'86 CJ7 with 360 sputters and lacking fuel like issues mostly when I use up 1/4 to 1/ - JeepForum.com
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post #1 of 27 Old 07-11-2020, 08:39 AM Thread Starter
burchdog32
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'86 CJ7 with 360 sputters and lacking fuel like issues mostly when I use up 1/4 to 1/

Seeing issues on my '86 CJ with 360 (purchased about 6 months ago). Engine is awesome with tons of power when not experiencing this issue, but I am running into problems where I lose my acceleration and although I get enough gas to keep running, I can barely get the jeep to pull its own weight. This typically doesn't happen when I have a full tank of gas. Tylically start to see it after using about 1/4 to 1/2 of tank, but sometimes see it even with full tank. This issue shows itself when cold or hot, so don't think it is a temp thing.

Things I have tried that haven't fixed it:

*Taken off gas cap (allow air flow).
*Added in spacer under carb (issue very similar to vapor lock).
*Installed 1 in 2 out fuel filter (return line on top).

I think I definitely have some fuel line or fuel delivery issues here. Can anyone help me with where I should start, and what to look for? Thanks in advance!!

Added pics of hoses going to tank. Previous owner has vent bypassed, but i tried running without gas cap on and still seeing issues, so I don't think it is that. First pic is looking up at tank. 2nd pic is from the side.

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post #2 of 27 Old 07-11-2020, 12:39 PM
John Strenk
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What fuel pump are you running? Mechanical or electrical?


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post #3 of 27 Old 07-11-2020, 02:18 PM Thread Starter
burchdog32
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Mechanical pump
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post #4 of 27 Old 07-11-2020, 09:14 PM
Fourtrail
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Put a clear fuel filter between the pump and your new 2 in 1 out filter and watch it for any air bubbles. That will help you know if you are sucking air with either a bad pickup tube or a crack in the rubber chunks in the suction line.

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post #5 of 27 Old 07-11-2020, 10:17 PM Thread Starter
burchdog32
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Good idea. I'll add the clear filter in before the (1in to 2) existing filter to help see what is going on.
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post #6 of 27 Old 07-12-2020, 12:43 PM Thread Starter
burchdog32
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Okay, installed clear filter (should have done this a long time ago, thanks for the idea). Drove jeep for about 40 miles and running great (was on a full tank). Even with it running good, noticed I am seeing air in there too. Is that normal?


Will drive it some more this week to get the jeep down to where it will start seeing the problem. Next time I experience the problem, I will send a comparison pic of filter.

Pic attached is when I first started up and then after it ran for a while (no bubbles, but air on top). Jeep was still running strong when 2nd pic was taken.
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post #7 of 27 Old 07-12-2020, 01:04 PM
Fourtrail
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Looks like you are sucking in air somewhere. A small bubble is normal, but that bubble shouldn't grow in size. Looks like you may be dropping the tank in the near future.

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post #8 of 27 Old 07-12-2020, 01:37 PM Thread Starter
burchdog32
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Damn...okay. May be my project next weekend. Thanks for the response. I have the 15 gallon tank. If it is the fuel sending unit (suspecting that at this point) should I get a new one, or buy a new tank, too? Any recommendations?

Once I drop tank, any recommendation on how to test things out or what to look for?

Bad thing is my problem leaves me with about a half tank of gas. That will make things fun trying to take off. 🙂
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post #9 of 27 Old 07-12-2020, 03:57 PM
LumpyGrits
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You should run a 3/8" line from the tank to the fuel pump.
Run steel as much as possible.
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post #10 of 27 Old 07-12-2020, 05:39 PM
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Quote:
Originally Posted by burchdog32 View Post
Damn...okay. May be my project next weekend. Thanks for the response. I have the 15 gallon tank. If it is the fuel sending unit (suspecting that at this point) should I get a new one, or buy a new tank, too? Any recommendations?

Once I drop tank, any recommendation on how to test things out or what to look for?

Bad thing is my problem leaves me with about a half tank of gas. That will make things fun trying to take off. 🙂
this is one of those times when you got it out, do you really not want to replace everything so you don't have to do it again.
Do you want to take the tank out and then find out how rusty it is. Maybe a good plastic tank that you will never have to replace again???

Start spraying every thing down with some rust penetrant so it will be ready to go next weekend.

You want to look into the tank hold down strap also. Those always go bad on me.


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post #11 of 27 Old 07-13-2020, 11:55 AM
oldschool74cj5
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hello
i last year had to take my fuel tank down and go through it. i replaced all the rubber fuel line in my jeep at the same time. my lines were cracked and started leaking fuel on the top of the tank. the two nipples sticking out of the tank on the upper driver side is for venting of the tank. my original roller over and liquid valve were gone so i t'ed together then to a rollover valve then to the steel line that goes to the canister. my frame was originally a v8 frame so my fuel and return lines were on the passenger side. the P.O. had a t on it to the pump when i bought it. thats why he had to fill up every 45-50 miles. because as soon as it uncovered the return in the tank. the pump sucked air. being a 258 in there now i copied the steel line going from the pump to the carb. then i made another line bent the same but smaller for the return. on a 6cyl frame the lines run different. the feed line still on the passenger and the return line is on the driver side. i found a couple of pics of someone's v8 on here that showed the factory style lines. where they took the feed line behind the engine. i would use a setup like that. since they calculated for fuel vapor locking. the only difference you will have is the return after the filter having a u bend back to the driver side to the return line.

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post #12 of 27 Old 07-16-2020, 07:55 PM Thread Starter
burchdog32
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Been driving the jeep to use up as much gas as possible and finally got it to reproduce the issue and it does look like a lack of gas getting to carb.

Something else I have noticed. I have only probably driven 50 miles since installing the new clear filter and it has turned a rust color. I am thinking of getting a new tank anyway, but is this a bad thing?

I attached pics of brand new, and 50 miles later.
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post #13 of 27 Old 07-17-2020, 04:43 PM
turbogus
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Yep, sorry to say it may very well be rust in the tank. Also the orientation is critical as I found on mine of the OE fuel filter.

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post #14 of 27 Old 07-17-2020, 06:23 PM
LumpyGrits
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Do you have a metal tank then?
OEM was plastic.

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post #15 of 27 Old 07-18-2020, 08:42 AM Thread Starter
burchdog32
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Dropped the tank this morning. Was metal. Sender arrives tomorrow, new tank doesn't get here until next week. Going to buy all new hoses and have it ready when tank arrives.


Attached pics of old tank.
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