86 2.8 mj fuel pump

[terrygw63]

Have gotten really confused after search the links. I have an 86 mj with the 2.8 and the fuel pump is electric not mechanical and mounted on the inner fender not in the tank. I have replaced it with two different pumps from the local parts store and can’t get any flow also making the worst sound ever. Ticking. Lightly put. Where do I go from here????  

[HOrnbrod]

The correct fuel pump for the 86 MJ w. the craptacular GM 2.8 V6 is part number 83502715 and is a mechanical pump mounted on the engine. What you must have is an aftermarket external electric pump installed by some previous owner. W/o seeing it who knows? Post some pics up. Do you still have the original electric pump that went bad? Was this thing running when you got it? 

 

Also, if your external pump isn't pulling fuel the fuel tank vents on top of the tank could be clogged shut cutting off pump's suction..

[Pete M]

maybe something is leaking along the path, letting air into the system?

[87MJTIM]

Is the fuel sending unit the same for the 86 2.8 and the later 4.0?  Can it be adapted to 4.0 23 gal tank?  There's an 86 2.8 in the JY near me.

[Green Mesa XJ]

Originally it’s a mechanical pump on the side of the block. Whatever Electric pump is there is done by a Previous owner.

 

So at some point we can assume the mechanical fuel pump died and they just wired in a new electric pump, the way these usually go is the original pump is left as is and the lines are routed to the new electric pump. something in the mechanical pump could have finally fully failed blocking the fuel flow. The mechanical pump is activated by the camshaft, maybe the odd clicking sound is related.

Very strong possibility that 2.8 is not original and might be a newer block with no place for the fuel pump, you’d have to check it and see if the original pump is there.

 

Or something else further down in the fuel in the line blocked,

 

But those after market generic pumps are notoriously bad, so it could just be bad luck.

 

 

The 2.8 fuel sender does not have the place for the jeep fuel pump although the 1986 plug had the place to put a power wire, but it just a blank place into the plug casing.

In theory a 87-90 fuel sender with electric pump may work, but have to match it to the tank and a way to power the pump, not sure if the body harness would have the power wired in.

 

 

Sent from my iPhone using Tapatalk Pro

 

 

 

[terrygw63]

I had wondered about the electric pump but the other “similar trucks I had run in the past had the inline electric pumps. I’m no in depth mechanic but just wanting to get it running so I can do mybthink with it, the body. This was a truck my dad had wanted and we bought it right before he passed. If I can get it shaped up like I want my plan is to have the motor swapped. Hopefully with the cheapest and easiest swap.  I’m attaching pictures of the pump that was there when we bought it and the last one I swapped out. Just wondering for my purpose should I continue on getting this electric system going or to replace the mechanical.  Which until now I haven’t even looked for but guessing it is located somewhere on the drivers side of the block seeing that’s where the lines from the tank come from. Also I am in the process of pulling the bed. Wanting to pull tank and clean out and check all lines back there. Thanks for all the help. Like I said just a guy with a few tools and a little knowledge. But most of my tools are for collision repair. 

[terrygw63]

Might need help here. Any guidance on posting pictures??? 

[Pete M]

if you're on a 'puter there should be a "choose files" button right below your text box.  there is a cap on the file size per pic (like 2 mb?).  we're in the middle of writing code to auto-shrink things but it's taking longer than expected.   

[terrygw63]

Thanks Pete. Yeah I was trying to use a pic off my phone  not sure what size the pic was but site was giving me the size that was allowed. I’ll figure something different. 

[Green Mesa XJ]

I use the Tapatalk app, they host the picture and you can pick how big the image is.

On the laptop I hit the data limit uploading pictures and refreshed the page to add more pictures.

Not sure where the limit is but new phones can blow away a few mb with a high resolution image.

Sometimes I email myself the pic so the phones software resizes it to inbox limit sizes.

Far as resizing the image through software it’s kind of tricky, I’ve helped set a forum up, we used a mod but had to change it a couple of times because the way it resizes images wouldn’t always work in all browsers. Not sure which php mod finally worked, if trying to set it up today I’d try to copy however Wordpress utilizes uploaded images and resizing. The current WP is much more streamlined than most php forums or even Wordpress 6 years ago.


Sent from my iPhone using Tapatalk Pro

[terrygw63]

That was one idea I hadn’t thought of is to email it to me I can then resize it thanks 

[terrygw63]

[Green Mesa XJ]

Hmmm. I’m not sure what that pump is. Looks kind of like ones Holley used to sell.

Looks like it connects to the fuel line and goes straight to the carb. So the original pump is out of the equation, not sure where the return line is routed.
well there are three lines, a return line and vent too.


As long as the direction/ the inlet and outlet are pumping right it ought to get fuel to the carb. A lot of unknowable things just looking at pictures.


The mechanical fuel pump would be to side of the engine mount towards front of the motor, doesn’t look like much, on every model after 1986 it’s either a plate or a blank spot where the pump would go.



