96 Caravan no start

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  #1  
Old 05-03-08, 09:08 AM
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96 Caravan no start

Parked it after getting gas and the next morning it would not start. The engine cranks, has intermittant fire at plugs, fuses are good,fuel pump runs,
camshaft & crankshaft position sensors and coil pack are new. ASD relay is ok.
Any clue as to what to look at next or if I'm missing something? Any help appreciated!

96 Caravan 3.3
 
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  #2  
Old 05-03-08, 09:36 AM
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camshaft & crankshaft position sensors and coil pack are new. ASD relay is ok.

This highly depends on your definitions of "NEW " and "OK"

Intermittent spark, without involving the previous mentioned components would be a failed PCM.

New doesnt necessarily mean good.....and Good is dependent on how it was determined to be good...
 
  #3  
Old 05-03-08, 09:48 AM
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the camshaft, crankshaft postition sensors and the coil pack were replaced with new ones. The ASD relay was switched with the fuel pump realy ( same parts) the fuel pump runs so my conclusion was that the ASD was good. Is there any positive way, test procedure, to determine the PCM is bad?
 
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Old 05-03-08, 09:54 AM
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the fuel pump runs so my conclusion was that the ASD was good.
Sorry....I missed that.

Intermittent fire at the plugs.........Are you getting intermittent spark, or does the engine make momentary attempts to start?

Sorry to sound like a Hard arse, but miscommunication here will send you down the opposite path.
 
  #5  
Old 05-03-08, 10:11 AM
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Originally Posted by Unclediezel View Post
Sorry to sound like a Hard arse, but miscommunication here will send you down the opposite path.

Don't be sorry....sometimes clarity can be lost in this type of 'talk'..

I have intermittent spark at the plugs. The engine cranks...occassionally it might hit but most often not...just cranks
 
  #6  
Old 05-03-08, 10:39 AM
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I have intermittent spark at the plugs. The engine cranks...occassionally it might hit but most often not...just cranks
Now we're getting somewhere.......

Ok, The intermittent "Fire " can also be caused by Intermittent "Injector pulse".

4 things determine whether or not an internal combustion engine will run. Fire, fuel, air , and compression, or mechanical "SOUNDNESS" of the engine.
Unless rings or valves or other internal components are damaged, In your case, compression and air can be considered a given.

On a fuel injected engine, Fuel is not a given, just because the tank is full. It has to get into the combustion chambers to be considered Useful.
Spark in the given cylinder, at the given time and consistently , constitutes The "SPARK" category.

With a "Coil pack " ignition, you have no distributor,so your computer will Time and Ignite sparks based on Crankshaft speed and position. THis crankshaft measurement is also used for injection pulse and Fuel delivery.

That Coil pack and sensors werent cheap.... Make sure of which "ELEMENTS OF COMBUSTION" are actually missing before spending any more money.....
 
  #7  
Old 05-03-08, 11:20 AM
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It has consistant injector pulse, (checked with a noid light),
It has high and low voltage signals going to ECM from cam and crank sensors (checked with a volt meter)
It maintains 50psi fuel pressure.
It's getting fuel, just not fire consistantly.
The sensors and coil pack were replaced after the test procedures indicated theyy were bad.
Checking the coil ignition driver signals from the ECM to ignition coil found 2 of the signal wires with 10 volts constant and 1 with 4 volts constant- no fluctuation.
Now has NO spark...period!
 
  #8  
Old 05-03-08, 12:05 PM
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It has consistant injector pulse, (checked with a noid light),
It has high and low voltage signals going to ECM from cam and crank sensors (checked with a volt meter)
It maintains 50psi fuel pressure.
It's getting fuel, just not fire consistantly.
The sensors and coil pack were replaced after the test procedures indicated theyy were bad.
Checking the coil ignition driver signals from the ECM to ignition coil found 2 of the signal wires with 10 volts constant and 1 with 4 volts constant- no fluctuation.
That is what I was waiting for....
Carefully, With a jumper lead and the "Noid"....Dont use a standard test light for this..... Check across the 4 wire connector at the Coil pack. You have 1 power supply wire(Im thinking the green one..but Im not positive) and The other 3 are Coil (-) triggers from PCM....... The live wire will not be live until after the ASD relay engages, Which is probably about 1-2 seconds after cranking.

