How does boost affect the running of the fuel pump? Works fine up to 3 psi then crap. I have other threads on this if you care to read. No supercharger belt and no problem.

[NOTE FROM MODERATOR] This thread is going to seem a bit confusing, but it "merges" four different threads posted about the same problem. Without "merging" there was important info missing from several of the posts, and no one knew what had already been suggested and rejected. It really hurts your chances of solving a problem if you continually start new threads and don't at least include "links" to the old ones.

 

well, you might be needed more fuel then the pump can supply, if so, the pressure will drop off at the point you notice the power loss

 

I read one of the threads and they say pressure is important but volume is the true test of the pumps ability. The pressure tests fine. How do i check the volume? I did use the bleed value on the pressure gauge and it would drop even with the slightest draining and would lose most of the 40 psi with 20% pushed in.

 

You did hook the FMU up to the return line, right?

 

The fmu is hooked up to the fuel coming from the regulator and to the return line but has no brand name and came with no instructions so i hope it is right. If it were on backwards what would happen?

 

I read about lt1's falling flat on there face over 4500 rpm under wide open throttle. Could this be from spark blow out and what would you do to check this?

 

is your car falling on its face or are you asking a question in general about all lt1's?

 

Assuming your talking about your setup, you shouldn't be getting blow out unless maybe you have them gapped wrong. You should have them gapped around .035 vs the .050 stock gap.

Ken R.

 

I am having problems that sounds like this. I loose all fuel pressure when it crashes for a second and loose all power, then back like it never happened. I wouldn't think that spark blow out would cause fuel pressure loss. Always looking to give others ideas. I put new plugs and gapped them at .35 as instructed. Is it also possible for the boost to effect the fuel pressure and cause it to suddenly stop? Over 2 psi it will happen and the rpm's go way down and it will be fine till it hits 2 psi again. What about voltage drop causing the pumps to stop? Can my alternator be the culprit and what do i do to check it? I have old threads with more info on my problem.

 

I have had this happen passing through 4500-5000 rpm. Initially I thought the ECU was pulling out a lot of advance but then found re-tensioning the belt stops it. BTW I do have the LT4 knock circuit installed. I'm planning to have 2 additional grooves cut in the crank pulley and get an 8 groove supercharger pulley. I'll try a 7 rib belt first. That's about all the PD tension pulley will support width wise. Goodyear makes a 7 rib belt that's 1.5 inches longer (4070425 - 7PK1080).

 

Could the computer be doing this for some reason? It really feels like it is turning off the fuel to the rails. If the fuel flow was not enough i would think the gauge would read a drop in fuel pressure and not 45 psi to 0 psi in a split second. I will try the belt tighter idea, but if it was slipping wouldn't the boost drop and not the fuel pressure.

 

will any of the sensors keep the motor from staying running?

 

ok, so it starts, then stalls?

how is the fuel pump wired?

 

was it running before or a new swap into a blazer.

 

Did the car have vats that it came from?