again, I'm wondering about the scan tool compatibility with the vehicle computer.

OTOH, "no RPM signal" is itself a problem.

 

[Schurkey]

I have replaced the crank sensor and also the distributor and timed it.

HOW, exactly, did you "time" the distributor if there's no crank sensor signal? If there's no crank signal, there's no command to fire the coil, so you couldn't have used a timing light (which is of little use on a Vortec anyway.)

If there's no crank signal, there's no way to run the engine to ~1100 RPM to verify that the crank sensor and cam sensor signals are aligned (the right way on a Vortec.)

 

[Thatbluek1500]

I timed it by setting no 1 to tdc for now then once it is running I would fine time it using a scan tool, I was also thinking the computer was at fault considering the snap on scan tool I used I have used in the past for other problems and it would read the data just fine.

 

[Kevmore007]

I am in the same boat with my Yukon. It died while on the freeway. Just like it shut off. I suspected the distributor because it is new Chineseium. I have 50 ish pounds of fuel pressure, new fuel pump. Replaced dist. no difference. New module, new coil. new plugs. No RPM on tach while cranking. Spraying in some ether also does not fire, but it seemed to turn over faster. At this point I am longing for points ignition. At least they were easy to troubleshoot.

 

[Schurkey]

I suspected the distributor because it is new Chineseium. I have 50 ish pounds of fuel pressure, new fuel pump.

50 at prime, or 50 when running? Low 50s is ok when running, not enough during the prime cycle.

Replaced dist. no difference. New module, new coil. new plugs.

Did you ever check for spark? Did you replace these parts before or after you noticed there was no RPM showing?

No RPM on tach while cranking.

Instrument cluster tach? Have you verified ALL the fuses? Assured that the molded-plastic connectors at the module and ignition coil were snapped properly into place--not loose, no bent pins?

Good chance this is a failed crank sensor/reluctor, or crank sensor wire harness. MAYBE a failed ECM, but not likely.

Verify that the computer has no RPM signal with a scan tool.

No RPM signal = no spark, no injector pulses.