:confused:

[Phantom]

I posted a thread last April & got some great advice - but it hasn't resolved my problems...yet.

Here's my set-up & issues that I'm hoping some of you world class mechanics can diagnose:

84 GN with recent rebuild on all motor internals
10/10 stock crank
.030 cylinder bore with hypereutectic pistons
Poston's GN107T cam
green stripe 30# injectors
Kirban's billet adjustable f/p reg
160 degree t-stat
Walbro 340 w/hotwire kit

The car was starting, idling, & running great through the gears but at constant RPM would start to buck then backfire hard through the throttle body & blow black smoke out the exhaust. This was with TS42's & stock regulator (& it was gas fouling the plugs at ~150 mile intervals.

I had AC TS42's in it with stock regulator. I've sort of concluded that it was running way fat with the cam, inj, cold plugs, & stock reg, so went to TS43's & adjusted the f/p down (a mechanic installed the adj reg & plugs & at this point I don't know for sure what PSI is on the rail). He also found that the boost line to the wastegate sensor was blowing off causing overboost.

In the process, the ignition quit firing on 1, 3, &5. ECM & crank sensor were swapped with '84 parts, coil pack & module was swapped with 'known good' C3I setup from 87 but the 'mechanic' that installed it didn't know there are differences in the pin assignments. According to him, no changes with any of the ignition changes.

I'm at a loss here - - yup, confused. Any ideas??

 

[6SENSE]

a mechanic installed the adj reg & plugs & at this point I don't know for sure what PSI is on the rail

Make sure your not running some rediculous amount of fuel pressure.

In the process, the ignition quit firing on 1, 3, &5. ECM & crank sensor were swapped with '84 parts, coil pack & module was swapped with 'known good' C3I setup from 87 but the 'mechanic' that installed it didn't know there are differences in the pin assignments. According to him, no changes with any of the ignition changes.

2 cylinders are firing simutaneously with our SFI/wastespark setup, so if 1,3,5 arent firing I doubt 2,4,6 are either. As far as the '87 module. Are you saying that it is currently installed without correct pin changes?

P.S. heat range plugs you mentioned shouldnt be an issue (43s are still cold compared to what stock was for our cars: stock was 45tsx's gapped @ .060). By the way what are you gapping them at? Also, your cam shouldnt be an issue (unless its bad ), its just a step over stock (202/202 if I recall).

 

[WFO]

a word of advice:learn to turn your own wrenches.it'll save you a lot of $$ and headaches down the line.

your "mechanic" is a tithead.is the car running at all now?

 

[Mr.Buick]

Ignition

In the process, the ignition quit firing on 1, 3, &5. ECM & crank sensor were swapped with '84 parts, coil pack & module was swapped with 'known good' C3I setup from 87 but the 'mechanic' that installed it didn't know there are differences in the pin assignments. According to him, no changes with any of the ignition changes.
If you are running 87 ignition and coil pack you need an adaptor from caspers to change the pin out. CCCI Module Converter $56.00, Coil base adapter $30.00 (aluminium plate)
If you are interested I have the module converter that I did not need because I changed the complete engine wiring harness. ($40.00 + shipping)

 

[6SENSE]

You need to take some time and take a look at all the great info over at www.gnttype.org
There is detailed instructions for converting the ignition module connector there. It is just a matter of switching a few pins. I cant remember how many, its been awhile, but its not many and its not hard to do.

a word of advice:learn to turn your own wrenches

 

[Phantom]

I've done some more testing. There's spark at all 6 cyl's, verified timing & reset the cam sensor. Had the car running (real rough) for a couple minutes but it currently won't fire. Smells rich.

Still not sure if the adj regulator was ever adjusted or what it's set to now - I need a F/P gauge. The ign module/coil pack is '84 so no pin changes necessary.

BTW - I've been wrenching on this car for the last 6 years now. Rebuilt the motor, suspension, most of the interior, & rear end myself & finally got frustrated with this backfire problem. I'll NEVER let anyone else touch it with a wrench again unsupervised by me - & damn sure won 't leave it again.

 

[6SENSE]

Is the cam sensor in there right? Make sure its not 180 degrees out. Timing chain on right? Sounds like a timing problem. Make sure these are okay first. Always start with the basics.

 

[turbofish38]

I had a simular problem with one of my hot airs. Double check and make sure that the ground for the ignition module is good. The ground is made through the mounting bracket. Make sure all 4 nuts are there that hold the module to the bracket and the two nuts that hold the bracket to the manifold are there. A bad ground here might give you a no start or mis-fire problem.

 

[Phantom]

It ran GREAT through the gears & fired up just by twisting the key before I took the car to someone else. I verified the cam sensor - it's in right. Don't think the timing chain's an issue (& really don't want to crack the timing cover again yet) - it's steel double roller instead of the stock crap. Haven't checked the ign module ground but I can say that I's believe that the grounds - all of em - are suspect. That is/was to be my next project so it's good to see that I'm at least on the right track.

Thanks for all the input!!!!!

