Dedicated fuel pump circuit.

[DeLorean03]

So, as we all know, fuse #7 gets HEAVILY taxed by the electrical system. It is responsible for powering the RPM relay, the frequency valve, and the lambda ECU - among other current-drawing goodies. Naturally, fuse #7 gets pushed to its limits in a stock DeLorean. I don't know the current that DMCH's new pump/sender combo pulls yet, but with a stock DeLorean, fuse #7 gets pushed close to its max of 20A - not good. We all know, have heard of or seen, or even own a DeLorean where fuse #7 has gone into meltdown and had to be bypassed with a fuse extender or some other such method. Well, I look to resolve two reasons for this strain on fuse #7 - inferior gauge wiring and distributing the load to a direct circuit.

This all started when I was having some random intermittent lack of power issues while driving around Dayton. From time to time - completely and totally randomly - my car if going from 0-15MPH, would just randomly stall. If I was going say - 20mph and over - the car would buck - almost as if it was about to die, but the car would hang on and I could keep going. It started in September 2012, went away for all of Oct and Nov 2012, and then decided to resurface in Dec 2012. I tracked down nearly anything I could - lambda relay, rpm relay, air/fuel mixture - finally it came down to the connectors to the fuel pump and terminal 87 of the RPM relay.

I cleaned up the connectors going to the pump, and then I inspected the female socket to the RPM relay, and I saw brown burn marks around terminal 87 of the connector. So out came that wire, tightened the female end of it, and plugged the RPM relay back in. So far all has been good - but then I noticed something that alarmed me. I have run John's baffle setup with fuel pump filter for a long time. Well, the fuel pump filter had COME OFF, and the pump was completely unfiltered.

At that point, I pretty much KNEW I was sucking contaminants up into my fuel pump, and my car stalling was the pump trying to die. Thankfully, I never had the pump freeze up on me, and as of today I have a new hose and filter (thank you DMCMW!) installed on my pump along with the fuel pump/sender combo ready to install from Toby at DMCNW - once I come back from Christmas vacation with Jessica.

So, all of this has described my situation and train of thought leading up to today: I want fuse #7 safe. I don't want ANYMORE problems with my fuel pump. It is time to come up with something to help both keep the pump running and fuse #7 safe. So, after studying the fuel pump schematic a bit and talking to Casey, Dave Swingle, and Toby Peterson in exhaustion, I decided to do the following - eliminate the fuel pump from fuse #7. To do this, I have the following plan:

1. Run a dedicated 12 gauge wire directly from the battery to terminal 30 of the RPM relay. This 12 gauge wire will have a fuse extender spliced in the middle of it with a 20A fuse protecting the circuit.

2. Run a second 12 gauge wire from terminal 87 of the RPM relay to the fuel pump directly. Remember, the wire that goes from the battery to terminal 30 of the RPM has a 20A fuse in the wiring, so the wire from terminal 87 to the fuel pump does not need a fuse.

3. Run a dedicated 12 gauge ground wire from the fuel pump to the frame. I am either going to put it on the driver's horn bracket or the bolt that anchors the driver's side of the radiator to the frame. I still haven't decided on that one yet. Either ground point such take less than 3 feet of wiring.

Per Dave Swingle's suggestion, my wire from the pump to the electrical relay compartment is running from the area behind the center console where the A/C pipes run to the front of the car. This makes the length of the wire MUCH shorter than my original plan (ask if you want to know). The wire reaches from the pump to the relay compartment with less than 12 feet of 12 gauge wiring.

With the backing of Dave, Toby, Casey Barlow, and Dave (Bitsync) - I have been extremely confident in doing this mod. Here are some pictures of my progress so far:

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So here the journey begins: the 12 gauge wire in the fuel pump area. I attached a mounting ring to the side for the fuel pump. You may have noticed there's no "break a way" point in this wire. That is because DMCH's fuel pump/sending unit combo will be installed Jan 2013, and Toby sent me the appropriate female connector along with the unit. So when the time comes, I'll splice the female connector to my wiring, install the new fuel pump/sender combo and "Bob's your uncle" so to speak (BYU = everything is all good).


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So, at first, I tried to wiggle the 12 gauge wire up and around various areas of the car to get it to the passenger side of the back of the center console - no such luck. I decided since the only purpose this rubber boot seems to serve is a "junction point" for the car that a small hole to run the wire through won't be an issue. Besides, the rubber will help support the wire and keep it from rubbing up against sharp edges of the underbody, possibly causing the insulation of the wire to get hacked and slashed over the years.

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Here is the view from inside the car with your face nearly in the passenger footwell looking up towards the windshield. As you can see, the wire passed through the rubber boot with no issues, and it is away from the heater hoses - thereby keeping this wire safe from the heat of the hoses.

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And here is the wire with plenty of slack. As of posting this picture, the wire has been hidden by running it alongside the center console of the passenger side, and it enters the electrical relay area through the small hole between the wood shelf and the center console.

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Here is the dedicated wire I made. It is a 12 gauge wire with the ring terminal that the anchoring battery bolt will run through, and the fuse extender (20A) is spliced on the end of the wire.

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Lastly, here is where I stopped for the night. Unfortunately, the 12 gauge wire is too big to run through the RPM relay female socket, and even if I did run it through the female connector and plug in the wire separately to the RPM relay male connectors, the insulation of the female connector to my red 12 gauge wire would catch the female molex connector of the RPM relay - thereby not allowing the rest of the male spades to connect to the female connections of the RPM relay. Only real solution: disconnect each wire out of the female molex connector and place them on the male spades of the RPM relay. At first, I was a bit "mmmmmmm... no" about this, but there are plastic spikes all around the male/female terminal connection points of the RPM relay, assuring me that the terminals will not come into contact with anything in the electrical compartment. I wouldn't be surprised if I put some electrical tape around the junction point of the male/female spades just to be safe, or I could use some of that "liquid electrical tape" stuff. We'll see - bottom line, as long as it's safe - I'm good.

So there's my progress and what I have gotten done tonight. I felt after 2.5 hours, it was time to end for tonight - let my mind/body rest as it is easily to get caught up and start making errors and miscalculations as you work. To me, these kinds of things are best spread across 2-3 evenings. I just work better like that than trying to do something like this for 4-6 straight hours. Yes, I know that's a long time for something like this. I am very methodical as I go. I prefer to do things "right" rather than "again" - as we all know those are the two kinds of ways to do things on automobiles.

So, what do I have left?

1. Strip the end of the battery wire and plug, crimp appropriate connector, and connect it to terminal 30 of the RPM relay.
2. Same as above for dedicated pump wire but have it go to terminal 87 of the RPM relay.
3. Take out the other 4 wires from the female molex connector and connect them each individually to the RPM relay.
4. Run my dedicated ground wire to either the horn bracket or the bolt that anchors the driver's side portion of the radiator to the frame.
5. Hook both wires up to the fuel pump.

Some may ask, "Well you're about to install the new fuel pump/sender combo - why do this twice?" Well, I want to make sure my idea is sound before merging it with the fuel pump/sender combo. I'd rather know it will work first before bringing it in conjunction with another kit (combo unit) I have yet to install.

Anyways, I know - it is a long post - nearly a book. But I like to be descriptive with everything, from the idea and inspiration to do this, to the process to coming up with this solution, to carrying it out step by step, to the fruition of it working.


That's that - for now (: ...