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Unread 04-08-2010, 01:42 PM   #1
justinm1177
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350 conversion...having problems

Hi...

Wanted to see if anyone had experienced any of the same problems I am having. I just bought my 79 CJ-7 on Saturday, from about 45 minutes away from where i live. The guy i bought it from had never experienced any of the problems I had on the way home. After driving it about 30 minutes at 65 miles an hour, it suddenly lost power and started sputtering. I pulled off the side of the road thinking i was possibly outta gas since the gas gauge doesn't work. But i had just put 4 gallons in it, topping it off. After a while i started it up and made it about another 15 miles and then the action repeated itself. I finally got it home and parked it. The next day I replaced (well, put in) a new thermostat, flushed the radiator, new coolant, new fuel filter and a new pcv valve. Thinking i was good, i took it out the next day. It drove fine there and back. Got home, grabbed something (maybe 5 minutes), fired her back up and when i pulled out the driveway, the problem hit again. I've been reading and searching since and have found a vast array of what people have given advice to others...but none were a conversion to a Jeep...all still in Chevys.

Anyone got anything?

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Unread 04-08-2010, 03:40 PM   #2
Mike Romain
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Lots of times on conversions they forget to keep the charcoal canister working which is the gas tank vent. They figure it is some power robbing emissions thing, not a passive gas tank vent that only keeps fumes away.

If they blocked the lines to the canister from the gas tank the tank will get a vacuum on it and your jeep will run out of gas and act just like you describe. This has happened to me several times after running the mud pits and the $2.00 air filter on the bottom of the canister got blocked. I then had to run home with the gas cap cracked open which is the quick test, just crack open the gas cap and see if you get a whoosh and it then runs ok with it loose.
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Unread 04-08-2010, 03:45 PM   #3
dwloop
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One more thing that will cause this issue in a rusted gas tank. Has happened about four times to me over the years. The rust sediment builds up in the tank and when you sit it for a period it drops from the inlet screen allowing it to start and run. When you start it and drive it the sediment get stirred up and plugs the screen causing fuel starvation...

If the Jeep has been sitting for extended periods before you bought it, that is my bet.

HTH

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Unread 04-08-2010, 03:57 PM   #4
crcj7
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deff sounds like vapor lock to me . make shure there are not any high loops in your line or its not ruted where it gets hot . when it shuts off it shounds like a fuel starveation issue and if it dose die you cant just fire it right back up... but once it cools it fiers up ... vapor lockkk check it
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Unread 04-08-2010, 04:04 PM   #5
Redmanchew
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what era 350? dont want to sound like an SA but is carbed, Throttle body injected or direct?
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Unread 04-08-2010, 04:10 PM   #6
TBailey
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I had this happen to me on an sbc with an Edelbrock carb.The float would occasionally stick in the downward position.When the float bowl would overfill it ran directly in the carb flooding it and the engine would shut down.I would let it sit for 10-15 minutes and it would fire rite back up.
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Unread 04-08-2010, 08:44 PM   #7
sbc61
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If you are using an HEI distributor, the ignition control module can cause the problems you describe. When the engine is cool, it will run fine. However, when the engine warms up and the module gets hot, it increases the resistance in the module causing poor engine performance, stalling, and hard to start or no start conditions.
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Unread 04-08-2010, 08:54 PM   #8
specwarCJ
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I would start with the cheapest. Replace the fuel filter and get a clear one so you can see what you are pumping through it. If it looks like tang I would replace the tank and sending unit.
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Unread 04-08-2010, 08:54 PM   #9
justinm1177
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All of these are great suggestions for me to look at. Best I can tell, I was told that the engine was out of a 97 silverado but turns out when I bought parts they didn't fit. After doing some research it was out of a 1996 full size van. It has throttle body injection. I don't know the state of the gas tank yet. I was planning on dropping it to just go ahead and replace the sending unit in case that was the problem with the gas gauge not working. The kid that had it before me only made one decent trip with it and he said he didn't have any problems. He had it less than a year and drove it occasionally to work about 10 minutes away. In all of the case y'all have told me. He wouldn't have experienced any of these problems. I don't know what the distributor is. To me it looks like a stock ac delco by looks. I'm planning on replacing that to new as well. By talking to him, he didn't know a lot about cars in general except how to buy them. You can look and tell that it hasn't had a tune up in a while. I'm almost slightly scared to even think of what to expect.
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Unread 04-08-2010, 10:00 PM   #10
1986cj
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What do you have for a fuel pump? maybe mounted to high? going out? A 1996 full size van didn't come factory with throttle body injection. Do you have a fuel rail? Can you find the fuel pump? Maybe he has riged something up for a in tank pump, may explain why your gas gage dont work. TPI and MPI have around 45 to 60 lbs of pressure. I have had a MPI Chevy do the same thing. Run great then start sputtering or just quit. Start right back up and go again. Found out the fuel pump would only put out about 20 lbs of pressure when it would die. I think 1995 was the last year for throttle body injection.

Last edited by 1986cj; 04-08-2010 at 10:31 PM..
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Unread 04-09-2010, 05:28 AM   #11
Mike Romain
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If you just start tossing parts at it, well, hope you have really deep pockets....

Here is a good place to start when trying to get the gauges to work, John's links:

Basic Troubleshooting for CJ gauges
CJ Gauge Specification Chart
CJ Speedometer Gauge Quick Test
The new Gauge Page
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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Unread 04-09-2010, 08:51 AM   #12
justinm1177
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Hmm...interesting. When i pulled the air filter off it has two injectors sitting on top of the throttle body. I could be from an older year. I haven't pulled the exhaust manifold to get the vin of the engine yet. The manifold part number matched an 1987-1996 full size van. When i was looking for parts, i looked for the difference in the ones i had bought since most of them were the same...except this one model. I think late 95 was when they started swapping over to the Vortec fuel system. Changed the fuel filter the other day. Gas did run clear out of it. And no trash. Think the rusty tank might be out as a problem. The fuel pump is a Holley. They mounted it under the hood not far from the steering column. Fuel filter is right under it. I don't know the series it is tho. The fuel filter whines...and it is distinct...i never heard it quit. Hahaha...yeah Mike...no deep pockets here! I'm just putting in alot of new parts because i have to idea how old they are or when a tune up was done to the engine. So i'm just getting alot of it out of the way so i know for myself that it was done. Thanks for the links for the gauges! I'm hopefully working on them this weekend, along with checking the brakes and more tune up, and all of these suggestions to check! Nothing like a problem to get the blood flowing and motivation to fix it!
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Unread 04-09-2010, 10:12 AM   #13
1986cj
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If it has injectors in the throttle body it is TBI. Swapped in motors who knows what they may have done. If you have a fuel pressure gauge you may want to see what pressure you have. Most of the treads I have read your pump needs to be mounted close to the tank and as close to the bottom of the tank as possible. It just sounds to me that you are running out of gas. Mounted that far away form the tank may be more that the pump can handle especially if the pump is a pusher rather that a puller. Search for TBI fuel pump mounting, there are a few treads about where and why to mount the pump for TBI.
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Unread 04-13-2010, 03:59 PM   #14
lendawg
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Control module

I had a similar issue which was the ignition contol module. Replaced the control module and never had an issue again. DOn't know if this was replaced when they converted to the sbc.
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Unread 04-13-2010, 06:42 PM   #15
TBrock
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I suggest you do what the first response suggests. Does it have the vapor recovery cannister? If not, drive it with no gas cap and see what happens.

I have a very similar set up and can tell you that is exactly what will happen if the tank is not vented. My jeep's PO never had a problem either...
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350 conversion , power loss , sputtering , stalling

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