Schematics (NOT "wiring diagrams") for 558-328?

[clcorbin]

Folks, I'm getting ready to install a Super Sniper Stealth on my 1981 F100 with 351W in it. I plan on using the single 558-328 wiring harness for the EFI and HyperSpark ignition. (I really don't like having a jumble of wiring under the hood if it can be avoided.) In the installation guides, it only shows a wiring diagram with a LOT of details missing (such as what wires are going to what terminals on the relays).

Did Holley ever actually release a true wiring schematic for this harness (or the other harnesses for that matter)? Has someone made one of their own that they would be willing to share? Thanks for the time & help! Clint

[Candu SNO]

Short answer regarding true schematic with connector cavity legends is "No". In my opinion, Holley chooses to supply adapter harnesses with limited information in order to avoid the problem of random wiring by some low-IQ MacGyvers, there are some crazy automotive wiring pictures on the web.

The subject of automotive EFI-rated connectors and Holley's use of them is very broad and confusing. Trying to identify specific connectors and terminals is difficult. You may have read these but here are two informative Forum posts:
ECU Connectors & Terminals - Holley EFI
Wiring considerations for Holley EFI systems

All the individual components are supplied with their required "pig-tails" and a wiring diagram with a color legend. If you are going to integrate them into your own custom Sniper harness, it is simplest to choose your own preferred connector type for the rest of your under-hood harness and match your custom Sniper harness main connector to that. I prefer Delphi Metri-Pack 150 (now called Aptiv since GM went broke and sold Delphi), but many people prefer Deutsch DT series (see link below).

This Volvo modification website has very many interesting articles (the mid-90s Volvo radiator fan relay is especially useful with Sniper switched ground relay control). Here's its section on custom wiring and Deutsch:
Harness Crimping Page

[a b c]

Have you seen the pin-out explanation in the basic instructions around page 17 or so, it's just below the basic wiring overview? I don't know how much more you would need unless you want to get into the ECU pin-outs and it doesn't look like Holley is going to share that anytime soon.

[Danny Cabral]

Does the Sniper ECU itself have a pin-out, or is it a bunch of wires epoxied (potted) into the ECU?

[a b c]

The connections are just potted in the ECU, but they do list the pin-outs on the connectors.

[Danny Cabral]

Yeah, I was just curious how the wires attached to the Sniper ECU. Thanks.

[clcorbin]

Have you seen the pin-out explanation in the basic instructions around page 17 or so, it's just below the basic wiring overview? I don't know how much more you would need unless you want to get into the ECU pin-outs and it doesn't look like Holley is going to share that anytime soon.

The problem is I'm going to use the Sniper & HyperSpark integrated harness AND I'll be integrating it into a proper power distribution and relay module. So the 40A relay in that harness will not be used. The BIG problem is the way the relays are controlled in that Eaton relay/fuse block means they have to be active low controlled (i.e. the relay is turned on by outputting a ground on the control wire). The diagram just shows a generic relay with a blue +12V wire going to the pump. Ah, and it DOES show the other terminal being grounded. NO information whatsoever on how that relay is controlled. Active low control is the industry standard for good reasons, so I HOPE that Holley went that route and I'm worried about nothing.

When my harness and other parts get in, I'll probably Ohm everything out and build my own schematic for that harness in KiCAD and test the actual outputs and be done with it. It'll make it MUCH easier to track what I'm doing over all if I put everything on a single schematic with wire color notes.

On the bright side, the diagrams DO provide a good starting place for the connectors and pin-outs at the connectors along with wire color coding. Given I have four weeks or so before Holley actually ships some of the stuff I ordered, I that will keep me a little bit busy I guess.

And thanks for the replies! It is appreciated! Clint

[clcorbin]

Candu SNO, I have both those links bookmarked. Andrew's thread is what turned me onto the Eaton power distribution block. It was pretty much perfect for my '81 Ford F100. It also looks like I will need five relays to control everything:

1. EFI system power (replacing the one in the integrated harness. I hate those little stand alone relays).
2. Fuel pump relay (turns fuel pump power on/off).
3. Fuel tank pump selector relay (dual tanks, each tank has an in tank fuel pump).
4. Headlight high beam power relay (I had to add stand-alone headlight relays several years ago when I was seeing nearly TWO volts drop to the bulbs).
5. Headlight low beam power relay (as above).

I'm also thinking about doing the fuel pumps like I do the headlights. The low beam is triggered by the low beam headlight wire (that would normally go to the low beam element), and the high beam relay is triggered by the high beam headlight wire (ditto). They're completely isolated from each other and can never be on at the same time. With the fuel pumps, I could have the side tank pump connected to the normally closed contact on it's relay and then have the rear tank pump connected to the normally open contact on it's relay. Both relays (and the Holley dual pump tank valve) would be triggered by the stock tank selector switch which is low for side tank and high (+12V) for rear tank. That would also allow me to wire a single 12 AWG (overkill) from each relay to each fuel pump. No crossing things over at a single relay.

