Author Topic: 20r engine acceleration issues (Read 12963 times)

rcbro · « **on:** Oct 27, 2008, 12:43:29 PM »

Hey Guys,
I've been trying to hunt this probem down forever and just can't find it.

I have a 20r motor, hedman header, 2.25 exhaust and a 32/36 weber carb.

Anywhere after 3/4 throttle my engine bogs and nearly shuts itself off. Doesn't matter if I gradually give it throttle or slam it. Runs great up until that last 1/4 of throttle. Anywhere in the 3/4 range truck runs great, I just can't give it any more.

It also bogs horrible under load such as cilimbing steep inclines or being in sand/mud.

I have a very small air leak between my header and exhaust flange, but don't think this is the problem because it was much worse before I attended to it and I didn't notice a change. I also got a weber jet kit and played around with jet settings for a week and never got a difference.

It could be my fuel filters but there only 2,000 miles old, but it could be my distributor isn't advancing right too. Anyone else have some ideas? Wenesdays my day off and I'm going to tackle it some more.

jonathan82toy · « **Reply #1 on:** Oct 27, 2008, 02:16:07 PM »

Run a stock toyota carb....problem solved

emsvitil · « **Reply #2 on:** Oct 27, 2008, 02:30:51 PM »

Weak Ignition, spark plug gap too big, defective spark plugs.

79coyotefrg · « **Reply #3 on:** Oct 27, 2008, 03:32:48 PM »

Quote from: jon82toy on Oct 27, 2008, 02:16:07 PM

Run a stock toyota carb....problem solved

NOT

well not for me anyway

rcbro, what size jets are you running because your running WAY to big of fuel jets and need bigger air jets

see what you have and let me know

rcbro · « **Reply #4 on:** Oct 27, 2008, 08:11:19 PM »

I had it written down somewhere what I was running but lost it, I'll have a look come Wednesday as to what jets I got in there.

rcbro · « **Reply #5 on:** Oct 28, 2008, 03:07:19 PM »

Quote from: 79coyotefrg on Oct 27, 2008, 03:32:48 PM

what size jets are you running because your running WAY to big of fuel jets and need bigger air jets

see what you have and let me know

Here's what I'm running now, let me know where to go from here, any advice is much appreciated!

79coyotefrg · « **Reply #6 on:** Oct 28, 2008, 04:27:30 PM »

WOW those are big jets for a 20R

leave the 140 where it is but change the 155 for a 130 or 125

swap positions on the 180 and 170 jets the bigger should always be on the secondary side

rcbro · « **Reply #7 on:** Oct 28, 2008, 05:12:56 PM »

just tried what you suggested with no difference... any other ideas lol

79coyotefrg · « **Reply #8 on:** Oct 28, 2008, 05:32:36 PM »

Quote from: rcbro on Oct 28, 2008, 05:12:56 PM

just tried what you suggested with no difference... any other ideas lol

well the smaller jets will greatly improve your fuel mileage cause they were really big for a 20R

what size did you install?

have you cleaned the rest of the carb??

what gap are you running on the plugs??

rcbro · « **Reply #9 on:** Oct 28, 2008, 05:55:37 PM »

I changed the 155 to a 135 and swapped the two as you said. I'm running what the factory required for gap

79coyotefrg · « **Reply #10 on:** Oct 28, 2008, 06:11:34 PM »

do you have anything around 120??

rcbro · « **Reply #11 on:** Oct 28, 2008, 06:13:03 PM »

nothing that low

79coyotefrg · « **Reply #12 on:** Oct 28, 2008, 06:28:40 PM »

something must be restricting your exhaust,

ok i went back and read the first post,do you have a timing light??

if so, set the timing to 5* at low idle, then hold the light on the timing mark and slowly raise the idle up and see if the timing advances itself

rcbro · « **Reply #13 on:** Oct 28, 2008, 07:05:08 PM »

its at 8* (factory) right now and doesn't change. Not an air leak as it runs and idles perfectly below that 3/4 mark.

79coyotefrg · « **Reply #14 on:** Oct 28, 2008, 07:45:42 PM »

Quote from: rcbro on Oct 28, 2008, 07:05:08 PM

its at 8* (factory) right now and doesn't change. Not an air leak as it runs and idles perfectly below that 3/4 mark.

it doesnt change at all when you run the rpm up?? sounds like the mechanical advance is stuck, you need to take it apart and see whats stuck/broke/binding

did you have the vacuum advance hooked up??

