why won't it start? - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

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post #1 of 16 (permalink) Old Sep 15th, 02, 07:31 PM Thread Starter
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just got a 91 Beretta given to me. for free. it has the 3.1 V6 and just will not start. cranks real nice, but absolutely no fire. has fuel pressure at the rail- don't know how much, but i did push in the check valve with a screwdriver and had gas shoot me in the face. has spark. has 170-180 psi compression in all the front cylinders. injectors pulse- checked with a test light. what am i missing?
for the record, it has a brand new GM fuel pump, and the computer was replaced with a junkyard ecm. the guy just gave up. now it's my problem....

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post #2 of 16 (permalink) Old Sep 15th, 02, 07:53 PM
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How do the spark plugs look?

Any codes present in that ECM, set while cranking?

I know you said it has spark, but is it nice and strong, or a little yellow?

The crank sensor and ignition module/coil packs are about all that's left.

Of course the crank sensor is just above pan rail on "right" side of engine. This is a common failure on those.

I understand it's a new pump, but stranger things have happened. Just for fun, you might want to put a fuel pressure gauge on it to know for sure. 35 to 42 psi, and holding would be good.

Also,I believe that year uses a MAP sensor remotely mounted on firewall with a long vacuum hose. I've seen the MAP go bad, but usually it will at least run, but not very well.. Maybe it's time to throw one on for a test, it's worth a try.

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post #3 of 16 (permalink) Old Sep 15th, 02, 11:59 PM
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VATS?

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post #4 of 16 (permalink) Old Sep 16th, 02, 01:09 AM
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Don gave a good one, spark plug examination.
MarkC gave a good one, VATS.

My suggestions are:
Remove the ECU coolant sensor connector at the sensor, two wires. Use an ohmmeter to check resistance in both directions. One, check sensor, s/b @70*F 1Kohms, 32*F 10Kohms.
Two, check into ECU harness for continuity, at the harness connector, place ohmmeter to DIODE function, place each meter lead into a wire, Note resistance reading, swap test leads, note resistance reading, s/b 500-1K in one direction, 10K-20K in the other direction.

If both items check out okay, sensor & wire harness to ECU, then plug into the ECU harness connector a 10K-12K, 1/4 -1/2 watt resistor. Then try to start, The high resistance places the ECU into cold start, and provides more fuel.

If car is equipped with VATS, wait three minutes after initial starting and retry with same key.

If you have the original ECU, make sure the calmap chip is changed also.

How long has the car been sitting? Injectors may be varnished. Spray some starting fluid in the intake hose/line, If it starts, then you know the next job...

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post #5 of 16 (permalink) Old Sep 16th, 02, 07:57 AM Thread Starter
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i tried the ether, but it didn't even try to fire. i pulled the plugs and replaced them with a set of relatively new rapidfires i used to have in the Nova. the old plugs had a HUGE gap on them, and were all carboned up. a few were wet with gas, so fuel is getting into at least a few of the cylinders. spark looks good- nice and bright spark. dunno. all the wires go to the correct coil, at least going by the numbers on the coil packs. the computer was replaced with a different one by the guy who gave it to me, and nothing changed. will have to play with it some more. i do have an extra fuel rail with injectors and regulator, just need to ambition to try that out.
i love the electronic cars...

------------------
1971 Nova(looks like 69 camaro from underneath!)
355sb, vortec heads, HOT cam,T-10 tranny, 3.70 gears 16X8" IROC wheels. 12" Corvette brakes on the way.
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post #6 of 16 (permalink) Old Sep 16th, 02, 08:57 AM Thread Starter
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i was just out playing with it. i noticed that the cooling fan comes on with the key. did the paper clip code pulling thing, and it keeps doing the same pattern- on for a second, then off for a second, then on twice. code 12? it almost fired when the paper clip was jumping the wires- one or 2 cylinders would fire every once in a while. pulled the paper clip out of the plug, and nothing.

------------------
1971 Nova(looks like 69 camaro from underneath!)
355sb, vortec heads, HOT cam,T-10 tranny, 3.70 gears 16X8" IROC wheels. 12" Corvette brakes on the way.
see pics here http://community.webshots.com/user/novaderrik
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post #7 of 16 (permalink) Old Sep 16th, 02, 09:02 AM
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I'd follow Don's advice, dump the ECU memory of faults, and start over with a fresh battery and clean ECU.