What do you know about the history of this MJ? Was it running when bought? If it ran with this setup before I’d think just check it set up the same and on the right fuel line, maybe test pump some fuel out in to a cup or bottle to see if it works up to that point.

I’m kind of leaning towards a bad fuel pump.
WHat kind of sound is the ticking?

If the engine is toast you can upgrade it to a 1995 Camaro 3.4 which is a stronger engine, bolt per bolt a 2.8, just swap over all the accessories like a long block swap. Other motors with that bolt pattern that will bolt up as well, you’ve already got the electric fuel pump you’d need for a 3.4 swap.


Sent from my iPhone using Tapatalk Pro

[terrygw63]

Yeah the jeep was running and I drove it one summer back and forth Tony he farm also a little around town. But when I started having trouble with it the flow of fuel coming to the inline filter didn’t look right. As far as the noise kinda makes me think of an old alarm clock on steroids. Just a very fast very loud metal tapping noise 

[Green Mesa XJ]

Is the noise coming from the pump or engine?

You might try disconnecting it from the carb and see what it pumps out.




Sent from my iPhone using Tapatalk Pro

[Eagle]

Remember, carburetors don't feed fuel to the engine by pressure, they feed by suction. The pump just delivers fuel to the fuel bowl (reservoir) in the carburetor, and typically a fuel pump for a carbureted engine only delivers 5 to 7 psi. Then the fuel just sits there in the bowl until the engine starts pulling suction, at which point the gas is literally sucked out of the carburetor through the jet(s) and into the intake manifold. If everything but the pump is working, even a low flow should be enough to fill the reservoir and allow the engine to start and idle. It's only at higher speeds and/or heavier load, when you need more fuel volume (the pressure remains constant) that you need higher flow rates.

[Green Mesa XJ]

The rear drive shaft breaking free of the yoke bent and linked my fuel line but I got back home with limited fuel being supplied, believe me on the hills I thought it would stall because it ate the fuel up faster that it pumped.

I was just suggesting the fuel flow be tested to see how much is being pumped and what condition.
After one of the hurricanes here (years ago) on my Dad’s old Chrysler I disconnected the fuel line from the mechanical pump and hooked up an external pump from my old car, worked beautiful, got about two days of gas for the generator.


Sent from my iPhone using Tapatalk Pro

[terrygw63]

Thanks guys I do have some things to check now. And the noise is definitely out of the pump. Just power to the pump without motor being cranked. Really feeling like my problem is a stoppage between the pump and the tank if not at the tank. And I will definitely be looking into the 3.4 swap so if anyone had anymore info on that I’d definitely love to hear it. 

[HOrnbrod]

There's a fuel filter on the end of the suction line inside the gas tank. It's probably never been cleaned and/or changed and clogged shut.

[Green Mesa XJ]

When I finally replaced the original battered tank in my XJ the sock/filter designated, I think it was as I removed it, could be years before I don’t know for sure.
It was a pain to find because most catalogues get these first run jeeps parts wrong. Someone in one of the forums posted the right part I think it was correctly listed in a same era carbureted wrangler part catalog.

If the sock deteriorated it may have sucked up rust and clogged the line someplace. If it is I guess just disconnect the line from the tank and from the engine bay push compressed air through until it clean the line out. That’s is the in tank filter can’t be cleaned and replaced.


Sent from my iPhone using Tapatalk Pro

[Green Mesa XJ]

On the 3.4 swap this guy has a good write up, one of the pioneers it’s a old site but he keeps it online I guess because people still use it. Also plenty of good threads here on the topic as well. I’m honestly shocked how many of these old 84-86 jeeps are still being repaired. I was going to say still in the road but that might be a stretch.

One of the threads here we were talking about other v8 that could drop in with the same bellhousing pattern.

 

http://www.lunghd.com/Tech_Articles/Project_XJ/Project_XJ.htm

 

 

Sent from my iPhone using Tapatalk Pro

 

[86FUBAR]

Most all electric pumps are better pushing fuel than they are pulling it ! Not to say it won’t work at least for a little while but it needs to be mounted as close to the tank as possible . Also you need to remove the stock pump on the engine and cap the hole , on all the 2.8 Iv seen had a return line to the tank on the pump as well that you don’t need so cap that and make sure you are pulling fuel from the corect line. If you suspect the line is plugged unhook it from the pump and blow air back to the tank ( only a couple psi ) and see if it blows freely , I have a pree filter mounted inline on the rubber hose between the tank outlet and the hardline running to the front and my pump is mounted only 2 feet from the tank .

[terrygw63]

Really appreciating all the feed back. Yeah I probably wouldn’t be bothering with this if it wasn’t for the sentimental aspect. But really wanted to hang onto it because of my dad. Think I’ll be starting with testing the pump. I’ve got a setup of fuel to connect to the pump to see what I got there and then move onto the tank and see what’s going on back there. I do really appreciate the time you give to share this input.