Sorry, got to thinking out loud with this post! Thanks, Clint

[GPatrick]

The only relay I'm aware of on the Sniper harness is the fuel pump relay. What are you referring to as the EFI System Power? There's a pink wire that's the ignition trigger, I prefer to use a relay with the ignition switch as a relay. But I don't think the Sniper supplied harness has a relay for this. The main power & ground (large black and red wires) must go direct to the battery, no relays. If you turn off and on the main Sniper power wire the system will get very confused, especially when running the Wizard and loading a tune. If the ECU main power is removed at key-off it won't take the Config File. There's an in-line fuse for the main power lead. This supplies power to the fuel pump relay and the Sniper, this cannot be put on a switch or relay, but it can be relocated closer to the battery if desired. If you don't have your system running yet, I suggest simple wiring connections per the instructions first. This will allow the system to start & run. If it doesn't run, then it's easier to troubleshoot the basic Holley supplied wiring. Once the system has been proven to run, then consolidate wires/relays. Might seem backwards, but there have been a number of cases where the rewire occurred before the first start and the engine wouldn't go.

The Sniper supplied fuel pump relay provides an important safety function. The small blue wire is the relay trigger wire. This trigger wire is only powered during fuel pump prime and then again once it senses an RPM signal. In the event of an engine shutdown (accident or it just quits) the Sniper will drop out the fuel pump trigger so the pump will shut off. You can move the relay or the relay function to a relay panel/box, but continue to use the Sniper supplied trigger signal for the safest operation as designed.

[clcorbin]

GPatrick, the integrated Sniper/HyperSpark harness has a built-in system relay that powers the whole thing in addition to the built-in fuel pump relays. I'll be replacing both of these relays and using the ones in the power distribution center I'm adding instead.

In the end, it will end up wired similarly to the stock setup (constant power from battery + pink switched +12V). I DO like your idea of leaving the factory harness alone for initial testing. That will be easy to do and it will eliminate a few questions if I have issues getting things to run initially.

And yes, the blue wire (or whatever wire is triggering the existing fuel pump relay) will be the trigger for my fuel pump relay(s) as well. One relay will use the normally closed power contact, and the other one will use the normally open contact so only one pump will receive power at a time, determined by the tank selector switch in the cab.

[GPatrick]

I'll have to look at the latest harnesses, I'm not familiar with the integrated harness. Sounds like you have a good plan.

[clcorbin]

GPatrick, the integrated harness is very clean with less connectors and no adapter harnesses needed. It only requires four wire connections to the vehicle: Fuel pump, switched +12V, battery +12V and battery ground. Everything else plugs into the harness directly. This does not include any optional I/O you want to use of course.

While laying in bed TRYING to get to sleep last night, I had an epiphany about the fuel pump wiring. In short, I CAN'T wire the two tank pumps up like I did the high/low headlight beams. For headlights, in addition to the high beam and low beam "signals", it also has the headlight switch that turns both signals off at the same time. And while I used two relays (one for high, one for low), both were wired to the NO contact on the relay.

I wouldn't have that with the fuel pumps. I would have the on/off signal from the Sniper, but if I used the NO & NC (either on a single relay or with two relays), the pump connected to the NC terminal would be on any time the Sniper fuel signal is off. Not good.

Oh well. I'll leave it like originally planed with one relay as the on/off relay that provides power to the second side/rear relay (that relay WILL use both the NO & NC contact).

I wonder what other details I'll think of while trying to get to sleep tonight.

[a b c]

I'm sure if you think about it long enough, maybe even study some modern trucks, you'll find a way to make it much more complicated. Although, I guess if we wanted it simple, we wouldn't be running EFI in any form. Holley's marketing does a great job at making just about anybody that thinks they want EFI to believe that it's easy and you can do it. In reality, it's just as difficult as a carburetor with the main difference being, carburetors have been around for more than 100 years and many people have a basic understanding of a carburetor. When those same people are presented with all the digital data EFI has to offer, they tend to get overwhelmed. As long as they slow down, think it through, put the time in, it'll work out just fine.

[clcorbin]

True enough! Part of my plan is to replace as much of the 40+ year old factory wiring as necessary and shore up things like grounding system (not really a priority back in '81). I'd rather spend a little bit more time up front and get the wiring RIGHT and not have to worry about it (ever?) again. On the BRIGHT side, this is EFI! It's NOT a vacuum/computer controlled bastard carburetor of the early/mid '80s. Those things were a nightmare when they were new, and time did NOT improve them any.