I am swapping a 350 TBI into my 95 YJ (has a 4cyl MPI).

I'm wondering what the pressure output is of the stock pump in the tank.

I wonder if it's too much for the pressure regulator in the 350's TB unit to handle. Does anyone know?

Charly

95 YJ fuel pressure is about 39 psi.

I'm not sure, but I think the Chevy units use a lower pressure. Somebody else will confirm that I'm sure.

:usa:

The CPI unit uses 12 lbs of pressure.. If the regulator and return line does not resrtict the flow it should be fine but if their is too much restriction then pressure my be too high resulting in a rich mixture..

Yeah the TB unit needs 9-13 psi.

When calling Howell and Centech about their harnesses, they both expressed concern about using the stock, in tank MPI fuel pump. Comments were made like "it will explode your TB unit!".

So, 39 psi, thanks, did you find that in the FSM?

What about those who have done YJ TBI swaps ....what do you use?

Thanks,

Charly

the 98 4.0 MPI pressure is 49psi +/- 5 psi. the in pump regulator send back anything over 49 into the tank. dont know what the 95 4 banger pressure but any MPI fuel pump will be WAY more than any TBI system. not to mention that the mpi system stays pressurized 24/7 even when the engine is off. the TBI only has pressure when the key is turned on. sorry, a new pump and regulator will be needed. consider the pump from an older 4 banger TBI. dont know the specs on pressure, but it should fit in your existing tank physically. dont quote me on any of this.

I went the exact opposite direction. I went with a Tuned Port Setup that I put in place of my TBI 90 4 banger. I swapped fuel tanks with a 93 4 banger and it worked perfectly.

I'd suggest swapping tanks with a 87-90 4 cyl YJ to be the easiest swap. It's only capable of 15 gallons, unlike the later fuel tanks, but 15 gallons is still enough for most people on a trail rig.

For the most part, you will need to match up the fuel pump pressure to the injection method. TBI needs to stay with TBI, MPI with MPI.

MPI also requires different quality fuel line and hose clamps, too. It won't be an issue for you, since you will already have the stronger ones (MPI), but to go like I did, you have to change everything out.

Matt

You can install a pressure regulator in lone to reduce the pressure.

This will need a return line ( which I think you already have) to return the excess fuel to the tank.

So good luck....

Alright, this is what I've found.

These are all Airtex brand PNs and specs (available at Carquest):

----------------------------------- GPH at WO --- Pressure shutoff

E8229 95 YJ 4cyl MPI --------- 45 --- 80-100 psi

E7001 88 YJ 4 cyl TBI ---------- 40 ---- 30-46

E3902 89 Chevy G20 Van 350 TBI --35 ----- 12-17


So, what's surprising to me is that the 350 (same for the 454) provides less flow than either 4 cylinder pump. I expected it to be the contrary.

And the best thing is that dimensionally all three pumps look like they'd be interchangeable (all are same diameter...4 cyl TBI pump is a bout 1" longer than the other two). the intake filter socks have slightly different mount diameters, but it looks like if you keep the sock with the correct pump, it will work fine. Wiring is two wires.

This is great news, because by all appearances, I can keep my tank and just change the in tank pump.

Hate to bring up an old thread but does anyone think the E8229 would be enough for the 5.3l LMS Chevy swaps? I have the metal yj tank, and have a line on a cheap e8229.

Bump?