Need some ideas
Thread Starter
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
Need some ideas
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.
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.
Last edited by Midnight 85; Jul 4, 2013 at 08:58 AM.
Thread Starter
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
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?
Melting Slicks
Joined: Sep 2010
Posts: 2,422
Likes: 202
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..
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..
Last edited by THE 383 admiral; Jul 4, 2013 at 02:41 PM.
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Race Director
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From: moraga ca
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
Thread Starter
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
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?
Thread Starter
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
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.
Melting Slicks
Joined: Sep 2010
Posts: 2,422
Likes: 202
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..
Thread Starter
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
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.
Thread Starter
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
Thanks, I have a new Walbro ordered. 
Safety Car
Joined: Sep 2001
Posts: 4,157
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From: Glenbeulah Wi
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%.