Electrical issue?
02-05-2008 | 01:37 AM
#1
Thread Starter
Registered
Joined: Nov 2003
Posts: 825
Likes: 30
From: Antioch, IL
Electrical issue?
I have been having a problem. At WOT and only WOT with a Modified ProCharged Injected 454 Mag I have a problem when I trim the drive I have a voltege drop down to abot 11.5 and lose fuel pressure and ignition at the same time ( it basically falls on it's face and breaks up we have chased down grounds, etc,). I am running the red Aeromotive and 7PSI boost M3 SC at about 85 PSI when this occurs. I can work it out by triming first but if you want to adjust at speed it is an issue. Anyone ever seen this?
02-05-2008 | 05:55 AM
#2
Registered User
Joined: Feb 2005
Posts: 891
Likes: 0
From: St. louis, East Sider
Maybe you have a short in the trim pump or switch. I had something similar happen in my boat with a the cigarette lighter believe it or not. It ended up being a short on some half ass wiring form the previous owner.
Last edited by 320es; 02-05-2008 at 06:50 AM.
02-05-2008 | 06:22 AM
#3
Charter Member #601
Joined: Dec 2000
Posts: 3,276
Likes: 5
From: Holland, Mi USA.
RBeyer,
I have seen what you are talking about, but not to the extent that you see it. When I log a pass with my EFI, I can see when I hit the trim switch. But I dont see it go to 11.5. I think it is more like .5v drop. What alternator are you using, one wire? If not a one wire, how is your ECU wired? Is the 12v source for the ECU a long way from the reference for the alternator? What about connections on the positive side of the circuit?
One thing that does through a flag.. 85psi on the injector. If at WOT the need for 85psi is necessary, you many be drawing more current to run the injectors than you have supply for, when you add the trim pump load. Are you injectors low impedance? My opinion is that running injectors at that high psi is hard on the injectors (heat) which will take more current to opperate.
What happens at say 3 or 4psi of boost. Can you see a proportional drop or is it a normal drop.
I would look at all of the connections from the battery to the alternator and to the ECU. If they all look good, then I would suspect you are drawing more current (between the injector load and the trim pump load) than the alternator can supply at WOT.
Hope this helps.
Dick
I have seen what you are talking about, but not to the extent that you see it. When I log a pass with my EFI, I can see when I hit the trim switch. But I dont see it go to 11.5. I think it is more like .5v drop. What alternator are you using, one wire? If not a one wire, how is your ECU wired? Is the 12v source for the ECU a long way from the reference for the alternator? What about connections on the positive side of the circuit?
One thing that does through a flag.. 85psi on the injector. If at WOT the need for 85psi is necessary, you many be drawing more current to run the injectors than you have supply for, when you add the trim pump load. Are you injectors low impedance? My opinion is that running injectors at that high psi is hard on the injectors (heat) which will take more current to opperate.
What happens at say 3 or 4psi of boost. Can you see a proportional drop or is it a normal drop.
I would look at all of the connections from the battery to the alternator and to the ECU. If they all look good, then I would suspect you are drawing more current (between the injector load and the trim pump load) than the alternator can supply at WOT.
Hope this helps.
Dick
02-05-2008 | 06:35 AM
#4
Gold Member
Joined: Jan 2001
Posts: 2,123
Likes: 1
From: Brooklyn Park, Md USA
Also make sure that your batteries are big enough and are FULLY charged. I have seen that a low battery will cause the voltage drop when running hard and trimming. They are low enough that it will rob voltage from the ignition and cause it to break up. Load test each battery if you can and make sure all wires are tight with a good connection.
02-05-2008 | 07:50 AM
#5
Registered
Joined: Feb 2004
Posts: 3,710
Likes: 2
From: MT. JULIET, TN.
Also make sure that your batteries are big enough and are FULLY charged. I have seen that a low battery will cause the voltage drop when running hard and trimming. They are low enough that it will rob voltage from the ignition and cause it to break up. Load test each battery if you can and make sure all wires are tight with a good connection.
02-05-2008 | 07:56 AM
#6
Charter Member #232
Joined: Oct 2000
Posts: 18,417
Likes: 6
From: Carlisle, MA USA
Make sure that your battery and ground cables are good. Look for ANY corrosion on them. If you see any replace them. I had this exact issue and it was my battery cables. The problem in my case was that I was using the output of the alternator to trim the pump not the battery. Also check the continuity from your alternator power output to the battery and so on.
__________________
Put your best foot forward!
Put your best foot forward!
02-05-2008 | 06:56 PM
#8
Thread Starter
Registered
Joined: Nov 2003
Posts: 825
Likes: 30
From: Antioch, IL
RBeyer,
I have seen what you are talking about, but not to the extent that you see it. When I log a pass with my EFI, I can see when I hit the trim switch. But I dont see it go to 11.5. I think it is more like .5v drop. What alternator are you using, one wire? If not a one wire, how is your ECU wired? Is the 12v source for the ECU a long way from the reference for the alternator? What about connections on the positive side of the circuit?
One thing that does through a flag.. 85psi on the injector. If at WOT the need for 85psi is necessary, you many be drawing more current to run the injectors than you have supply for, when you add the trim pump load. Are you injectors low impedance? My opinion is that running injectors at that high psi is hard on the injectors (heat) which will take more current to opperate.
What happens at say 3 or 4psi of boost. Can you see a proportional drop or is it a normal drop.
I would look at all of the connections from the battery to the alternator and to the ECU. If they all look good, then I would suspect you are drawing more current (between the injector load and the trim pump load) than the alternator can supply at WOT.
Hope this helps.
Dick
I have seen what you are talking about, but not to the extent that you see it. When I log a pass with my EFI, I can see when I hit the trim switch. But I dont see it go to 11.5. I think it is more like .5v drop. What alternator are you using, one wire? If not a one wire, how is your ECU wired? Is the 12v source for the ECU a long way from the reference for the alternator? What about connections on the positive side of the circuit?
One thing that does through a flag.. 85psi on the injector. If at WOT the need for 85psi is necessary, you many be drawing more current to run the injectors than you have supply for, when you add the trim pump load. Are you injectors low impedance? My opinion is that running injectors at that high psi is hard on the injectors (heat) which will take more current to opperate.
What happens at say 3 or 4psi of boost. Can you see a proportional drop or is it a normal drop.
I would look at all of the connections from the battery to the alternator and to the ECU. If they all look good, then I would suspect you are drawing more current (between the injector load and the trim pump load) than the alternator can supply at WOT.
Hope this helps.
Dick
Yes they are low inpedance injectors, everything else has checked out ok. It only happens at WOT and high RPM. It could be a draw problem the alternator is the stock unit for a 1998 454 Mag.
02-05-2008 | 06:57 PM
#9
Thread Starter
Registered
Joined: Nov 2003
Posts: 825
Likes: 30
From: Antioch, IL
Also make sure that your batteries are big enough and are FULLY charged. I have seen that a low battery will cause the voltage drop when running hard and trimming. They are low enough that it will rob voltage from the ignition and cause it to break up. Load test each battery if you can and make sure all wires are tight with a good connection.
02-05-2008 | 06:58 PM
#10
Thread Starter
Registered
Joined: Nov 2003
Posts: 825
Likes: 30
From: Antioch, IL
