Help! Engine developes miss after hitting bump

[Torxhead]

It would probably be a good time to replace the fuel pickup sock, I have seen a stainless version available, maybe at Morris. Also make corrections to the fuel level readout at the float height. Plan on cleaning the that collects in there out.

 

[007]

If that's your path, just route your fuel line to a gas can and bypass your tank, etc. If the problem remains it's not in your tank and you save the work. If it goes away then your on to something.


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[Munypit]

I really don't want to drop the tank. so while stuck in the house with 2 sick kids, I've been brainstorming and thought of what change I made when this The cylinder leaked from day 1 and I replaced it with a new unit. This is what got me to thinking, could I be losing vacuum at the reman booster, causing the carb to loose fuel pressure? It seems I can hear a vac leak with the engine idling but can't pinpoint it.

 

[hdgapeach]

Questioning the brake booster? You can always disconnect it from the manifold / carb base, block off the leaking port, and give it a short drive to rule it out. Just gotta be careful 'cause you won't have power brakes till you hook it back up. You'll have to stand on the whoa pedal hard to work the brakes, but it's doable.

That would rule out the booster and associated hose if it solves the issue.

 

[Peanut Butter]

Based on one of your earlier post, "the PO made several changes to the fuel system", It would be a good idea to check all of the fuel lines.

The fuel runs from the tank to the fuel pump. Just before the pump there is usually a clear fuel filter. From the pump it goes to the top of the engine where there is another fuel filter. This one is a round silver barrel looking filter. There are two lines that run out of this filter. One to the carb and one to the return fuel line. The return line must be on top. There are also lines that run to an evap canister usually located on the driver's front fender. If any of the vapor lines or the return line are missing, you could have problems like you describe. Here is a picture of the second fuel filter. Rod

 

[Munypit]

The PO installed a single inlet/outlet fuel filter going to the carb with no return line hookup. It ran fine like this up until 3 months ago. I've had the jeep for a little over 2 years now.

 

[IOPort51]

Just to humor me, take a look at the motor mounts and the grounding strap.

I broke a mount once and it would all but shut down going across a RR track.

 

[Techlight]

My vote is going for electrical somewhere if you found one problem with an old wire there's probably another one somewhere...but

It's a long shot but...Do you have the pulse air on that jeep (smog stuff: small pipe that comes of the exhaust pipe at the CAT and routes on either side of the engine at the firewall and into the stock intake). I'm pretty sure this is a CA model thing, but I'm not sure and ya never know. Mine has acted up with the symptoms you mention like that twice, like it was out of fuel and coughing and it was my pulse air injection check valve.

 

[Munypit]

Just to humor me, take a look at the motor mounts and the grounding strap.

I broke a mount once and it would all but shut down going across a RR track.

IO I have checked the ground strap and I also have another ground #8 wire from the battery to the block and a #8 ground to the frame. All this I have read over the last 2 years about grounds had me putting grounds everywhere.

 

[Munypit]

I went ahead and pulled the tank. to check the sock, fuel lines, sending unit. Sending unit and sock were replaced last winter. and both still looked good. The main fuel line was a little "soft". Going to replace all the rubber lines tonight and reinstall tank. My brain keeps telling me to go back to vac lines.
P.S. Needed to pull tank anyway to hook up new wiring harness to sending unit for the Speedhut cluster.

 

[Torxhead]

While you are at it a close inspection of the 5/16 fuel line just might show some cracks indicating your problem. Extending ground line from the sending unit would work best if it were run all the way to the battery negative. Hope you find your problem.

 

[Munypit]

Sitting in my office trying to eliminate possibilities. In my thoughts if the brake booster vac linewas bad The engine should not idle. (I have had to replace the 1/4 vac line to the canister due to this) and it comes off the same vac port on the intake. But I am not sure about a 3/8 vac line that I ran from the vapor canister to the carb. this line is hooked to a T that is connected on the front of the carter carb. i also noticed when I pulled the top of the carb off to check the float that the little plate in the top front of the carb that is held down with 3 little screws was loose and 1 of the screws will not tighten up this is also where the 3/8 vac line that I ran is connected.

 

[Munypit]

While you are at it a close inspection of the 5/16 fuel line just might show some cracks indicating your problem. Extending ground line from the sending unit would work best if it were run all the way to the battery negative. Hope you find your problem.

I am going to change these fuel lines tonight.
The new wiring harness for the Sending unit to the Speed hut guages has the ground coming all the way to the guage under the dash, where I plan on running a new dedicated ground just for the new guage cluster.

 

[007]

Another 2cts...

If/when you go replacing vacuum lines, use as much fuel line as you can. Any time you can get a better rubber hose than a vacuum line that will fit (even if you have to clamp it) you're better off. They last longer, handle fuel vapors better and are less likely to collapse.

Secondly...

I'm R E A L L Y interested in your Speedhut stuff. I'm doing that as well this spring. What all comes with it? What do I need to be prepared for?

 

[Munypit]

007, I did not buy the complete guage set, just the speedometer cluster with built in tach. It came with a new wiring harness to the fuel sending unit, new temp probe and sending unit, GPS antenna ( still have not decided where to mount) By the way this thing looks NICE! and hooks up kinda like a new stereo. i.e dedicated ground, all time power so the gps does not have to search for satelites every time you crank it, and switch power.

 

[Munypit]

She ran! and she ran good. Blew out all the fuel lines, replaced every 30 year old rubber fuel and vapor line, took apart "check valve/needle?" at fuel inlet of carter carb. inspected sending unit, Found aftermarket sock was pushed all the way up the inlet tube to the point of the plastic end cap on sock could have been restricting flow. She idle rough for a little while hit the skinny and it would try to die. disconnected pcv valve vac line, let some air go through it then hooked it back up. Took the jeep on a test run. Boy was I happy when we passed the spot that it had been dying at with out even a hiccup. drove about 5 miles out and back staying hard on the skinny pedal and she never missed a lick! I feel about 90% sure that I have corrected the problem but you never know with these things.

 

[Torxhead]

Thanks for the update, glad to hear it works.

 

[Hedgehog]

So you had a stuck or fowled PCV valve? Makes sense, pressure build up in the engine.