The car was sitting for 3 weeks (working on restoring the interior). It fired up fine back then. Now it just cranks. After reading all the posts on this problem I am still at a loss......

Only DIC code was for #72 Vehicle Speed Sensor Loss, #53 System Voltage Low and #11 Malfunction Indicator Lamp Circuit. I cleared all codes and no new ones appear

Tested fuel pressure by pressing the valve on the fuel line at the back of the fuel rail, then cranked the engine.....no problem, lots of gas shooting out.

The engine was rebuilt 10 months ago with new fuel injectors, wires, plugs, water pump, optispark, altenator, fuel pump, (and I know I am forgetting a bunch of other stuff). prior to this no-start, the engine ran great.

DIC indicates 12.1 volts and 11.1 while cranking. Also tried it with the battery charger connected and set to "Start" which produces 25amps.

Also checked the fuel with a stick, shows at least 3/4 of a tank and the gas is only about 6 weeks old.

Last item, the oil pressure sending unit (at the rear of the engine on the passenger side of the block) wire is disconnected. since the last successful start I found this wire badly frayed with only about two strands remaining so I disconnected this and have a new one to install but since this is only a 2 wire sensor it should have nothing to do with not starting.

Any suggestions on a next set of steps to diagnose this problem?

 

Just read in another post where 94Z07fx3 suggested to turn off the ASR (key to run, turn off ASR, start) but this did not work either.

 

Spark? Fuel injector pulse?

 

how do I test for an injector pulse and spark? wouldn't the engine at least "hiccup" during start if atleast one plug/injector was working?

 

Injector pulse is checked by a noid light (cheap at any parts store) to see if there is any pulse and by an ociliscope (expensive and needs the right inductive pickup) to determine pulse width and magnitude. You can also hear them with a mechanic's stethoscope. (cheap at any parts store)

Spark is best checked with a spark test tool (cheap at any parts store) that fits inline between the plug and the wire. But it can be done by carefully holding the wire's bare end close to ground. A bright spark should be visible in sunlight. If you do the hand held test the grab the back of your pants/belt, do it with one hand, and stand well clear of the car's ground. You never want your body to be the shortest path for the spark. You can also use a jumper cable and an old spark plug. With the old plug in the wire's boot, grip the threads of the plug with the jumper cable and attach the other end to the frame.


(BTW That ASR bit was because of that OP's report of ASR light on after IAC fiddlings.)

 

Thanks 94z....I will pick up a spark tester and noid light this weekend. Is there a common component that would cause a loss of all spark or injector???? Wouldn't the engine start and only miss-fire on the cylinder with the bad injector/spark????

 

Well, the injectors are working....15 ohms resistance on each one. cant find anything in the service manuals that helps.....

 

And what if you connect a piece of wire between the loose wire and oil pressure sending unit, just for checks.

 

made the connection, but still no start.....just a lot of very healthy crank.....I am at a loss

 

Tested fuel pressure by pressing the valve on the fuel line at the back of the fuel rail, then cranked the engine.....no problem, lots of gas shooting out.


I know You check it, but if you had a fuel pressure gauge you could tell if the pressure was holding. When I went to start mine I had good pressure but just that quick it would drop to zero. The check valve in the pump was bad, allowing the gas to flow back into the feed line after the pump stopped. Even with the bad pump it would still leak gas when I hooked up the fuel pressure gauge. I hope this makes sense and helps


Ed

 

Hmmmm....interesting thought, will find/beg/borrow/buy a fuel pressure gauge and check....thanks

 

Are your injectors "new" or did you just have them cleaned. If everything checks out OK and you find no problems take another look at those injectors.......spray some ether into the intake for ~ 10 seconds and see if the car starts....if it does it sounds like you need another set of injectors.....I recommend the Bosh III (ethenol compliant)....that's what I run now. I had a similar problem in early 2007....the injectors ohmed OK and I could run them on a bench injector tester...but the damn things would not work on the car. I replaced the injectors and car ran like a champ.

Good Luck!

