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KatahGii

Cranks but won’t turn over...

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Ok I’ve been working on my ‘86 2.5L 4cyl TBI  for a while.. I bought it not running. I replaced the whole sending unit, fuel filter, spark plugs and in the process required a whole new tank... I put gas in it went to start and it still would crank but not turn over. I can keep it running if I have the key held in the start position and spray starting fluid in the TBI. I popped the top off the TBI and tried to start it and no fuel was coming from anywhere. Any ideas?

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You said you replaced the fuel sending unit. Did you replace the pump?

 

When turning the truck on do you hear the pump prime for a second or two?

 

Have you tested for spark as well? CPS is known to be a culprit for non firing conditions. 

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fuel filter?  have you checked the condition of the pump's ground behind the taillight? 

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5 minutes ago, Pete M said:

fuel filter?  have you checked the condition of the pump's ground behind the taillight? 

No I didn’t. Hmm idk where exactly that is.

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1 hour ago, eaglescout526 said:

You said you replaced the fuel sending unit. Did you replace the pump?

 

When turning the truck on do you hear the pump prime for a second or two?

 

Have you tested for spark as well? CPS is known to be a culprit for non firing conditions. 

I didn’t do a proper spark test I assume since it runs on starting fluid that the spark is good. And I can’t hear the pump. I hear a click from the passenger side in the cab. I assume that the fuel pump is good because it came with the sending unit. Also I checked to se that power is going to the unit and used a multimeter on the plug and it was getting power. I assume that I can’t hear it because the hum of the key being in the ignition.

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filter is under the truck.  ground is behind the drivers side taillight.  also there is a harness connector under the truck near the taillight that is known for corrosion issues.  the ground runs through it.  I ended up splicing a ground into the harness right near the pump at the frame for a better connection.  If you haven't done them yet, the link in my sig has a link to Cruiser's MJ tips and you should do all that apply :L:  (most deal with the poor wiring design)

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11 hours ago, KatahGii said:

No I didn’t. Hmm idk where exactly that is.

IMPROVING THE FUEL PUMP GROUND

The fuel pump and fuel tank sending unit ground at a sheet metal screw up behind the spare tire on an XJ, XJ-Body-Ground.jpg?resize=300%2C162and behind the driver’s taillamp on an MJ.

Not only is a sheet metal screw a lousy way to ground things, this ground path is long and travels through some connectors that are prone to corrosion and moisture.

Locate the black wire on  the HARNESS side of the fuel pump/sender 3 wire connector. Remove a 6″ length of the split loom covering. Strip back about 1/2″ of insulation from the BLACK wire.1-fuel pump ground MJ

Take your new ground wire, preferably at least 14 gauge and 12 to 18 inches long as needed, strip it about 3/4″, and wrap it around the exposed part of the harness plug wire.1-fuel pump ground mj-002Solder the connection. Tape it up and reinstall the split loom covering.1-fuel pump ground mj-003

At the other end of your new ground wire, add a crimp on eyelet. Attach the eyelet under a bolt that goes directly into the chassis. Be sure to clean the attaching point til shiny and apply OxGard to the contact surfaces.1-fuel pump ground mj-004

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14 hours ago, KatahGii said:

... I put gas in it went to start and it still would crank but not turn over.

 

 

Cranking is turning over. What you mean is that it turns over but won't start.

 

The rest of your description doesn't compute, however. Once it fires, if you're using starting fluid it should keep running without having to keep the starter motor engaged as long as you keep spraying the ether.

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12 hours ago, KatahGii said:

I didn’t do a proper spark test I assume since it runs on starting fluid that the spark is good. And I can’t hear the pump. I hear a click from the passenger side in the cab. I assume that the fuel pump is good because it came with the sending unit. Also I checked to se that power is going to the unit and used a multimeter on the plug and it was getting power. I assume that I can’t hear it because the hum of the key being in the ignition.

 

Ignition keys don't hum. That hum you hear may be the fuel pump. If it keeps humming rather than stopping after 5 to 10 seconds, the fuel pump isn't building pressure.

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8 hours ago, Eagle said:

 

Ignition keys don't hum. That hum you hear may be the fuel pump. If it keeps humming rather than stopping after 5 to 10 seconds, the fuel pump isn't building pressure.

Ok I’ll end up figuring out how to post a video. And it’s not a hum it’s a full on buzz like the warning that your key is in the ignition.

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That’s the belt not buckled buzzer. There’s a hum that happens just before you start the truck. Have someone either turn the key or get under the fuel tank and listen for the pump to prime. 

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Click the seat belt into place (or pull the buzzzer)  open the drivers door window .....close the door.....now no reason for any buzzer to go off

Reach in though the window and turn the key to power....pump should hummmm then stop......

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7 hours ago, yxmj said:

Click the seat belt into place (or pull the buzzzer)  open the drivers door window .....close the door.....now no reason for any buzzer to go off

Reach in though the window and turn the key to power....pump should hummmm then stop......

Where is the buzzer wires. I want it gone in general lol 

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2 hours ago, KatahGii said:

Where is the buzzer wires. I want it gone in general lol 

 

44 minutes ago, eaglescout526 said:

On the fuse box. Big rectangle box closest to the wall on the drivers side kick panel. It will either be blue or black

86s should be blue and look like this.

15755117320545502520785478006129.jpg.b18de225d4f63e04c3ece787ce120763.jpg

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I think that buzzer does double duty, acting as the alert for a couple or three different functions. I disable the seat belt alert by unlugging the connector under the seat and jumping the terminals on the chassis harness side. That leaves the buzzer active for whatever else it needs to do.

 

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headlights-left-on alert comes to mind :D 

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11 hours ago, Pete M said:

headlights-left-on alert comes to mind :D 

 

Also opening the door with the key still in the ignition.

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