ignition problem - next step?

[PrairieDrifter]

Sounds like a fuel pump, and yeah I dont run the filter in the carb. Be sure to check rubber hoses in the system also, cheap and some extra reassurance.

 

[turpentyne]

Yeah, I was on the phone with my dad and that's what he said he does (drives same truck, but 350 & 2-barrel. He took the filter out of his carb and put an inline filter underneath.

I went ahead and put the in-carb filter in, since I'd bought it. Then I replaced the one underneath, out end toward carb... and noticed there's even a THIRD inline filter for a later add-on gas tank (That I haven't been using)

I hope there's not something goofy with the switch over valves. I hadn't messed with them, and I've only used the factory tank. But I wonder if I kicked them and caused a problem. (Yes, you read right.. plural. Instead of one switch valve there's a separate switch for each tank )

My day is ending for now, so I guess next weekend I'll have to tackle the fuel pump. I'm running out of things to check! (All needed stuff, anyway - considering I just bought it ) But if there's any other stuff to check, let me know. It now seems narrowed down to fuel pump though, I'm assuming?

UPDATE: I fiddled with the two gas tank levers, and loosened the fitting to the new fuel filter underneath to see if I was getting fuel there. And I did. I tightened things down, started up the truck, and it ran for about 20 seconds before running out of fuel. I think I'll replace that third filter, put some gas in the second tank, and try it again before I go replacing the fuel filter - just to see what happens. Thoughts?

UPDATE 2: Because I'm stubborn, I went out and tried another thing. I disconnected the fuel line to the filter... still nothing really coming out. A little. but not much. Tracked back to the line from my main tank into the t-valve for the tank switchover. Stilllll hardly anything. Getting creative and perhaps a little stupid, I left that line undone and dangling into a jar, took a deep and blew through the tank fill tube until some gas came out the dangling tube. Some came out, but I didn't have enough oxygen in me to blow..

 

[Sprockmonster]

Do that with a rag and compressed air.

 

[PrairieDrifter]

You can do it with a rag and air compressor like said above, but it really wont tell you much other than letting you know the fuel line isn't plugged.

You can disconnect the lines and blow air through them to clear any debris.

 

[turpentyne]

quick follow up on HEI wire

quick follow-up on this. The problem was solved with a new fuel pump and a couple replaced gas lines.

Once I started the truck up, it idled just fine, but when I put it under load by driving down the road, it seems to not like accelerating and runs a bit rough. Once up to a steady speed, it goes fine.

I double checked the plugs and wires, then dropped the gap to .40 and I did notice an improvement, but still rough.

So, I think for my next step I'll check that wire to the HEI, but I thought I'd ask how on here - to make sure I don't do something stupid. I've got a little multimeter, but I'm not really well-versed in electrical. I'm assuming I'd be checking how much voltage is getting to the BAT wire, coming from the ignition switch - but what do I ground to? Or I'm understanding wrong?

Help a semi-beginner understand the best way to do this part?

 

[firebane]

quick follow-up on this. The problem was solved with a new fuel pump and a couple replaced gas lines.

Once I started the truck up, it idled just fine, but when I put it under load by driving down the road, it seems to not like accelerating and runs a bit rough. Once up to a steady speed, it goes fine.

I double checked the plugs and wires, then dropped the gap to .40 and I did notice an improvement, but still rough.

So, I think for my next step I'll check that wire to the HEI, but I thought I'd ask how on here - to make sure I don't do something stupid. I've got a little multimeter, but I'm not really well-versed in electrical. I'm assuming I'd be checking how much voltage is getting to the BAT wire, coming from the ignition switch - but what do I ground to? Or I'm understanding wrong?

Help a semi-beginner understand the best way to do this part?

Easiest and most simplest way is look at the distributor. There are 3 plugs... 1 plug connects to the distributor itself and the other two plugs connect to a "tach" and "bat".

The "bat" connection should be fed directly to a 12v source controlled by the ignition. A lot of times when people convert points to HEI they use the same wire for the points to power the HEI and this is not correct.

So just trace the wire that connects to the "bat" and see where it leads you. If it leads to the square box on the firewall then either a) Someone has done the wire properly like I redid or b) They are using the points wire.

To check and see if its the points wire just look at it and it'll say "resistance wire".

 

[turpentyne]

ok.. this could be a problem..

I pray, pray, pray that when you say "black box on the firewall" you mean the fusebox in the cab. Problem is, I don't think that's what you mean.