With the noid across the power line to each of the driver wires , one at a time, while cranking , you should have a steady pulsing noid.....If not, test from power wire to ground for voltage.

Also....If equipped, Does the TACH "Bounce" when Cranking?
 
  #9  
Old 05-03-08, 05:54 PM
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Using the noid light, 2 of the 3 wires have a steady pulse. The 3rd ( the 2-5 coil pack) stays on.
The tach does show RPM when cranking....
 
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Old 05-03-08, 08:10 PM
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Ok, now break out the test lamp.........

The 2/5 coil driver is either shorted to ground, or the PCM has been damaged.

Clip on positive, probe on the 2/5 driver wire......Unplug the pcm. If the light goes out, Pcm is cooked...if not , find the short.
 
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Old 05-04-08, 05:32 AM
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Bad fuel?

"Parked it after getting gas and the next morning it would not start. "

What are the chances of getting bad fuel? I have had water in my tank before which mimics intermittent fire and the engine stalls periodically. Have not heard of any fuel problems with high sulfur content lately. Just found it odd that the vehicle did not run the same after filling the tank.
 
  #12  
Old 05-04-08, 06:00 AM
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Originally Posted by bugsiev8 View Post
"Parked it after getting gas and the next morning it would not start. "

What are the chances of getting bad fuel? I have had water in my tank before which mimics intermittent fire and the engine stalls periodically. Have not heard of any fuel problems with high sulfur content lately. Just found it odd that the vehicle did not run the same after filling the tank.
That's where I'd start my investigation too !
 
  #13  
Old 05-04-08, 09:19 AM
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Originally Posted by Unclediezel View Post
Ok, now break out the test lamp.........

The 2/5 coil driver is either shorted to ground, or the PCM has been damaged.

Clip on positive, probe on the 2/5 driver wire......Unplug the pcm. If the light goes out, Pcm is cooked...if not , find the short.
As suspected, following the test above, when the PCM is unpluged the light goes out. Will have to order the computer....but will followup when I get it. Thanks a million for your help. Using the noid light on the coil test was something I hadn't thought of. I'd been using the volt meter instead. Thanks again.
 
  #14  
Old 05-07-08, 02:10 PM
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PCM came in today, installed it and the van fired right up! Thank you Unclediezel for taking the time to 'talk' me thru the test procedures. It's great that you're here !
 
  #15  
Old 05-07-08, 06:29 PM
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Youre quite welcome.......



Now, the downside......

In the package with the PCM, was a small card which instructs you to "FLASH" the pcm.... Program the "Vehicle specific Data" into the unit....

Ive had mixed result by Doing or not doing this. If ANy driveability issues arise, or accessories that dont work....Cruise Control, Trip monitor, or the like....It will need to be done....
 
  #16  
Old 05-09-08, 12:46 PM
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Originally Posted by Unclediezel View Post
Youre quite welcome.......



Now, the downside......

In the package with the PCM, was a small card which instructs you to "FLASH" the pcm.... Program the "Vehicle specific Data" into the unit....

Ive had mixed result by Doing or not doing this. If ANy driveability issues arise, or accessories that dont work....Cruise Control, Trip monitor, or the like....It will need to be done....

At the parts store, I was offered 2 different units, one that would need to be taken to the dealership to be 'Flased' and one that had already been done/programed and I chose the latter. Inside the box, as you said, there was a card that stated we would need to have the VIN # entered in the PCM via a scan tool....I can't do that with my scan tool...is entering the VIN and FLASHing the same thing? Or is this an additional step I need to do? Or maybe the parts guy had it wrong....
the van runs pretty good, had an additional problem with spark plug wire...new one fell apart....go figure...but other than that....not bad
 
  #17  
Old 05-09-08, 08:58 PM
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is entering the VIN and FLASHing the same thing?
Technically ....Yes....

If it were to go to the dealership to be flashed, the Vin would be entered during the procedure, with a whole load of other info. This is the "Blank" unit that you passed on....My compliments....smart move

The Generic scan tools will not do this. However, any local repair shop , with a Snap-on "BRICK" scanner can do this for you......
The Vin entry is more or less a LEGALITY , and I usually dont say things like this, But if you dont live in an Emission Inspection locality.....Dont lose sleep over it.
 
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