Here is an example pf the misfiring/backfiring issue I'm having with my 20r. Before I adjusted anything I wanted to see if there was anything obvious I should check first.

I did make a thread about verifying timing, which I will be doing tomorrow.
https://toyotaminis.com/forum/threads/how-to-properly-set-timing-20r.26550/

 

Whats the condition of the rotor and cap?

Is the carb bowl actually full up? Mine would do stupid shit like that and i got rid of the FPR and its working fine. But im running a carter fuel pump

 

Almost sounded like it was spitting out the carb and that would be a lean condition. Are you running the 2 piece spacer? Might what to get some carb cleaner and spray her down. If you had a valve hanging open you would get backfire and no compression on that cylinder.

 

Sounds a little electrical to me, check the coil tower distributor cap and rotor for signs of arcing or corrosion, you will see a black mark that looks like a crack. check the distributor shaft for wear (grab the rotor and see if there is any play in the bearings this will cause the points gap to change). If it has points replace the condenser. Also, the ignition switch or broken wire can cause backfiring, to check the power supply run a wire from the battery positive to the ignition side of the ballast resistor if it has one and take it for a drive. The engine will not turn off on the key but it is a good test to see if the fault goes away

 

The rotor and cap have less than 3,000 miles on them.

Can I check the fuel bowl visually with the filter off on a Weber?

I've heard other people having trouble when running a FPR but from everything I'm reading, I need to limit the fuel pressure to 3psi on a Weber. How can I limit this without one?

 

Checked compression on all cylinders and they are within 156-160 psi

I believe I'm running the two spacers. I'll need to double check. I guess I could hit it with some carb cleaner just to make sure.

 

Thanks. I'll add this to the list of items to check. Haha

 

You can check the fuel bowl, just pop the filter off and theres 2 slots where you can look into the bowl.

Ive been running a Carter 4070 with no FPR and no problems.

 

The 2 piece a known to leak. Without a fuel pressure regulator if it goes past 3psi it will push past the needle and make a very rich mixture. Is this happening only after it gets hot? Are you running a return or dead head? Electric pumps pretty much cook the fuel. It seems like vapor lock now that I think of it. I'm guessing this is the rv in the picture and goes on the road for long periods. Not something you see in a going around town rig really. But a highway rig it's a common problem. I think you can get a gm fuel filter or something with a return for a quick fix.

 

I guess it would be a good idea to keep the FPR for now. Would I need a different manifold to run a one piece weber?

Currently I'm not running a return line. Do most toyota owners that swapped in the weber run one?

Do you have a link to the GM filter?

 

I'll check this the next time I drive it. Thanks

 

Transdapt makes a one piece adapter. About 60 bucks. It takes forever to ship though. I didn't run one but had this fix in mind if I ever ran into it. Alot of guys still run a mechanical that has a return. Mechanical pumps aren't recommended with weber's though. I don't have a part off hand I can recommend but a simple search of "fuel filter with return" will bring something up. You should be able to confirm what's going on if you have a clear filter near the carb. You'll see bubbles.

 

I've swapped out the fuel filter a couple of times last year since this sat for years with old fuel in the lines. I recently just swapped to a clear filter so I can keep an eye on things. So it will be obvious when it bubbles? I'll check on this when I take it out next.

 

Yeah the bubbles will be from it boiling. Also you'll feel heat on the lines. The big give away that you are experiencing vapor lock is the hard hot restarts.

 

Looking into vapor lock more it could be because of heat soak heating the carb up. Knowing there is an expansion hole for coolant right under the carb the bowl may be boiling. Gas boils at 185 degrees. If you have a temp gun might want to check that. The 1 piece adapter probably would help some if thats a problem. It's a bit taller.

 

I currently have a coolant line on the intake manifold. Would it be beneficial to cap this off and reroute the line, or would that increase temps in the manifold?

 

Is this the adapter you were referring to?

https://www.jegs.com/i/Trans-Dapt/969/2120/10002/-1

I see they also sell this model but it was listed specifically for the 22R. I'd hope I could use it on both because I'd eventually like to swap in a 22R.

https://www.jegs.com/i/Trans-Dapt/969/2181/10002/-1

 

Thats the one. Pretty sure the bolt patterns different but you may be able to get a 22r carb to 20r intake adapter. But You'll be back to a 2 piece setup. I don't think capping off the line will be beneficial. You'll still have coolant flowing through the intake.

 

You want to leave the coolant line attached to the manifold. It’s necessary for your thermostat to open correctly. Blocking it off will also allow the temperature to buildup in the rear section of the manifold. This could create vapor lock conditions.

 

Thanks to Pearce posting the proper way to time the early 20r motors I found out it had been set incorrectly for a while. Which I find weird that it ran as good as it did.

To give you an idea it was more aligned with the first mark (the one on the left), and the dist was almost maxed out (turning clockwise). I know have it properly aligned with the second mark (on the right), and the dist not sits in the middle of the adjustment range.

Test drive #1 - 10 miles. Driving around our town and 2-3 runs up to 65mph with no issues.
Test drive #2 - Few days later, 40-50 miles roundtrip. Within 1-2 miles I had one small backfire from the carb going uphill. Two separate backfires later on, but the last 20 miles at 50-60mph I had no issues.

It still has a small quiet backfire after I shut the engine off. Takes 2-3 for that to happen.

No visible sign of bubbles in the fuel filter. Fuel lines didn't feel too hot and the engine idled just fine.

Does the engine need a bit more timing? It's currently at 8