Attempt to start, and check for codes.

Spark ain't happening at the right time or weak, or no starting vacuum.

Everett
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post #8 of 16 (permalink) Old Sep 16th, 02, 09:02 AM
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You have 3 individual coil packs on that engine.....make sure all 3 are getting spark...they will usually run, very rough, on two....but.....I've seen them very hard to start that way...esp if the old ones sre fouled...
Throw Your used plugs in the trash and put a fresh set in...

Just reread original post....ummmm...how about compression on the REAR cyl's???

Also, since it didn't fire with the ether(yuck), changing the fuel rail would be a wast of time IMO...

If comp checks out OK and there is spark present on all coil packs....change the plugs and try starting it with the accelerator pedal to the floor....this will put the engine in "clear flood mode" by cutting off the injector pulse.....perhaps the intake etc is filled with fuel and immediatly soaked Your new used plugs....

[This message has been edited by 18436572 (edited 09-16-2002).]
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post #9 of 16 (permalink) Old Sep 16th, 02, 11:05 AM
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Does it have a mass air flow sensor?
You need enough spark to jump the gap under compression, which is much more juice than it takes on a test plug, unless the test plug has a very wide gap. Check for arcing to ground of the coils when cranking.

Also if the exhaust system is plugged up, the engine can't run... check the cat converter, etc.
David

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post #10 of 16 (permalink) Old Sep 16th, 02, 12:59 PM
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I was going to say... could the coil be bad or wired backwards?
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post #11 of 16 (permalink) Old Sep 17th, 02, 12:59 AM
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ND, You mentioned code "12" with the paper clip. Thats normal it means the ECM has the ability to do a diagnostic check of itself and "talk" with the ADAL connector. Cooling fan running during this test is OK also.

Have to agree with Don mentioning the crankshaft postion sensor, that's a common failure.

Good Hunting, Drew

[This message has been edited by drew69 (edited 09-17-2002).]
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post #12 of 16 (permalink) Old Sep 17th, 02, 01:26 AM
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Drew is correct, code 12 from the ECU means ECU is okay and can do a diagnostic test.

With ALDL connector shorted, EGR valve control circuit, its solenoid is energized so vacuum can be applied from the start of the vacuum line to actuate the valve. Idle Air Control is extended out and seated against its port, this is good to set base idle. Charcoal cannister solenoid is energized to allow cannister to be purged. Spark control is returned to base timing.

I'd have an assistant attempt to start the car with the lights off in the shop and check for spark jumping to ground.

As others here mentioned, crank sensor can go bad. Use AC voltmeter to measure the AC pulses from the sensor while cranking.

Use ohmmeter to check coilpaks, primary side will measure approx 5-8 ohms, secondary side will be 8-10 Kohms.

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post #13 of 16 (permalink) Old Sep 17th, 02, 08:34 AM Thread Starter
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this is the part where i get real confused.
i just got it running. there was another ecm laying on the floorboard, so on a lark, i plugged it in. it started right up and purred real nice.put it in gear- fine. ran like a champ. then, i made the mistake of shutting it off. now, it will only fire if i hit the gas pedal while cranking, then it only runs for like 5 seconds. but it does sporadically fire while cranking without touching the gas, just won't start. what now?

------------------
1971 Nova(looks like 69 camaro from underneath!)
355sb, vortec heads, HOT cam,T-10 tranny, 3.70 gears 16X8" IROC wheels. 12" Corvette brakes on the way.
see pics here http://community.webshots.com/user/novaderrik
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post #14 of 16 (permalink) Old Sep 17th, 02, 08:36 AM Thread Starter
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oh, and the cooling fan ALWAYS runs, no matter if the papaer clip is in or not. that doesn't seem normal to me.

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1971 Nova(looks like 69 camaro from underneath!)
355sb, vortec heads, HOT cam,T-10 tranny, 3.70 gears 16X8" IROC wheels. 12" Corvette brakes on the way.
see pics here http://community.webshots.com/user/novaderrik
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post #15 of 16 (permalink) Old Sep 17th, 02, 09:42 AM
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Could it be the fan switch harness on the back side of the motor is fried or shorted to ground allowing the fans to stay on? Or A/C is always selected?

There is the knock sensor wire harness between firewall & engine block, it may have gotten hot enough to fry the harness causing it to retard timing a whole lot?

Could always dump ECU memory and start over, take codes after shut-off.....

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