 

Well, I bought a fuel pressure gauge.....39PSI with ignition in "on" position as fuel pump charged the lines. When I crank the engine, I get 41 PSI. Also checked for spark --- None on either of the two wires I checked with a spark tester (which worked on the other vette). ALso pulled a plug wire and put it close to the heat shield but did not get a spark. The injectors and Optispark and wires and plugs were all new 10 months ago and only have about 500 miles on them.
NEED SOME MORE DIAGNOSTIC HELP -- what do I check next without starting to replace parts (can't afford that route)....thanks

 

Further testing....no spark from the ignition coil when cranking. the COIL itself is loose, I can move it about 1/16 inch side to side.....IS THIS NORMAL? Is it also normal that the PCM would not set a code for no-spark??? Just wondering if I am going down a bad path. I used the service manual diagnostic tree for "Distributor Ignition System Check". I have 10V from the Ignition Coil Module Connector Terminals A & D to Ground, also when I tested terminal C to ground the test light came on so I have a good ground. Before I buy a new coil, is there some other test or do I just swap parts? Its unusual, but I still do not get any DIC codes.

 

Since you have a '95, keep this in mind:
http://www.corvetteactioncenter.com/...Replace+CCM%29

Tom Piper

 

Thanks Tom, my vin is just under this bulletin but the symptom is not the same. My engine cranks, its just starved for spark from the coil. Think I am going to have to replace the coil and coil module since I don't know anyone local that I can test mine on their car.

Hope someone can answer this:

Is it possible for the ICM or Ignition Coil to be bad and NOT have any PCM Error code (such as DTC 16, 41 or 42)???

 

Well, another long afternoon and no success.....changed out the ICM and Coil with new GM Delco..... but still have the same "Crank no start" problem. From the look of the old coil and ICM, they were original and needed replacing. The coil was rusted and the ICM heat sink silicon gel was all dried up to a powder.

Anyways....following the SM diagnostics, the ICM connector has 12 volts in on two wires, solid ground on the third and the fourth wire has good continuity to the PCM.
Did the same checks on the Opti connector and everything is what the SM indicates.
Also pulled the ignition coil wire and inspected -- it was new last year and still looks new....also tests out with 5300 ohms.
Also did the SM test to jump the two "B" wires for the coil and test the "A" with the test light while cranking the engine.....this is suppose to cause the test light to flash, but NO FLASH....so guess what, the SM says either the ICM is bad or the ICM connector is bad -- no way all their tests said everything was good......HMMMMMMMMMMMM

Also cranked the engine and did the wire jiggle dance......no start.

Also rechecked every fuse with the DVM (just in case I had a sneaky non-visible break)....they all tested good

Here is the last thought.......the ONLY thing I did after the last start (Yah, I know, I just remembered it today as I was thinking through all the possible causes) was I got a keyless entry fob from the dealer. anyways, we tested it at the dealer and it programmed their 95. When I tried to program my 95, I could not get the computer to enter into programming mode (light on the diagnostic center never came on). I tried it several times but gave up thinking it needed the power door lock connectors plugged in (have all the door panels off to redo the weather stripping).

So my question is, could I have somehow disabled the start programming because I could not get into the keyless entry program???? I am grasping for anything now.

Thanks for your continued help.....nothing worse than a vette with an attitude

 

Verified with a 94 owner with the same PKE problem. They never fixed theirs but it has noting to do with preventing the car from starting.

So, I checked all the codes in the computers, CCM 1.2, 1.3, 1.4. all these settings are normal and indicate the CCM is communicating to all the sensors correctly. So this tells me the CCM GROUNDS ARE GOOD. Also verified again there are no stored DTC codes in the PCM/ECM/ABS/TCS/DERM.

Back to looking for bad connectors by doing a continuity test on all the wires....someone tell me there is an easier way.

Anyone in the McKinney Texas area with a TECH 1 diagnostic or any experience with this?

 

I know this may be a longshot, but have you pulled the fuel rail to see what the injectors look like? Is it possible they are plugged with crap such as being gummed up or corroded from the sitting? I had a problem after mine had sat for a while. I went through the same thing you did only to find out after I pulled the injectors that they were all gummed up and corroded. R/R'd the injectors and car started up perfect. Good luck and keep us informed.

 

you need to isolate a fuel problem from an ignition problem, this can be done very simply by the use of a timing lite, install the inductive clip over any one of your ignition wires, and crank the engine over, if you observe a "strobe" then you can feel confident the ignition is performing, if you see a strobe, then shoot a very small anount of "quick start" into the throttle body opening, if the engine starts and then dies, this indicates a fuel starvation problem.

mike