79coyotefrg · « **Reply #15 on:** Oct 28, 2008, 07:48:03 PM »

post pics of the distributor when you remove the cap, and below the plate that holds the pickup coil

Marlin · « **Reply #16 on:** Oct 29, 2008, 08:44:01 PM »

I once had a '79 with an electric fuel pump in the gas tank that had the same problem. After rebuilding the factory carb and replacing the dirty fuel filter, it made very little improvement. I proved that it was a fuel delivery problem by using a new can of carb cleaner and a long section of small clear vinyl hose that I ran through the firewall and into the air cleaner housing where I taped it in place so it would spray into the primary throat. When I got on the gas, I hit the nozzle and the truck kept pulling. It ended up being an worn out, dragging fuel pump.

Marlin

79coyotefrg · « **Reply #17 on:** Oct 30, 2008, 11:24:02 AM »

hey there ya go, rcbro, do you have a 79 model??

rcbro · « **Reply #18 on:** Oct 31, 2008, 11:27:04 AM »

no its the 80, fuel pump is in the engine bay of the head. Got a new pimp to try.

Yotaman80 · « **Reply #19 on:** Oct 31, 2008, 07:56:35 PM »

im not very familar with the 32/36 carb but i had the same problem on my 80 with a 20r and stock carb. it would run cherry up til about 3/4 throttle or over 55 mph and it would start clunking and start bogging it self down. as soon as i let off the throttle and it can back under 55 it ran fine. my problem was the secondary vaccum advance to the carb, the diaphram had a pin hole in it. all it took was a 25 dollar rebuild kit from auto zone and the problem was fixed. im not sure if the 32/36 is a vaccum secondary but i hope that helps. tell me if you need any more help.

rcbro · « **Reply #20 on:** Oct 31, 2008, 08:01:59 PM »

again I know nothing, but its worth a shot? Anyone know if I have one lol

79coyotefrg · « **Reply #21 on:** Nov 01, 2008, 08:54:45 AM »

Quote from: rcbro on Oct 31, 2008, 08:01:59 PM

again I know nothing, but its worth a shot? Anyone know if I have one lol

did you fix your distributor?? i told you if the timing didnt advance when you reved the engine then your mechanical advance (centrifugal weights under the pickup coil) or the vacuum advance wasnt working aka pin hole in the diaphram

Rocksurfer · « **Reply #22 on:** Nov 01, 2008, 09:27:46 AM »

I have a bad vacuum advance, been to lazy to fix it. If I have the vacuum lines plugged in I will get the same issues you currently have. Try this, unplug both vacuum lines and either plug them or just run them back into each other. Now drive it and see if there is a difference, if it goes away you know where the problem is.

rcbro · « **Reply #23 on:** Nov 01, 2008, 08:33:58 PM »

I have a distributor in the mail, and got a fuel pump today

79coyotefrg · « **Reply #24 on:** Nov 02, 2008, 06:58:42 PM »

Quote from: Rocksurfer on Nov 01, 2008, 09:27:46 AM

I have a bad vacuum advance, been to lazy to fix it. If I have the vacuum lines plugged in I will get the same issues you currently have. Try this, unplug both vacuum lines and either plug them or just run them back into each other. Now drive it and see if there is a difference, if it goes away you know where the problem is.

20R should only have one vacuum line

Rocksurfer · « **Reply #25 on:** Nov 02, 2008, 08:06:22 PM »

Forgot about that since my 80 had a 22r/20r. Of course I had to stuff a bb in my vacuum line on the 80 so it wouldn't ping.

Yotaman80 · « **Reply #26 on:** Nov 03, 2008, 07:51:02 PM »

Quote from: 79coyotefrg on Nov 02, 2008, 06:58:42 PM

20R should only have one vacuum line

they have two vacuum lines if its a federal or canidian models

79coyotefrg · « **Reply #27 on:** Nov 04, 2008, 05:24:54 PM »

Quote from: Yotaman80 on Nov 03, 2008, 07:51:02 PM

they have two vacuum lines if its a federal or canidian models

ive never seen a 20R with 2 vacuum lines to the distributor

if you had one i'm sure it was a 22R distributor in a 20R because they are compatible

Yotaman80 · « **Reply #28 on:** Nov 04, 2008, 06:17:02 PM »

ill take a picture of my truck its a federal model and has two vacuum lines on it. its has a sub diaphram and the main diaphram.

rcbro · « **Reply #29 on:** Nov 04, 2008, 10:03:03 PM »

well figured out the issue thanks to some helpful eyes tonight. Turns out the copper tube that squirts the fuel in on the secondary side had twisted upside down. So instead of shooting the fuel downward, it was shooting upward.

Pulled it out and turned it around and now the sucker screams!

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