Midnight 85

Hi all and Happy 4th of July! I am finally getting everything sorted out on my Pro Flo XT project. It turned out the injectors I had were not the size they were supposed to be so I got a set of remans from FIC. 30 lb. set at 43.5 with vacuum disconnected. I now have a huge hesitation when I stab the throttle, if I just roll in to it it just starts pulling & won't stop but if I just hit it hard, be it rolling or sitting still it just won't go. I just need some things to look for that will cause this. If I set the tps down to where it is supposed to be it is real bad, if I set it up to just over 1 volt is gets better but is not eliminated and the high setting causes it's own problems. Timing is at 10 degrees just what the tune calls for, if I try to advance it a bit more it won't run right at all. If you have any ideas let me hear them.
I should add that I had to open the throttle blade more with the new injectors which makes it hard to set the tps down where it is supposed to be.

cumbercr

I wonder if the tune tables for accel enrich need to be looked at.

THE 383 admiral

that's Strange I'm sure the Pro Flow will end up similar to a HSR 10 deg was just a starting point... 12 -16 deg on my previous 89 build... made a huge difference...

Midnight 85

I did some more playing around and I noticed the fuel pressure would either stay the same or even drop a few pounds when I would rev it. I jacked the pressure way up and all the problems went away but I had 70 lbs of pressure. If it is the pump, would I be able to raise the pressure that much? And if it is the regulator how can I be sure?

THE 383 admiral

Ok it would appear your pump is weak.. your adjustable regulator is doing its job...
Maintaing pressure untill you command more fuel.. 70# would just about double your injector flow! What happens when you pull the vacuum from the regulator? An no if you pulled the regulator you would not have pressure..

Midnight 85

Thanks, that's what I was thinking but wanted to be sure before I bought the wrong part. Looks like a new Walbro is in order.

THE 383 admiral

Did the incorrect size injectors have the same hesitation??

Midnight 85

No they did not, this all started with the new injectors.

THE 383 admiral

Hmmmm.. that is not a good sign... what are the specs on the remans.. & flow chart tested?? What about your tune????

383vett

With my ACCEL dfi management system there are a couple adjustments similar to the throttle squirt of a carburetor. Sounds like you need to find this and increase the acceleration enricbment

Midnight 85

30 lb remans from FIC and a pcmforless tune and another tune from another source, both act the same.

THE 383 admiral

Can you Data log???
If you where close i would test with my 30# ads super injectors..
You need the complete spec sheet for the injectors and compare your tune constants

Midnight 85

You both may be on to something, it does act like it needs a pump shot. I pulled the regulator off & took it apart to see if there was anything wrong inside, it looks good. I really find it hard to believe that two different tunes would both act pretty much the same, the pcm tune is calling for more fuel than the other one but it doesn't seem to make any difference which tune is in the ecm.
When I did have the old injectors in the engine I took it to Bloomington Gold and I had been getting a code 24 for lean then so I raised the pressure to try & compensate but it did no good I still had a check engine light coming on all day.
The fact still remains that when I rev the engine the pressure either stays the same or drops a few pounds, if it was in the tune this would not happen would it?

Midnight 85

I can datalog and that will probably be my next step once I exhaust all other possibilities. I have complete faith in FIC's injectors and I just have a gut feeling it is the pump. I changed the filter already this morning hoping that might be the cause but it was not.

THE 383 admiral

You are correct your pressure is manually controlled from the AFPR.. two upgrade tunes & 2 sets of injectors most likely lean. Just for giggles email your tune to check your constants, PE, LV8, accel enrich tables..

Midnight 85

I just went out & put the regulator back on, I set it at 39 lbs. vacuum off, just for the purpose of testing. Vacuum on, 38 lbs. and dropping 1-2 lbs when I rev the engine. No climbing of pressure under load, (revving). It used to climb between 5-10 lbs when I would rev the engine. My neighbors are about ready to lynch me since I am messing around making noise while they are enjoying the holiday so I am done for today.

cumbercr

You mentioned having trouble adjusting your TPS. One of the accel enrich tables adjusts fuel using delta TPS.

THE 383 admiral

Fuel pump just like i mentioned first *****Happy 4th*****

Midnight 85

The reason I was having trouble setting the tps is because it is not really adjustable so I had to elongate the holes so it would rotate enough to set it. Then with the new injectors I had to set the idle up so much that I could not adjust it down far enough to be in a reasonable range. This should go back to normal once the fuel pressure is right again.




Thanks, I have a new Walbro ordered.

bjankuski

This is not a fuel pump problem, it is a tune problem. You need more acceleration fuel. The pressure will drop when you rev the engine in the driverway because your intake vacuum goes up. On the road at wot the vacuum will drop and pressure will go up. You already raised pressure to 70the psi, if the pump was shot that would not happen. One other note doubling fuel pressure only raises output 41%.