I have a 1991 Cavalier with the 3.1 V6. The Car ran well then one day it just quit. It has spark, injector pulse, and 45 psi fuel pressure. We checked the timing chain and gears and it all lines up and looks good. We changed the crank position sensor and the computer. We changed the coil pack. It will not start, burp or even backfire. Just turns over without starting. I thought maybe the camshaft had broke so I removed the valve covers. The valves all open and close like they should when you crank it.

Any Ideas??

My guess youre timing chain has broke.

The timing chain looks good and when we removed the valve covers the valves and rockers open and close when the motor is turned. This indicates the camshaft and timing gears are working properly'

Ah ha u did not replace the prom did you?If u did not that may be the culprit.IF u have 12 volts at each injector that would lead me to believe ur prom is the problem even tho u change the ecm.Unless ur connections at the coil packs has crimp or bad connection to prevent the proper voltage the car should have started.Replace ur prom,thats my recomm based on previous knowledge and info I have learned thru other sources.Ok

Thanks for the reply. What do you mean when you say "prom"?

Ok here's alot of info are u ready?Prom= programmable read only memory .This is inside the ECM which is which is a separat part.This contains VERY specific information about ur car like weight,eng,transaxle etc.When buying a new ecm they DO NOT come with a NEW PROM,or a cal-pak,or mem-cal.Cal-pak is calibration pack,mem-cal is memory and calibration.IF u bought a new ecm all of these must be removed from the OLD ecm and installed in the NEW ecm.A special tool should be used and normally are provided when u purchase a new ecm.So basically u NEED a Haynes general motors repair manual book # 38015 that covers yr models 82-94 which has a step by step install and removal of these parts from the old ecm. with pictures.Be very carfull not to damage the electrical components.And probably why ur car will not start,U DO NOT HAVE THESE in ur new ecm.U have to do as above and put the old ones in the new unit,which contain info so u car knows how to run.By the way did u ever bother to do a CODE check,the codes for the prom are 51 five flashes pause one flash.Cal-pak is 52 Five flashes pause two flashes.I hope this book I just wrote can HELPPPP u fix ur car back to running condition.

What is the status of ur cars situation right now.Just checking since u have not reposted a reply if its fixed yet or not.

The car has been sitting for a while because the mechanic that has it has been to busy. He is putting it back together and towing it back to my garage. I will work on it myself when he brings it back. That should be this week sometime. Thanks for the inquiry. I will keep you updated as the mystery continues.

Ok let me know IF the information I provided was useful.I tend to think ur ecm u replaced is the issue,bc it did not contain the prom,calpak,mem which unless came out of a car with the EXACT specs like ur model eng,trans,weight were the same the car WOULD never start!!!Thanks for touching base.

Ron,

Thanks for the help. I got the car home and then the electric was off for three days so no lights in the garage. I finally got to work on it. I verified the crank position signal was correct with the new sensor. I checked the wires from the ignition module to the ECM and they are continuos. I replaced the ECM with a new ECM from Autozone and they changed the prom from the old one to the new one. I changed the ignition module to a new one from Advance auto parts. I disassembled the timing cover and all the other stuff and checked the timing chain and sprockets. It all lines up like the Haynes manual says too. I checked the spark at each cylinder with a spark tester, and they all have good spark. I put in the jumper to generate codes and got the continuos code 12.

I ran compression checks on all cylinders and got 65 to 90 PSI depending on the outdoor temperature. At the coldest I got 65 PSI.

After all this I have decided that maybe it has a fuel problem. When I pull the plugs they are not very wet. There are traces of gas but not a lot. Should there be a lot of gas on the plugs after cranking a while? Could the Feul Pressure regulator cause it not to start? The fuel pump appears to be working as there is pressure at the shrader valve on the fuel rail. I relieve the pressure and it pumps back up. I guess I will remove the fuel rail and injectors next.

Do a psi check to verify the pump itself it at the recommended spec.If the pump checks ok,u may have a faulty injector or injectors.Ur psi should be 41-47 psi .Thats for the multiport fuel inj non turbo car.U can check the resistance at each injector which should be 11.8-12.6 OHMs.In the haynes manual it says alot ,so it does point to the pressure regulator as a possibility but just use the manual it takes u step by step on the fuel pressure check.U should be able to determine whats going on and go from there.

Ron,

Sorry for the delay again. Its hunting season so I haven't worked on it until tonight. I checked the fuel pressure and the pump puts out 45PSI at the schrader valve. Then I relieve the pressure and it pumps back to 45PSI. I checked the resistance on the injectors. They are all in range except one which reads 9 ohms. I changed the plugs and cranked it but there is no gas on the plugs. I removed the fuel rail and verified its not blocked. The injectors look ok. I tried to measure the voltage going to the injector by hooking an analog meter to the plug and cranking the motor. I do not get any voltage but I thought that the meter may not load the ecm enough to make it think its an injector. I will try to find a NOID light tester tomorrow. I checked the wires back to the ECM and everything reads O.K. I checked the pink wires with the black stripe which feeds the injectors and they do have battery voltage. Any other Ideas?

James

I am pretty tired tonight long long day.I first thought maybe ur coil pack or maybe the wiring for it may be faulty,but I looked above to see u replaced that.I would recom a voltage check at the coil anyhow.I will do some reading tommrrw I may have enuff time to do so and see if I am just overlooking something.I will try and post once I may have some other ideas that may resolve the issue at hand.Ok

Have you checked all grounds to make sure they are connected and clean. Good luck.

