I need a little 2.5 info.

Hi everyone.
I have an 85 2.5l carburated with the ax-5 and 207tc. I had 2 of these rigs and blew the electrical in one, and the engine in the other.

That doesn't look too good for me does it? :wierd: Both are/ were very tired.

On to my question. I have swapped parts and combined both into 1 decent rig. The problem is that I still have an old tired motor with 265k in my rig.

Today I picked up a 2.5l that came out of a 94 wrangler. It has 30k on a rebuild, then sat for about 2 years. I plan on re doing all the gaskets. The cylinder walls look good so I think I am ok there.
I am curious tho and need some thoughts. Looking at the new motor today I can tell that my mechanical fuel pump will not work. I have done some google searching and know there are a few ways to put a fuel pump in but I would like a few suggestions on what some of you would do.
Another thing is.. I am thinking that since I did not get a wiring harness with the new motor it might be easier to make it carburated. Once again some thoughts from you.

I have been teaching myself how to work on my XJ using and my FSM for just over a year. I have already done an engine swap and plenty of other work trying to bring an 85 back from death. I still have lots and lots to learn. However since my thought is to run an inline fuel pump, and slap my webber carb on I figure I had better get some input on what someone else would do first.

One last thing if I had the money to upgrade to a newer rig with a 4.0 I most likely would.. :roll:
Any input would help me out.

short of buying a MPI wiring harness and ECU, you are gonna definitely want to keep her carbed. I'd find a quality aftermarket electric pump and an adjustable fuel pressure regulator and plumb them in line.

Electric pumps are great "pushers" but are not very good "pullers" --
--make sure you put the pump as close to the fuel tank as you can to help it last

Carburetors need constant fuel available at around 3-4psi--
-- make sure your pressure regulator is set low enough that your fuel pressure doesn't unseat your inlet needle (or you'll be flooding at idle/low RPM)

Thank you, I would have put it close to the same position of the fuel pump I have.
Do you know very much about the mechanical fuel pump? I know that the same hole is in the block that my pump goes into. But it is only half the hole. I could take a pic to explain better. I am not quite sure how my fuel pump really works in there. But is it a bad idea to cut out the rest of the hole in the new motor and keep the mechanical pump? Or is an electric pump just better working and better to use.. I really don't think it is a good idea to cut on the block, I am just curious.

I converted a 2.5L with the Carter YFA carb over to the TBI injection. It made a huge difference in power.

spikeypuck said:

Thank you, I would have put it close to the same position of the fuel pump I have.
Do you know very much about the mechanical fuel pump? I know that the same hole is in the block that my pump goes into. But it is only half the hole. I could take a pic to explain better. I am not quite sure how my fuel pump really works in there. But is it a bad idea to cut out the rest of the hole in the new motor and keep the mechanical pump? Or is an electric pump just better working and better to use.. I really don't think it is a good idea to cut on the block, I am just curious.

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although I've never investigated the 2.5L specifically, mechanical pumps are usually driven by a lobe on the camshaft that, while turning, moves an arm that's connected to a diaphragm. The MPI camshaft likely doesn't have the lobe cast into it and you'd probably need to install a carburetor specific cam to use the mechanical pump (after opening the block and drilling and taping the mounting holes)

old_man said:

I converted a 2.5L with the Carter YFA carb over to the TBI injection. It made a huge difference in power.

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absolutely quite a difference in road manors between the two beasts-- but I think the OP is looking for the least expensive approach. Conversion would be the "best" option, but without the donor harness et al, it probably isn't going to be the easiest/cheapest.

If you're swapping an engine in already... and you picked up another engine instead of using yours... WTF is the point in keeping the gutless 2.5 and not picking up a 4.0?

mcantar18c said:

If you're swapping an engine in already... and you picked up another engine instead of using yours... WTF is the point in keeping the gutless 2.5 and not picking up a 4.0?

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With the years before they started making the 4.0 the engine bay is not big enough. I would have to cut the firewall. I am somewhat trying to teach myself to work on my rig as well as fab my own bumpers, sliders and such. I don't think I am at a point where I would want to cut and fix the firewall yet. I had thought about that or something else I have read about is the camaro 3.4l, but that has some issues of its own as well.
The reason for the motor I just got over the one I have is mine has over 200k on it and the new one has 30k on a rebuild. I just need to make it thru this layoff then upgrade rigs to one with a 4.0

Shorty, Thank you as I am teaching myself here I figure out how things come apart and go back together but not how everything really works. Now I understand that a little more.

Just go with a solid-state electric fuel pump and a quality adjustable fuel pressure regulator.

Unless you have a donor vehicle to get all of the harness and engine management electronics I would not try to convert it over.

joe_peters said:

Just go with a solid-state electric fuel pump and a quality adjustable fuel pressure regulator.

Unless you have a donor vehicle to get all of the harness and engine management electronics I would not try to convert it over.

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X2^^ werd!

Thank you Joe. I am starting today replacing the gaskets and cleaning the motor up. I appreciate the help.

When buying a fuel pump, just look for a low pressure inline electric pump, that you can wire up when the key comes on. I used to install these in the air cooled VW's I used to run all the time. Same goes for the regulator. Sometimes theyre needed and sometimes they arent, but youre better off having one anyways so get one. These parts arent expensive, but you may have troubles with the parts store idgets trying to get what you want, as you arent buying anything for a specific vehicle. We used that same Weber 2bbl carb on VW's too, pretty decent setup. This would be the easiest and cheapest for you to do to get you going again. If you have any dune buggy shops in your area, you might try to go there to look for the parts you need, they probably have them on the shelf. The other way to go would be to buy online, and hope it works out. Good luck.

Avoid those "fuel pressure regulators" with the chrome body and big knob you turn, they restrict flow.

This is the kind I'm advising you to stay away from: http://www.amazon.com/Spectre-2517-Chrome-Pressure-Regulator/dp/B000CQ46H0

Note that this design has been sold under something like 500 different brand names.

Spend a little more on the regulator, you won't regret it.

Thank you guys. I don't want to cheap out on the pump or regulator. I have most of the other parts I will need so I can afford not to be cheap there..

I would like to ask one more thing while I have the thread going. The motor I have in the rig now is run with V belts, The new motor is serpentine. have not run a serpentine belt before and have extra V belts in the garage, so I am planning to go with V belts. Is there any reason one is better than the other?

It is likely the WP on the serpentine belt engine is a reverse rotation.

I wasn't expecting that. this may be a dumb question then. Will this effect my alt, ps pump, or anything? It doesn't matter what way they turn does it?

serpentine belt set up still drives your other accessories the same direction. The water pump is the only thing that needs to be matched to the belt type (along with the correct pulleys for the belt used)

An easy way to determine which direction each accessory is supposed to turn is to look at the pulley:

grooved pulley= matches crank direction
smooth pulley= reverse rotation

hey i have an 85 xj with the carbed 2.5 as well. I have a 97 tj motor in mine. I run a holley red pump mounted close to the tank an then under the hood i have a fuel pressure regulator with dual outlets. instead of plugging the unused outlet i threaded a fuel pressure gauge in one so i can monitor the pressure. I run around 3.5 psi with the 2 barrel and it seems to work pretty well.

as far as the belts and accessories if u have all the stuff from your jeep and it all worked i would run that. like previously stated you will have to swap the water pump but i don't see why one for your jeep wouldn't fit this motor. i went the other route and ran the serpentine set up. but then you end up with other issues like having an externally regulated alternator.

but good luck with your swap its good to see other guys keepin the vintage xjs alive