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Unread 04-04-2013, 02:56 PM   #1
Ericgormsenjr
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1987 YJ Wrangler 
 
Join Date: Feb 2013
Location: Moreauville, La
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Fuel flow problem with '87 2.5 tbi

I have a fuel issue problem with my '87 YJ. Engine is the 2.5 with TBI. This has occurred once before about 4 months ago. Engine will only run at idle or under 1000rpm. Last time i put new inline fuel filter, changed the throttle body injector and replaced the fuel pump. Engine ran the same. I then took out the new injector and put the old one back. For some reason this fixed the problem. The old fuel pump was weak. Yesterday after a little mud riding on my hunting club I pulled into local car wash to clean the jeep. I did not wash engine or get any water on it in any way. After wash, I started jeep and it immediately killed. Started it again, same thing. Jeep would only run at idle and somewhat rough at that. I limped it home (about 12 miles). I installed a new injector which did not help. Put old one back on and eliminated that part. Took TPS off and had it checked which showed it working fine. Checked fuel pressure. It holds around 20 - 25 lbs. If I pour gas in the throttle body engine runs fine but stop pouring and is kills. Will re-start instantly but only run around 400- 700 rpms. Fuel return line is not clogged. Should I invest in a new throttle body assembly? I'm hoping someone, somewhere can help me with this problem. I'm at my wits end! HELP!!!


Last edited by Ericgormsenjr; 04-04-2013 at 03:57 PM..
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Unread 04-04-2013, 06:44 PM   #2
pete1991YJ
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I'm not an expert on the TBI systems, Que is. Mine is MPFI. But here is a guess or 2 OK? Its definitely a fuel prob, it isn't getting any. How is the filter? Is there any water or junk in the gas tankl? that killed mine for a summer. What about the grounds, the injector grounds thru the computer into the sheetmetal where the computer is bolted onto. Thats just a few ideas but I'm not totally familiar with them.

When the engine is cold it sets the fuel mix off the temp sensor and a pre-programmed map. Then it switches over to the O2 sensor in closed-loop after it warms up. The injector is timed off the distributor pickup.
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Unread 04-04-2013, 07:28 PM   #3
Ericgormsenjr
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The tank was clean when I changed fuel pump a few months back. Just don't know. I hate to spend $400+ on a new TB if thats not the problem. Could that part of computer gone out just like that?
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Unread 04-04-2013, 07:44 PM   #4
pete1991YJ
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Yeah, but what about the external filter? I would never buy a new TB when they are so easy and cheap to rebuild. You can do it yourself on the kitchen table for less than $100. Schaef had a good write-up about how he did his on here. With pics. I really doubt that one part of the computer went out like that. Its usually the whole thing. More likely its a wiring or sensor problem instead of a computer problem. I would for sure check the wiring and grounds.

Its probably best to wait for Que since he knows the TBI models better than me, he owns one and he's the electrical expert. He's usually on in the mornings.
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Unread 04-04-2013, 07:57 PM   #5
Xpress
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Can you see the injector spraying fuel into the intake, or is it not really putting much fuel out?
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Unread 04-04-2013, 08:16 PM   #6
Que89YJ
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You have too high of fuel pressure. It should be 14. Pressure regulator or a pinched return line.
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Unread 04-04-2013, 08:35 PM   #7
pete1991YJ
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Thanks Que, I never would have known. Should he rebuild the TB with a new regulator? I'm trying to find that thread Schaef did about his.
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Unread 04-04-2013, 09:01 PM   #8
Que89YJ
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He should check for the fuel return line first. Since he was wheeling before it happened. Get a gas can and some hose. Disconnect three return line and use the house to run it to the gas can. Setup to measure the pressure and see what you get.
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Unread 04-05-2013, 05:04 AM   #9
Mark05059
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Quote:
Originally Posted by Que89YJ View Post
He should check for the fuel return line first. Since he was wheeling before it happened. Get a gas can and some hose. Disconnect the return line and use the hose to run it to the gas can. Setup to measure the pressure and see what you get.
Que... you need more coffee Fixed the auto correct issues for the OP
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Unread 04-05-2013, 07:17 AM   #10
Que89YJ
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That is funny! Coastguard the house I meant hoist.

Spell check nothing.It's swype.

hose

LOL
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Unread 04-05-2013, 06:52 PM   #11
Ericgormsenjr
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STILL HAVING FUEL ISSUE WITH '87 2.5 w/ TBI

I disconnected the return line near the tank. Blew air from throttle body connection and it was clear. Reconnected rubber tank line to metal line and blew complete line out. I removed the gas cap and can hear gas gurgling in tank so I assume entire line is clear. Book states pressure valve can be adjusted but, after taking TB off I noticed a plug in the bottom of bowl where adjusting screw is. Looks like lead plug from factory. Took valve down and I can see threads on screw at bottom of bowl so apparently it can only be adjusted by dealer which in my area cannot work on "that old a Jeep" no computer to read codes. I also checked all parts, the diaphram is fine, spring is good and all fuel passages are clear. No water, dirt or trash anywhere. I checked voltage to injector and get a reading of 3.57 volts but don't know what voltage reading should be. I don't have noid light to check properly. When I can get it to hold a rough idle there is no fuel spray, just a drop once and a while.
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Unread 04-05-2013, 08:09 PM   #12
Que89YJ
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Look up shaef fuel pressure up on the forum search. Yes you can adjust fuel pressure and his thread shows you how. Are you sure you didn't flip the supply and return lines? Does the fuel pump run when you are trying to start it? Not just when it primes when you turn on the ignition?
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