I am still doing some research and thought,did u by chance check to make sure the ecm's fuse was not blown?This is just a small idea but,I did not have enuff time today to do some reading and so forth.Also ur ground wires being clean are a good idea too as stated by the prev post.No fuel on the plugs umm,tends to make think of some other things which I have not considered and will do my homework to c if there is something I overlooked on that one.

Okay, Here is what I want you to do.
1) Use some starting fluid. Did it work ? If yes GoSub 2 Else GoSub 3.

2) Fuel Problem Check for a blown fuse or cut in the wiring harness leading back to the fuel pump.

3) No Spark or Compression. Use a Snap-On Modis to read the ECM KOSC data and stored codes.



Tach Out Motorsports
Option D Inc.

I do believe the problem lies here and it is the crankshaft position sensor and the ignition module are bad.I realize that ur new computer on shows the 12 meaning no codes.But there could either be a short or kink in the wiring harness or connectors.U could check those individually and insure a solid connection.After do some research this will cause the car NOT to start.These two items affect the timing which if the sensor is not working the car will not fire!Advance auto sales both parts the crankshaft sensor is part # css7 price is $16.96. The ignition module part # EL138 price is $82.44.I would strongly check these items and replace them since either both are bad or one but,if the connections are poor or something is loose this would cause ur problem.I feel pretty sure this is the culprit and the info book wise is in the haynes manual on 5-7 to check the ignition mod and crankshaft sensor.Ok

I have been working out of town and just today got to work on it again. Today I checked the fuel pressure again and it builds to 45psi but when the pump stops it bleeds back off, so i bought a new fuel pressure regulator and it still does the same. I am thinking the fuel pump check valve is bad but i would think it still would start. I lifted the fuel rail and had my wife turn it over while i watched the injectors. The number one injector sprayed but the others seemed to dribble. To sum it all up so far.

New computer with my prom
New ignition module
New crankshaft position sensor
New fuel pressure regulator.
New plugs and wires.

I have checked all of the signal wires to and from the computer and they all read good.
The timing chain and spockets look good and line up correctly. There is compression in all cylinders. the spark is good on all cylinders. The fuse's are good. The grounds are good. The number two cylinder shows a lower compression than the rest. If it had a valve stuck open would that stop it from starting or just make it miss?

Good to see u did replace the two parts I recomm.I would think if the valve was stuck it would prob miss,just guessing since it may be like a plug wire off or loose and cause the same prob.I will do some more reading and or research to assist u since u are slowly narrowing down the problem.I will post as soon as I have something concrete that should hopefully cure it,I hope.

I hv done some reading etc and while sometimes a faulty oil temp sender can cause the fuel not to spray,this is not the case bc the oil sender is tied into the fuel pump circuit and if it was bad the pump would not work.So rule that out and as it is now u have fuel up to the injectors and the info points to the check valve as being the issue,unless for some unknown reason u have several bad injectors.I would replace the check vavle and go from that.That is what I have to share to so far since the vavle controls the fuel specs to each injector and basically ur getting no fuel into the combustion area to fire it.I bet if u poured some fuel into the system injectors removed or other parts it would fire.Thats my educational guess but,think based on whats been done it would run 2 -5 secs and die as it now.If I learn any more I will share it with u.

What's the status of ur finds on the issue u have.I have not seen u post anything new in for evar.Post up if anything is different.I will try to consider other options I have been busy myself and just thought of ur old post so,I thought I would ask.

Quote:

has spark, injector pulse, and 45 psi fuel pressure.

Is the 45 psi at Key On System Check or Key On System Running? How did you check your spark?


Tach Out Motorsports
Option D Inc.

Well guys I know its been awhile since i responded. I have been out of town working in Alabama and California since January 28th. i finally got to work on it again so i lifted the fuel rail and the injectors are not firing. i disconnected the computer and I can make the injectors fire by grounding the injector signal wire coming from the ECM. i have checked all grounds and power signals to the computer and everything checks out. I got another ECM from a running car and installed my prom but it still won't work. I installed a Prom from a 91 Beretta but it still doesn't fire the injectors. I guess the next step would have to be a new Prom? Any other Ideas?

Umm like the prom from another car not being a J and exactly like urs with the eng,trans, which is crucial to make it run in the first place.Just a note the prom and mem-cal and cal pak are specific to the letter for ur car ONLY! Using another prom from a different car model and yr would not work on ur car regardless.As for a new ecm most DO not come with new prom,calpak,or memcal from advance or auto zone to the best of my knowledge.Unless its offerred as a separate part by them or the dlr I do not know.I may have enuff time tmmrrw to do some research into this issue with ur ecm and what part stores may offer for a straight hook up without changing over the memcal,calpak and prom.My guess is the ecm may be bad or the prom itself,but worst case junk yard search is in order for a used prom.I have done alot of studying on this stuff and the prom is prog for ur cars eng,trans body weight etc and only works for ur yr,body, etc.So the berretta would never have worked regardless.

Ron,
I gave up on the junkyard parts and ordered a new prom from the local chevy dealer. it cost $105 including tax and is coming from Memhis. I might have it by Friday. I promise to keep this post updated.

thanks for your time and effort.
James