Seeking Advise: Carburetor/Timing/Vacuum Advance

[Cecil14]

I burned up a 258 while pulling my hair out trying to figure out a vacuum leak, turned out to be a loose intake. By the time I finally figured it out, the damage was done and I'd cooked a piston. You may consider a new intake/exhaust manifold gasket regardless. That'd also give you an opportunity to get the EGR fixed correctly, if that's something you're interested in doing.


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[bagusjeep]

Is it a "Made in Spain" weber? It has to be cast into the body "Made in Spain". There are copies out there sold as Genuine Webers which are not and are often difficult to balance.

Did you read the instructions for the 32/36 very carefully when installing? Did you make sure the manifold adapters were totally flat (I rub mine on emery paper on top of glass). Do you still have the original phenolic spacer? Yes, the right size jets makes a lot of difference, but the Webers work with an idle circuit and a progression circuit before you hit the full load. The throttle butterfly, when adjusted with the curb idle speed screw, should not uncover the progression port. This makes off idle poor. It is covered in the instructions.

Secondly, you have a choice to connect the distributor to ported or manifold vacuum i.e. to have no vacuum advance or maximum advance at idle. I find on the 258 that using the manifold vacuum source at the base of the carb gives a much better response. (I have Weber 38 DGMSs on 2 of my 3 258s).

Advance at idle with the vacuum disconnected of 8 to 10 degrees is fine. However you should verify the ignition markings first, the crank damper can turn on the crank and throw the markings out.

Lastly the real Webers can only handle stock fuel pressures of about 6psi. You can get a Viton seat which will handle more. If you have the original mechanical pump and a return line to the tank from a 3 way filter near the carb, it would run fine. The 3 way filter needs to be horizontal and have the return at the 12 o'clock position. if you are on electric, it depends which one, high pressure pups are useless and require a FPR to tone them down, but they still benefit from the tank return and filter.

[bagusjeep]

Thanks wiley-moeracing!

I also noticed a vacuum line (I believe it's a vacuum line...) that connects to the back of he intake manifold and goes to a black cylinder mounted above the engine on the fire wall. What is this, and could it be the source of the vacuum leak...

Aloha,

Could be a vacuum reservoir or a purge cylinder. Either way I suggest you disconnect and plug all ports until the engine gets running smooth, that includes the EGR, brake booster, only leave the distributor connected.

[Ophale]

Aloha Bagusjeep,

Sorry for the delayed response to your informative post. I was visiting mom on the main land for her birthday the last two weeks and when I returned my wife just purchased a 2008 BMW X3 for her birthday and I needed to fix some things... Headliner is drooping, expansion tank leaking, brakes needed to be bled. It has 44K miles, and with a little detailing, it should shine and be good to go for sometime. I guess I have a thing for inline 6 cylinder engines... My other car is a unicorn 2009 BMW 328i touring with 6 speed manual. I do have the daily driver, 2004 Tacoma 2.7 4 cylinder 4x4 regular cab...

I digressed...

Yes, it is made in Spain and packaged by Redline. I purchased it new a few months ago.

I have pulled the manifold plates a month ago and wet sanded them down, as I read somewhere this was an issue. I'm pretty sure they are flat and are not leaking (no reaction when I sprayed carb cleaner around the plates).

I also have taken the carb off numerous times to physically see that the progression ports are not exposed and that I'm at or less than 1.5 turns in from contact of the idle screw when choke is completely open.

Currently, I have the distributer port not connected, but was planning to use the port vacuum. My port vacuum line is connected to a vacuum gauge while I'm trying to determine the stalling at idle issue. I been trying to adjust to zero vacuum at idle and keep the engine running. I also have a tachometer connected to the HEI Distributor. When I'm close to zero vacuum (maybe 2-3" Hg) the tachometer is at 250 - 350 rpm.

I think I have a vacuum leak... So far there is nothing connected to the manifold or port vacuum lines to the carb with the exception of vacuum gauge I explained above and the brake booster. I'm now considering that I have a leak in the brake booster system (Check Valve or the booster itself) or the manifold gasket.

My next step is to cap off the brake booster system and see where I'm at. I may pull the manifold off and replace the gasket. I'm a little hesitant to do this first, as I don't want to snap any bolts... I've already tightened the intake/exhaust manifold bolts.

As for fuel pressure, I have a mechanical pump with the discharge going to the fuel filter. Bottom discharge port from fuel filter goes to a Holley fuel pressure regulator set at 2.5 psi. I have a fuel pressure gauge on one side of the low pressure port on the Holley and the other port goes to the weber bowl. Top port from fuel filter goes back to the tank.

Not sure what the vacuum reservoir or purge cylinder is? Is this the round cylinder that is on the fire wall that connects to the intake manifold? I disconnected that too, and capped off. I put a brand new EGR valve in, but it is not connected to the exhaust or the vacuum lines. Capped the exhaust port with an NPT plug and have a end cap on the vacuum nipple.

