One last shot... Breaking up!

SloGN

SloGN

9Sec Alky V6
Re: One last shot... Breaking up!

BoostedSUV said:
Well I ran a 40" 4ga cable from the same bolt my battery grounds to on the block, into the cab and bolted it to the brake booster bolt/ brake pedal bracket. Turned my ground readings from 13.2 to 4.6 ohms inside the cab, and they dropped to around 2ohms with the truck running. I also cleaned up firewall grounds and thats the best I can get it to be.

I tried the truck again and it made no difference. I also tried testing volts to the firewall junction block and I'm getting a steady 12.4 to it with the truck off. When I start the truck that same point at the junction block jumps around from 16 - 19 volts even though my readings off the ALT and BATT are a steady 13.8. The only other place I get those high voltage readings is right off the Coil side that isn't plugged in (MSD adapter). The strange part is my ECM feeds off of that junction block and it reads a steady 13.8.

I'm so ready to just give up... there's nothing left!
Click to expand...



I really think that your getting a reverse voltage spike. how about try swapping out the coil for a stocker.

also if you can try a stock style dist.
 
BoostedSUV

BoostedSUV

Active member
Re: One last shot... Breaking up!

SloGN said:
I really think that your getting a reverse voltage spike. how about try swapping out the coil for a stocker.

also if you can try a stock style dist.
Click to expand...

I tried my stock coil that I have laying around and that didn't accomplish anything. I really don't want to buy another Dizzy just to guess again... so frustrating!
 
cloneman315

cloneman315

Active member
Re: One last shot... Breaking up!

if it is a true ground you should show almost a dead short maybe.5 at most,if not something is for sure wrong.you should not be seeing 16 to 19 volts anyplace on that truck.what junction block?
 
WyoSyclone

WyoSyclone

Active member
Re: One last shot... Breaking up!

BoostedSUV said:
The WBO2 just provides a display and datalogging, it does not have any control over the ECM. The truck still uses the factory O2, WB is for monitoring purposes only. I could use its narrow band signal in place of my O2 but it's not wired that way.
Click to expand...

So you've got a patch to use the factory narrowband as a wideband with your 3 bar map, but your PLX is wired in via B9 and E14 for datalogging thru ALDL.....

I still suspect the O2 sensor... I guess you have that coming in this week.

The voltage readings at the B+ junction are very strange... only thing I could think of is the coil leaking and the DVM just being too slow to pick up the pulses... that would surely account for an RPM related issue. I think you said you tried another coil though...
 
SloGN

SloGN

9Sec Alky V6
Re: One last shot... Breaking up!

WyoSyclone said:
So you've got a patch to use the factory narrowband as a wideband with your 3 bar map, but your PLX is wired in via B9 and E14 for datalogging thru ALDL.....

I still suspect the O2 sensor... I guess you have that coming in this week.

The voltage readings at the B+ junction are very strange... only thing I could think of is the coil leaking and the DVM just being too slow to pick up the pulses... that would surely account for an RPM related issue. I think you said you tried another coil though...
Click to expand...



does it still have the cap bolted to the firewall?
 
cloneman315

cloneman315

Active member
Re: One last shot... Breaking up!

what are you using code 59?You have a set of 50s or 75s?I have a few chips I think that should be very close to that build from mine if you want to try that.Honestly I think it has wire issues someplace,are you real familiar with reading wire schematics?
 
WyoSyclone

WyoSyclone

Active member
Re: One last shot... Breaking up!

BoostedSUV said:
The only other place I get those high voltage readings is right off the Coil side that isn't plugged in (MSD adapter).
Click to expand...

Can you post the part numbers of the MSD parts you're using Matt? Sounds like maybe a coil and a harness adaptor? I remember another post somewhere about there being a problem with one of the MSD harnesses.

Can you post a pic of that junction block/dizzy/coil area?
 
T

turboj91

New member
Re: One last shot... Breaking up!

One thing (of many) that I do not get is if it was a wiring or ground issue, how does that relate to a VERY specific and consistant rpm issue. It's like clockwork, the same rpm, everytime. Another curve ball in my confusion is the new injectors moved the problem up the rpm range by a few hundred rpm. Again, consistant and specific. If a wire or ground was bad, how would a larger fuel injector have an effect on the wire or ground?
 
T

turboj91

New member
Re: One last shot... Breaking up!

Matt, check your pm's. I sent one (earlier this evening) but I might have screwed up the sending part.
 
BoostedSUV

BoostedSUV

Active member
Re: One last shot... Breaking up!

cloneman315 said:
if it is a true ground you should show almost a dead short maybe.5 at most,if not something is for sure wrong.you should not be seeing 16 to 19 volts anyplace on that truck.what junction block?
Click to expand...

I'm ohm testing grounds, should I be using the volts side of VOM to test them? The only ground I can get under .5ohms is the block.

I'm getting 16-19 volts at the junction block on the firewall near the FP relay with the truck running...
 
BoostedSUV

BoostedSUV

Active member
Re: One last shot... Breaking up!

cloneman315 said:
what are you using code 59?You have a set of 50s or 75s?I have a few chips I think that should be very close to that build from mine if you want to try that.Honestly I think it has wire issues someplace,are you real familiar with reading wire schematics?
Click to expand...

No code59 and I'm running 63lb injectors now. I took the 50's out last week... I've been getting better at reading schematics and I've been going through the service manuals. I've learned a lot chasing this issue!
 
WyoSyclone

WyoSyclone

Active member
Re: One last shot... Breaking up!

turboj91 said:
One thing (of many) that I do not get is if it was a wiring or ground issue, how does that relate to a VERY specific and consistant rpm issue. It's like clockwork, the same rpm, everytime. Another curve ball in my confusion is the new injectors moved the problem up the rpm range by a few hundred rpm. Again, consistant and specific. If a wire or ground was bad, how would a larger fuel injector have an effect on the wire or ground?
Click to expand...

That's why I was thinking about a bad diode tree in the alternator, or a coil leaking....both are very RPM dependent. The new injectors are probably pulling a tad more current which could move the issue one way or the other.

The high voltage at the junction block can't be caused by the alternator going bad because the entire truck would be seeing that voltage if that was the case. I'm really leaning towards a problem with the MSD box, ignition wiring, or coil.... but Matt did replace the coil so that may rule that one out.
 
BoostedSUV

BoostedSUV

Active member
Re: One last shot... Breaking up!

WyoSyclone said:
Can you post the part numbers of the MSD parts you're using Matt? Sounds like maybe a coil and a harness adaptor? I remember another post somewhere about there being a problem with one of the MSD harnesses.

Can you post a pic of that junction block/dizzy/coil area?
Click to expand...

I will get pics, I actually just put the MSD box in with the adapter harness a few weeks ago. I will try and get part numbers but I'm using an MSD 6A, MSD "ready to run" Dizzy from RPM, and MSD pin 8876 coil harness. I will have to check on the coil part number.
 
WyoSyclone

WyoSyclone

Active member
Re: One last shot... Breaking up!

BoostedSUV said:
I will get pics, I actually just put the MSD box in with the adapter harness a few weeks ago. I will try and get part numbers but I'm using an MSD 6A, MSD "ready to run" Dizzy from RPM, and MSD pin 8876 coil harness. I will have to check on the coil part number.
Click to expand...

So that kind of rules out the MSD being an issue if you just installed it a few weeks ago.....
 
T

turboj91

New member
Re: One last shot... Breaking up!

Where in the harness does the rpm get picked up? Cranking at 6300 rpm may be a clue to something.
 
You must log in or register to reply here.
Top