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If this doesn't fix it...I'll have parts for sale

918 views 7 replies 4 participants last post by  BigDumbBear 
#1 ·
I'm going down to the shop to start the large cap "team rush" conversion to attempt fixing my backfire issues. If this doesn't fix it... I will be very tempted to sell a 304 motor and auto trans. It's 90% rebuilt. lol

I've driven this Jeep about 8 miles total over the 8 months I've had it. most of those miles have been in and out of the garage. I realize that's part of having a jeep(especially a CJ)... but seriously this is getting rediculous. It runs better everytime, but it still ain't right.

Sorry, just wanted to rant for a minute. I'll go back to work now.
 
#3 ·
the rockers are non-adjustable and are torqued to spec., the cylinder with bad compression had a bent valve and has been fixed, all the valves have been lapped, valve stem seals replaced, timing set replaced, fuel system replaced, ignition system replaced, TBI system installed....

It has good even compression, it has good smooth vaccuum, and everything else I or several mechanics can think of checks out perfect. There's something wrong with the ignition and I hope the large cap fixed it. I also upgraded to MSD 8mm wires and re-routed the ignition pick-up wires away from the plug wires.

I haven't just been throwing parts at it though. Nearly everything I did needed to be done and helped it run a little better with each change. There's just something left. I have a few things to deal with before I fire it up in the morning. My fingers are crossed but I'm out of parts and energy tonight.
 
#4 ·
When you say 'Backfire',
Do you mean it blows down through the pipes (80% of the time that's ignition),

Or do you mean it 'Sneezes' through the intake (that's usually fuel mixture, but can be ignition).

Since it was rebuilt, have you VERIFIED the crankshaft/distributor placement?
 
#5 ·
It shoots a flame out of the throttle body a few inches. That's telling me that it is firing the ignition waaaay to early or not closing the valves. But, the compression is good so the valve should be closed. I've checked, verified, and rechecked the timing of crank to cam, firing order, distributor rotation about ten times. I never actually opened the bottom of the engine up. I did pull the heads off to do the valve work. I over-exagerated the "rebuilt" thing as far as the motor goes. But I've got tons of new stuff under the hood, but I can't make it run good enough to bother closing the hood. I'm gonna go down there shortly and try to fire it up and reset the timing and go from there.
 
#7 ·
I've tried the timing light. With the wire disconnected to set base timing, I can set it to 0deg. and it does run there. However, I have to set it back to about 20deg. btdc to get it to run smoothly and have good vaccuum. I did all that today and tried to drive it after I hooked the wire back up and it couldn't get past about 10mph and still had some hesitation. Atleast it didn't seem to backfire this time but it's running kinda rough. I'm gonna tinker with the timing a little and see if I can work it out. The cap adapter to step up to the larger distributor cap doesn't seem to set real stable. I need to check into that before I go any further because I can push on the cap a little with it running and make it run a lot worse. I had a similar issue with the replacement cap I had before and had to file down the base of it a little to get it setting firmly without rocking back and forth. That could be a big problem while accelerating...It is a borg-warner cap adapter and the MSD cap sets on it great.

Thanks for the input. I will take any help I can get and according to the doctors, I need a lot.
 
#8 ·
Okay. I think I've got it! The cap seemed to fix the backfire issues and it runs pretty good, it just lacks power and stuff. After putting a fuel guage inline I thought the pressure was a little low so I dead-headed the fuel line before it hit the motor and was only able to get 10 PSI.... Turns out I put the wrong pump on there for the fuel injection. The one I used was intended for a carbureted vehicle. OOPS!

Now I get to buy a new fuel pump and maybe a sending unit while I'm at it cuz the guage doesn't work... I know I know, test the sending unit first. Will do. What's another hundred bucks though. It's just a push on a shove at this point.

Thanks for trying to help. I love this board for all the good info and help.
 
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