Engine hesitation (1 Viewer)

[Skreddy]

Is the hesitation momentary or?
I think I saw you are running the vacuum retard distributor, is the vacuum retard hooked up or capped off?
How old is the gas?

 

[Chuckha62]

There’s an old saying that probably applies here. 90% of carburetor problems are ignition. Think weak coil, bad condensor, bad 12v wire, dirty/loose/corroded primary connection. Those things will start to show themselves under load. In my case, a similar problem was chased back to a loose connection at the ignition switch.

 

[Brian/99uzj100]

There’s an old saying that probably applies here. 90% of carburetor problems are ignition. Think weak coil, bad condensor, bad 12v wire, dirty/lose/corroded primary connection. Those things will start to show themselves under load. In my case, a similar problem was chased back to a loose connection at the ignition switch.

I like that saying. Same thing happened on my rig. Engine stumbling in 3rd or 4th gear under load, usually going uphill.
I changed the fuel filter, fuel pump, and even had the carb rebuilt, but the problem remained.
I found an old post by mud member Pinhead that stated stumbling under load in higher gears is an ignition problem.
I started looking at the wiring around my coil and igniter and found a broken wire at the condensor.
$10 part and the problem was gone.
I'm sure I broke the old brittle wire by throwing a rubber car mat over the passenger fender to avoid scratching the paint while working under the hood.

 

[Groucho263]

Guys...sorry I didn't see the replies above...not sure how I missed them. I got around to replacing the fuel filter and that fixed the issue. I had done so much before with the carb/distributor/coil, etc. I was pretty sure it wasn't any of that. I think when the truck sat around with the Power Steering install, that the old filter which was probably dirty...got crusty, etc. Anyway, new filter and no hesitation. Thank you guys for the posts.
And @Brian/99uzj100, I capped off that air cleaner port. Thanks for noticing that!

 

[Groucho263]

Back to the drawing board. The fuel filter didn’t fix the issue and I have no clue what’s going on.

Here is what it’s doing. It starts easily with choke, immediately push the choke all the way in and it idles with no problem. I let it warm up for a couple minutes then drive. No problems…then I sometimes run into issues.

Sometimes I can drive 20 miles and it runs perfectly. Sometimes when I get less than a mile I run into problems and have to nurse it home. Sometimes I can drive 10 miles, park it then go into a store…come back out and start and drive for a minute and have problems.

Here is what it’s doing. The engine hesitates and as gas pedal is applied, it wants to quit and will literally go quiet. If I don’t do anything it will die. If I pull the choke out, it spits out a bunch of smoke (mostly black) and will keep running but roughly. If I quickly go to half choke it runs well, just at higher rpm. Sometimes this is how I have to nurse it home…at half choke. Yesterday as I was coasting down hill in gear, the motor quit and I noticed it quit when I came to a stop. Always starts again with full choke.

It has a City Racer carb. Fuel is just above half in the bowl (I adjusted this as the level was at the bottom of the glass). Fuel filter is brand new, and pump is new. Fuel lines from gas tank haven’t been changed. FJ60 distributor and timing is about 8-9 btdc. Do I need to adjust valves? Only has a couple hundred miles since last adjustment.

Carb adjusted…3 turns ccw adjusted idle to 675-700. Turned mixture cw until the idle drops slightly. Adjust idle to 675ish. Even tried more rich settings using suction which is about 20psi. Idle solenoid pretty new.

I feel like it’s a fuel delivery problem, but can’t figure out how. Is it a vacuum leak that causes it to die when adding gas pedal? Could it be the carb jets? Carb only has a couple hundred miles on it.

Any help is appreciated. Really want to be able to trust the motor and drive it.

 

[fjc-man]

Try a test drive with a jumper wire between the Positive battery terminal and the positive side of the coil bypassing the ignition switch to eliminate the possibility of intermittent / poor connection through the electrical portion of the ignition switch.

