got fuel but no spark - any ideas?

[Joseph Dell]

I've never had this happen... re-assembled the motor after replacing a head gasket and now when i try to start the car, it cranks but doesn't start. I have verified that it is getting fuel, but it isn't getting any spark.

very weird.

Using a VEC2 at the moment... and it is hooked up right. fuel pressure is good. spark plugs are getting wet.

Any ideas on how to troubleshoot this?

Thanks!

Joseph

 

[Jack B]

Have you used a scan tool for a pending code.

 

[Joseph Dell]

i wish i had a code... none so far.

 

[Schulmann]

1.Check the program in the VEC2.
2. If you have the logging enabled try to trace what is going on.
3. Check the connections in the back of the engin. Coil and the other staff.
4. Check the VEC2 wiring
5. Check your PCM's connections
6. Check the cranking sensor harness

No more idea for the moment ...
Any check engin light ?
Hookup a scanning tool to check what the PCM sees.

 

[twinturbo3150]

Im a newbee, but how long has it been sitting before you changed the gasket, maybe the battery it so week to creat a spark. just my .02

 

[Joseph Dell]

Charged the battery once and am charging it again as we speak. It was 100% when I started this excercise earlier in the week.

Going to go back through and double-check everything. Replaced the VEC2 and that didn't fix it (even w/ a different program). also checked all the ground(s). don't have a scan tool but have the EASE software from ROE. Is that close enough?

Oh yeah... replaced the PCM... that didn't help either.

Thanks for your continued support!!!

Joseph

 

[twinturbo3150]

have u always had your vec 2 prior to head gasket replacement?

 

[Joseph Dell]

Affirmative. I even started the car with this exact configuration previously w/ the VEC2.

here is what i've checked:

- replaced PCM
- replaced VEC2
- verified fuel pump and fuel pressure. pressure at rails is good.
- verified that there is no spart on the plugs
- verified that fuel is getting into the motor

what could i have broken? coil packs?

Maybe the better question is: can I test that the PCM is sending a signal to the coil packs?

personally, i'm quite lost right now...

JD

 

[Schulmann]

Yes, you can test the ignition signals but you need a logging tool. I don't think that you killed the coils. They are tough.

Have a good night, drink a good wine, then tomorrow start by verifying all year electrical connections. And reload your vec2 with a basic program.

 

[Mr Hemi Head]

Charged the battery once and am charging it again as we speak. It was 100% when I started this excercise earlier in the week.

Going to go back through and double-check everything. Replaced the VEC2 and that didn't fix it (even w/ a different program). also checked all the ground(s). don't have a scan tool but have the EASE software from ROE. Is that close enough?

Oh yeah... replaced the PCM... that didn't help either.

Thanks for your continued support!!!

Joseph

Joseph EASE software is a scan tool. I would connect and verify that all the sensors can be read. I'm thinking the PCM may be missing an input which will prevent the engine from starting.

 

[J DAWG]

I know you dont have a dead battery but have you thought about trying >>>this<<<


my offer still stands on the shift light.

 

[J DAWG]

Oh yeah the EASE will work at least to tell you if the sensors are working or seeing a signal. Just hook up the Ease and turn the ignition on and it should connect/communicate with the car.


I know on the standard VEC2 setup there are no relays but I am not sure of your current wiring. Everything right now is just a guess and I know you are gonna go back over all the grounds, crank sensor hookup for the VEC2 and any wire you may have tapped into at the pcm to get a tach signal even though that is usually off an injector driver.


hmmmmmmmm.....I wish I could think of something. this is gonna bug me.


John

 

[HP]

i wish i had a code... none so far.

If the PCM has not acquired a code - you can pick up any new codes by
cranking the motor 3 times - 15 secs each crank

 

[cgmaster]

1st are you sure you are not getting spark? Could the engine be set 180 deg out. I do not have my service manual with me right now to even know if there is a cam position sensor but if there is I would check it. Then I would check the crank position sensor.

Also start by checking the simple things first. And get someone else to take a look at it. It is nice to get another point of view.

 

[Joseph Dell]

I'm starting to think CPS or CPS. will check crank first and cam second. good info from y'all. it has to be something simple. there just isn't that much to this car.

and i definitely need another set of eyes on it. if no luck tonight, i'll have a BBQ either near, of, or on my car tomorrow.

jdawg - Thanks for the vote of confidence! when i part it out, your prices are now going to be 5% higher than everyone elses.

