I am hoping some of you guys can give me some insight into how I should set up the fuel system on a transplanted 2001 5.3 L Vortec Motor. The engine in question has been installed in a 1985 Jeep CJ7, adapted to an SM-465 transmission. I had been using the stock CJ fuel tank with a rail mounted high pressure fuel pump - 3/8" supply and 5/16" return (although this has to be reduced to 1/4" at the tank.)

I am in the process of switching to a baffled fuel tank that will use a stock Jeep YJ in-tank sending unit and pump. Will again have the 5/16" to 1/4" issue at the sending unit.

I have not been able to find answers to a couple of questions and I hope there is some expertise here I can tap into. The questions are:

1. Should I be making provisions for an evap canister or is that not necessary?
2. Should I be using a vented or unvented gas cap?

With the prior set up (unvented cap and no evap canister), the engine ran reasonably well, but once it warmed up the idle was not consistent and would vary between about 400 and 800 rpm.

Appreciate any help or thoughts you care to share. Sure there will be other information I should share, but can't think of what it is right now.

Kevin

If you have access to tuning, then I would turn all EVAP/Emission crap off. Then you won't have to worry about the canister. But either way, don't install it.

If the tank does not have any other type of vent system installed, you will need a vented cap for it.

If you don't have the software to custom program your PCM there are many company'* that you can send your PCM to to program it. Your going do need to delete a few things like the EVAP system as stated earlier, if your going to run cats your going to need to delete the post cat o2 sensors. Need to delete the auto trans inputs if your doner truck had a auto transmission. As tight as the engine bay is I would delete the mas air flow sensor and program it to set mixture off of the BARO and o2 sensors so you can put a K&N air filter directly on the throttle body. As far as the fuel delivery I would make my own fuel lines with AN fittings and use a bulk head fitting on the gas tank like they do with race car fuel cells.

I happened to have a bulkhead fitting in my toolbox.

Thanks for the help. This engine has been running in the Jeep for quite a while with eh stock tank, etc. As I was thinking about the change to the baffled tank and the in-tank sending unit, I began to wonder if I had done everything correctly the first go-round. Howell did my original PCM set up - deleting the auto trans, post cat O2 sensors, etc. I have a friend here in town who is a GM tech and refined the tuning once I got everything running. I do still have the Mass Airflow sensor with a K&N set-up ahead of that. No EGR as I didn't have enough room in the engine bay. Running a set of center-dump Headman headers.

Sounds like I should put it back together with a vented cap and go from there. Is there a good tuner out there that people like that does everything you need without requiring a new mortgage on my home?

Again, thanks for the insights.

Should have read that a little more closely before hitting the post button. Meant to say no EGR because I didn't have room in the engine bay for the stock exhaust manifolds. Hence the Headman headers.

I'm doubting your idle problem has to do with the fuel tank. I'm betting since you still have the mass air flow sensor it is dirty or bad causing the surge.

I'm with William, a complete reprogramming of the PCM for an emissionless engine is needed in an application such as this.

If you get a chance and are able to, scan for codes.

i dont know about the jeep stuff but the pump in the truck is capable of about 58psi key on engine off and over 60 running if you watch it getting on it, wont run right without that much. assuming to that you have the line connected to the stock regulator on the rail

Thanks again. I will check the Mass Airflow Sensor to see if that fixes the idle issue and will scan for codes and get my buddy to come over and retune as necessary.

Will report back when I get a chance to get this all done.