I got a TBI system from someone who said he got it from eBay. I was told it was from a 350 Chevy truck and does have a 7747 ECM. It's on an AMC 360 in a Full-Size Jeep Cherokee. I've been having fueling issues and I think I've narrowed it down to the injectors being too small. It idles okay, but I get very lean conditions all the time (even at idle) and it won't gain RPM's under load. My BLM's are reading in the 140's and 150's and that's down from the starting point when they were at ~170+. As far as I can tell the fuel pressure is steady at 13psi. I can't see it when driving, but I've held the throttle open while sitting in the driveway and it doesn't seem to drop at all (running an E2000 pump). There are no error codes being thrown by the computer. I don't have VSS, EGR or the Knock sensor enabled.

Can anyone help me identify these injectors? I've asked on other boards and nobody knows!

 

Is there any way I can measure something to figure out what these injectors might be from? Can injectors like this be modified to flow more fuel?

 

Do you have any other data from the vehicle? What are the O2s reading? IAT? CTS? MAP? Any vacuum leaks? Exhaust leaks?

 

I've got data.

Here's one of my latest logs

And here's one of my latest BLM tables

Those were from the first attempt to take it around the neighborhood. The BIN's VE1+VE2 tables are adding up to greater than 100 in a few places already.

No vacuum or exhaust leaks.

 

Those look like aftermarket injectors. I am almost positive that they are not GM Rochestor Product like the others. Your best method is increase the fuel pressure until the lean goes away and things richen up. Most injectors can take 35 PSI easily, the pod is good for 45 PSI or better, and the fuel pump is atleast good for 40 PSI ( I have personally run 40 PSI on a set of 4.3 injectors with the same fuel pump). Finding the right spring for the fuel pressure regulator is the challenge though.

Have you disabled the EGR in the .BIN file? Looks like you are already tuning.

Assuming stock fuel pressure (12 PSI), 61# 350 injectors, and 360 cubic inches, you should have a Base Pulse Width constant of 139, and max out at about 235-250 FWHP depending on the Brake Specific Fuel Consumption (BSFC).

 

I've got someone on another forum telling me not to touch the BPW (at least not yet). I'm not sure why. Does it affect anything other than fuel? Just how high can you go on the total fuel calc before the injectors go static? The BPW is set to 135 now.

Holy cow! 40 psi?? I might try bumping the fuel pressure higher. I think I've got a spring around that is about the right diameter, but much shorter. The spring rate is so much higher it might get the pressure up to where I need it. I hope I don't blow any hoses up/off! The hoses will probably take it, but some of the hard lines don't have the enlarged area at the ends to help hold the hoses on.

EGR is disabled. I'll probably run it in the future. I have the controller part, but not the connector.

 

Here is how to calculate the BPWC, it should match your injector flow and engine displacment for proper operation. It only effects fueling calculations, in both open and closed loop.

Use this for calculating injector flow, stock 350s are 7.759 gms/sec or 61 lbs an hour at 12 psi.

http://www.csgnetwork.com/fiflowcalc.html

Then use the number that you get from the increased pressure to calculate the BPWC here.

http://www.fortunecity.com/rivendell...24/gm_inj.html

Disable the EGR in the .BIN by setting the EGR enable temp as high as it will go and disable the error flag.

As far as the hoses go, you can get fittings to screw into the TBI that adapt it to AN lines. I currently have stock TBI Van fuel lines to the stock TBI van tank, but had the AN setup (TBI setups use Saginaw style power steering fittings) when I had the Weiand 142 on there.

 

Definately need to do something with the tubing ends. I've found using the compression fitting rings and soldering them to the ends of the lines works. Supposedly Earls makes a tubing beader but I haven't found it. Once over 12psi or so should use the fuel injection hose.

RBob.

 

Just as a test I once bumped the BPW up to something like 180. The jeep was still running lean. I knew about the calcs, but the person I was talking to kept saying not to change it. Of course we're still working with unknown injectors and a BPW set for a 350 should be close enough.

All my hoses are EFI hoses. I'd like to find the tool they use to put that little bulge at the ends of hard lines. I might just use some type of flare fitting to adapt to a barb since I have one of those tools. I started looking for my strong spring to bump up the pressure this weekend, but I think I'm going to stick with *normal* TBI pressures instead and get larger injectors.

So, nobody recognizes those injectors?