 

[Groucho263]

Copy. I will try that Tuesday when I get back to it. So, just to make sure I don’t mess up…just connecting a wire, but does it need to be a certain gauge? Thank you.

 

[69FJ40HILIX]

Guys...I'm close to being able to drive this thing (1975 desmogged). I have spent so much time working on the electrical and thanks to @Cromagnon and @Coolerman I am almost there! Turn signals don't flash (hazards flash)...but getting there. Thanks to everybody on this forum.

My new issue...while driving the engine hesitates or skips. For some reason the PO put in an electric fuel pump, but kept the engine driven pump. So, I have 2 fuel filters (one OEM, one aftermarket) an electric fuel pump and engine driven pump (one fuel tank). I think I need to bypass the engine driven pump and cut out one of the fuel filters?

Things I have done on the engine...timing is right on, valves adjusted, new carb, adjusted rich/lean and RPMs at 660-670, vaccum reading close to 20. Engine runs great at idle and sometimes it runs great (2-3 min), but within a couple minutes it goes back to hesitating/skips/pops/stutters. Could it be the fuel delivery?

Any help is always appreciated!

I would look down the carb throat when it is running to see if it is dumping fuel and if so maybe something in the float bowl, float level or the needle valve may have trash in it. I had this issue once and after exhaustive searching and replacing parts I found my distributor advance unit was sticking & the points plate had oblong worn holes where the advance turned the base plate. It would work fine at an idle but would get stuck in advanced position intermittently. Have you checked the vacume at the distributor and have you tested the advance with vacuum? Just a thought, hope that helps.

 

[Chuckha62]

Back to the drawing board. The fuel filter didn’t fix the issue and I have no clue what’s going on.

Here is what it’s doing. It starts easily with choke, immediately push the choke all the way in and it idles with no problem. I let it warm up for a couple minutes then drive. No problems…then I sometimes run into issues.

Sometimes I can drive 20 miles and it runs perfectly. Sometimes when I get less than a mile I run into problems and have to nurse it home. Sometimes I can drive 10 miles, park it then go into a store…come back out and start and drive for a minute and have problems.

Here is what it’s doing. The engine hesitates and as gas pedal is applied, it wants to quit and will literally go quiet. If I don’t do anything it will die. If I pull the choke out, it spits out a bunch of smoke (mostly black) and will keep running but roughly. If I quickly go to half choke it runs well, just at higher rpm. Sometimes this is how I have to nurse it home…at half choke. Yesterday as I was coasting down hill in gear, the motor quit and I noticed it quit when I came to a stop. Always starts again with full choke.

It has a City Racer carb. Fuel is just above half in the bowl (I adjusted this as the level was at the bottom of the glass). Fuel filter is brand new, and pump is new. Fuel lines from gas tank haven’t been changed. FJ60 distributor and timing is about 8-9 btdc. Do I need to adjust valves? Only has a couple hundred miles since last adjustment.

Carb adjusted…3 turns ccw adjusted idle to 675-700. Turned mixture cw until the idle drops slightly. Adjust idle to 675ish. Even tried more rich settings using suction which is about 20psi. Idle solenoid pretty new.

I feel like it’s a fuel delivery problem, but can’t figure out how. Is it a vacuum leak that causes it to die when adding gas pedal? Could it be the carb jets? Carb only has a couple hundred miles on it.

Any help is appreciated. Really want to be able to trust the motor and drive it.

Been here, done this. Do the hotwire. You most likely have a bad 12v connection in the ignition. The reason the choke seems to make a difference is that a slightly richer mixture ignites easier with a weak spark. Ask me how I know and how long I spent trouble shooting.

 

[70fj40]

It would not hurt to replace fuel lines coming from the tank. You indicated those had not been replaced.

 

[Groucho263]

Thanks guys. Out of town today. Will do the hotwire when I get back. That makes sense with how it’s acting.

Will also try the others too. It probably needs new lines. I was thinking maybe the gas tank had crap in it, but it was newish from the PO and I’ve put plenty of fuel through it so it should be good.

