Light throttle ping from stoplight on hot days

[69-]

Every now and then I try to get hold of some leaded AvGas. Great stuff.
No pinging ever and even smells oldschool.

 

[Aspen500]

Gas is formulated for EFI and efi fuel pressure. Hot starts on hot days with a carb can be a problem. With the lower vapor pressure the gas boils and basically floods the engine during a hot soak. Just like water, higher pressure equals higher boiling point.

I really miss the station that was a few blocks from my house. They had a 110 race fuel pump. Unfortunately it closed a few years ago. Reason? A huge Kwik-Trip (big surprise) went in a block away. Used to put a gallon or two along with 91 octane in my Aspen. It would eliminate even the slightest ping on hot days, plus the exhaust smelled AWESOME! Only downside, it was $7.59/gal

 

[Voeltagear]

I use ethanol free 91 or higher octane (depends which station I go to). Cold starts are great. Hot starts on hot days? I hold down the starter and pray. Either the fuel is leaking down or it's simply evaporating out of the carb.

Getting gas from places that sell boat gas or sell 100 octane for the fancy cars is definitely the way to go. Someone working there will know where the gas came from and what kind of oxygenates are in that gas.

I haven't had starting problems, just the detonation on hot days. So far so good with the BP fuel. I now have moved the initial timing to 6° BTDC from 4° ATDC and I no longer have any detonation. That's a significant improvement. There was also certain RPM that the exhaust droned very loud, fingers crossed it's also resolved. Just for peace of mind I replaced all the rubber fuel hoses today as well. I also had to tighten up the vacuum advance spring because it started to jerk "trailer hitching" under light throttle with no load.

 

[Voeltagear]

I love the smell of race fuel! The BP ultimate doesn't smell to bad FWIW.

 

[Voeltagear]

It's possible. Worse though, ethanol accelerates deterioration which can cause a fuel leak. Regardless, it's not a bad idea to replace potentially 40+ year old hoses anyway.

Unless it says ethanol free, whether it's 87, 89 or 91 octane, gas may contain "up to 10%" ethanol. Might have none, might have 10%. Last time testing was done around here, ethanol blended fuel had anywhere from 0% to 6%. Suppose all depends on the station and where they get their fuel.

Hoses said fuel injection on them so not the original ones. I replaced them anyway. There was some black garbage in the line when I took it off the sending unit.

 

[Voeltagear]

I pulled my trailer today and had no pinging issues. I think I have sorted out. I'll have the O2 sensor bungs welded in the weekend of the 29th. Then I can see where my air/fuel ratio is.

 

[Voeltagear]

Today I pulled the distributor and went through everything. I missed the timing mark by a couple degrees and turned it back. The distributor didn't move right away so I checked how many degrees of crankshaft rotation it had before the rotor turned. It ended up being 6°. So that's at least 3° of distributor timing (or am I calculating it backwards? 12°?) . I'm thinking timing chain stretch? I don't know if that would make it ping but it's something to consider.

 

[Voeltagear]

So I've been running 91 octane without ethanol for almost 2 weeks now. At this point I don't have any pinging whatsoever. It feels like it has less power. I'm running 6° initial advance timing now, up 10° from 4° atdc. I'm dropping it off tomorrow to have O2 bungs put in tomorrow. I'll have data logs to look at next week.

 

[Duke5A]

Did you ever verify the balancer didn't slip?

 

[Voeltagear]

Did you ever verify the balancer didn't slip?

I did not.

 

[Voeltagear]

I have the wideband hooked up now. I found the step up was coming in way to late so I put the old spring back in. That helped with part throttle AFR. It is a bit fat, running 13's while cruising and 14.5-15 with a little bit of acceleration. 11. 5 to 12.5:1 under moderate acceleration. Something weird happens though. After about 20 minutes of in town driving it started going lean. It hit 16:1 at idle! And 17 to 18:1+ under light throttle! It was idling a little rough. I cruised around the block in my neighborhood accelerating, braking and turning left to right. It started to come back to rich then went lean again. Once I got home I parked and watched it. It stayed lean. So I hit the throttle and it went rich and climbed back up. I hit it again, it stayed a little richer. I hit it again, still richer. After 4 or 5 times the idle was back to normal and the AFR was about 12:1 again. Rich I know but it went lean last night and I thought I had leaned it out to much. I hadn't experienced what happened today. So my question is, what the hell would cause it to go lean cruising at 30 mph? Then get richer with a handful of throttle blips? And then stay that way at idle for several minutes of idling. My first thought is hot fuel but wouldn't it go lean again while idling with the heat soak under the hood. I never tried blipping the throttle in traffic to see if it stopped the ping. I didn't know it was leaning out in this manner.

