Crank no Start Article
 

Crank no Start

I see a lot of this complaint on this forum. There are two choices: proper diagnostics, identification and repair or trynostics with the parts cannon. I am not a fan of part swapping so here is a proper diagnostic flow. I offer this complete roadmap so that you have a complete guide to fixing your problem and to give you an appreciation why stabbing at random part changing can be expensive and frustrating. If your starter will crank but the engine will not run, 95% of the reasons are either:

1) Fuel pressure
2) Ignition
3) Fuel injector pulses
4) Timing
5) Security issues
6) ECM/grounds/power/sensors
7) Mechanical problems

Once you confirm that an area is functioning properly then move on to the next section, no need to do all the tests. If however you have say no coil spark then keep going in that section until you find the problem and restore spark. These sections are listed in the order of most likely problems. Feel free to change sections if you have codes or symptoms that give you a more appropriate starting point.


1) Fuel pressure

The first thing to do is a fuel pressure and leak down test as described here:

https://blazerforum.com/forum/2nd-ge...eakdown-88305/

If you fail here it is either:

A) Fuel pump
B) Regulator
C) Fuel lines
D) Fuel filter
E) Leaking injectors or spider
F) Wiring/connectors/fuse/grounds


2) Ignition

A) Test for 1” of strong blue spark at a couple of plugs
B) Inspect Distr cap/rotor/gear play
C) Spark from the coil
D) Power to the coil
E) Power and lo ref to the ICM
F) Ground side switch pulses to the coil
G) Ignition pulses from the ECM to the ICM
H) Sensor input for ignition such as the crank and camshaft sensor (do you show rpm during cranking?)
I) Are the plugs fouled?
J) Check engine and ECM grounds


3) Fuel injectors/pulse control

A) Check for 12V to the pink power wires to the injectors
B) Check for lo side ground switching from the ECM to the injectors by substituting a noid light or test probe with 3W or less bulb for an injector
C) Check for security lockout
D) Do an injector balance test.

Here is a discussion of injector low side control testing:

You Tube

4) Timing

A) Is CMP retard within +/- 2?
B) Are there any distributor issues
C) Distr. gear play
D) Timing chain issues
E) Harmonic balancer shifted


5) Security

Passlock or other security system problems that might be disabling the fuel injectors, fuel pump or ignition. Is there an aftermarket remote start installed or the remnants still attached to the wiring? What is the security light doing?


6) ECM/sensors

A) Key on engine off sensor power/gnd values for TPS, ECT, IAT, MAP, Baro
B) O2 sensor waveforms/function
C) Check all ECM power and grounds
D) Check all ECM connectors and wiring
E) Substitute a known good ECM if available

7) Mechanical problems

A) Compression to confirm
B) Valves/timing
C) Head gasket
D) Excessive back pressure (cat converter, etc)


Here is a good example of some of the overall flow until Eric finds the problem:

You Tube

You Tube

If you need any help with any of these tests start a new thread and we will help you get back on the road.



George

Making it a sticky and closing thread.