 

[Pighead]

If I quickly go to half choke it runs well, just at higher rpm. Sometimes this is how I have to nurse it home…at half choke.

Classic sign of a non-operating fuel cut off solenoid. Which you say is new. Perhaps a poor connection in the wiring to the solenoid? You can also jump 12 volts straight to the solenoid (listen for the click) and drive it to rule out a fault in the wiring to it.

 

[Engineer8000]

I read your tale of woe with your engine. It can be frustrating.

Check the wiring to that fuel cut solenoid too. I had a car with Lucas wiring that had a bad terminal crimp that would be intermittent when hot. I got out the heat gun with it sitting in the driveway running and was able to find the bad connection that way.

 

[Groucho263]

@Pighead @Engineer8000 you guys were right on the money...I really hope. The fuel cutoff solenoid that I installed a while back had a plastic connector on it with the male wire inside. It was made for the female side to connect to it...but I didn't have that plastic connection so just attached a spade type female connector (it fit, but not super tight). When I started the motor and wiggled that connection, the engine struggled...when I pulled on it slightly, the connections came apart and the engine quit. I removed the male plastic connector and put the correct connection on it...then shrink wrapped the connection...and the truck runs like it should. Couple of test drives and no more symptoms. I'll keep driving it to see, but I think this may have been the issue. Thank you guys!

 

[Groucho263]

Well that wasn’t it. Drove around for a bit today with no problems. Then on the way to the store…same issues.

Im going to try the jumper between the coil and battery.

 

[Chuckha62]

Well that wasn’t it. Drove around for a bit today with no problems. Then on the way to the store…same issues.

Im going to try the jumper between the coil and battery.

When mine did what yours is doing, I ultimately traced it to a loose wire at the back of the ignition switch. I chased my tail for the better part of 4 months before finding it.

 

[Groucho263]

Test drive with the jumper from pos coil to pos battery. Just to make sure I did it right, the engine didn’t turn off using the ignition. This is correct?

First part of the drive was good for about 7 min. Ran normal. I went to the gas station to get gas then back to the house. Halfway back to the house and it starts to act up per usual. This time though I was unable to manage it as well with the choke. Had a couple times where it would just quit and not react to the choke. Took about 2 times the effort to get it home.

At one point after it quit, I got out and wiggled the pos and neg battery cables out of sheer no ideas…got back in to start and it ran normal all the way home.

Most of the time full choke gets the motor rpm’s high enough that I can get it into 2nd and idle. This time the choke only helped to get it started then the motor would almost die even with me pushing the choke in to catch the rpm etc. It acts like it’s out of gas when it does that. But starts up and fires right up after it dies with full choke.

On the igniter/coil there are 2 wires that have matching connections, are these supposed to be connected?

 

[Chuckha62]

I haven't looked back in this thread to see all you have tried, but have you checked for a vacuum leak? Richening the mixture with the choke is a very common "solution" with a vacuum leak.

 

[Groucho263]

Yeah, I did look for leaks. I didn’t thoroughly look though. It’s right at 20psi from the brake booster. Should I look from another location?

 

[Chuckha62]

Yeah, I did look for leaks. I didn’t thoroughly look though. It’s right at 20psi from the brake booster. Should I look from another location?

It's unlikely 20 psi, it's probably HG (inches mercury), which is not bad. A vacuum leak at the intake gasket or base of the carburetor however will lean out your fuel charge and cause it to run like you're describing. Adding choke enrichens the mixture and can partially make up for the lean condition. I found a vacuum leak at the carburetor base of a Blown 392 Hemi awhile back with a can of WD 40, believe it or not. You're not necessarily looking for something overtly flammable like starting fluid (which will atomize and be picked up by the air cleaner), to find a vacuum leak. You just need something very localized to spray around your gaskets and seals. If the RPMs pick up and the engine smooths out, you're getting close.