diagnose this plug pic

[Hozer 88GTConv]

After a complete upper engine rebuild and cylinder head overhaul, I still have a problem in number 5.
Guides, valves, springs, seats, gaskets all new, checked good.

Could this be fuel?
The plug still fouls after a couple of hours.
All other plugs look good.

I am pissed off beyond belief.

What do you think of this plug?

Thanks.

[raptor]

Well ya if the top end and gaskets are new I would try a different injector. It is a fuel issue by the look of the plug.
good luck

[GhOsT6_9]

I agree with raptor. Looks like it could be a plugged injector, cuz you're havin a fuel delivery problem.

[Hozer 88GTConv]

I really don't know much about troubleshooting injectors.

Do I just take 'em out and go get them flow tested and resistance checked?

The only problem is I have swapped injectors several times over the past few months and I still have the same problem in number 5.

I went up two heat ranges in cylinder number 5 (autolite 3926's) to see if that makes a difference. All others are 3924's at the prescribed .035"

Thanks...

[302 LX Eric]

Have you done a compression check of all the cylinders? If so, how did #5 look in comparison to the rest?

E

[Hozer 88GTConv]

Compression is good, about 118 psi in number 5.
Number 6 was 118 also.
7 and 8 were 120.
Taken about 2 weeks ago, just prior to the upper teardown.

I have rebuilt the cylinder heads, new head gaskets, intake gaskets, etc....
I know I had a oil problem in 5, but I fixed it with some new teflon valve seals.

I am really zeroing in on my fuel pressure, 02 sensors, and the thermostat.

My motor never gets above 180. I get 18 MPG and I have a feeling it's due to the computer sensing that the car never gets to operating temp, so it keeps the mixture constantly rich by staying in open loop.
That, has in turn, fouled my 02 sensors to boot.

I am going to change to a 192 degree t-stat today and get some off the shelf fuel injector cleaner.

I also have verified my fuel pressure at 39 PSI.

[302 LX Eric]

I had a similar issue with my old 302 combo in that I was running too cold of a thermo. I think I was running a 160* at the time (don't laugh too hard) and the darn thing was running soooo cold with my huge Griffen radiator.

If it's been a while since you changed the O2's it's a good idea regardless. However, if it is the O2s and you're running too rich, wouldn't all the plugs be fouled?

Let us know how the 192* thermo and new O2's work out for you.

Good luck,
E

[USMC302]

If you have swapped injectors and the problem is not following the injector it's not clogged. i remember reading this a while ago when you were about to pull the heads. Check for the pulse on the injector wire to be for sure that it's triggering the injector to fire. make sure the injector wiring harness is extremely grounded too. I am amazed #5 is still acting up, it's getting to me now.

[juiceman]

so whats the problem? is it just that you dont think that plug is as pretty as the others? it doesnt looked fouled bad to me, have you had a problem like a miss in the motor? maybe you have a weak spark in that cyl. if the injector was clogged you wouldnt get fuel, so hence its not an injector if the plug is fouled. if your car is running fine and you have good gas mileage why you messin with things?

[Hozer 88GTConv]

Yeah, I'm anal.

But the reason why I am doing all of this is because my car is a daily driver and I need it to be in the best working order so I can put my supercharger back on.

I put a 195* t-stat on and it runs great. Juiceman, the original reason behind all this is that number 5 was fouling after only a couple of hours of use.
I haven't checked number 5 in a couple of days, but the motor isn't missing at all.

It still is very rich at startup. Yeah, I know the 02's don't work until the motor warms up a little. But it's rich beyond that point. I haven't replaced the 02's yet, b/c I wanted to see how the t-stat affected things.

Today, 02's...and a peek at number 5. Might sneek in a dyno run today.

After pulling the heads, I can't believe it's starting to look like mostly a fuel problem...

[USMC302]

but the motor isn't missing at all.

Then the plug isn't fouled.

[Nixon1]

At only 39 psi of fuel with the vacuum on, you shouldn't be running all that rich unless, like you said, you're never reaching closed loop operation, or there's some other problem, like bad O2's that you mentioned....

That's about how one of my plugs looks right now, except yours are a little worse. I think we diagnosed mine as high speed glazing and slightly lean. That was at 40 psi. My pressure is currently at 45 psi and it runs a little rich but the extra fuel gave it a VERY strong low-end boost and it's got more tip-in power now.

If you've got an AFPR, and I assume you do, I'd give it a few more psi of fuel pressure once you get the other issues sorted out. Still strange though that cyl #5 is the only plug looking like that. Do the others look similar but not as bad, or does it look like it came from an entirely different motor...?

[juiceman]

ok then, generally a fouled plug in only 1 cyl. is an idication of either a weak spark, or a weak cyl. its obviously getting the fuel but its not burning it. of course there is the posability that you are not getting as much air flow to the 5 cyl, but i assume you have a good intake and your valves are adj properly. if it were an o2 sensor prob. where the comp was in open loop operation then it would affect the whole motor not just 1 cyl. i honestly wouldnt worry much about it as it seems the car is running fine. youre not gonna get a perfectly balanced cyl motor from the factory.