Fuel type question

Hi

I bought my jeep last november, and I did not ride it much this winter, only short run around the block, couple of miles each ride. At a point, I needed to put some gas in. So I took the snowblower gas. It is what we call here ``super`` (higher octane or something...) Before I bought it, i tried the jeep and there was no problemm at all. Now it backfires and idles erratically.

Let's suppose that the P.O. did put some regular gas in it, and I put some ``super`` gas in it, can it be the cause of this behavior ???

I'm about to check the ignition timing tonight, but do you think that if I switch back to regular fuel, it will be ok ?? (or better than it is now ?)

With the prices of gas, I think I'll keep it on regular....what do you all think ?



Thanks for listening

Bob in Sherbrooke

 

Higher octane usually won't cause a benefit or a problem inless the engine is built for it. you can get in trouble running too low of octane. I'd say it is timing or something else.

 

a few things come to mind.
1. what year is your jeep? is it designed for unleaded (hardened valve seats?)
2. is it stock? the 225 had 9:1 compression which is perfect for super unleaded (91-93 octane). you can advance your timing and gain extra mileage (and hp) from doing this. the more you advance it, the better it runs on the highway. too high compression and too low of octane will give you premature detonation (knocking and pinging). the octane slows the burning down so it doesnt detonate (explosion faster than the speed of sound). you want it to burn slowly to push all the way to the bottom of the cylinder. too much octane on a low compression engine will cause it to burn too slowly and still be on fire big time when it comes out the exhaust valve. this can burn the valves up and deffinately cause backfiring through the exhaust. i dont know if jeeps back then were setup for unleaded or if you have to run octane additive in them.
my advice is to drain the tank and wash it with mid grade or higher. if you have the 225, and you set your timing up to run it, you can get better mileage from running super unleaded than with regular unleaded. enough to off set the price (plus way more power and efficiency).
check timing before you drain the tank because it could be off which can cause alot of back firing, but if you didnt do anything but add gas and run it, i dont know that it would just jump.
keep us updated.

 

The gas in the tank couldn't have water in it from winter condensation could it? Water in the fuel definently causes issues.

 

Thanks for answering you all

My dad came home last night to check the timing with me. The label on the hood is partially erased, especially the part where the ignition timing number is written, so I checked in the haynes book and we timed it like it says, 1 to 5 deg. if I remember correctly. So we set it at 3.

The engine runned fine afterward (better than when we started). We had removed the top of the air filter, but when we put it back, the engine was dying, so we unplugged the tube that come from under the ``nose`` of the air filter (not sure of the correct name in english...)

There is some sort of trap that is supposed to open when the air get hot, or something like this, but mine was stuck.

Then it was time for the first real ride. My wife sat next to me and we got down the street. After 1 mile or less, the engine gave a little backfire
and it was dying when I press the gas pedal. On idle however, it ran fine. We did the ride back home in three attempts. it started fine, ran for a little, than died at some time. So I got to the side of the road, stop the engine, let it sit for a minute or so, and started all over again...



Are these symptoms of a carb ajustement issue ?? Too much gas in the mix ???


What do you think ??

Bob in Sherbrooke, Province of Québec


I have a CJ-5 1977, 258, with a YF 1 bbl carb

 

Sounds like a possible vacuum leak or something keeping fuel from getting to the carb. Try a new fuel filter, your short rides and stored gas may have plugged an already dirty filter.