92 PA will crank but not start

[mjhicks]

My 92 PA is currently at my mechanic but he is having trouble figuring out what is wrong partly due to well meaning friends disconnecting the battery thinking it was a glitch that might clear its self.... All trouble codes cleared,

Battery output, alternator and charging circuit all seam to be OK. Crank and cam shaft sensors have been manually checked and are not a problem.... Fuel pressure is only slightly low - expected for the age of the vehicle. Next step is to manually check the ignition control module.
Short history of problem:
Purchased used in Sept 2011. Vehicle had excellent maint and never had a starting problem. I had some trouble starting it a few days ago... seamed to not be getting fuel or spark but eventually started. Later the same day it cranked but would not start. No spark was confirmed prior to disconnecting the battery. Besides the ignition control module what else might cause it to have no spark? And act up briefly before failing completely?

[HotZ28]

Originally Posted by mjhicks

Besides the ignition control module what else might cause it to have no spark? And act up briefly before failing completely?

Crank Postion Sensor. (CKPS)

[autojoe]

if you have a carnk sensor problem you also will have no injection pulses which can be checked with a noid light if injectors are not buried under a plenum.disconecting battery will not affect crank sensor unless you had a computer(PCM)problem.......key on engine off is your check engine light on during bulb check when it will not start......your mechanic should have a good scan tool and look at crank sensor on data pid and during cranking it should state that.pretty easy......if pcm is stating crank and then would have to troubleshoot the crank circuit from crank sensor including crank sensor including wiring including the pcm itself and maybe powers and grounds.

[Tech II]

When a car cranks, but won't start, a very easy car to diagnose.....either no spark, no fuel pressure, no injector pulse, no compression, bad MAF(try starting with the MAF disconnected), etc.

[mjhicks]

Originally Posted by autojoe

troubleshoot the crank circuit from crank sensor including crank sensor including wiring including the pcm itself and maybe powers and grounds.

My vehicle is working fine now. My mechanic did run most of the tests you mentioned including disconnecting each sensor and manually checking each wire. After manually checking the ignition control module wiring and cleaning connections the darned thing started. It was hot the day it acted up before failing to start at all. Its possible that dirty connectors plus heat just caused a connection to be lost... cleaning and reconnecting cleared the problem.

[HotZ28]

You may have a wire from the CKPS to the ICM that is partially broken & when moving the wiring harness, it created a better contact. Only time will tell the full story.

[Tech II]

"Drag Test" should be performed on the ICM and crank sensor harnesses.......

Unfortunately, I don't think your problem is solved....

[mjhicks]

Used cars are a pain in the... wallet! As well as other places. Engine, trans, and other mechanical parts are all in good shape - just electrical or electronic problems...

Its been almost 2&1/2 years since changing the ICM. The stall and crank but no start problem went away til a few weeks ago... Would start just fine then after warming up would stall then do the crank but no start. I found some of the wires on the ICM connector were bad. Ten days ago a friend who is an electronic specialist replaced the connector, carefully splicing, soldering, & shrink wrapped each connection. A couple of other bad spots in the wiring were fixed as well as a main ground and power connections checked. Test drive went fine... problem returned the next day GRRRR!! Stall after it warmed up or if I stop for gas or other errand it would crank but not start til it cooled down completely. Some research suggested the Crank position sensor... no longer having the physical ability to pull the harmonic balancer I bought a crank sensor from Oreily's and took the Buick to my mechanic. He read the codes... no code showed for crank sensor but the cam sensor and EST shows up. Mechanic says if only the outer part of the cam sensor was changed the other half. magnet, under the timing chain cover is probably broken... I explained what had been changed before and asked if he could clear the codes and start fresh if it would start, let it warm up til it stalled again then re read codes... He was about to do so when it developed some sort of power connection problem... dash lights dimmed. New battery just prior to the problem returning so he is now looking for a bad power connection... He asked me if I want to keep fixing things... His labor charges are reasonable - he usually takes mercy on me, as he says, so I can afford to have him fix some things but what should I have him tackle. I think my car is the oldest and most uncooperative vehicle he works on LOL

[Tech II]

First, a cam sensor is not going to cause your vehicle to stall and not restart....a bad cam sensor will let you restart, bu the idle may be a little rough, since there is a one chance in 6 that it will be in the correct sequential timing....

Second, if it restarts after waiting a few minutes, the four likely culprits, are the crank sensor, the ICM, the ECM, or the fuel pump.....

As I stated over two years ago, it's easiest to diagnose when it won't start.....

Do you have spark on all wires? If yes, than the crank sensor is ok......

Do you have good fuel pressure, checked by a gage? If yes, then it's not the fuel pump......

Do you have injector pulse? If no, then we could have a problem with the ICM or the ECM......try spraying carb cleaner into the throttle body while someone cranks the engine....if it almost starts, or runs as long as you spray, the injectors are not firing....the fact you have an EST code, could be a wiring problem between the ICM and ECM, or a problem with either of them.....

Also try starting the vehicle with the MAF disconnected, and check the vac line to the fuel pressure regulator, for the presence of fuel....a leaking regulator will not cause a hard start on a cold engine, but it can cause a stall, and hard start on a warm engine....

[mjhicks]

Its in the hands of my mechanic... He suspects ECM problem. He cleared all codes and the only ones to return wee throttle position sensor and EST. He repeated tests and the TPS code and or EST would sometimes show sometimes not... he says this is symptom of a bad
ECM. The check engine light has not been coming on. I thought the bulb was burned out but the mechanic says that's another symptom of a bad ECM. He is going to check the bulb. If its good then at least part of the problem is the ECM and it will get replaced.

[mjhicks]

Ruled out the crank position sensor... mechanic changed it but no change in behavior... A couple of codes keep coming back without even cranking...
41 - no camshaft reference signal - not related to the no start but shouldn't show up without cranking
And 43 ESC module... Could having these two particular codes show without even cranking be sign of some other screamingly unrelated problem?
For example once when the fuse for the stereo blew the interior lights came on and would not go off til the fuse was replaced.

With cranking 22 - throttle position sensor too low and 42 EST control problem show up
On top of all this the check engine light does not come on.... Mechanic is going to check if the bulb is burned out - if the bulb is good then there is a computer problem.

[Blue Bowtie]

Remind your mechanic not to overlook the wire harness itself. I've found this kind of thing more than once:

[Tech II]

Blue, how many times have you pulled an ECM/PCM out of the air box, and found a mouse nest, and the little buggers have eaten the insulation off the wires?

[DeltaP]

I know I have. Even found the kids still home once!

[Blue Bowtie]

Originally Posted by Tech II

Blue, how many times have you pulled an ECM/PCM out of the air box, and found a mouse nest, and the little buggers have eaten the insulation off the wires?

That happens, along with all kinds of other interesting things that get into air boxes. The harness in the photo was damaged due to abrasion/interference with the harness routing and construction. The flexing harness had caused the wires to abrade against each other. The wide factory tape whipped over the harness was not even damaged.