Bad fuel economy and warm starting issues

396 Views 3 Replies 4 Participants Last post by Luckymac, 6 mo ago

ThisGoodBoi

Discussion Starter · 6 mo ago

Hello folks I'm back with a bit of a laundry list of symptoms hoping I can get some advice so that I'm not chasing my tail.
After remounting the Weber I started doing some work trying to get the YJ some better fuel mileage. I am currently getting around 30L/100Km (7.8Mpg) city and about 15L/100km (15Mpg) highway.
Ive done a lot of searching on the forums after buying the jeep and so far this is what I know about it.

1990 YJ with 4.2L I6 manual
TeamRush ignition upgrade done with all new parts
32/36 Weber Carb with manual choke installed and tuned with vacuum gauge
Timing adjusted to 8* with timing light
Nutter Bypass done.
Holley fuel regulator installed between carb and filter set to 3psi
New spark plugs
Stock tire size.
Fuel filter has return line

So here's what is going on. The YJ starts nice and easy when it is cold and it runs great for as long as I'd like it to. No rough idles when at running temp and no issues with acceleration or power. When I turn the jeep off I can start it up again if I try within 5 minutes and she will start no problem. If I wait longer than that the jeep takes forever to start. The starter cranks for a second sometimes two and sounds like its going to start then instead of cranking (I believe that's the right term) it begins to make a whirring or spinning sound. That will continue for as long as I hold the key in the start position. I wait for the spinning sound to stop and then try to start the jeep again. This will continue anywhere from 1 minute up to 15 minutes. It will either decide to start or the engine will cool down and then it will start no problem. Ive tried the hammer trick but its never worked. Sometimes it feels like it is going to start but if I give it gas it immediately stops and begins spinning. If I pump the skinny pedal too much or if I hold it down it won't crank at all. Again once its started it stays running and has no issues. Ive pulled the starter and the bendix gear has a bit of wear on it but not too much, the fly wheel is in good condition.

Other issues I've noticed that may or may not be related: The spark plugs have light brown corrosion on them that I believe indicates a lean condition. However the exhaust smells rich and if I hold up a piece of paper to the exhaust it shows black soot, same with on the snow while running at temp or when warming up. The exhaust has a low popping sound that is kind of sporadic. Like someone is hitting a tiny bass drum in it. The idle sits high at around 1000rpms and the idle mixture screw is almost all of the way in. The idle speed screw is completely backed off.

The fuel mileage is my main concern followed by the starting issue. With the cost of gas in BC its almost $60 just to drive 100km or 60 miles. Ive ordered a new K&N fuel filter and it should arrive in a couple of days. Any clues on where to start with this would be incredibly helpful.

See less See more

Save

1 - 4 of 4 Posts

Got it at last

· #2 · 6 mo ago

Your laundry list is pretty inclusive of any and everything that can go wrong.
15 mpg is about as good as it gets. The 7.8 city sounds like your rich at idle which is also indicative of pumping the pedal and flooding occurring. Methinks your Idle is a little too rich.
With the manual choke make sure you close it off within a minute or two of starting. It's only designed to draw fuel into carb on cold start. Once the temp gauge starts to register close it. Your ambient temp will affect this.
Colder block temps will require longer choke time.

Is your pressure regulator before or after the fuel pump? Might make a difference on fuel getting to carb from pump working too hard..or not. Just a theory/question in my head.

If it idles at 1krpms with no idle screw pressure your throttle cable my need adjusted out, vacuum leak or your needle seats may be damaged and too much fuel getting by. Especially if the needles are are most closed off.

See less See more

Save

Reactions: 1

Rauland04

· #3 · 6 mo ago

As for your problem re-starting once the engine is warm, it sounds like vapor lock. I had this issue when I first got my YJ. Basically, the fuel in the line above the engine block gets warm and vaporizes. You have to wait until it cools down and condenses before the engine will start and run.

I replaced me mechanical fuel pump and it solved this problem. I just bought a cheap one from Summit. You should also be sure your return line, to the gas tank, is clear and fuel can flow back freely.

15mpg on the highway sounds pretty good to me.

Save

Luckymac

· #4 · 6 mo ago

ThisGoodBoi said:
Hello folks I'm back with a bit of a laundry list of symptoms hoping I can get some advice so that I'm not chasing my tail.
After remounting the Weber I started doing some work trying to get the YJ some better fuel mileage. I am currently getting around 30L/100Km (7.8Mpg) city and about 15L/100km (15Mpg) highway.
Ive done a lot of searching on the forums after buying the jeep and so far this is what I know about it.

1990 YJ with 4.2L I6 manual
TeamRush ignition upgrade done with all new parts
32/36 Weber Carb with manual choke installed and tuned with vacuum gauge
Timing adjusted to 8* with timing light
Nutter Bypass done.
Holley fuel regulator installed between carb and filter set to 3psi
New spark plugs
Stock tire size.
Fuel filter has return line

So here's what is going on. The YJ starts nice and easy when it is cold and it runs great for as long as I'd like it to. No rough idles when at running temp and no issues with acceleration or power. When I turn the jeep off I can start it up again if I try within 5 minutes and she will start no problem. If I wait longer than that the jeep takes forever to start. The starter cranks for a second sometimes two and sounds like its going to start then instead of cranking (I believe that's the right term) it begins to make a whirring or spinning sound. That will continue for as long as I hold the key in the start position. I wait for the spinning sound to stop and then try to start the jeep again. This will continue anywhere from 1 minute up to 15 minutes. It will either decide to start or the engine will cool down and then it will start no problem. Ive tried the hammer trick but its never worked. Sometimes it feels like it is going to start but if I give it gas it immediately stops and begins spinning. If I pump the skinny pedal too much or if I hold it down it won't crank at all. Again once its started it stays running and has no issues. Ive pulled the starter and the bendix gear has a bit of wear on it but not too much, the fly wheel is in good condition.

Other issues I've noticed that may or may not be related: The spark plugs have light brown corrosion on them that I believe indicates a lean condition. However the exhaust smells rich and if I hold up a piece of paper to the exhaust it shows black soot, same with on the snow while running at temp or when warming up. The exhaust has a low popping sound that is kind of sporadic. Like someone is hitting a tiny bass drum in it. The idle sits high at around 1000rpms and the idle mixture screw is almost all of the way in. The idle speed screw is completely backed off.

The fuel mileage is my main concern followed by the starting issue. With the cost of gas in BC its almost $60 just to drive 100km or 60 miles. Ive ordered a new K&N fuel filter and it should arrive in a couple of days. Any clues on where to start with this would be incredibly helpful.

Highlighted text sounds like it might be a weak starter bendix.drive. You state it has a bit of wear.
An AC Delco drive is $63.00 on Rock Auto. A re-man starter is $92.00 at NAPA. I think I'd go with the re-man starter. That way you'd have all new (re-manned) rather than spending $63.00 and finding out it's the solenoid that's bad.

You may be able to find a Weber manual on Amazon. Quadratec used to sell them but they haven't listed them in years.
Webers are reported to be difficult to keep in tune. If I were choosing a different carb other than a stock one, I'd go with a MC2100 or MC2150.

Keep us posted on what you do and what works. It's sure to help the next guy.

Good Luck, L.M.

Save

1 - 4 of 4 Posts

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.

Top Contributors this Month