It's dark here now, but with a flashlight, it looks to me like it goes from the bat connecter, into the cab and then a plug that also has an orange wire. Then it continues on to the fuse box, connecting at the top right, by where it says A/C

Either I managed to look at the wrong wire, or something doesn't make any sense at ALL. 0h, and it's a newer wire - no writing on it, nothing that says resistance wire

(Unless I traced the Tach wire without realizing it? Too damn dark to see. I'll check again tomorrow)

 

[firebane]

The black box is the bulkhead connector under the brake booster. But you say it goes inside the truck so this leads me to believe that it has been wired properly

Not sure what the orange plug is but you can unhook the connector from the distributor for the power and measure voltage with the truck off and it should be 0v. Then turn the key over but don't start and it should show 12v

 

[chengny]

Once I started the truck up, it idled just fine, but when I put it under load by driving down the road, it seems to not like accelerating and runs a bit rough. Once up to a steady speed, it goes fine.

This is a textbook symptom of a fouled fuel filter.

You just did a lot of disruptive work on your fuel system. It very possible that in the process of making those repairs, you knocked loose some of the debris that formed over 42 years.

Check/change your fuel filters. If you still have your stock Rochester carburetor don't overlook the internal filter - it's under/behind the gas inlet connection.

 

[turpentyne]

Except that I already replaced both filters. When i realized it was a fuel problem, that was the first thing I replaced. Along with a few fuel lines. The only thing left is to see if maybe there's a clog in the metal portion of the fuel line

I drove the truck to work today, and it really chugs going up the parking garage. I'm stumped.

UPDATE: question... Could it still be a problem with my fuel pump? It's brand new, but I'm wondering if it's possible for the lever not to matched up to the fuel pump push rod well? Or is this a situation where it either works or doesn't? It was hard to get the pump in under the rod but I'm assuming that once bolted in place, as long as the rod is above it, it'd be kinda hard to be wrong. I did tighten the bolts down as evenly as I could.

 

[turpentyne]

sorry to be a nuissance.

Just wanted to add that I checked the wire to the distributor, and it's fine. 0 volts when off, 12.4 when the key's turned on. So that eliminates that as any problem. ( I keep forgetting to add: The spark plugs I removed were at .35. I know it's not what HEI is supposed to be at, but that's where it was when running fine. Perhaps I should drop the gap on the new plugs to .35, just to see? )

I'm just stumped because the truck ran fine before it went down, I solved the problem and now it's rough. Only things touched are fuel pump, fuel lines, spark plugs, wires and ignition module. I didn't do anything that would turn the distributor. Is there a vacuum line somewhere that I might've missed? I'm pretty sure I've got that covered. There's one that goes into the carb, right?

I'm open to any other suggestions, or I'll have to take it to a mechanic to dig deeper, and I'm one poor ****.

 

[PrairieDrifter]

I would gap your plugs at .40-.45 and unhook the fuel lines at certain points and blow the lines out with an air compressor to clear anything out. Have you checked timing?

 

[turpentyne]

quick update. Got a timing light last night. This morning I checked the idle timing and came up with 8 before TDC

I'll have to check it at 2500 rpm later, when I have somebody to hold down the throttle for me.

But 8 seems not too far off from the norm, right? What is normal? abut 10 before TDC?

 

[firebane]

quick update. Got a timing light last night. This morning I checked the idle timing and came up with 8 before TDC

I'll have to check it at 2500 rpm later, when I have somebody to hold down the throttle for me.

But 8 seems not too far off from the norm, right? What is normal? abut 10 before TDC?

8-10 is the norm for most trucks. Your checking this with the vac advance not connected right?

 

[turpentyne]

that is correct. In fact, to be sure, I closed off both the hose and where it connects onto the carb.

So, next step, tomorrow I'll head out to my dad's where there's an air compressor, and see what happens when I blow threw a few lines. The only spots that could be plugged at this point are the metal line along the frame, and a remote possibility that the tank pickup is clogged. ( I blew into the tank manually and got some gas spit out the tube. )

If that doesn't solve it, next suggestions, short of "Help me, Mr Mechanic?"

My thoughts are to take off the new fuel pump and reinstall it to be sure, to drop the gap down to .35 just to see if it changes anything ( I know it's wrong with the HEI, I'm just trying to find where things are different ) Then... I dunno? Replace the distributor? Double check I'm not down a cylinder for some reason?? I'm stumped.