OK, to recap- 91 caprice wagon (TBI LO5, 7747), swapped in a .030 350, Edelbrock's MPFI manifold kit/fuel pump(converts TBI to MPFI), and did the re-pin to a 7730. Burned a stock AUJP with vats disabled, but it still won't light. It coughs to life with a splash of fuel down the TB, and dies. I checked the fuel pressure per the manual, and I am only getting 14-15 lbs at the gauge, and the pump runs continuously, not stopping after a couple seconds. Is there something that allows me to change the FP, (which seems like a big change to 47-51) or is there a regulator somewhere I'm not aware of? I would assume the new stock burn would have that correct for the MPFI, but there is something new to learn at every turn in this project. What am I missing?

Thanks!

Darryl

 

I had that conversion kit for a short while on my 94' Suburban 5.7. Didn't like it so I converted to a TPI. That's a very long story

So you have the MPFI conversion kit on a 350, using a 7730 ECM and stock AUJP bin. Here's a few things to consider:

1. The injectors are only rated at 19 psi. So you will need to change your injector constant.

2. The fuel pressure regulator on that system is a LT1 type, non adjustable. At least my system was.

3. My TBI system did not have an air temp sensor stock. Neither did the MPFI conversion kit. Do you have an air temp sensor installed for input to the 7730?

4. 14-15 psi is too low for the MPFI conversion kit. You need to start there. My conversion kit did not come with a new high pressure fuel pump. If you have not changed the TBI tank pump, that is your low fuel pressure problem. If you changed out the pump and you reused the short section of rubber hose inside the tank, chances are pretty good it split. Trust me, it will happen.

Ed

 

Thanks Ed for the quick(almost instant) response!

1. I am aware of the 19 lb. injector issue. That is on the list.

2. I have the same regulator, no plans to change it as of yet.

3.The Caprice came with an IAT, I'll have to check my ECM re-pin chart to verify if I connected it to the 7730.

4. I did replace the fuel pump with the one for the MPFI. I am starting to lean towards the split line in the tank thoery for starters. I think that would explain the pump running continuously and not reaching the req'd pressure to turn off. Crap. Time to drop the tank and take a look.

I keep thinking about the knock sensor, and I'm not sure which one to get to replace the stock 305 one I have now. Camaro? Impala SS?

I'm going to spend some time reading through your 'long story', and see if I can learn anything I haven't come across yet.

Thanks again!

Darryl

 

Pump running continuously also is probably wrong, if you're controlling it with a 730 (but yes 15 psi is not going to start your engine either). You may have burned the chip wrong, you may have a bad 730, or your wiring is wrong. The pump itself isn't "looking" for pressure to turn off, the ECU controls it blindly. Yours isn't controlling it correctly, so fix that too.

 

I'm adding that to the list, and now that I think about it, I need to verify that before I drop the tank.

Will advise.

 

If you put gas in an old fashion oil can, the pump-squirt type and keep squirting fuel in, does it continue to run? I know it will be rough and go up and down the rpm range based on your fuel shots...

If it runs like you would expect it to run in this situation, then I would definitely start with the fuel pump and regulator (39 to 42 psi at the injectors).

Good luck

 

Dropped tank and pulled pump. I did use the new short section of hose, and its not leaking or cracked. Crap. I'll put it all back together and try the continuous gass feeding down the TB to see if it will stay running. I'm thinking it will if I can feed it smoothly enough. Where do I go next? Time to go back and read read read.....

 

be sure they gave you the right pump, i have seen a few TBI pumps that will only produce about 15 PSI dead headed. if you do have the right pump, when you get it back together try this, with the fuel pump running, crimp the rubber return line & watch the pressure gage. if it doesn't come way up, there is something wrong. if it does come up, look for a problem with the regulator. i would say you should see at least 60~70 PSI & maybe even over 100 PSI dead head.
also, if the pressure does come up, don't run the pump very long with the return hose crimped off, it may blow the in tank hose out or off, or damage the pump. you only need to crimp the return hose for a very few seconds & then release the clamp, 2~3 seconds is plenty to know if the pump can build
pressure.

 

No change in pressure with the line crimped (still 13- 14). Going to pull it completely out of the tank, and rig it to check it dead-headed.

 

Wow. Its been a LONG time since I posted, mainly because other things put themselves in line in front of the wagon. So, from the last post on this thread- Pulled the pump and dead-headed it, and lo and behold, Edge was correct. Split the original line with the higher pressure pump, so I replaced it and reinforced it with 4 FI clamps. Pressure is back where it should be. Swapped the KS, and still have the same no start condition. Time to put this one back in the front of the line. My daily driver Turbo Tbird has 321K on it, and I'd like the utility of the wagon back.

Cheers.

Darryl

 

Did you put your chip in the wrong way?
When I burnt my first chip, I installed the chip w/ the little notch pointing towards the zif handle (the same way as on the burner).
Yeah, that was wrong, it points away from the handle in the ecm! When I turned the key to on, the fuel pump ran continously and would not fire, just like you describe!
Did you put the chip in wrong?

 

Wow. I don't THINK I did, but I guess anything is possible at this point. I'll check it today to verify.