 

[WFO]

Originally posted by Phantom
I've done some more testing. There's spark at all 6 cyl's, verified timing & reset the cam sensor. Had the car running (real rough) for a couple minutes but it currently won't fire. Smells rich.
Still not sure if the adj regulator was ever adjusted or what it's set to now - I need a F/P gauge.

any idea what the "mechanic" gapped the plugs at?i'd say they're all fouled now,so go get 6 fresh cr43ts's,gap em at .035 and start over.

Originally posted by Phantom

The ign module/coil pack is '84 so no pin changes necessary.

so you swapped back to the 84 stuff?cuz earlier you said it had an 87 setup...

check those grounds,good luck.

later,sean

 

[Phantom]

I pulled #1. It's new & gapped @ .040. Don't think it was ever fired on these plugs.

The mechanic that had the car also had 2 87's in his shop - poor suckers that own 'em. He swapped in the late model ignition then removed it. Guess I didn't spell that out too well.

So I'm off to clean up all the grounds & hunt up a F/P gauge.

 

[WFO]

kewl,you need to pull those plugs and gap em down to .035 MAX.

i'd be willing to bet you have too much fuel pressure.was the plug you pulled fouled/wet?

 

[Phantom]

I had a simular problem with one of my hot airs. Double check and make sure that the ground for the ignition module is good. The ground is made through the mounting bracket. Make sure all 4 nuts are there that hold the module to the bracket and the two nuts that hold the bracket to the manifold are there. A bad ground here might give you a no start or mis-fire problem.

I pulled the ign module & checked all grounds internal & external. All nuts are in place & tight. On the wiring tieing the coil pack to the ign module, #1 wire is light blue, #3 - green, #5 - yellow/black, and 2,4,6 are dark blue (grounds?). Are these the correct positions?

Also, where is the neg battery cable supposed to connect? Mine's tied in with the harness ground at the aluminum accessory bracket. The only other block to frame ground I have is at the firewall. Should there be more?

I had the headers rewelded (both sides were cracked) by a guy in Sarasota, FL several years ago. From the quick visual I gave them, I noticed a bit of slag inside the tubes - too far in to grind off. Would that corrupt the flow enough to cause the constant RPM backfire problem?

 

[turbofish38]

My shop manual says #1 is yellow/black, #3 is blue/black and #5 is green/black(or gray/black) for the 84-85 coil-module. Ididn't have a hot air coil handy but I'm looking at a 86-87 coil and its the same color routing on the wires. Yes the only two grounds are the battery cable to the alt bracket and the ground strap to the firewall. I was also reading on another post a couple of weeks ago and the cure for a simular problem was a bad terminal on the module connector. Apparently moisture had corroded the terminal so it wouldn't make a connection. All turbos have the welding slag from day one so that shouldn't cause a problem. I also rebuilt the short block on my 86 a few months back and I got #3 and #5 plugs wires backwards and had a simular problem. The car idled smoothly but the minute you put a load on the engine it would backfire.

 

[Phantom]

GREAT INFO!!!! I'll switch them when I get home. It started snowing here in KC today so it's my cue to get the beast back on the road.

 

[Mr.Buick]

Backfires

Some over looked items to check, wastegate solenoid, EGR solenoid, vapor canister solenoid, must have at least 20 ohms of resistance or they will cause ECM failure. My vapor canister solenoid took out 4 ECM's before I found the problem. The filter at the bottom of the vapor canister was so dirty that no air could get through. Check your EGR valve I have seen them rust out and leak all the time.

 

[Mr.Buick]

Ignition wiring

The wiring for the ignition module to the coil pack is #1 yellow, #5 green, #3 blue, and #4,2,6 Dark blue

 

[6SENSE]

Ditto on checking the plug wires. I have had a similar situation. Car ran good until I got into it and it would backfire bad out the intake.
Problem was that the plug wires on the passenger side couldnt hold up to the heat. Two of them had broken down on the inside and seperated from outside layer. Almost felt like mush in my hands. At night I opened up the hood and could see the spark escaping and arcing against metal. (Wires were Autolites ordered through Advanced Auto).

 

[Phantom]

Well.....the coil's wired right but as I'm pulling the right side of everything apart to swap the DP I took the O2 out & got smacked by an exhaust full of raw gas. Think it's a wee bit rich?!? Enough to melt/eat the lead off the fresh donut at the turbo. Guess I'd better toss in the new plugs while it's apart. Save a knuckle or 2! Already have brand new Delco 681 plug wires (cold air, but they fit). Solenoid's will be the next check along with the F/P gauge that should get here next week.

 

[HOTSIX]

OKay...here's one to add...

I had a no start condition after the rebuild on my car last year. I was frustrated to no end with all the sensor checks, grounds, coil pack, module etc etc.

Drove me nuts.

It turns out to be my injectors. They were cleaned and flow tested but not installed right away. Sat for about 1 month while engine got rebuild. It turns out the fluid they use to clean the injectors has to be removed (by using them) within 24 hrs or so or else they will seize up.

Unless you tell 'um they won't be used right away then they might not clean the solution out for you. Re-cleaned and tested = no problem started up right away.

Just my nightmare shared with you in case it helps.

I was told a hundred times...check for gas on plugs, check for gas on plugs....even try to spray some in TB while you crank it (dangerous tho) to see if it fires.
GAS + SPARK + COMPRESSION = FIRE