Misfire, wont smog test. Need some advice

Just re-reading this post.
So, no personal history with the truck.
Did you say how many miles are on it?

ArdWrknTrk wrote

Just re-reading this post.
So, no personal history with the truck.
Did you say how many miles are on it?

No, just bought it about 6 mo this ago. Odo says 80k but probably 180, interior is in great original shape so I dont think it's more than 180

Certainly is a really cherry looking truck.  
The previous owner must have kept up on maintenance.

Still not a bad idea to see if there's a bunch of slop in the chain.
These trucks came with a nylon cam gear that wears right out.

That's why I always recommend a double roller, steel gear timing set from a later EFI 460 as replacement.
Cloyes makes one you can get from Amazon for under $50

Ok, in addition to checking the timing chain as Jim suggested, pull the plugs out, see what brand/heat range they are and line them up in order and take pictures of them so those of us who know how can "read them".

85lebaront2 wrote

Ok, in addition to checking the timing chain as Jim suggested, pull the plugs out, see what brand/heat range they are and line them up in order and take pictures of them so those of us who know how can "read them".

Okay thanks all, really appreciate all your common sense help thus far. I went to a bullnose facebook group and wasnt getting anywhere. I'm going to take a break from this thing for Easter but I will get back to it on monday to try these suggestions and post my findings.

I posted a picture of my spark plugs a few weeks back.
They seemed about perfect (to me) even though my truck smells rich at idle.

85lebaront2 wrote

Ok, in addition to checking the timing chain as Jim suggested, pull the plugs out, see what brand/heat range they are and line them up in order and take pictures of them so those of us who know how can "read them".

Okay Monday Update: I am getting back to working on this today. I pulled the distributor cap and turned the crank clockwise then back counterclockwise. The rotor turned instantly when turning back counterclockwise so there doesn't appear to be any timing chain slack as far as I can tell.

I pulled all the plugs and took a few pics. Let me know what you think? Are these okay to put back in or should I get new ones?

5&6 look ok.
What's up with #2?
With that much carbon on the insulator I don't know how it could NOT be tracking...

I won't use Autolite plugs any more.
NGK UR4/6630 is my choice now.

ArdWrknTrk wrote

5&6 look ok.
What's up with #2?
With that much carbon on the insulator I don't know how it could NOT be tracking...

I won't use Autolite plugs any more.
NGK UR4/6630 is my choice now.

Okay got it. Im going to go pick up a new set and just replace them all. Time to get gapping. Will post results once finished.

I've never (in 40 years) had an NGK that wasn't in spec.

.042-.046 is the spec for DuraSpark.
Mine are always .044-.045

Replaced all the plugs, still running rough although I was able to start it without pumping the gas so there is a little improvement and it didn't die when in park, idled okay, dies immediately when i put it in gear but that's what it was doing before. Have to get it rolling (just smash the gas when you switch it to Drive) then it seems to drive fine. Not sure if that's a separate issue.

I think that maybe i have a fuel system issue that's causing the missfire/running rough. The previous owner installed a Holley Red-top fuel pump in it and there is a switch added to the dash that you have to turn on before you start it so the fuel pump is always running. I know that the red-top has a set psi so there is no need for a regulator but the pump itself looks old and the fuel lines are kinda a mess. There is also a very slight fuel leak from some sort of canister thing connected to fuel lines under the driver's door. Should i start a new thread?  

You have what's called the 'Hot Fuel Handling' electric pump system.

There are a few threads already about fixing this, but you're always welcome to start a new thread.
We'll be there to walk you through it.

ArdWrknTrk wrote

You have what's called the 'Hot Fuel Handling' electric pump system.

There are a few threads already about fixing this, but you're always welcome to start a new thread.
We'll be there to walk you through it.

Reading through some of the posts on here related to the "Hot Fuel Handling" system it is my understanding that these came from the factory with in-tank electric fuel pumps. Is that correct? My fuel pump is a holley red-top that sits outside the rear tank.

Also, based on this info it sounds like the vapor separator regulates the fuel psi but could it still be too high or low because of this different pump? I think maybe it is too high because i had to really adjust the rear float on the new carburetor i installed as fuel was coming out the rear bowl vent.

If you have the vapor separator before the carb it is (was?) Hot Fuel.
The separator is not a regulator, but it can limit fuel to the carb if the screen inside is all gummed up.
You seem to have the opposite problem.
Do you have a gauge to test fuel pressure?


I do not know what pressure the Holley Red Top is providing.
Float adjustment on the 4180 is (IIRC) parallel, with the bowl inverted.


I don't know why someone hacked up the fuel system.
Do both tanks work, but only the rear needs that pump?
Is the rear (Holley) the only one working?

Let's go down the wiring rabbit hole.
We'll start with the fuse and links, get past the inertia switch, and move to the oil pressure switch and relays. (Pump power and selector)

Check your VIN to see what engine it came with. The canister, if it has 6 lines going to it sounds like it is for an EFI 302. The hot fuel handling package on Darth was a 6 port motor operated valve that changed tanks by switching which pump was powered and changing the gauge to that sender. If your truck originally had a 302 and someone stuck a 1984 460 in and was clever enough to change the section with the emission information also that could be some of the issues.

I don't know if that would ever fly in California.
Besides, 302's were never found in 250 HD's.

Maybe a 351 H.O., but not a 2V.

Here are some pictures, will check the VIN here shortly.

The canister that is leaking, guess its a filter


The Fuel Pump


The previous owner wasn't sure if the front tank worked. i have not tested it yet and have just been using the rear.

Here is the vin info so it looks like this is the original powertrain

Wow, so they just ripped everything up and went around it?

A 6 port switch valve from Pollak can be adapted to replace the missing.
(Don't even need to adapt the lines, because they're gone now)
It's available as a kit (with plug, etc) for ~$85 on eBay.

We'll need to find what's left of the wiring to see how much of that you need.
Relays are cheap, so is a oil pressure switch.
The tank selector is in the center dash bezel and the inertia switch is in the passenger footwell. Either on the side of the tranny hump or in the kick.

Gary says "Florida man was here"
I say tweakers are everywhere.

So, look for a pair of relays near the driver's side hood hinge, and look at the center back of the engine -right up near the firewall- for the oil pressure sender.
It's a little time can looking thing, like an old time fuel filter with a wire on top.

Can you take pics of these things too?