JD

 

[J DAWG]

There is a cam sensor which is not hard to replace. The way it is offset it is pretty much in the right place or shredded by the sprocket if inserted to far.


I dont know if your stock pcm will at least crank the car with your injectors. In otherwords may wanna try pulling the VEC2 completely off as well as the crank sensor plug and seeing if the stock pcm will at least give some spark. I know you have tried another VEC@ but just a thought.

 

[Joseph Dell]

I'm going to try that as well. too many electronics in the mix at this point. On the other hand, the CPS may have been going bad and i didn't know it. the symptoms have always had me wondering... so i'm off to play.

you are back to 0% penalty now.

JD

 

[Joseph Dell]

More info -

When testing voltage:
- cam position sensor fluctuates during cranking.
- crank position sensor goes right to 5v and stays there.

Can someone confirm if this is what the crank position sensor is suppose to do? I don't think it is, but i'm not sure. maybe i just found the problem?

Joseph

 

[Jack B]

Joe:

please don't get mad over this, but, does the time allocated for this specific head change increase your overall average of two hours per job - LOL.

 

[Joseph Dell]

LOL!

I was waiting for that.

touche' !

JD

 

[1TONY1]

Joe:

please don't get mad over this, but, does the time allocated for this specific head change increase your overall average of two hours per job - LOL.

Was it supposed to run after the two hours ??????????

 

[Jack B]

Tony:

that is a good point.

Joe:
At the PCM try the following:

1. With the key on, do you get 5V on A17 (PCM orange). This supplies both the crank and cam sensors their 5v supply.

2. With the engine cranking and PCM connected, do you get a repeating 0 to 5 volts on the A8 (crankshaft sensor) This is a gray wire with a black strip. A scope or DRB should show equally displaced notches of 5V followed by 0 volts, then, another 5V spike.

3. The cam position sensor should set a code after 32 revolutions/cycles without a signal. This is probably not a hard code, therefore, you will have to use the EASE software to find the code. This an identical circuit to the cam position sensor, you can look for a signal at A18 which is tan with a yellow stripe.

Good Luck

 

[Steve-Indy]

Started to write a long "theory" here, but decided against same...feel that you are on the right track with the crankshaft position sensor (CKP) as the signal SHOULD vary with cranking if you are indeed testing the signal side of the CKP...BUT, some things still do not make total sense to me when pondering the ASD, PCM, and the injectors/fuel pump/coil pack/ etc. interplay...especially since no DTC has been set.

If you need any info/diagrams from the Viper Tech Student Workbooks (Engine Management and/or Electrical), let me know...remembering that I'm NOT a Viper Tech.

 

[HP]

More info -

When testing voltage:
- cam position sensor fluctuates during cranking.
- crank position sensor goes right to 5v and stays there.

Can someone confirm if this is what the crank position sensor is suppose to do? I don't think it is, but i'm not sure. maybe i just found the problem?

Joseph

The CKPS output should alternate 5.0v and .03v depending on where the cuts in the flywheel fall on the sensor - (5v slots - .03v metal) It's a Hall effect type sensor.

 

[HP]

Check the clearance between the sensor and the flywheel - too much and the sensor will not pick up a signal. Also check the sensor ground for bad connection.

 

[cgmaster]

Ok where is the sensor on the flywheel? I am just wondering because I have a Tilton C/C clutch and flywheel I installed recently and it did not have a position sensor near the flywheel.

 

[HP]

Ok where is the sensor on the flywheel? I am just wondering because I have a Tilton C/C clutch and flywheel I installed recently and it did not have a position sensor near the flywheel.

It's mounted on the right side of the block - just above the oil pan - it is covered by a shield

Normally these type sensors are around the front of the block - near the pulleys - but the Viper sensor reads off the notches in the #5 counterweight(near the midsection of the block)----
-----Sorry I misled with the term - 'flywheel' I should have said crank counterweight.

 

[Joseph Dell]

Thanks for the tips, y'all! I'll have an update shortly (including a test of the ground and a borrowed sensor to see if that fixes it [thanks Rich! I know it pained you to watch me pull that sucka out]!)

More to come...

JD

 

[Joseph Dell]

Re: update

well, it isn't the sensor. but i'm making a new harness as we speak and going to wire it clean to the PCM to see if that is it.

more to come...

Tested each of the signal wires and they SEEM to be fine from the PCM to the sensor... we shall see.

CPS stil shows 5v only and doesn't fluctuate...

JD

 

[Jack B]

Re: update

Joe:

Did you check for the DTC, you will have to use the Ease to review it.