2000 zr2 4.3
most days runs and starts fine.but increasingly when t go to start it will fire once and then just roll...wait. 10 minuts then will start fine..any ideas

 

So it always cranks, but sometimes it will not run? Not sure what roll means?

If I have that right then you have to be prepared to catch it when it is cranking but wont run and at least find out if its spark or fuel to start narrowing this down. Fuel pressure gauge ready to connect while cranking and checking for spark at a few plug ends. 1" of strong blue spark with a regular cadence.

In the meantime perform the fuel pressure test in the sticky at the schrader and watch the leak down result. The fuel pump may need repeated cycles to get to operating pressure. Try to do this when it cranks but won't start.


George

 

All thats good think its tje ignition module just wondered if anyone else had the problem

 

This could be caused by many things:

Fuel pump
Fuel pump relay or wiring
Fuel injectors
VCM
ICM
Coil
Distr
Ignition wires
Timing
Crank sensor
Many other sensors
....

but If you suspect the ignition module and want to start there then you would confirm as follows (all during crank no start):

1) No spark from the coil output while cranking but good power to the coil on the pink wire, then

2) No ground control pulses from the ICM to the coil on the wht/blk wire but Good power and ground to the ICM on pink and blk/wht wires

4) Good ignition pulses from the VCM to the ICM on the white wire

If you are unable to diagnose as outlined above then sometimes you can use heat and cold to force the ICM to fail on command. This is not as reliable since the problem is intermittent anyhow. Another approach is to swap with known good parts if you have them on hand at no cost.

OR

You can start the parts cannon but if your guess is wrong then cost and time may start climbing and the vehicle may still be unreliable. In addition you may be replacing superior AC Delco parts that work with inferior after market parts. Let me know if I can help further.


George

 

Theres fire and fuel at first like I said it fires one time acts like its going to start then just rolls over under starter power..and will keep doing that till I let it set for a few minutes. good pressure at the schrader valve..it may do it in the morning first start of the day or may be after driving...may not do it for a week...might do it 2 days in a row verry random and of course when I wanna put on a machine it runs fine...never quits or runs rough when started just on startup...verry frustrating

 

So roll over means that the starter cranks but the engine does not run?

By fire and fuel do you mean spark and proper fuel pressure? Have you checked for proper spark at a couple of plug ends and proper fuel pressure when it cranks but will not start? If the answer is yes you have and the outcome was normal spark and fuel then next up is to check for fuel injector pulses when it cranks but will not start. Let me know if you need help with that. If you have checked spark and fuel when it cranks but won't start and there is no spark then it might be the ignition module as you suggest but it could also be the wires, distributor, coil, power/grounds to the ICM and coil, ignition pulses from the ECM, crank sensor, timing.

If you are willing and able I will help you get your truck fixed but it needs to be properly diagnosed.

George

 

Ok so the blazerlet me down this weekend ..I did change the ignition module and it appeared to fix the problem since ithadnt done it since ...but the gremlin came back....left work...stoped at the store...left the store to the gas station went to leave the pump and boom no start..it acts like it wants to start.. it fires on the first roll and then just keeps rolling over..so since this problem has happened before I just left it set for about 10 min and tried agian....no start..so long story...I left it set with a dead battery went back the next morning and jumped it..got in hit the key and fired right up and ran great sat..sun went to leave and no start again and out of curiosity I sprayed some either in the breather and it took right off..so in thinking fuel so I'm gonna hook up a gauge and see what it does but the problem is so intermittent I can bet ile go to start it and there won't be a problem so short of just driving it till it does it again I don't know.. any ideas...and when it does this there is pressure at the Schrader for fuel..I don't know how much cause I'm never ready for it but it sprays out with some force...I've heard the fuel pressure regulator is an issue on these...excuse me but I'm usually a 318 man you know fuel ..spark ..go...this is my first " gen " vehicle..🤣🤣..so George when I get those pressures I'll let you know...or give me an idea what to look for on that gauge...I've heard of there's a bleed down you should pinch off lines to isolate it

 

Usually when I've sprayed either it would stop after it's burnt up...why would it keep the fuel after that..just a thought

 

As I said, you need to travel ready to diagnose the problem when it cranks but will not start. Does roll mean starter crank but no engine run? I do not suggest using the parts cannon. Sure the ICM could be bad but so could 2 dozen other parts or it could be wiring, connectors, etc. and cost almost nothing to fix properly. If you are unlucky in the order that you guess then you could spend $1K fixing a $50 problem and be at this for weeks. Lets diagnose it properly and then replace or fix the failed part/wire/connector/ switch/sensor/spider/regulator/...... If it runs after a parts replacement with no initial diagnosis given that the problem is intermittent then you have no idea if its fixed yet. This is what happened with your ICM except now you likely have an inferior aftermarket part that replaced an AC Delco oem part that may have been perfectly fine.

I will re-iterate: be ready to check for proper spark (you call it fire), not just some spark, and cranking fuel pressure (min 55 psi) when it cranks but wont start (roll I think is what you call it) and make sure that you have good battery voltage at rest and during the crank. Do fuel pressure first since it sounds like it runs on ether. I have performed hundreds of vehicle repairs in the last 50 years and have not used a can of ether since the 70's. A fuel gauge is $20 or free from the parts store and gives us more information.

If all of this checks out OK then we move on to other things like injectors/crank sensor/security system/etc

George

 

I am not sure what "keep the fuel" means so I can't answer this question.

George