 

[Voeltagear]

I just went for another drive. Cooler weather. It still creeps towards lean but not nearly as bad. 13.5:1 at idle and 15.5-16:1 cruising. Blipping the throttle several times makes it go rich and it stays that way for 10+ minutes.

 

[Voeltagear]

Maybe the vapor line is plugged? I'll check it later today. I'm thinking about adding a return line. Any suggestions where to plumb it into the tank? Can the vapor line from the carbon canister be used? Assuming it is not plugged.

 

[Voeltagear]

Today I plugged the charcoal canister purge line. It runs a lot smoother and holds the A/F ratio steady. Now I have to figure out what to do with the fuel tank vent. If its even hooked up to the tank.

 

[Voeltagear]

Did you ever verify the balancer didn't slip?

I checked it Friday. It is spot on.

 

[Voeltagear]

So the pinging came back in 90° weather. Watching the AF ratio shows 12-13:1 when it happens. I stepped up the accelerator pump just to see what would happen. The pinging stopped. I think someone needs to come up with new carb rebuild setup specs for today's gasoline . I'm not sure why it was going lean with the canister purge hose hooked up unless there is an orifice missing in the system. There doesn't seem to be any restriction and the line is connected to the tank.

 

[PED]

First off. I hope that when you deleted your EGR that you installed an open breather on the vale cover to vent pressure from the engine. If not, you should.
But what I believe is likely happening, is that your fuel line is placed to close to an engine heat source - intake manifold, exhaust header/manifold, etc.
When you are idling at high outside temps, the heat is causing your the fuel inside the line to percolate, and separate air from the fuel inside the line, which then gets pumped into your carb instead of fuel.
As a result the fuel level in your carb starts to lower - the longer it idles the lower it gets. When you accelerate, you don't get a full shot of fuel, so you get a hesitation. Once you are moving the higher RPMs get the fuel moving again and the fuel bowl fills and the power comes back. Rerouting or insulating the fuel line should cure the issue. Hope this helps.

 

[Remow2112]

I live in AZ. I have not caught what carb you are running. But if it is an AFB style and you don't have a decent phenolic spacer. It will boil the gas. It also helped to reroute the fuel line out and around vs. the original path past the alt and brackets.

You can also adapt the hose from fuel pump to carb to 3/8 which will get it more fuel volume that should help to keep it cooler.

 

[Voeltagear]

First off. I hope that when you deleted your EGR that you installed an open breather on the vale cover to vent pressure from the engine. If not, you should.
But what I believe is likely happening, is that your fuel line is placed to close to an engine heat source - intake manifold, exhaust header/manifold, etc.
When you are idling at high outside temps, the heat is causing your the fuel inside the line to percolate, and separate air from the fuel inside the line, which then gets pumped into your carb instead of fuel.
As a result the fuel level in your carb starts to lower - the longer it idles the lower it gets. When you accelerate, you don't get a full shot of fuel, so you get a hesitation. Once you are moving the higher RPMs get the fuel moving again and the fuel bowl fills and the power comes back. Rerouting or insulating the fuel line should cure the issue. Hope this helps.

Thanks, I didn't delete the EGR, it was done by a previous owner. I think your are referring to the PVC valve. It is still intact and works as it should. Heat doesn't cause air to separate from the fuel, it just vaporizes, meaning it takes up more space but it's still the same chemicals that make up gasoline. If I'm getting air in the system that's a whole different issue. I'll hook up a fuel pressure gauge this week and see if it's a vapor issue.

 

[Voeltagear]

I live in AZ. I have not caught what carb you are running. But if it is an AFB style and you don't have a decent phenolic spacer. It will boil the gas. It also helped to reroute the fuel line out and around vs. the original path past the alt and brackets.

You can also adapt the hose from fuel pump to carb to 3/8 which will get it more fuel volume that should help to keep it cooler.

It's numbers matching carter bbd. I'll hook up a fuel pressure gauge this week.