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?

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.

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

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.:D

I had the same problem and it was a weak/dead cell bat. Try the bat first.

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.

i had same thing it was the plug on top of motor it has pins take srew driver pry the pins clean and put elictic lube crc that work for me

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.

New battery fully charged. That said I only run one would two help?

Worth a try.
Thanks

I adapted a 130 amp alt on my boat to replace the oem 53 or 63 amp it had for similar reasons,voltage wouldn't hold at wot running all the extra stuff,a big fuel pump at 75 plus psi will draw 20 plus amps if not 30 (I have blown a 25 amp fuse),plus aftermarket ignition,plus your injectors and all the other stuff. You might want to try running some bigger wires too from your batteries/alt to the engine and computer harness,I ran a small battery cable from my alternator to the connection running to the battery to ensure I got full advantage of all the extra power,Smitty

Hi Smitty,
Can you give some more detail as to what was needed to make that adaptation for the alternator. Do you have any pics, etc,.
Bob

I found a alternator in a catalog rated for marine use,it was very close to fitting except it used a v-belt instead of a serpentine. I used a small spacer(about .050 or .100 thick) and the dia of the shaft to get my pulley to line up opn it and not rub the alt body,it bolted to my stock bracket (it had 3 holes and one of them lined up,I attached the only pic I could find),couldn't tell you much more except its definately fatter in diameter (the old one was a hitachi style),it was 5 or 6 years ago,Smitty

Thanks, I will look in to that option.
Bob