4.2 with weber wont start cold - JeepForum.com
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Unread 02-17-2013, 10:01 AM   #1
jr4x4
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1996 ZJ 
 
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4.2 with weber wont start cold

hi. ive read all i can find & no go. so just picked up 1990 4.2 auto yj. i put a weber 34 on with manual choke & just did team rush mod. idles fine runs good. BUT wont start cold without a squirt of starter fluid . then she fires right up and all is good after that. i thought the choke was it. so i pumped gas 3 or so times and by hand set choke (stepper) to almost closed and she just turned over & over. 1 small squirt of eather and boom-fires right up. WTF... i just tried nutter bypass twice and jeep wont fire up at all. tried adjusting timing & nothing. so hooked it all back up & all is good. why wont this cold engine fire up without a squirt of eather???/ thanks

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Unread 02-17-2013, 03:25 PM   #2
jollyroger1
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1990 YJ Wrangler 
 
Join Date: Oct 2011
Location: Nashville, TN
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I have the same engine and it does not like cold starts.My ritual,turn key mash pedal to floor once and release,crank for a few seconds stop,crank a few more,engine hits stumbles and dies.Crank again and it usually comes to life getting better and going to high idle after a few seconds.
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Unread 02-17-2013, 04:43 PM   #3
jr4x4
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its got to be something. it dont enen catch or stumble. even with choke not on it starts up with a small shot of eather. otherwise i will just kill my battary. it cranks like i have coil unplugged. wont catch even a little. timing is at 8btdc . once started all is good. i can shut it off and she fires right up first crank with no gas. when i got the carb the choke canister was not there. there was jst that prong sticking out that i now have a cable hooked to. if i pull cable back while pushing on gas it sets stepper cam & choke plates are closed 7/8 of the way. but that dont seem to affect anything. when first running the stepper cam has it at fast idle but if i open or close the butterfly by hand it doesent seem to chang idle,
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Unread 02-17-2013, 05:19 PM   #4
jollyroger1
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It seems like on mine the fuel is bleeding back and the carb is dry in the morning,but the colder it is the worse it is
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Unread 02-17-2013, 06:05 PM   #5
jr4x4
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if thats the case wouldnt 3-4 pumps of cas at least get it to catch. i mean a 1 second shot of eather gets it to grab. then its mint.. i think something is wrong with my choke.. oh & i set my fuel filter level & the return on the filter at 12 o-clock. i dont understand why when cold the gas dont catch. notta... not even a stumble.. thanks for your info on this.
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Unread 02-17-2013, 06:08 PM   #6
Mark05059
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change your fuel pump. It sounds like its getting weak... the shot of ether is just enough to make it spin fast enough for the pump to push fuel in.
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Unread 02-18-2013, 05:22 AM   #7
90DesertTanYJ
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Check the fuel pump output and look to see if you still have the return line style fuel filter. The small line should be at the 12 oclock position. If it isnt. the fuel will drain back into the tank. Since you now have the Weber, you can eliminate this vent line if you wish, it goes to the charcoal canister IIRC
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Unread 02-18-2013, 12:05 PM   #8
zeus87gn
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Quote:
Originally Posted by Mark05059 View Post
change your fuel pump. It sounds like its getting weak... the shot of ether is just enough to make it spin fast enough for the pump to push fuel in.
^^ this ^^
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Unread 02-18-2013, 04:41 PM   #9
Lrasser
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1998 TJ Wrangler 
 
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This is a typical weber issue. First... they are correct this could be a weak pump. for the $20 they cost just swap it out. Second.... With the original carter carb there is a phenolic spacer under it. This is a plastic heat resistant sapcer. The weber does NOT come with one. Given the design of the 4.2's crappy intake the carb gets extremely hot. When you turn off the truck and park it the remaining fuel evaporates out. So when you go to start it you would have to wait for the pump to refilll the lines, bowl and filter. When you hit it with starter fluid this causes the pump to spin faster and refill the lost fuel. Hense make it run. I had this same issue as well as several people i know. There is a cheap fix and has worked on every vehicle i've done it on so far. first make sure you are using a fuel pressure regulator set to 3.5psi. Remove the return line to the fuel tank and install a normal filter. (we used a one way fuel check valve on the return line so the vent still pulls air $5 on ebay) install a 1in Phenolic spacer plate.($20 with new gaskets on ebay). run your motor to temp and fell the carb. It will be hot as hell. after the spacer is installed try the same thing. It's an amazing difference. I would have to crank for about 30-45 set to get it to start. now i pump the gas 3 times and crank for about 3 seconds. well worth the $30 investment. I've done this on 4 truck and its worked every time.
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Unread 02-18-2013, 06:12 PM   #10
jr4x4
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Quote:
Originally Posted by Lrasser View Post
This is a typical weber issue. First... they are correct this could be a weak pump. for the $20 they cost just swap it out. Second.... With the original carter carb there is a phenolic spacer under it. This is a plastic heat resistant sapcer. The weber does NOT come with one. Given the design of the 4.2's crappy intake the carb gets extremely hot. When you turn off the truck and park it the remaining fuel evaporates out. So when you go to start it you would have to wait for the pump to refilll the lines, bowl and filter. When you hit it with starter fluid this causes the pump to spin faster and refill the lost fuel. Hense make it run. I had this same issue as well as several people i know. There is a cheap fix and has worked on every vehicle i've done it on so far. first make sure you are using a fuel pressure regulator set to 3.5psi. Remove the return line to the fuel tank and install a normal filter. (we used a one way fuel check valve on the return line so the vent still pulls air $5 on ebay) install a 1in Phenolic spacer plate.($20 with new gaskets on ebay). run your motor to temp and fell the carb. It will be hot as hell. after the spacer is installed try the same thing. It's an amazing difference. I would have to crank for about 30-45 set to get it to start. now i pump the gas 3 times and crank for about 3 seconds. well worth the $30 investment. I've done this on 4 truck and its worked every time.
cool thank you i will try that. now i have a fuel pressure regulator in the box.sitting because all i hear is with a weber dont use a FPR. just use the OEM fuel filter and thats it.. so il try it . thanks . oh and il do the new fuel pump. it was making a slight clinking noise at idle so i thought it was time to get new anyway. i did notice the aluminum spacers for the weber suck. i had to seal the hell out of them to not suck in air..
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Unread 02-18-2013, 07:19 PM   #11
Lrasser
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you will still need to use the alum spacer since it's an adaptor as well. I simply added it directly under the carb and it seemed to seal better. prior to that i had a lot of vacuum issues. Webers have weak float stops and with too much pressure the can pump fuel past and cause it to run rich. obviously some people say they have no issues without it but the same amount say they cant run without it. In my case it ran much less rich and the raw fuel smell was gone and easier to tune.

http://www.ebay.com/itm/PHENOLIC-SPA...b39ec8&vxp=mtr

http://www.ebay.com/itm/5-16-Check-V...fcf296&vxp=mtr

This is the spacer and check valve i used. I got a clear fuel filter from autozone so i could visually see if the pump was pushing the fuel and and make sure the fuel stayed while sitting. I've been running this setup for about a year and it's been fine starting through all seasons even the 20 deg weather we have now. Good luck if you have any questions let me know.
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