Topic: 90 TBI to 97 MPI

[dono man]

I swapped out my '90 2.5L and installed a '97 2.5L. Why? Because it sounded fun
Every thing seems to be going as expected but I haven't found an answer to the fuel pump.
Option A is to go with a used TJ pump and I'm good to go (maybe, I have no idea really) but it's used
Option B would be to go with a new in-line pump and rig or remove my pump to work as a pick up.
What about the return line with plan B?
Your thoughts please.
later

Guinness

[bidi]

Well, I can't say much about option B.  I'd steer clear of option A though.  The in-tank fuel pump is nice and everything, but is extremely difficult to replace.  Mine short circuited on a trail when I tried to go through a small lake.  I don't know who the hell designed that thing in there, but I thought it was really stupid at the time.

[Mr_Random]

I swapped out my '90 2.5L and installed a '97 2.5L. Why? Because it sounded fun
Every thing seems to be going as expected but I haven't found an answer to the fuel pump.
Option A is to go with a used TJ pump and I'm good to go (maybe, I have no idea really) but it's used
Option B would be to go with a new in-line pump and rig or remove my pump to work as a pick up.
What about the return line with plan B?
Your thoughts please.
later

Guinness

Do you mean the whole engine? so now you have a YJ that thinks it's a TJ?

My XJ is gonna think it's a YJ soon! (94) I can't wait!

If you can get an inline that can produce 45PSI and has a built in pressure relief system, then go for it! But I doubt that will happen...

You see, the TJ fuel rail doesn't have it's own regulator; it's built into the fuel pump! So either swap in a OBDI YJ pump and fuel rail with an inline pump to match the higher OBDII PSI and somehow change the regulator on the rail to allow the higher pressure... or um... go the easier route and use a TJ fuel pump!

[dono man]

Do you mean the whole engine? so now you have a YJ that thinks it's a TJ?

My XJ is gonna think it's a YJ soon! (94) I can't wait!

If you can get an inline that can produce 45PSI and has a built in pressure relief system, then go for it! But I doubt that will happen...

You see, the TJ fuel rail doesn't have it's own regulator; it's built into the fuel pump! So either swap in a OBDI YJ pump and fuel rail with an inline pump to match the higher OBDII PSI and somehow change the regulator on the rail to allow the higher pressure... or um... go the easier route and use a TJ fuel pump!

This is where I'm confused because my TJ rail does have a regulator on it and the return line comes off the back of that.
Like this

[dono man]

edit option?

Yes, my YJ thinks it's a TJ.
TJ flares
TJ motor
and possibly pump
GM tranny though

[Jeffy]

This is where I'm confused because my TJ rail does have a regulator on it and the return line comes off the back of that.
Like this

Interesting...  That's a carry over from OBDI.  The TJ shouldn't have a return and the fuel filter/regulator should be on the top of the tank.  I'm wondering how early this '97 was made.  Probably a transition so that would put it in mid to late '95 or early '96.  I've heard/seen of '95.5's with '97 parts but not a '97 with '95 parts.

If that's the case then I'd just an MPFI YJ pump with the returns.  Not to mention, you won't have to screw around swapping the gas level sender unit.  Otherwise, run an inline pump and leave your stock one in the tank.

[dono man]

Interesting...  That's a carry over from OBDI.  The TJ shouldn't have a return and the fuel filter/regulator should be on the top of the tank.  I'm wondering how early this '97 was made.  Probably a transition so that would put it in mid to late '95 or early '96.  I've heard/seen of '95.5's with '97 parts but not a '97 with '95 parts.

If that's the case then I'd just an MPFI YJ pump with the returns.  Not to mention, you won't have to screw around swapping the gas level sender unit.  Otherwise, run an inline pump and leave your stock one in the tank.

All I have to say is...
UGH!!!! Not the whole fuel pump year question but just that I could not get it to fire.
The previous owner had a jerry rigged relay panel thingy and I have no idea what's the problem.
First sign of trouble was the Mean Green starter wouldn't turn. Opened it up and the copper contacts were black, wet and just ugly.
Cleaned it up and got it back together and it worked great but no fire.
So now I don't know if it's the coil, CPS or what that's causing the problem.
I'm still using the original '90YJ fuel pump but I should be able to get it to fire, right?

later

[dono man]

Mine does that and it could be a couple of things.
1- pressure bleed down. You fuel system is under pressure. Once that pressure is release and due to the overall size of the system, it may take the pump some time to get the system up to pressure requirements. The pump may also not be as strong as it once was.

So what's the consensus on my Yj pump being able to at least create some fire?
Thanks 

[Jeffy]

So what's the consensus on my Yj pump being able to at least create some fire?
Thanks 

Can you hear the pump prime?

[Matt vs YJ]

The '90 YJ pump is probably for the TBI system, which runs at 15 psi. The regulator is built in to the throttle body, so I'm not sure what that pump is actually capable of putting out.

I don't know the exact pressure, but you're probably gonna need around 40 psi to run the '97 system.

As far as being enough to get it to crank... I don't know, but I have a feeling that it's not.

[dono man]

Can you hear the pump prime?

Yes, the pump primes.

The '90 YJ pump is probably for the TBI system,

As far as being enough to get it to crank... I don't know, but I have a feeling that it's not.

Yes, it's for the TBI and I have a suspicion that it is the problem but is the system that sensitive?

[Jeffy]

Yes, the pump primes.Yes, it's for the TBI and I have a suspicion that it is the problem but is the system that sensitive?

Have you checked the fuel pressure at the Schrader valve?  I'll go with; the engine is starving for fuel since the pump can't keep up.

[aw12345]

Hook up a pressure gauge and block the return line and see where the pump dead heads at. It could very well make enough pressure to get the engine running, as long as it manages to make something close to 40 psi

[Jeffy]

Hook up a pressure gauge and block the return line and see where the pump dead heads at. It could very well make enough pressure to get the engine running, as long as it manages to make something close to 40 psi

If the TBI pump is rated for 15psi, it's kind of a stretch to get 40psi out of it.

[dono man]

I haven't had time to do squat these past few days but I did manage to order an in-line pump.
Now I need to know one more thing. In the picture below you see two fuel lines entering the fuel rail, one is a supply and the other is the return.
Which one is which.
Reason I'm asking is because the previous owner regulated the fuel at the pump not using a return and had the supply hooked up to the 5/16 line with the regulator input capped. Make sense? I assume the input is through the regulator but need to make sure.


Thanks