I also have the PCV system not connected to any vacuum source.

I believe I tested the crank shaft marking by slowly hand cranking the engine until it was top dead center with a chop stick in cylinder one. I believe the marking was very close to zero. I may need to reconfirm with a better method.

Mahalo for all your questions! I think I'm close to getting the old girl to run. I'd like to move on to brakes next...

Aloha,

[Ophale]

It's working!!!

I found out why my weber 32/36 wouldn't idle at 0"hg . The spark plugs... When I purchased the Weber and HEI distributer, I decided to replaced all the spark plugs as a cheap and preventative insurance to make things work well right from the start. Didn't think new spark plugs would be an issue... However it turns out that the plugs I purchases were the NGK Platinum plugs. I recently found out Platinum plugs don't work well with the 4.2 l engines. What works well is the "cheap" copper plugs. I stumbled on this when I was talking with my neighbor as he was struggling with tuning his Porsche 356 speedster kit car's carburetor. It ended up that he purchased platinum plugs too and got a tip from a master VW mechanic to replace them with "cheap" copper plugs. He suggested I do the same thing. After searching the CJ forum, more people over there with 4.2 liter engines, I found several members suggesting the platinum plugs made their engine not run well and rich. I now can idle at 0" of Hg and the exhaust doesn't smell like unburnt fuel. Will work on the tuning little more, but I believe I'm basically 95% there...

Next, the brakes... Hopefully this task will be strait forward...

Thanks for all the help, and I hope the suggestions on the resolution to my carburetor issues will be helpful for other members.

Aloha!

[wiley-moeracing]

interesting that the platinum plugs would make that happen? more like the plug or plugs were damaged from the get go and or your coil/ ignition system is weak. if all else checks out you may have a burnt valve or a sticking valve...

[rang-a-stang]

Yay! Progress!!!

[Ophale]

Hi wiley-moeracing, I was skeptical about plugs mattering too. I was offered a choice at the Oreilly-Zone... between the $2 plug (copper), $6 plug (platinum), and the $10 plug (iridium). Not receiving a PhD or performing any research on spark plugs, I naturally chose the middle price point. This strategy has served me well in the past, the cheap stuff is too cheap, the middle of road stuff usually balance quality, cost, and performance, and the expensive stuff usually gives minimum benefit for the increased cost, usually at the expense of reliability. Besides the Wagoneer project truck, I own two BMW, and a Toyota Tacoma. I can definitely tell you where the engineers leaned (performance vs. reliability) when deciding the components to use for each of the vehicles...

Anyway, over at the Jeep Forum there are a few threads discussing "which plug for the 258?". It seems several members suggesting "in there application" the platinum plugs didn't work out so well.

https://www.jeepforum.com/forum/f8/spark-plugs-258-a-1328450/

https://www.jeepforum.com/forum/f8/258-spark-plugs-1344030/

What I can cull from both of these threads is that Platnium plugs were designed for application where there are individual coils for each plug... Don't know if this true. However, there is a strong suggestion that the platinum plugs don't work as well as the copper ones in the 4.2L application with a distributer ignition. Then the threads degrade to the Autolite 985 vs. Champion RFN14LY tribe arguments...

Of course this could be just be a bias that seems to show up on forums where if something doesn't work out, you have a few "vocal" people commenting on the issue, while there is a 100,000 people that have experienced a positive outcome and have no need to comment. It gives the appearance that things are far worse than they really are...

Aloha

[Ophale]

Yay! Progress!!!

Hi rang-a-stang! Yes, progress! I have been stuck at this point for 6 months and started to loose interest because I had no good ideas to try. Once I put the plugs in and started the engine, I new right away it made a difference. No more gas smell in the exhaust and when I disengaged the choke, the engine idled at 0 port vacuum. This was huge, because now I can start the process of setting the fuel mixture screw. I need to fine tune things with the timing, but I will leave that for another day.

Next on the list:

I have a whole box of brake parts that need to be installed including new rotors and pads for the front axle, pads and drum brake kit for the rear axle, and a new hydraulic brake proportioning valve (rear axle seems to lock up prematurely)

After the brakes, I need to move on to the coolant system. My radiator is looking very sad but not leaking (probably because the fluid is 1 part coolant, 1 part H2O and 1 part stop leak...).

Finally, I need to address the little issues to make sure I can get the Wagoneer to pass a Hawaii State safety inspection. This will probably include addressing the gauges in the cluster (which I may need to lean on you for some expert advise), windshield washer fluid pump, running lights (hopefully just a blown bulb), and new safety belts for the font seats. I may need to weld in new floor boards as there are a few spots that seem a little thin with irregular ports that have excellent views of the tarmac below...

Maybe in a few months I will address the exterior rust and start improving the cosmetic issues. However, I'm beginning to see your "point of view" on leaving things alone and just driving it.

Aloha!